Ambient Air Pollution and Chronic kidney disease risk in Deltan communities: A Policy Brief, 2023

Ogochukwu Okoye; Elaine Carnegie; Luca Mora

doi:10.12688/f1000research.145904.1

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Policy Brief

Ambient Air Pollution and Chronic kidney disease risk in Deltan communities: A Policy Brief, 2023

[version 1; peer review: 1 approved, 1 approved with reservations, 1 not approved]

Ogochukwu Okoye ^1,2, Elaine Carnegie¹, Luca Mora³

PUBLISHED 15 Apr 2024

Author details Author details

¹ School of Health and Social Care, Edinburgh Napier University, Edinburgh, Scotland, UK
² Department of Medicine, Delta State University, Abraka, Delta, Nigeria
³ Business School, Edinburgh Napier University, Edinburgh, Scotland, UK

Ogochukwu Okoye
Roles: Conceptualization, Data Curation, Formal Analysis, Funding Acquisition, Investigation, Methodology, Project Administration, Resources, Software, Validation, Writing – Original Draft Preparation, Writing – Review & Editing

Elaine Carnegie
Roles: Methodology, Supervision, Writing – Review & Editing

Luca Mora
Roles: Methodology, Supervision, Writing – Review & Editing

OPEN PEER REVIEW

REVIEWER STATUS

Abstract

Chronic kidney disease (CKD) is a persistent, devastating, yet neglected, non-communicable disease in developing and emerging countries. National, regional, and international agencies’ communications and reports on non-communicable diseases intentionally or non-intentionally do not feature CKD. The traditional risk factors for CKD, such as hypertension and diabetes, which have received relatively ample attention, do not sufficiently explain the high burden of CKD in these countries.

Ambient air pollution is an emerging significant environmental risk factor for CKD; however, epidemiological data and evidence are lacking for susceptible populations in developing countries. The Niger Delta region of Nigeria is a petrochemical hub known for environmental degradation, including air pollution, and thus, serves as a good case study for investigating the association between air pollution and CKD. This brief is based on the results of a mixed-methods study conducted in four communities situated near an oil and gas refinery in Warri, Nigeria.

Air pollutant concentrations measured in partnership with citizen scientists showed that all except one air pollutant (ozone) exceeded the WHO acceptable limits in all four communities.

The overall prevalence of CKD was high (12.3%) but even higher (18%) in a socially deprived semi-urban community closest to the oil refinery. Hypertension, diabetes, other behavioral risk factors, and exposures associated with CKD were prevalent among the inhabitants of the four communities. However, public environmental health information and education are lacking.

A multifaceted approach is required to mitigate air pollution and the associated health risks in the state. Public inclusion is strongly recommended for the planning and implementation of future interventions. Kidney disease prevention and treatment should be emphasized in health policies and insurance schemes.

Keywords

air pollution, chronic kidney disease, petrochemical industry, particulate matter, environmental health

Corresponding author: Ogochukwu Okoye

Competing interests: No competing interests were disclosed.

Grant information: This project was partially funded by Edinburgh Napier University's Public Engagement Fund.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Copyright: © 2024 Okoye O et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

How to cite: Okoye O, Carnegie E and Mora L. Ambient Air Pollution and Chronic kidney disease risk in Deltan communities: A Policy Brief, 2023 [version 1; peer review: 1 approved, 1 approved with reservations, 1 not approved]. F1000Research 2024, 13:265 (https://doi.org/10.12688/f1000research.145904.1) First published: 15 Apr 2024, 13:265 (https://doi.org/10.12688/f1000research.145904.1) Latest published: 10 Jan 2025, 13:265 (https://doi.org/10.12688/f1000research.145904.3)

Introduction

Chronic kidney disease (CKD) is a persistent, devastating, yet neglected non-communicable disease (NCD) especially in developing and emerging countries (Vanholder et al., 2021). Chronic kidney disease is responsible for 3.4 million deaths worldwide and ranks 10th among the risk factors for global deaths and DALYs (Global Burden of Disease Collaboration, 2019). However, national, regional, and international agency communications and reports on non-communicable diseases intentionally or non-intentionally do not feature CKD. Traditional risk factors for CKD, such as hypertension and diabetes, which receive relatively ample attention, do not sufficiently explain the high burden of CKD in these countries (Garcia-Garcia et al., 2015; Stanifer et al., 2016).

The disproportionately higher prevalence and severity of CKD in the young population of low- or middle-income countries (LMIC), despite preventive interventions, is a matter of global concern. Since the traditional risk factors for CKD, such as hypertension and diabetes mellitus, do not sufficiently explain the CKD epidemiology in LMIC, attention is shifting towards other environmental exposures, such as air pollution, which is the leading environmental risk factor for NCD (World Health Organization, 2018). Systematic reviews and meta-analyses have shown that air pollution increases the risk of kidney dysfunction by 4–70%, and persons residing or working near point sources of air pollution are at an increased risk (Okoye et al., 2022; Wu et al., 2020; Ye et al., 2021). However, these reviews were based on methodologically heterogeneous studies. In contrast, there is a proliferation of epidemiological and toxicological evidence of air pollution-associated respiratory and cardiovascular diseases. Evidence for air pollution associated with CKD is almost non-existent in Nigeria and Sub-Saharan Africa, and environmental epidemiological researchers from the Niger Delta region have stressed the general paucity of scientific evidence, advocating for research support to examine and assess the health risks associated with petroleum-related exposure (Ordinioha & Brisibe, 2013; Orisakwe, 2021).

Coincidentally, similar to CKD, air pollution and its negative health consequences are worse in disadvantaged countries, placing an additional burden on already-strained health systems. Few reliable epidemiological studies on air pollution and kidney disease have been conducted among susceptible people living in the Niger Delta, Nigeria’s greatest petroleum hub, with CKD prevalence exceeding 10% (Chukwuonye et al., 2018). The irreversible and progressive nature of CKD, the high prevalence and incidence rates, adverse outcomes, enormous costs of treatment, and the strain on individual and collective health costs should prompt all stakeholders to take action. The persistence of a combination of CKD and ambient air pollution (two top-ten risk factors for global deaths) despite existing environmental health regulations is concerning and deserves attention.

This document provides epidemiological evidence of air pollution associated CKD in susceptible communities in Niger Delta, Nigeria, the implications for policy and recommendations for action. The Ethical Review Committee of the Hospital Management Board, Warri, Delta State, Nigeria (CHW/ECC VOL 1/226) and the School of Health and Social Care Research Integrity Committee, Edinburgh Napier University (2782647) approved the study.

Policy outcomes and implications

Despite the high burden of CKD in Nigeria, there is currently no renal care policy, plan or programme. Although the updated National Health Policy published in 2016 (Federal Ministry of Health, 2016) explicitly states that all tiers of government and private sectors should commit to attaining health and good quality of life for all citizens, CKD was surprisingly not identified as one of the major NCDs requiring attention. The implication of this grave omission is that while resources are channelled towards the prevention and control of NCDs such as hypertension, cardiovascular disease, stroke and asthma, the prevalence of CKD remains high and outcomes, abysmal.

The nephrology research community are well place to generate the needed evidence that may persuade policy makers to action. This brief therefore provides epidemiological evidence of high CKD burden in susceptible communities in the Niger Delta, Nigeria and the possible association with the greatest environment risk factor for diseases - air pollution.

Evidence of high ambient air pollutant levels in Warri

No air monitoring data existed in the State at the time this study was conducted. Ambient air pollutants were measured in collaboration with eight citizen scientists from four communities at varying distances from the petrochemical refinery: A (3 km/semi-urban), B (3.5 km/urban), C (10 km/urban), and D (13 km/rural). The mean concentrations of PM_2.5, PM₁₀, and volatile organic compounds (VOCs) exceeded the WHO acceptable limits in all four communities, whereas CO₂ was acceptable only in the communities farthest from the refinery (Table 1). Ozone (O₃) was within the acceptable limits in all communities. The mean PM₁₀ concentration was highest in the two communities closest to the refinery (A and B), while PM_2.5 was highest in the urban community closest to the refinery (B). Higher than acceptable levels of NO₂ were recorded on certain days in all communities, whereas for most other days, it was negligible. Table 1 shows the estimated hazard quotient (HQ) of the air pollutants in the four communities. The HQ was estimated by dividing the mean concentration of the individual air pollutants by their respective WHO minimum acceptable limits. An HQ ≤1 is considered a negligible hazard, while >1 indicates exposure concentrations exceeding the reference limit, but not necessarily a statistical probability of harm occurring. The calculated HQ for PM_2.5, PM₁₀, VOC, and CO₂ based on the WHO minimum allowable limits, were elevated in all four communities.

Table 1. Hazard Quotient of air pollutants exceeding WHO 2021 annual acceptable limits in the four communities.

Pollutants	WHO upper limit (annual mean)	Communities A 3 km	B 3.5 km	C 10 km	D 13 km
		Mean Conc. (HQ)
CO2 (ppm)	<600	630.58 (1.05)	652.41 (1.08)	599.04 (1.00)	584.25 (0.97)
PM₁₀ (μg/m³)	15	55.54 (3.70)	55.43 (3.69)	40.68 (2.71)	46.13 (3.07)
PM_2.5 (μg/m³)	5	25.32 (5.06)	28.01 (5.60)	22.82 (4.56)	26.18 (5.24)
VOC (ppm)	0.220*	0.32 (1.46)	0.28 (1.26)	0.30 (1.36)	0.31 (1.40)
Total HQ		11.27	11.63	9.63	10.68

* Indoor threshold limit, which is typically higher than outdoor.

High prevalence of CKD and the risk factors

A health survey was conducted over a period of six months to assess the prevalence and risk factors of CKD among 1460 community members selected by multi-stage sampling from the four communities. Adults aged 18-64 years who had resided in their respective communities for at least 5 years were recruited.

The overall prevalence of CKD, defined as dipstick proteinuria and/or an eGFR <60 ml/min was 12.3%. The prevalence was highest in community A closest to the refinery (17.9%) compared with 13.1%, 10.5%, and 8.0% in communities B, C, and D, respectively (X²=18.292, p≤.001). Proteinuria alone was detected in 6.8% of all participants, while 6.6% had a reduced eGFR of <60 ml/min. Two-fifths of the participants with CKD were in stage 3A (i.e. eGFR 45-59 mls/min) which represents a mild to moderate decrease in kidney function requiring monitoring (Figure 1).

Figure 1. Stages of CKD among participants (N=180).

The risk factors significantly associated with CKD were older age, low level of education, proximity to the refinery, residence in urban/semi-urban areas compared to rural areas, use of hair dyes, spending more time indoors, hypertension, and diabetes. However, after adjusting for confounding factors, the independent risk factors for CKD were older age, low level of education, proximity to the refinery and hypertension. The overall prevalence of hypertension, obesity, and diabetes was 33%, 28.5%, and 6.0%, respectively.

Social determinants of CKD risk

One-third (31.5%) of the population had less than secondary-level education, and 50.5% earned less than the minimum wage. Although 86% of the population was employed, 68% were self-employed, and only 3.8% were employed by the government. Of the 68% self-employed, the majority were petty traders. Several social risk factors and toxic environmental exposures associated with CKD and NCDs were prevalent among residents of the four communities. Behavioural factors included grossly inadequate fruit (90%) and vegetable ingestion (70%), low physical activity (47.2%), use of kerosene (44%), alcohol consumption (41%), use of herbal concoctions (40.8%), and cooking with solid fuel (37.1%). Four-fifths of the population was regularly exposed to petrochemical products as part of their daily lives, 72% used household chemicals regularly, 53.2% were regularly exposed to pesticides, and 49% were exposed to toxic chemicals or dust in their jobs. Other risk factors that were relatively less prevalent included hair dye use (19%), excess salt intake (15%), use of mothballs (14.4%), use of skin lighteners (12.7%), and current smoking (3.8%).

Low air pollution health risk literacy in Warri

Two-fifths of the 1460 survey participants perceived that their outdoor air was polluted, and the proportion was significantly higher (65%) among those residing near the refinery. Heightened perception of air pollution was significantly more common among young people, those who lived near refineries and urban areas, those who spent more time outdoors, and those who cooked with propane gas. Refinery activities were cited as the most popular source of air pollution. A higher proportion of those residing near the refinery attributed air pollution to the refinery/gas plant: 40.6% and 18.0% for communities A and B, respectively, compared to 7.2% and 6.1% for the furthest away communities C and D, respectively. Other perceived sources of air pollution include poor environmental sanitation, traffic emissions, generator fumes, open waste burning, and illegal oil refining (Figure 2).

Figure 2. Participants’ perception of sources of air pollution (N=628).

Others=Bakery, other industries, dust, overcrowding, sawmills, septic pits, swamps.

Most participants (70.1%) perceived that air pollution is associated with health risks, 13.4% responded negatively, and 16.4% did not know. The majority of study participants (60.1%) were unaware of any medical conditions associated with air pollution. Figure 3 shows the participants’ responses when asked about the specific health conditions associated with air pollution.

Figure 3. Medical conditions the participants associated with air pollution (N=1460).

Only 12.3% of the participants agreed that the ambient air environment was well controlled and up to 60% placed responsibility solely on the government. Among those who agreed that they had a role to play, the responses included maintaining environmental sanitation (53%), complaining to the government and advocacy (32%), and using personal protective measures (3.7%).

Implications for policy

There is currently no renal care policy in Nigeria or Delta State, and the most recent National Health Policy does not capture CKD among NCDs. This critical omission needs to be urgently addressed as the enormous burden of CKD is not debatable. Furthermore, CKD is often associated with mortality in patients with both NCDs and chronic infections.

In the broadest policy terms, increasing efforts towards environmental risk protection, including environmental risk communication and transparency, and reducing poverty and investment in public health services, would improve population health and reduce inequalities in general, but more so for susceptible persons. Specifically, poverty and ignorance of health-promoting information increase the burden of CKD via mechanisms related to access to health care, unhealthy behaviors, biological factors (e.g., low birth weight, inadequate nutrition), and environmental factors (e.g., exposure to pollutants, communicable diseases, lack of clean water, and sanitation). Therefore, multisector integration, interdisciplinarity, and public inclusion in shaping policies and planning health interventions are needed to ensure effectiveness and reduce inequalities.

This study reveals that communities in Warri are simultaneously exposed to household, community, and global environmental risks, depicting a Triple Risk Overlap (Smith & Ezzati, 2005). Due to the high prevalence of CKD risk factors and low awareness of CKD and NCD status among the study participants, it appears that health literacy is low, and the public is yet to embrace routine health screening. The implication is that current public health education interventions are not persuasive enough or effective. Out-of-pocket payments are an additional hindrance to positive health-seeking behaviors.

Actionable recommendations

• A National Renal Care Policy is needed and should be integrated with the existing National Health Care Policy.
• Kidney health prevention and treatment should be covered by National and State health insurance schemes. Re-introducing the Delta State haemodialysis subsidy should be considered to address the suffering of people already living with kidney failure.
• All primary health centers (public and private) should be equipped to carry out basic kidney screening tests, including blood pressure monitors, urinalysis dipsticks, and portable point-of-care serum creatinine or cystatin C analyzers.
• The public requires more persuasion to adopt healthy behaviors and routine annual health screenings. For instance, a medical certificate of fitness should be required before a driver’s licence or international passport renewals.
• Environmental risk factors such as air pollution should feature prominently in strategic plans for NCD prevention. The current National Health Policy does not explicitly highlight the role of mitigating environmental exposures such as air pollution in achieving sustainable health.
• Public environmental health education is needed and should be planned and executed in collaboration with all stakeholders, including relevant government agencies, public health professionals, educators, environmental scientists, sociologists, industries, non-profit organizations, and community leaders/members. Training is required for trainers who are environmental health champions that will sustain the campaign for clean air at the community level.
• Nigeria lacks continuous air monitoring data and has met only one out of the nine Clean Air Targets (United Nations Environment Programme, 2021).
There is an urgent need to invest in air monitoring services and data, cleaner technologies (e.g., electric transportation, solar, and wind power), and environmental risk communication through various media channels.
• Preserve forests and green spaces. Encourage and support citizens to maintain green spaces around their homes. The Delta State Ministry of Environment has initiated a number of tree-planting campaigns, which are commendable and should be sustained.
• There is a need for socially empowering policies to improve the indices of susceptible populations that have suffered long-term environmental exposure. Job creation and skill acquisition training is required in these areas.
• All tiers of government, regulatory bodies, and urban planners should commit to improving air quality by enforcing stringent air pollution standards, regulations, and legislation. Environmental impact assessments should be conducted in accordance with ethical standards.
• There is a need to support the research community through grants to generate robust, credible, and reliable evidence that will inform effective health and social interventions. Although the National Health Policy stated the importance of “strengthening the evidence”, this can only be achieved by partnering with the experts and providing the resources to support credible research in areas of need.

Limitations of the study

Air monitoring was conducted for a period of 4 weeks only, due to the high financial implications and tenure of the research. Urine protein was tested using dipsticks rather albumin: creatinine ratio which is more reliable, due to high cost of the test. However, dipsticks test is highly specific though less sensitive in detecting low levels of proteinuria. Lastly, the diagnosis of CKD was based on a spot- assessment due to the participants’ unwillingness to repeat their test and possibly confirm a new disease. The lack of a repeat test may have led to an over- or under-diagnosis of CKD.

Conclusion

The main purpose of this briefing is to draw attention to the seriousness of chronic kidney disease, the possible causative role of environmental exposures such as air pollution, and to provide information that may support decision makers in developing and implementing policies and strategies to address the problem.

The evidence presented strongly suggests that long-term exposure to ambient air pollution increases the risk of chronic kidney disease and hypertension, which is consistent with previously published evidence. In addition, there is evidence of the socioeconomic and indirect health impacts of air pollution in an already vulnerable population with poor environmental health literacy. Environmental injustices such as disparities in access to clean air and environmental health information are significant threats to sustainable health and require urgent attention. Therefore, the co-benefits of effective air pollution mitigation surpass environmental sustainability to include improvements in health, social well-being, and reduction in health inequalities.

Addressing air pollution-associated CKD requires a multifaceted approach involving decision makers, health care professionals, the academic community, industries, and the general public. By incorporating the issue of air pollution-associated health risks into policymaking, practice, health professionals, and public education, it is possible to reduce the burden of CKD and other NCDs and improve public health outcomes.

Data availability statement

Edinburgh Napier University: Ambient Air Pollution near Petrochemical Industries and Chronic Kidney Disease Risk: Integrating Citizen Science within an Exploratory Mixed Methods Study (dataset) https://doi.org/10.17869/enu.2024.3559366.

This project contains the following underlying data:

• AIR MONITORING DATA.xlsx
• Codebook - air pollution - 17-03-2022.docx
• GFR.xlsx

Data are available under the terms of the Creative Commons Attribution 4.0 International license (CC-BY 4.0).

Acknowledgements

• Management of Delta State University, Abraka, and Delta State University Teaching Hospital, Oghara.
• The management of Central Hospital Warri, Delta State.
• School of Health and Social Care, Edinburgh Napier University.
• Leaders and members of the study community.
• Research Assistants and volunteer health care professionals: Dr. Ejiro Orhewere, Dr. Oritseweyinmi Edema, Dr. Toritseju Ereku, Miss Chigozie Offiah, Miss Osarumen Uwadiae, and Mr. Clement Ugbunu.
• Community volunteers (citizen scientists)
• Dr Mininim Oseji, Permanent Secretary, Ministry of Environment, Delta State.

References

Chukwuonye II, Ogah OS, Anyabolu EN, et al.: Prevalence of chronic kidney disease in Nigeria: systematic review of population-based studies. Int. J. Nephrol. Renov. Dis. 2018; 11: 165–172. PubMed Abstract | Publisher Full Text | Free Full Text
Federal Ministry of Health: National Health Policy 2016: Promoting the Health of Nigerians to Accelerate Socio-economic Development.2016.Reference Source
Garcia-Garcia G, Jha V; World Kidney Day Steering, C: Chronic kidney disease in disadvantaged populations: The case of Africa. Afr. J. Prim. Health Care Fam. Med. 2015, Apr 28; 7(1): e1–e2. PubMed Abstract | Publisher Full Text | Free Full Text
Global Burden of Disease Collaboration: Global burden of 87 risk factors in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study.2019.
Okoye OC, Carnegie E, Mora L: Air Pollution and Chronic Kidney Disease Risk in Oil and Gas- Situated Communities: A Systematic Review and Meta-Analysis. Int. J. Public Health. 2022; 67: 1604522. PubMed Abstract | Publisher Full Text | Free Full Text
Ordinioha B, Brisibe S: The human health implications of crude oil spills in the Niger delta, Nigeria: An interpretation of published studies. Niger. Med. J. 2013; 54(1): 10–16. PubMed Abstract | Publisher Full Text | Free Full Text
Orisakwe OE: Crude oil and public health issues in Niger Delta, Nigeria: Much ado about the inevitable. Environ. Res. 2021, Jan 9; 194: 110725. PubMed Abstract | Publisher Full Text
Smith KR, Ezzati M: HOW ENVIRONMENTAL HEALTH RISKS CHANGE WITH DEVELOPMENT: The Epidemiologic and Environmental Risk Transitions Revisited. Annu. Rev. Environ. Resour. 2005; 30(1): 291–333. Publisher Full Text
Stanifer JW, Muiru A, Jafar TH, et al.: Chronic kidney disease in low- and middle-income countries. Nephrol. Dial. Transplant. 2016, Jun; 31(6): 868–874. PubMed Abstract | Publisher Full Text | Free Full Text
United Nations Environment Programme: Actiona on Air Quality: A global summary of policies and programmes to reduce air pollution. U. N. E. Program; 2021. Reference Source
Vanholder R, Annemans L, Bello AK, et al.: Fighting the unbearable lightness of neglecting kidney health: the decade of the kidney. Clin. Kidney J. 2021, Jul; 14(7): 1719–1730. PubMed Abstract | Publisher Full Text | Free Full Text
World Health Organization: Ambient (outdoor) air pollution.2018. December 11th. Reference Source
Wu MY, Lo WC, Chao CT, et al.: Association between air pollutants and development of chronic kidney disease: A systematic review and meta-analysis. Sci. Total Environ. 2020, Mar 1; 706: 135522. PubMed Abstract | Publisher Full Text
Ye J, Wang S-S, Fang Y, et al.: Ambient air pollution exposure and risk of chronic kidney disease: A systematic review of the literature and meta-analysis [Article]. Environ. Res. 2021; 195: 110867. PubMed Abstract | Publisher Full Text

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Version 3

VERSION 3 PUBLISHED 15 Apr 2024

Author details Author details

Elaine Carnegie
Roles: Methodology, Supervision, Writing – Review & Editing

Luca Mora
Roles: Methodology, Supervision, Writing – Review & Editing

Competing interests

No competing interests were disclosed.

Grant information

This project was partially funded by Edinburgh Napier University's Public Engagement Fund.
The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

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© 2024 Okoye O et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Okoye O, Carnegie E and Mora L. Ambient Air Pollution and Chronic kidney disease risk in Deltan communities: A Policy Brief, 2023 [version 1; peer review: 1 approved, 1 approved with reservations, 1 not approved]. F1000Research 2024, 13:265 (https://doi.org/10.12688/f1000research.145904.1)

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Reviewer Report 14 Sep 2024

Nicholas Osborne, The University of Queensland, Saint Lucia, Queensland, Australia

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https://doi.org/10.5256/f1000research.159925.r279715

Overall comments
This study proposes to discover association between air pollution and CKD. Unfortunately an accurate measure of air pollution was not available. Similarly an accurate measure of the health outcome, kidney function was not available. Diagnosis of CKD requires two measures of kidney function (usually by eGRF) at least 3 months apart. Consequently attempts to examine the relationship do not have data of sufficient quality to make the linkage.
The paper was not conducted as a policy brief. Large amounts of extant literature were missing from the evidence base presented.
The paper has a limited data reference list.

Specific comments
Abstract mentions CKDu in passing without mentioning its prevalence in certain LMIC settings. The disease CKDu in Sri Lankan and Mesoamerican settings.

Does the paper provide a comprehensive overview of the policy and the context of its implementation in a way which is accessible to a general reader?

No
Is the discussion on the implications clearly and accurately presented and does it cite the current literature?

No
Are the recommendations made clear, balanced, and justified on the basis of the presented arguments?

No

Competing Interests: Dr Nicholas Osborne received an honorarium for speakers’ fees from Reckitt, an honorarium from Taylor and Francis Publishing, and payment for assisting the Federal Court of Australia.

Reviewer Expertise: Environmental epidemiology

I confirm that I have read this submission and believe that I have an appropriate level of expertise to state that I do not consider it to be of an acceptable scientific standard, for reasons outlined above.

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Report a concern

Author Response 21 Nov 2024

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

21 Nov 2024

Author Response

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript.

Comment: This study proposes to discover association ... Continue reading We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript.

Comment: This study proposes to discover association between air pollution and CKD. Unfortunately, an accurate measure of air pollution was not available.
Consequently, attempts to examine the relationship do not have data of sufficient quality to make the linkage.
Response: Extensive methodological and statistical details were deliberately omitted as this document was targeted at policymakers. However, we have provided additional information in the text to describe how air pollution was measured and other details are available in the link to the underlying study. Page 4

Comment: Similarly, an accurate measure of the health outcome, kidney function was not available.
Diagnosis of CKD requires two measures of kidney function (usually by eGRF) at least 3 months apart.
Response: We agree with your observation. The authors initially set out to obtain at least two measurements from participants who have abnormalities but encountered challenges with participant retention. This limitation has been highlighted in more detail.
However, all biological samples were handled and processed by a reputable independent laboratory with documented standard operating procedures to ensure accuracy and reliability. Page 11

Comment: The paper was not conducted as a policy brief. Large amounts of extant literature were missing from the evidence base presented.
Response: Thank you for your valid observation. We structured the paper according to the journal's template for a policy brief. Our intention was to provide a brief summary of the underlying study before delving into the policy implications and recommendations. We deliberately excluded excessive statistical information to enhance readability for the non-academic audience. However, we have now included more data in the text figures and supplementary files.

Comment: The paper has a limited data reference list.
Response: The short reference list was to adhere to the limits of a policy brief. More references have been included in specific sections. Pages 3,5,6,7,14

Comment: Abstract mentions CKDu in passing without mentioning its prevalence in certain LMIC settings. The disease CKDu in Sri Lankan and Mesoamerican settings.
Response: Thank you for your comment. There may have been a mix up. CKDu was not mentioned in the abstract.
-
We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript.

Comment: This study proposes to discover association between air pollution and CKD. Unfortunately, an accurate measure of air pollution was not available.
Consequently, attempts to examine the relationship do not have data of sufficient quality to make the linkage.
Response: Extensive methodological and statistical details were deliberately omitted as this document was targeted at policymakers. However, we have provided additional information in the text to describe how air pollution was measured and other details are available in the link to the underlying study. Page 4

Comment: Similarly, an accurate measure of the health outcome, kidney function was not available.
Diagnosis of CKD requires two measures of kidney function (usually by eGRF) at least 3 months apart.
Response: We agree with your observation. The authors initially set out to obtain at least two measurements from participants who have abnormalities but encountered challenges with participant retention. This limitation has been highlighted in more detail.
However, all biological samples were handled and processed by a reputable independent laboratory with documented standard operating procedures to ensure accuracy and reliability. Page 11

Comment: The paper was not conducted as a policy brief. Large amounts of extant literature were missing from the evidence base presented.
Response: Thank you for your valid observation. We structured the paper according to the journal's template for a policy brief. Our intention was to provide a brief summary of the underlying study before delving into the policy implications and recommendations. We deliberately excluded excessive statistical information to enhance readability for the non-academic audience. However, we have now included more data in the text figures and supplementary files.

Comment: The paper has a limited data reference list.
Response: The short reference list was to adhere to the limits of a policy brief. More references have been included in specific sections. Pages 3,5,6,7,14

Comment: Abstract mentions CKDu in passing without mentioning its prevalence in certain LMIC settings. The disease CKDu in Sri Lankan and Mesoamerican settings.
Response: Thank you for your comment. There may have been a mix up. CKDu was not mentioned in the abstract.
-
Competing Interests: None Close
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COMMENTS ON THIS REPORT

Author Response 21 Nov 2024

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

21 Nov 2024

Author Response

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript.

Comment: This study proposes to discover association ... Continue reading We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript.

Comment: This study proposes to discover association between air pollution and CKD. Unfortunately, an accurate measure of air pollution was not available.
Consequently, attempts to examine the relationship do not have data of sufficient quality to make the linkage.
Response: Extensive methodological and statistical details were deliberately omitted as this document was targeted at policymakers. However, we have provided additional information in the text to describe how air pollution was measured and other details are available in the link to the underlying study. Page 4

Comment: Similarly, an accurate measure of the health outcome, kidney function was not available.
Diagnosis of CKD requires two measures of kidney function (usually by eGRF) at least 3 months apart.
Response: We agree with your observation. The authors initially set out to obtain at least two measurements from participants who have abnormalities but encountered challenges with participant retention. This limitation has been highlighted in more detail.
However, all biological samples were handled and processed by a reputable independent laboratory with documented standard operating procedures to ensure accuracy and reliability. Page 11

Comment: The paper was not conducted as a policy brief. Large amounts of extant literature were missing from the evidence base presented.
Response: Thank you for your valid observation. We structured the paper according to the journal's template for a policy brief. Our intention was to provide a brief summary of the underlying study before delving into the policy implications and recommendations. We deliberately excluded excessive statistical information to enhance readability for the non-academic audience. However, we have now included more data in the text figures and supplementary files.

Comment: The paper has a limited data reference list.
Response: The short reference list was to adhere to the limits of a policy brief. More references have been included in specific sections. Pages 3,5,6,7,14

Comment: Abstract mentions CKDu in passing without mentioning its prevalence in certain LMIC settings. The disease CKDu in Sri Lankan and Mesoamerican settings.
Response: Thank you for your comment. There may have been a mix up. CKDu was not mentioned in the abstract.
-
We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript.

Comment: This study proposes to discover association between air pollution and CKD. Unfortunately, an accurate measure of air pollution was not available.
Consequently, attempts to examine the relationship do not have data of sufficient quality to make the linkage.
Response: Extensive methodological and statistical details were deliberately omitted as this document was targeted at policymakers. However, we have provided additional information in the text to describe how air pollution was measured and other details are available in the link to the underlying study. Page 4

Comment: Similarly, an accurate measure of the health outcome, kidney function was not available.
Diagnosis of CKD requires two measures of kidney function (usually by eGRF) at least 3 months apart.
Response: We agree with your observation. The authors initially set out to obtain at least two measurements from participants who have abnormalities but encountered challenges with participant retention. This limitation has been highlighted in more detail.
However, all biological samples were handled and processed by a reputable independent laboratory with documented standard operating procedures to ensure accuracy and reliability. Page 11

Comment: The paper was not conducted as a policy brief. Large amounts of extant literature were missing from the evidence base presented.
Response: Thank you for your valid observation. We structured the paper according to the journal's template for a policy brief. Our intention was to provide a brief summary of the underlying study before delving into the policy implications and recommendations. We deliberately excluded excessive statistical information to enhance readability for the non-academic audience. However, we have now included more data in the text figures and supplementary files.

Comment: The paper has a limited data reference list.
Response: The short reference list was to adhere to the limits of a policy brief. More references have been included in specific sections. Pages 3,5,6,7,14

Comment: Abstract mentions CKDu in passing without mentioning its prevalence in certain LMIC settings. The disease CKDu in Sri Lankan and Mesoamerican settings.
Response: Thank you for your comment. There may have been a mix up. CKDu was not mentioned in the abstract.
-
Competing Interests: None Close
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Reviewer Report 11 Sep 2024

Nikola M Pavlović, University of Niš, Niš, Serbia

Approved

https://doi.org/10.5256/f1000research.159925.r292274

Ambient Air Pollution and Chronic kidney disease risk in Deltan communities: A Policy Brief, 2023.
Abstract

Comments:
- The abstract effectively highlights the importance of the study by addressing an

Ambient Air Pollution and Chronic kidney disease risk in Deltan communities: A Policy Brief, 2023.
Abstract

Comments:
- The abstract effectively highlights the importance of the study by addressing an issue that is often overlooked: CKD in developing countries. However, it could refine its focus on the study's objectives, methods, key findings, and specific policy recommendations.
Suggestions:
- Objective Clarification: Include a brief statement that clearly outlines the study's objective.
- Methodology Mention: Explicitly mention that a mixed-methods approach was used.
- Specific Findings: Highlight specific data points, such as the exact levels of pollutants that exceed WHO limits.
- Policy Recommendations: Summarize one or two key policy recommendations for a clear takeaway.

Introduction

Comments:
- The introduction is comprehensive, providing a strong background on CKD and air pollution, particularly in the context of developing countries. However, it somewhat repeats itself by discussing traditional CKD risk factors.
Suggestions:
- Streamlining: Consider consolidating the discussion on traditional CKD risk factors to avoid redundancy.
- Focused Transition: Ensure a smooth transition from discussing CKD globally to the specific context of the Niger Delta.
- Identification of Gap: Introduce the research gap on the link between air pollution and CKD in the Niger Delta earlier in the section.

Policy Outcomes and Implications

Comments:
- This section succinctly outlines the critical issue of lacking renal care policies in Nigeria. However, the link between CKD and air pollution could be articulated more forcefully to emphasize urgency.
Suggestions:
- Direct Link: Explicitly connect the absence of CKD in national health policy to the study’s findings on air pollution and CKD prevalence.
- Broader Implications: Discuss the broader public health implications if this policy gap continues, including potential long-term consequences.

Evidence of High Ambient Air Pollutant Levels in Warri

Comments:
- This section is rich in data and provides a clear picture of pollution levels. The use of a table to present hazard quotients is effective, but the narrative could be enhanced for better flow and readability.
Suggestions:
- Narrative Flow: Integrate the table with the narrative by referencing key figures directly in the text.
- Benchmark Against Global Standards: Briefly compare the findings with global or regional averages for context.
- Graphical Representation: Consider using a graph to visualize the levels of pollutants across communities for greater impact.

High Prevalence of CKD and the Risk Factors

Comments:
- This section effectively presents prevalence data and associated risk factors. The statistical significance is clearly noted, strengthening the findings.
Suggestions:
- Risk Factor Hierarchy: Present the risk factors in order of their strength of association with CKD.
- Visual Aids: While the current figure is useful, additional visual aids, such as bar charts or scatter plots, could further clarify the distribution of CKD stages across communities.
- Contextualization: Briefly contextualize the CKD prevalence data with national or regional statistics to highlight the severity.

Social Determinants of CKD Risk

Comments:
- The social determinants are well-captured, providing a comprehensive picture of contributing factors. However, the section could benefit from a more concise presentation.
Suggestions:
- Condensation: Consider condensing the list of behavioral factors by grouping similar items, such as unhealthy dietary habits.
- Clearer Connections: Draw clearer connections between these social determinants and the higher CKD prevalence, emphasizing the compounding effect of multiple risk factors.
- Implications: Discuss the potential public health implications of these social determinants in more depth.

Low Air Pollution Health Risk Literacy in Warri

Comments:
- This section addresses an important issue but could be more impactful if it connected low health literacy directly with CKD prevalence.
Suggestions:
- Direct Linkage: Explicitly link low literacy levels to poor health outcomes, particularly in the context of CKD and air pollution.
- Awareness Campaigns: Suggest potential public health campaigns or educational interventions to improve awareness based on the findings.

Implications for Policy

Comments:
- This section provides a strong call to action. The identified policy gaps are critical and well-presented.
Suggestions:
- Structured Recommendations: Present the policy implications in a more structured format, possibly using bullet points or numbered lists for clarity.
- Evidence Integration: Integrate specific study findings more directly into the policy recommendations to strengthen the argument for immediate action.

Actionable Recommendations

Comments:
- The recommendations are comprehensive and relevant but could be more prioritized or categorized.
Suggestions:
- Prioritization: Consider categorizing the recommendations into short-term, medium-term, and long-term actions.
- Stakeholder Engagement: Emphasize the role of specific stakeholders (e.g., government, NGOs, the public) in implementing these recommendations.
- Feasibility: Briefly discuss the feasibility of these recommendations, particularly in the context of existing infrastructure and resources.

Limitations of the Study

Comments:
- The limitations are transparently discussed, which is commendable. However, there is a risk that some of these might overshadow the study's strengths.
Suggestions:
- Strengths Emphasis: Counterbalance the limitations with a brief discussion of the study’s strengths, particularly its novel approach and the involvement of citizen scientists.
- Future Directions: Suggest specific areas for future research that could address these limitations, enhancing the study's impact.

Conclusion

Comments:
- The conclusion effectively summarizes the key points but could be more emphatic in calling for urgent action.
Suggestions:
- Stronger Call to Action: End with a more forceful call to action directed at policymakers, highlighting the urgency of addressing CKD in the Niger Delta.
- Summary of Key Points: Briefly summarize the most critical findings and recommendations to leave a lasting impression.

Overall Document Comments:

Consistency: Ensure consistency in the use of terms (e.g., CKD vs. chronic kidney disease) throughout the document.
Clarity: While the document is generally clear, some sections, particularly those with dense data, could benefit from simpler language and clearer transitions.
Visual Aids: Consider the strategic use of additional visual aids to break up text-heavy sections and improve reader engagement.
Proofreading: A thorough proofreading is recommended to correct any minor grammatical errors and ensure a polished final submission.

I believe these suggestions will assist the authors in refining their policy brief to make it more impactful and ensure it effectively communicates the urgency of the issue to both policymakers and the broader public.

Does the paper provide a comprehensive overview of the policy and the context of its implementation in a way which is accessible to a general reader?

Yes
Is the discussion on the implications clearly and accurately presented and does it cite the current literature?

Yes
Are the recommendations made clear, balanced, and justified on the basis of the presented arguments?

Yes

Competing Interests: No competing interests were disclosed.

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

CITE

Report a concern

Author Response 31 Jan 2025

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

31 Jan 2025

Author Response

We are grateful for your detailed and constructive critique which has helped to improve the merit and quality of our manuscript.

ABSTRACT
Reviewer comment: Objective Clarification: Include a brief ... Continue reading We are grateful for your detailed and constructive critique which has helped to improve the merit and quality of our manuscript.

ABSTRACT
Reviewer comment: Objective Clarification: Include a brief statement that clearly outlines the study's objective.
Author response: The objective has been clarified as follows:
“This brief is based on a mixed-methods study conducted in four communities situated near an oil and gas refinery in Warri, Nigeria to explore perceived and actual air pollution risk and determine whether long-term exposure to AAP increases NCD risk” (Page 2)

Reviewer comment: Methodology Mention: Explicitly mention that a mixed-methods approach was used.
Author response: Done as stated above

Reviewer comment: Specific Findings: Highlight specific data points, such as the exact levels of pollutants that exceed WHO limits.
Author response: Included as follows:
“Measured PM_2.5 ranged from 22.8 – 28.0 μg/m3, PM₁₀, 40.6 - 55.5 μg/m3, and CO₂, 584-652ppm”. 2

Reviewer comment: Policy Recommendations: Summarise one or two key policy recommendations for a clear takeaway.
Author response: Included as follows:
“The government needs to urgently invest in air monitoring services and data, cleaner technologies and environmental risk communication through various media channels. We strongly recommend public inclusion in planning, designing and implementing future environmental interventions. Lastly, environmental risk factors such as air pollution should feature prominently in strategic plans for NCD prevention”. (Page 2)

Introduction
Reviewer comment: Streamlining: Consider consolidating the discussion on traditional CKD risk factors to avoid redundancy.
Focused Transition: Ensure a smooth transition from discussing CKD globally to the specific context of the Niger Delta.
Identification of Gap: Introduce the research gap on the link between air pollution and CKD in the Niger Delta earlier in the section.
Author response: Thank you for your suggestions. We have reviewed this section accordingly. (Page 3)

Reviewer comment: Policy Outcomes and Implications
Author response: This section has been improved accordingly

Reviewer comment: Direct Link: Explicitly connect the absence of CKD in national health policy to the study’s findings on air pollution and CKD prevalence.
Author response: This has been revised as follows: “This lack of recognition of CKD and the environmental risk factors important in the disease epidemiology, may explain why CKD and related NCDs are persistent.” (Page 4)

Reviewer comment: Broader Implications: Discuss the broader public health implications if this policy gap continues, including potential long-term consequences.
Author response: “The long-term consequences of continually neglecting CKD in health policies include the persistence of hypertension and CKD with associated considerable morbidity and mortality; high health care expenditure which further impoverishes the affected members of society and their families”. (Page 4)

Reviewer comment: Evidence of High Ambient Air Pollutant Levels in Warr
Narrative Flow: Integrate the table with the narrative by referencing key figures directly in the text.
Author response: This section has been improved accordingly and highlighted in the text (Page 4-5)

Reviewer comment: Benchmark Against Global Standards: Briefly compare the findings with global or regional averages for context.
Author response: This section has been improved as follows:
“The PM2.5 concentrations for three of the communities are higher than Nigeria’s 2023 average of 23.9 μg/m3 (IQAIR) and five times higher than the WHO acceptable limit. Furthermore, these levels are much higher than 7.8μg/m3 achieved in Angola, the least polluted African country which ranked 114th out of 134 countries, while Nigeria was ranked the 35th most polluted”.( Page 4-5)

Reviewer comment: Graphical Representation: Consider using a graph to visualize the levels of pollutants across communities for greater impact.
Author response: A bar chart showing air pollutant levels in the 4 communities have been included. (Figure 1)

Reviewer comment: High Prevalence of CKD and the Risk Factors
Risk Factor Hierarchy: Present the risk factors in order of their strength of association with CKD.
Author response: Included as follows:
“The independent risk factors for CKD were proximity to the refinery [OR=2.00 (1.43 – 2.81], increasing age [OR=1.02(1.005-1.04)], hypertension [OR=1.61(1.12-2.31)], and level of education [OR=0.63(0.44-0.91)]. In a further logistic mixed model, which accounted for clustering effects at household level, only increasing age was an independent risk factor for CKD [OR=1.16 (1.07-1.25)]”, (Page 6)

Reviewer comment: Visual Aids: While the current figure is useful, additional visual aids, such as bar charts or scatter plots, could further clarify the distribution of CKD stages across communities.
Author response: A new figure showing the information requested has been included. (Figure 3)

Reviewer comment: Contextualization: Briefly contextualize the CKD prevalence data with national or regional statistics to highlight the severity.
Author response: Revised as follows:
The prevalence of CKD reported across Nigeria and Sub-Saharan Africa varies greatly depending on the population studied, CKD definition and methodology; from as low as 2% to >20% (Abd ElHafeez et al., 2018; Chukwuonye et al., 2018). However, our findings demonstrate a higher CKD prevalence in the nearest/semiurban community A, compared with a pooled prevalence of 10% and 13.7% reported for Africa and Nigeria, respectively (Abd ElHafeez et al., 2018; Raji et al., 2024). (Page 5)

Social Determinants of CKD Risk
Reviewer comment: Condensation: Consider condensing the list of behavioral factors by grouping similar items, such as unhealthy dietary habits.
Author response: Revised as follows:
‘Behavioural factors included unhealthy dietary habits (70-90%), low physical activity (47.2%), habitual exposure to potential nephrotoxins (37-44%)’. (Page 6)

Reviewer comment: Clearer Connections: Draw clearer connections between these social determinants and the higher CKD prevalence, emphasizing the compounding effect of multiple risk factors.
Author response: Revised as follows:
“The concentration of multiple social and environmental risk factors in the studied population may explain the high prevalence of CKD and other NCDs. These findings support the multicasuation theory, drawing attention to the need for a multi-faceted approach to CKD prevention.” (Page 6)

Reviewer comment: Implications: Discuss the potential public health implications of these social determinants in more depth.
Author response: Done as above. These points were further discussed in the section on implications for policy. (Pages 6,7)

Reviewer comment: Low Air Pollution Health Risk Literacy in Warri
Direct Linkage: Explicitly link low literacy levels to poor health outcomes, particularly in the context of CKD and air pollution.
Author response: Revised as follows:
“This low literacy level suggests that the necessary preventive measures such as individual behavioral changes, are lacking and this may contribute to the high burden of air pollution associated NCDs in the community”. (Page 7)

Reviewer comment: Awareness Campaigns: Suggest potential public health campaigns or educational interventions to improve awareness based on the findings.
Author response: These have been suggested.
“The high prevalence of CKD risk factors and low awareness of CKD and NCD status among the study participants suggests low health literacy and poor health-seeking behavior which necessitates more persuasive and inclusive public health educational interventions.” (Page 7)

Implications for Policy
Reviewer comment: Structured Recommendations: Present the policy implications in a more structured format, possibly using bullet points or numbered lists for clarity.
Author response: This section has been reviewed accordingly. (Page 7,8)

Reviewer comment: Evidence Integration: Integrate specific study findings more directly into the policy recommendations to strengthen the argument for immediate action.
Prioritization: Consider categorizing the recommendations into short-term, medium-term, and long-term actions.
Author response: We appreciate your comments. This section has been improved as is shown in Table 1. (Page 8-11)

Reviewer comment: Stakeholder Engagement: Emphasize the role of specific stakeholders (e.g., government, NGOs, the public) in implementing these recommendations.
Feasibility: Briefly discuss the feasibility of these recommendations, particularly in the context of existing infrastructure and resources.
Author response: These points have all been considered in the revised table of recommendations. (Page 8-11)

Limitations of the Study
Reviewer comment: Strengths Emphasis: Counterbalance the limitations with a brief discussion of the study’s strengths, particularly its novel approach and the involvement of citizen scientists.
Author response: This has been included as follows:
“Despite the limitations, the strength of the underlying study lies in the relatively large sample size, the extensive consideration and adjustment for confounding factors, the innovative combination of multiple research methods and involving citizen scientists in addressing a public health problem”. (Page 11)

Reviewer comment: Future Directions: Suggest specific areas for future research that could address these limitations, enhancing the study's impact.
Author response: This has been included as follows:
“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”. (Page 110)

Conclusion
Reviewer comment: Stronger Call to Action: End with a more forceful call to action directed at policymakers, highlighting the urgency of addressing CKD in the Niger Delta.
Author response: Thank you for your suggestions. The section has been improved. (Page 11,12)

Reviewer comment: Summary of Key Points: Briefly summarize the most critical findings and recommendations to leave a lasting impression.
Author response: Thank you for your suggestions. The section has been improved. (Page 11, 12)

Overall
Reviewer comment: Consistency: Ensure consistency in the use of terms (e.g., CKD vs. chronic kidney disease) throughout the document.
Author response: CKD is now used consistently throughout the text, except for where it was first mentioned.

Reviewer comment: Clarity: While the document is generally clear, some sections, particularly those with dense data, could benefit from simpler language and clearer transitions.
Author response: Thank you. The authors have made significant efforts to improve the clarity and readability of the document using a proof reader.

Reviewer comment: Visual Aids: Consider the strategic use of additional visual aids to break up text-heavy sections and improve reader engagement.
Author response: Additional visual aids have been introduced. e.g., more figures and the recommendations have been tabulated.
We are grateful for your detailed and constructive critique which has helped to improve the merit and quality of our manuscript.

ABSTRACT
Reviewer comment: Objective Clarification: Include a brief statement that clearly outlines the study's objective.
Author response: The objective has been clarified as follows:
“This brief is based on a mixed-methods study conducted in four communities situated near an oil and gas refinery in Warri, Nigeria to explore perceived and actual air pollution risk and determine whether long-term exposure to AAP increases NCD risk” (Page 2)

Reviewer comment: Methodology Mention: Explicitly mention that a mixed-methods approach was used.
Author response: Done as stated above

Reviewer comment: Specific Findings: Highlight specific data points, such as the exact levels of pollutants that exceed WHO limits.
Author response: Included as follows:
“Measured PM_2.5 ranged from 22.8 – 28.0 μg/m3, PM₁₀, 40.6 - 55.5 μg/m3, and CO₂, 584-652ppm”. 2

Reviewer comment: Policy Recommendations: Summarise one or two key policy recommendations for a clear takeaway.
Author response: Included as follows:
“The government needs to urgently invest in air monitoring services and data, cleaner technologies and environmental risk communication through various media channels. We strongly recommend public inclusion in planning, designing and implementing future environmental interventions. Lastly, environmental risk factors such as air pollution should feature prominently in strategic plans for NCD prevention”. (Page 2)

Introduction
Reviewer comment: Streamlining: Consider consolidating the discussion on traditional CKD risk factors to avoid redundancy.
Focused Transition: Ensure a smooth transition from discussing CKD globally to the specific context of the Niger Delta.
Identification of Gap: Introduce the research gap on the link between air pollution and CKD in the Niger Delta earlier in the section.
Author response: Thank you for your suggestions. We have reviewed this section accordingly. (Page 3)

Reviewer comment: Policy Outcomes and Implications
Author response: This section has been improved accordingly

Reviewer comment: Direct Link: Explicitly connect the absence of CKD in national health policy to the study’s findings on air pollution and CKD prevalence.
Author response: This has been revised as follows: “This lack of recognition of CKD and the environmental risk factors important in the disease epidemiology, may explain why CKD and related NCDs are persistent.” (Page 4)

Reviewer comment: Broader Implications: Discuss the broader public health implications if this policy gap continues, including potential long-term consequences.
Author response: “The long-term consequences of continually neglecting CKD in health policies include the persistence of hypertension and CKD with associated considerable morbidity and mortality; high health care expenditure which further impoverishes the affected members of society and their families”. (Page 4)

Reviewer comment: Evidence of High Ambient Air Pollutant Levels in Warr
Narrative Flow: Integrate the table with the narrative by referencing key figures directly in the text.
Author response: This section has been improved accordingly and highlighted in the text (Page 4-5)

Reviewer comment: Benchmark Against Global Standards: Briefly compare the findings with global or regional averages for context.
Author response: This section has been improved as follows:
“The PM2.5 concentrations for three of the communities are higher than Nigeria’s 2023 average of 23.9 μg/m3 (IQAIR) and five times higher than the WHO acceptable limit. Furthermore, these levels are much higher than 7.8μg/m3 achieved in Angola, the least polluted African country which ranked 114th out of 134 countries, while Nigeria was ranked the 35th most polluted”.( Page 4-5)

Reviewer comment: Graphical Representation: Consider using a graph to visualize the levels of pollutants across communities for greater impact.
Author response: A bar chart showing air pollutant levels in the 4 communities have been included. (Figure 1)

Reviewer comment: High Prevalence of CKD and the Risk Factors
Risk Factor Hierarchy: Present the risk factors in order of their strength of association with CKD.
Author response: Included as follows:
“The independent risk factors for CKD were proximity to the refinery [OR=2.00 (1.43 – 2.81], increasing age [OR=1.02(1.005-1.04)], hypertension [OR=1.61(1.12-2.31)], and level of education [OR=0.63(0.44-0.91)]. In a further logistic mixed model, which accounted for clustering effects at household level, only increasing age was an independent risk factor for CKD [OR=1.16 (1.07-1.25)]”, (Page 6)

Reviewer comment: Visual Aids: While the current figure is useful, additional visual aids, such as bar charts or scatter plots, could further clarify the distribution of CKD stages across communities.
Author response: A new figure showing the information requested has been included. (Figure 3)

Reviewer comment: Contextualization: Briefly contextualize the CKD prevalence data with national or regional statistics to highlight the severity.
Author response: Revised as follows:
The prevalence of CKD reported across Nigeria and Sub-Saharan Africa varies greatly depending on the population studied, CKD definition and methodology; from as low as 2% to >20% (Abd ElHafeez et al., 2018; Chukwuonye et al., 2018). However, our findings demonstrate a higher CKD prevalence in the nearest/semiurban community A, compared with a pooled prevalence of 10% and 13.7% reported for Africa and Nigeria, respectively (Abd ElHafeez et al., 2018; Raji et al., 2024). (Page 5)

Social Determinants of CKD Risk
Reviewer comment: Condensation: Consider condensing the list of behavioral factors by grouping similar items, such as unhealthy dietary habits.
Author response: Revised as follows:
‘Behavioural factors included unhealthy dietary habits (70-90%), low physical activity (47.2%), habitual exposure to potential nephrotoxins (37-44%)’. (Page 6)

Reviewer comment: Clearer Connections: Draw clearer connections between these social determinants and the higher CKD prevalence, emphasizing the compounding effect of multiple risk factors.
Author response: Revised as follows:
“The concentration of multiple social and environmental risk factors in the studied population may explain the high prevalence of CKD and other NCDs. These findings support the multicasuation theory, drawing attention to the need for a multi-faceted approach to CKD prevention.” (Page 6)

Reviewer comment: Implications: Discuss the potential public health implications of these social determinants in more depth.
Author response: Done as above. These points were further discussed in the section on implications for policy. (Pages 6,7)

Reviewer comment: Low Air Pollution Health Risk Literacy in Warri
Direct Linkage: Explicitly link low literacy levels to poor health outcomes, particularly in the context of CKD and air pollution.
Author response: Revised as follows:
“This low literacy level suggests that the necessary preventive measures such as individual behavioral changes, are lacking and this may contribute to the high burden of air pollution associated NCDs in the community”. (Page 7)

Reviewer comment: Awareness Campaigns: Suggest potential public health campaigns or educational interventions to improve awareness based on the findings.
Author response: These have been suggested.
“The high prevalence of CKD risk factors and low awareness of CKD and NCD status among the study participants suggests low health literacy and poor health-seeking behavior which necessitates more persuasive and inclusive public health educational interventions.” (Page 7)

Implications for Policy
Reviewer comment: Structured Recommendations: Present the policy implications in a more structured format, possibly using bullet points or numbered lists for clarity.
Author response: This section has been reviewed accordingly. (Page 7,8)

Reviewer comment: Evidence Integration: Integrate specific study findings more directly into the policy recommendations to strengthen the argument for immediate action.
Prioritization: Consider categorizing the recommendations into short-term, medium-term, and long-term actions.
Author response: We appreciate your comments. This section has been improved as is shown in Table 1. (Page 8-11)

Reviewer comment: Stakeholder Engagement: Emphasize the role of specific stakeholders (e.g., government, NGOs, the public) in implementing these recommendations.
Feasibility: Briefly discuss the feasibility of these recommendations, particularly in the context of existing infrastructure and resources.
Author response: These points have all been considered in the revised table of recommendations. (Page 8-11)

Limitations of the Study
Reviewer comment: Strengths Emphasis: Counterbalance the limitations with a brief discussion of the study’s strengths, particularly its novel approach and the involvement of citizen scientists.
Author response: This has been included as follows:
“Despite the limitations, the strength of the underlying study lies in the relatively large sample size, the extensive consideration and adjustment for confounding factors, the innovative combination of multiple research methods and involving citizen scientists in addressing a public health problem”. (Page 11)

Reviewer comment: Future Directions: Suggest specific areas for future research that could address these limitations, enhancing the study's impact.
Author response: This has been included as follows:
“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”. (Page 110)

Conclusion
Reviewer comment: Stronger Call to Action: End with a more forceful call to action directed at policymakers, highlighting the urgency of addressing CKD in the Niger Delta.
Author response: Thank you for your suggestions. The section has been improved. (Page 11,12)

Reviewer comment: Summary of Key Points: Briefly summarize the most critical findings and recommendations to leave a lasting impression.
Author response: Thank you for your suggestions. The section has been improved. (Page 11, 12)

Overall
Reviewer comment: Consistency: Ensure consistency in the use of terms (e.g., CKD vs. chronic kidney disease) throughout the document.
Author response: CKD is now used consistently throughout the text, except for where it was first mentioned.

Reviewer comment: Clarity: While the document is generally clear, some sections, particularly those with dense data, could benefit from simpler language and clearer transitions.
Author response: Thank you. The authors have made significant efforts to improve the clarity and readability of the document using a proof reader.

Reviewer comment: Visual Aids: Consider the strategic use of additional visual aids to break up text-heavy sections and improve reader engagement.
Author response: Additional visual aids have been introduced. e.g., more figures and the recommendations have been tabulated.
Competing Interests: None Close
Report a concern
Respond or Comment

COMMENTS ON THIS REPORT

Author Response 31 Jan 2025

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

31 Jan 2025

Author Response

We are grateful for your detailed and constructive critique which has helped to improve the merit and quality of our manuscript.

ABSTRACT
Reviewer comment: Objective Clarification: Include a brief ... Continue reading We are grateful for your detailed and constructive critique which has helped to improve the merit and quality of our manuscript.

ABSTRACT
Reviewer comment: Objective Clarification: Include a brief statement that clearly outlines the study's objective.
Author response: The objective has been clarified as follows:
“This brief is based on a mixed-methods study conducted in four communities situated near an oil and gas refinery in Warri, Nigeria to explore perceived and actual air pollution risk and determine whether long-term exposure to AAP increases NCD risk” (Page 2)

Reviewer comment: Methodology Mention: Explicitly mention that a mixed-methods approach was used.
Author response: Done as stated above

Reviewer comment: Specific Findings: Highlight specific data points, such as the exact levels of pollutants that exceed WHO limits.
Author response: Included as follows:
“Measured PM_2.5 ranged from 22.8 – 28.0 μg/m3, PM₁₀, 40.6 - 55.5 μg/m3, and CO₂, 584-652ppm”. 2

Reviewer comment: Policy Recommendations: Summarise one or two key policy recommendations for a clear takeaway.
Author response: Included as follows:
“The government needs to urgently invest in air monitoring services and data, cleaner technologies and environmental risk communication through various media channels. We strongly recommend public inclusion in planning, designing and implementing future environmental interventions. Lastly, environmental risk factors such as air pollution should feature prominently in strategic plans for NCD prevention”. (Page 2)

Introduction
Reviewer comment: Streamlining: Consider consolidating the discussion on traditional CKD risk factors to avoid redundancy.
Focused Transition: Ensure a smooth transition from discussing CKD globally to the specific context of the Niger Delta.
Identification of Gap: Introduce the research gap on the link between air pollution and CKD in the Niger Delta earlier in the section.
Author response: Thank you for your suggestions. We have reviewed this section accordingly. (Page 3)

Reviewer comment: Policy Outcomes and Implications
Author response: This section has been improved accordingly

Reviewer comment: Direct Link: Explicitly connect the absence of CKD in national health policy to the study’s findings on air pollution and CKD prevalence.
Author response: This has been revised as follows: “This lack of recognition of CKD and the environmental risk factors important in the disease epidemiology, may explain why CKD and related NCDs are persistent.” (Page 4)

Reviewer comment: Broader Implications: Discuss the broader public health implications if this policy gap continues, including potential long-term consequences.
Author response: “The long-term consequences of continually neglecting CKD in health policies include the persistence of hypertension and CKD with associated considerable morbidity and mortality; high health care expenditure which further impoverishes the affected members of society and their families”. (Page 4)

Reviewer comment: Evidence of High Ambient Air Pollutant Levels in Warr
Narrative Flow: Integrate the table with the narrative by referencing key figures directly in the text.
Author response: This section has been improved accordingly and highlighted in the text (Page 4-5)

Reviewer comment: Benchmark Against Global Standards: Briefly compare the findings with global or regional averages for context.
Author response: This section has been improved as follows:
“The PM2.5 concentrations for three of the communities are higher than Nigeria’s 2023 average of 23.9 μg/m3 (IQAIR) and five times higher than the WHO acceptable limit. Furthermore, these levels are much higher than 7.8μg/m3 achieved in Angola, the least polluted African country which ranked 114th out of 134 countries, while Nigeria was ranked the 35th most polluted”.( Page 4-5)

Reviewer comment: Graphical Representation: Consider using a graph to visualize the levels of pollutants across communities for greater impact.
Author response: A bar chart showing air pollutant levels in the 4 communities have been included. (Figure 1)

Reviewer comment: High Prevalence of CKD and the Risk Factors
Risk Factor Hierarchy: Present the risk factors in order of their strength of association with CKD.
Author response: Included as follows:
“The independent risk factors for CKD were proximity to the refinery [OR=2.00 (1.43 – 2.81], increasing age [OR=1.02(1.005-1.04)], hypertension [OR=1.61(1.12-2.31)], and level of education [OR=0.63(0.44-0.91)]. In a further logistic mixed model, which accounted for clustering effects at household level, only increasing age was an independent risk factor for CKD [OR=1.16 (1.07-1.25)]”, (Page 6)

Reviewer comment: Visual Aids: While the current figure is useful, additional visual aids, such as bar charts or scatter plots, could further clarify the distribution of CKD stages across communities.
Author response: A new figure showing the information requested has been included. (Figure 3)

Reviewer comment: Contextualization: Briefly contextualize the CKD prevalence data with national or regional statistics to highlight the severity.
Author response: Revised as follows:
The prevalence of CKD reported across Nigeria and Sub-Saharan Africa varies greatly depending on the population studied, CKD definition and methodology; from as low as 2% to >20% (Abd ElHafeez et al., 2018; Chukwuonye et al., 2018). However, our findings demonstrate a higher CKD prevalence in the nearest/semiurban community A, compared with a pooled prevalence of 10% and 13.7% reported for Africa and Nigeria, respectively (Abd ElHafeez et al., 2018; Raji et al., 2024). (Page 5)

Social Determinants of CKD Risk
Reviewer comment: Condensation: Consider condensing the list of behavioral factors by grouping similar items, such as unhealthy dietary habits.
Author response: Revised as follows:
‘Behavioural factors included unhealthy dietary habits (70-90%), low physical activity (47.2%), habitual exposure to potential nephrotoxins (37-44%)’. (Page 6)

Reviewer comment: Clearer Connections: Draw clearer connections between these social determinants and the higher CKD prevalence, emphasizing the compounding effect of multiple risk factors.
Author response: Revised as follows:
“The concentration of multiple social and environmental risk factors in the studied population may explain the high prevalence of CKD and other NCDs. These findings support the multicasuation theory, drawing attention to the need for a multi-faceted approach to CKD prevention.” (Page 6)

Reviewer comment: Implications: Discuss the potential public health implications of these social determinants in more depth.
Author response: Done as above. These points were further discussed in the section on implications for policy. (Pages 6,7)

Reviewer comment: Low Air Pollution Health Risk Literacy in Warri
Direct Linkage: Explicitly link low literacy levels to poor health outcomes, particularly in the context of CKD and air pollution.
Author response: Revised as follows:
“This low literacy level suggests that the necessary preventive measures such as individual behavioral changes, are lacking and this may contribute to the high burden of air pollution associated NCDs in the community”. (Page 7)

Reviewer comment: Awareness Campaigns: Suggest potential public health campaigns or educational interventions to improve awareness based on the findings.
Author response: These have been suggested.
“The high prevalence of CKD risk factors and low awareness of CKD and NCD status among the study participants suggests low health literacy and poor health-seeking behavior which necessitates more persuasive and inclusive public health educational interventions.” (Page 7)

Implications for Policy
Reviewer comment: Structured Recommendations: Present the policy implications in a more structured format, possibly using bullet points or numbered lists for clarity.
Author response: This section has been reviewed accordingly. (Page 7,8)

Reviewer comment: Evidence Integration: Integrate specific study findings more directly into the policy recommendations to strengthen the argument for immediate action.
Prioritization: Consider categorizing the recommendations into short-term, medium-term, and long-term actions.
Author response: We appreciate your comments. This section has been improved as is shown in Table 1. (Page 8-11)

Reviewer comment: Stakeholder Engagement: Emphasize the role of specific stakeholders (e.g., government, NGOs, the public) in implementing these recommendations.
Feasibility: Briefly discuss the feasibility of these recommendations, particularly in the context of existing infrastructure and resources.
Author response: These points have all been considered in the revised table of recommendations. (Page 8-11)

Limitations of the Study
Reviewer comment: Strengths Emphasis: Counterbalance the limitations with a brief discussion of the study’s strengths, particularly its novel approach and the involvement of citizen scientists.
Author response: This has been included as follows:
“Despite the limitations, the strength of the underlying study lies in the relatively large sample size, the extensive consideration and adjustment for confounding factors, the innovative combination of multiple research methods and involving citizen scientists in addressing a public health problem”. (Page 11)

Reviewer comment: Future Directions: Suggest specific areas for future research that could address these limitations, enhancing the study's impact.
Author response: This has been included as follows:
“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”. (Page 110)

Conclusion
Reviewer comment: Stronger Call to Action: End with a more forceful call to action directed at policymakers, highlighting the urgency of addressing CKD in the Niger Delta.
Author response: Thank you for your suggestions. The section has been improved. (Page 11,12)

Reviewer comment: Summary of Key Points: Briefly summarize the most critical findings and recommendations to leave a lasting impression.
Author response: Thank you for your suggestions. The section has been improved. (Page 11, 12)

Overall
Reviewer comment: Consistency: Ensure consistency in the use of terms (e.g., CKD vs. chronic kidney disease) throughout the document.
Author response: CKD is now used consistently throughout the text, except for where it was first mentioned.

Reviewer comment: Clarity: While the document is generally clear, some sections, particularly those with dense data, could benefit from simpler language and clearer transitions.
Author response: Thank you. The authors have made significant efforts to improve the clarity and readability of the document using a proof reader.

Reviewer comment: Visual Aids: Consider the strategic use of additional visual aids to break up text-heavy sections and improve reader engagement.
Author response: Additional visual aids have been introduced. e.g., more figures and the recommendations have been tabulated.
We are grateful for your detailed and constructive critique which has helped to improve the merit and quality of our manuscript.

ABSTRACT
Reviewer comment: Objective Clarification: Include a brief statement that clearly outlines the study's objective.
Author response: The objective has been clarified as follows:
“This brief is based on a mixed-methods study conducted in four communities situated near an oil and gas refinery in Warri, Nigeria to explore perceived and actual air pollution risk and determine whether long-term exposure to AAP increases NCD risk” (Page 2)

Reviewer comment: Methodology Mention: Explicitly mention that a mixed-methods approach was used.
Author response: Done as stated above

Reviewer comment: Specific Findings: Highlight specific data points, such as the exact levels of pollutants that exceed WHO limits.
Author response: Included as follows:
“Measured PM_2.5 ranged from 22.8 – 28.0 μg/m3, PM₁₀, 40.6 - 55.5 μg/m3, and CO₂, 584-652ppm”. 2

Reviewer comment: Policy Recommendations: Summarise one or two key policy recommendations for a clear takeaway.
Author response: Included as follows:
“The government needs to urgently invest in air monitoring services and data, cleaner technologies and environmental risk communication through various media channels. We strongly recommend public inclusion in planning, designing and implementing future environmental interventions. Lastly, environmental risk factors such as air pollution should feature prominently in strategic plans for NCD prevention”. (Page 2)

Introduction
Reviewer comment: Streamlining: Consider consolidating the discussion on traditional CKD risk factors to avoid redundancy.
Focused Transition: Ensure a smooth transition from discussing CKD globally to the specific context of the Niger Delta.
Identification of Gap: Introduce the research gap on the link between air pollution and CKD in the Niger Delta earlier in the section.
Author response: Thank you for your suggestions. We have reviewed this section accordingly. (Page 3)

Reviewer comment: Policy Outcomes and Implications
Author response: This section has been improved accordingly

Reviewer comment: Direct Link: Explicitly connect the absence of CKD in national health policy to the study’s findings on air pollution and CKD prevalence.
Author response: This has been revised as follows: “This lack of recognition of CKD and the environmental risk factors important in the disease epidemiology, may explain why CKD and related NCDs are persistent.” (Page 4)

Reviewer comment: Broader Implications: Discuss the broader public health implications if this policy gap continues, including potential long-term consequences.
Author response: “The long-term consequences of continually neglecting CKD in health policies include the persistence of hypertension and CKD with associated considerable morbidity and mortality; high health care expenditure which further impoverishes the affected members of society and their families”. (Page 4)

Reviewer comment: Evidence of High Ambient Air Pollutant Levels in Warr
Narrative Flow: Integrate the table with the narrative by referencing key figures directly in the text.
Author response: This section has been improved accordingly and highlighted in the text (Page 4-5)

Reviewer comment: Benchmark Against Global Standards: Briefly compare the findings with global or regional averages for context.
Author response: This section has been improved as follows:
“The PM2.5 concentrations for three of the communities are higher than Nigeria’s 2023 average of 23.9 μg/m3 (IQAIR) and five times higher than the WHO acceptable limit. Furthermore, these levels are much higher than 7.8μg/m3 achieved in Angola, the least polluted African country which ranked 114th out of 134 countries, while Nigeria was ranked the 35th most polluted”.( Page 4-5)

Reviewer comment: Graphical Representation: Consider using a graph to visualize the levels of pollutants across communities for greater impact.
Author response: A bar chart showing air pollutant levels in the 4 communities have been included. (Figure 1)

Reviewer comment: High Prevalence of CKD and the Risk Factors
Risk Factor Hierarchy: Present the risk factors in order of their strength of association with CKD.
Author response: Included as follows:
“The independent risk factors for CKD were proximity to the refinery [OR=2.00 (1.43 – 2.81], increasing age [OR=1.02(1.005-1.04)], hypertension [OR=1.61(1.12-2.31)], and level of education [OR=0.63(0.44-0.91)]. In a further logistic mixed model, which accounted for clustering effects at household level, only increasing age was an independent risk factor for CKD [OR=1.16 (1.07-1.25)]”, (Page 6)

Reviewer comment: Visual Aids: While the current figure is useful, additional visual aids, such as bar charts or scatter plots, could further clarify the distribution of CKD stages across communities.
Author response: A new figure showing the information requested has been included. (Figure 3)

Reviewer comment: Contextualization: Briefly contextualize the CKD prevalence data with national or regional statistics to highlight the severity.
Author response: Revised as follows:
The prevalence of CKD reported across Nigeria and Sub-Saharan Africa varies greatly depending on the population studied, CKD definition and methodology; from as low as 2% to >20% (Abd ElHafeez et al., 2018; Chukwuonye et al., 2018). However, our findings demonstrate a higher CKD prevalence in the nearest/semiurban community A, compared with a pooled prevalence of 10% and 13.7% reported for Africa and Nigeria, respectively (Abd ElHafeez et al., 2018; Raji et al., 2024). (Page 5)

Social Determinants of CKD Risk
Reviewer comment: Condensation: Consider condensing the list of behavioral factors by grouping similar items, such as unhealthy dietary habits.
Author response: Revised as follows:
‘Behavioural factors included unhealthy dietary habits (70-90%), low physical activity (47.2%), habitual exposure to potential nephrotoxins (37-44%)’. (Page 6)

Reviewer comment: Clearer Connections: Draw clearer connections between these social determinants and the higher CKD prevalence, emphasizing the compounding effect of multiple risk factors.
Author response: Revised as follows:
“The concentration of multiple social and environmental risk factors in the studied population may explain the high prevalence of CKD and other NCDs. These findings support the multicasuation theory, drawing attention to the need for a multi-faceted approach to CKD prevention.” (Page 6)

Reviewer comment: Implications: Discuss the potential public health implications of these social determinants in more depth.
Author response: Done as above. These points were further discussed in the section on implications for policy. (Pages 6,7)

Reviewer comment: Low Air Pollution Health Risk Literacy in Warri
Direct Linkage: Explicitly link low literacy levels to poor health outcomes, particularly in the context of CKD and air pollution.
Author response: Revised as follows:
“This low literacy level suggests that the necessary preventive measures such as individual behavioral changes, are lacking and this may contribute to the high burden of air pollution associated NCDs in the community”. (Page 7)

Reviewer comment: Awareness Campaigns: Suggest potential public health campaigns or educational interventions to improve awareness based on the findings.
Author response: These have been suggested.
“The high prevalence of CKD risk factors and low awareness of CKD and NCD status among the study participants suggests low health literacy and poor health-seeking behavior which necessitates more persuasive and inclusive public health educational interventions.” (Page 7)

Implications for Policy
Reviewer comment: Structured Recommendations: Present the policy implications in a more structured format, possibly using bullet points or numbered lists for clarity.
Author response: This section has been reviewed accordingly. (Page 7,8)

Reviewer comment: Evidence Integration: Integrate specific study findings more directly into the policy recommendations to strengthen the argument for immediate action.
Prioritization: Consider categorizing the recommendations into short-term, medium-term, and long-term actions.
Author response: We appreciate your comments. This section has been improved as is shown in Table 1. (Page 8-11)

Reviewer comment: Stakeholder Engagement: Emphasize the role of specific stakeholders (e.g., government, NGOs, the public) in implementing these recommendations.
Feasibility: Briefly discuss the feasibility of these recommendations, particularly in the context of existing infrastructure and resources.
Author response: These points have all been considered in the revised table of recommendations. (Page 8-11)

Limitations of the Study
Reviewer comment: Strengths Emphasis: Counterbalance the limitations with a brief discussion of the study’s strengths, particularly its novel approach and the involvement of citizen scientists.
Author response: This has been included as follows:
“Despite the limitations, the strength of the underlying study lies in the relatively large sample size, the extensive consideration and adjustment for confounding factors, the innovative combination of multiple research methods and involving citizen scientists in addressing a public health problem”. (Page 11)

Reviewer comment: Future Directions: Suggest specific areas for future research that could address these limitations, enhancing the study's impact.
Author response: This has been included as follows:
“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”. (Page 110)

Conclusion
Reviewer comment: Stronger Call to Action: End with a more forceful call to action directed at policymakers, highlighting the urgency of addressing CKD in the Niger Delta.
Author response: Thank you for your suggestions. The section has been improved. (Page 11,12)

Reviewer comment: Summary of Key Points: Briefly summarize the most critical findings and recommendations to leave a lasting impression.
Author response: Thank you for your suggestions. The section has been improved. (Page 11, 12)

Overall
Reviewer comment: Consistency: Ensure consistency in the use of terms (e.g., CKD vs. chronic kidney disease) throughout the document.
Author response: CKD is now used consistently throughout the text, except for where it was first mentioned.

Reviewer comment: Clarity: While the document is generally clear, some sections, particularly those with dense data, could benefit from simpler language and clearer transitions.
Author response: Thank you. The authors have made significant efforts to improve the clarity and readability of the document using a proof reader.

Reviewer comment: Visual Aids: Consider the strategic use of additional visual aids to break up text-heavy sections and improve reader engagement.
Author response: Additional visual aids have been introduced. e.g., more figures and the recommendations have been tabulated.
Competing Interests: None Close
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Reviewer Report 08 May 2024

Chao Yang, Peking University, Beijing, Beijing, China

Approved with Reservations

https://doi.org/10.5256/f1000research.159925.r268338

This study provides insights into the association between air pollution and CKD risk in Niger Delta communities. Comprehensive policy interventions and public education are needed to mitigate the CKD risk and improve overall health outcomes in these communities. Here are several specific comments for the paper:

1) The authors should provide a more detailed description of the mixed-methods approach used in the study. Clarify the specific quantitative and qualitative methods employed, sample sizes, and data collection techniques.

2) The paper mentions that air pollutant concentrations were measured and compared to WHO limits. However, the analysis of these data and their statistical significance is lacking. The authors should include a more thorough analysis of the air pollution data.

3) The paper discusses the association between ambient air pollution and CKD risk, but does not claim causality. The authors should clarify this distinction and discuss potential confounders or alternative explanations for the observed association.

4) The paper should acknowledge other limitations of the study, such as sample size, data availability, or methodological constraints. Additionally, the authors should discuss potential directions for future research to build upon the current findings.

5) The authors should discuss the generalizability of their findings to other communities and regions with similar industrial activities.

Does the paper provide a comprehensive overview of the policy and the context of its implementation in a way which is accessible to a general reader?

Partly
Is the discussion on the implications clearly and accurately presented and does it cite the current literature?

Partly
Are the recommendations made clear, balanced, and justified on the basis of the presented arguments?

Partly

Competing Interests: No competing interests were disclosed.

Reviewer Expertise: Public health

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard, however I have significant reservations, as outlined above.

CITE

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Author Response 24 Jun 2024

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

24 Jun 2024

Author Response

Thank you for your kind critique of the manuscript.
All your comments are valid and appreciated. Being a policy brief, the manuscript was intentionally shortened to provide the basic information ... Continue reading Thank you for your kind critique of the manuscript.
All your comments are valid and appreciated. Being a policy brief, the manuscript was intentionally shortened to provide the basic information in a simple way for the intended audience, which includes policy makers.

More detailed Original manuscripts for a scientific audience have been written and are currently undergoing peer review. However, the link to the Study Thesis was provided with this submission.

Thank you.
Thank you for your kind critique of the manuscript.
All your comments are valid and appreciated. Being a policy brief, the manuscript was intentionally shortened to provide the basic information in a simple way for the intended audience, which includes policy makers.

More detailed Original manuscripts for a scientific audience have been written and are currently undergoing peer review. However, the link to the Study Thesis was provided with this submission.

Thank you.
Competing Interests: None Close
Report a concern
Author Response 21 Nov 2024

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

21 Nov 2024

Author Response

REVIEWER 1

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript

1) The authors ... Continue reading REVIEWER 1

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript

1) The authors should provide a more detailed description of the mixed-methods approach used in the study. Clarify the specific quantitative and qualitative methods employed, sample sizes, and data collection techniques.
Thank you for your observations. Extensive methodological and statistical details were deliberately omitted as the manuscript was targeted at policymakers. However, we have provided additional details in the text.
The underlying study was an exploratory mixed methods study with an embedded citizen science inquiry. Details of the first strand which was a focus group has been published and we have provided a reference to the article. In the current brief, we focus on findings from the other strands of the study.
(Pages 2,3,5)

2) The paper mentions that air pollutant concentrations were measured and compared to WHO limits. However, the analysis of these data and their statistical significance is lacking. The authors should include a more thorough analysis of the air pollution data.
For the reasons mentioned above, we omitted these details. However, some additional data have been provided in the text and as supplementary files.
(Page 5, suppl 1, Figure 1)

3) The paper discusses the association between ambient air pollution and CKD risk, but does not claim causality. The authors should clarify this distinction and discuss potential confounders or alternative explanations for the observed association.
We agree with your observations. We have provided details of confounding factors considered and a supplementary file containing updated results from a binary mixed effects logistic model conducted to account for clustering effects.

We report that long-term exposure to ambient air pollution is associated with CKD risk, but does not independently increase its risk, after adjusting for clustering effects and confounders (age, gender, hypertension, level of education and diabetes).
(Page 6, suppl 2)

4) The paper should acknowledge other limitations of the study, such as sample size, data availability, or methodological constraints. Additionally, the authors should discuss potential directions for future research to build upon the current findings.

The section on limitation of the study has been improved and suggestions for future research as follows:

“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”.
(Page 11)

5) The authors should discuss the generalizability of their findings to other communities and regions with similar industrial activities.

This has been included.
“…. our findings are generalisable to similar vulnerable populations across the globe who reside near point emission sources” (Page 7)
REVIEWER 1

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript

1) The authors should provide a more detailed description of the mixed-methods approach used in the study. Clarify the specific quantitative and qualitative methods employed, sample sizes, and data collection techniques.
Thank you for your observations. Extensive methodological and statistical details were deliberately omitted as the manuscript was targeted at policymakers. However, we have provided additional details in the text.
The underlying study was an exploratory mixed methods study with an embedded citizen science inquiry. Details of the first strand which was a focus group has been published and we have provided a reference to the article. In the current brief, we focus on findings from the other strands of the study.
(Pages 2,3,5)

2) The paper mentions that air pollutant concentrations were measured and compared to WHO limits. However, the analysis of these data and their statistical significance is lacking. The authors should include a more thorough analysis of the air pollution data.
For the reasons mentioned above, we omitted these details. However, some additional data have been provided in the text and as supplementary files.
(Page 5, suppl 1, Figure 1)

3) The paper discusses the association between ambient air pollution and CKD risk, but does not claim causality. The authors should clarify this distinction and discuss potential confounders or alternative explanations for the observed association.
We agree with your observations. We have provided details of confounding factors considered and a supplementary file containing updated results from a binary mixed effects logistic model conducted to account for clustering effects.

We report that long-term exposure to ambient air pollution is associated with CKD risk, but does not independently increase its risk, after adjusting for clustering effects and confounders (age, gender, hypertension, level of education and diabetes).
(Page 6, suppl 2)

4) The paper should acknowledge other limitations of the study, such as sample size, data availability, or methodological constraints. Additionally, the authors should discuss potential directions for future research to build upon the current findings.

The section on limitation of the study has been improved and suggestions for future research as follows:

“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”.
(Page 11)

5) The authors should discuss the generalizability of their findings to other communities and regions with similar industrial activities.

This has been included.
“…. our findings are generalisable to similar vulnerable populations across the globe who reside near point emission sources” (Page 7)
Competing Interests: No competing interests were disclosed. Close
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COMMENTS ON THIS REPORT

Author Response 24 Jun 2024

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

24 Jun 2024

Author Response

Thank you for your kind critique of the manuscript.
All your comments are valid and appreciated. Being a policy brief, the manuscript was intentionally shortened to provide the basic information ... Continue reading Thank you for your kind critique of the manuscript.
All your comments are valid and appreciated. Being a policy brief, the manuscript was intentionally shortened to provide the basic information in a simple way for the intended audience, which includes policy makers.

More detailed Original manuscripts for a scientific audience have been written and are currently undergoing peer review. However, the link to the Study Thesis was provided with this submission.

Thank you.
Thank you for your kind critique of the manuscript.
All your comments are valid and appreciated. Being a policy brief, the manuscript was intentionally shortened to provide the basic information in a simple way for the intended audience, which includes policy makers.

More detailed Original manuscripts for a scientific audience have been written and are currently undergoing peer review. However, the link to the Study Thesis was provided with this submission.

Thank you.
Competing Interests: None Close
Report a concern
Author Response 21 Nov 2024

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

21 Nov 2024

Author Response

REVIEWER 1

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript

1) The authors ... Continue reading REVIEWER 1

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript

1) The authors should provide a more detailed description of the mixed-methods approach used in the study. Clarify the specific quantitative and qualitative methods employed, sample sizes, and data collection techniques.
Thank you for your observations. Extensive methodological and statistical details were deliberately omitted as the manuscript was targeted at policymakers. However, we have provided additional details in the text.
The underlying study was an exploratory mixed methods study with an embedded citizen science inquiry. Details of the first strand which was a focus group has been published and we have provided a reference to the article. In the current brief, we focus on findings from the other strands of the study.
(Pages 2,3,5)

2) The paper mentions that air pollutant concentrations were measured and compared to WHO limits. However, the analysis of these data and their statistical significance is lacking. The authors should include a more thorough analysis of the air pollution data.
For the reasons mentioned above, we omitted these details. However, some additional data have been provided in the text and as supplementary files.
(Page 5, suppl 1, Figure 1)

3) The paper discusses the association between ambient air pollution and CKD risk, but does not claim causality. The authors should clarify this distinction and discuss potential confounders or alternative explanations for the observed association.
We agree with your observations. We have provided details of confounding factors considered and a supplementary file containing updated results from a binary mixed effects logistic model conducted to account for clustering effects.

We report that long-term exposure to ambient air pollution is associated with CKD risk, but does not independently increase its risk, after adjusting for clustering effects and confounders (age, gender, hypertension, level of education and diabetes).
(Page 6, suppl 2)

4) The paper should acknowledge other limitations of the study, such as sample size, data availability, or methodological constraints. Additionally, the authors should discuss potential directions for future research to build upon the current findings.

The section on limitation of the study has been improved and suggestions for future research as follows:

“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”.
(Page 11)

5) The authors should discuss the generalizability of their findings to other communities and regions with similar industrial activities.

This has been included.
“…. our findings are generalisable to similar vulnerable populations across the globe who reside near point emission sources” (Page 7)
REVIEWER 1

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript

1) The authors should provide a more detailed description of the mixed-methods approach used in the study. Clarify the specific quantitative and qualitative methods employed, sample sizes, and data collection techniques.
Thank you for your observations. Extensive methodological and statistical details were deliberately omitted as the manuscript was targeted at policymakers. However, we have provided additional details in the text.
The underlying study was an exploratory mixed methods study with an embedded citizen science inquiry. Details of the first strand which was a focus group has been published and we have provided a reference to the article. In the current brief, we focus on findings from the other strands of the study.
(Pages 2,3,5)

2) The paper mentions that air pollutant concentrations were measured and compared to WHO limits. However, the analysis of these data and their statistical significance is lacking. The authors should include a more thorough analysis of the air pollution data.
For the reasons mentioned above, we omitted these details. However, some additional data have been provided in the text and as supplementary files.
(Page 5, suppl 1, Figure 1)

3) The paper discusses the association between ambient air pollution and CKD risk, but does not claim causality. The authors should clarify this distinction and discuss potential confounders or alternative explanations for the observed association.
We agree with your observations. We have provided details of confounding factors considered and a supplementary file containing updated results from a binary mixed effects logistic model conducted to account for clustering effects.

We report that long-term exposure to ambient air pollution is associated with CKD risk, but does not independently increase its risk, after adjusting for clustering effects and confounders (age, gender, hypertension, level of education and diabetes).
(Page 6, suppl 2)

4) The paper should acknowledge other limitations of the study, such as sample size, data availability, or methodological constraints. Additionally, the authors should discuss potential directions for future research to build upon the current findings.

The section on limitation of the study has been improved and suggestions for future research as follows:

“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”.
(Page 11)

5) The authors should discuss the generalizability of their findings to other communities and regions with similar industrial activities.

This has been included.
“…. our findings are generalisable to similar vulnerable populations across the globe who reside near point emission sources” (Page 7)
Competing Interests: No competing interests were disclosed. Close
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Version 3

VERSION 3 PUBLISHED 15 Apr 2024

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Chao Yang, Peking University, Beijing, China
Nikola M Pavlović, University of Niš, Niš, Serbia
Nicholas Osborne, The University of Queensland, Saint Lucia, Australia
Karl Kilbo Edlund, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden

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Reviewer Report

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16 Jan 2025 | for Version 3

Nikola M Pavlović, University of Niš, Niš, Serbia

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Approved

The authors have followed my instructions and comments, and I believe the article is now suitable for indexing. I have no further requests for revisions.

Competing Interests

No competing interests were disclosed.

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Reviewer Report

15 Views

30 Dec 2024 | for Version 2

Karl Kilbo Edlund, Occupational and Environmental Medicine, School of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden

15 Views Cite this report Responses(1)

Approved With Reservations

Okoye and colleagues have conducted a much-needed study of air pollution and CKD risk in communities residing near a petrochemical plant in the Niger river delta in Nigeria. They present timely policy advice that combines previous evidence and their own findings of air pollution levels, population health, population health literacy, and the relationship, in their data, between air pollution exposure and prevalent CKD. The authors highlight the need for expanded care options for Nigerans with CKD as well as the urgent need of reduction of PM emissions from the petrochemical industry. The text is mostly well-written and the recommendations mostly rest on a solid scientific literature. I believe their implementation would benefit Nigerians much along the lines described by the authors.

In this review, my main concerns relate to 1) the inclusion of considerable previously unpublished empirical data and analyses in this policy brief, which in this genre should rather be kept at a minimum, 2) the formulation of some of the actionable policy recommendation require further work. At the end of the review, I also include some minor comments for the authors’ consideration.

Starting with the first concern, regarding the inclusion of primary data and analyses in this policy brief. As highlighted by the authors, there is considerable previous evidence of adverse effects on kidney health associated with air pollution, and even some evidence specifically for petrochemical industry. This means that, in the context of this policy brief (notably unlike if this were an original article or a dissertation) the empirical, quantitative evidence put forth here do not serve the purpose of testing the hypothesis that there are adverse effects on kidney health of air pollution, but rather to emphasise that the adverse health effects seen elsewhere are highly likely to extend to the Niger river delta as well. In the first scenario, the data provided here, although filling an important gap in previously available data and describing the high prevalence of undiagnosed CKD in this population, do not provide particularly strong evidence for adverse kidney effects of PM from the petrochemical industry, above and beyond what is already available. Key limitations that need to be kept in mind are that these data are cross-sectional, that participant selection and sampling procedures are not described, that PM measurements were taken only during certain times and through a less standardised process and that no validation is described etc. (These limitations are of course fully understandable given the challenges of data collection.) On the other hand, these data are strong when instead considered as a validation that the likely large impact of PM on kidney health noted in previous literature also applies to this area.

With this in mind, I would suggest the authors restructure the section (“High prevalence of CKD and risk factors”) where the association between air pollution and CKD is presented. Firstly, it would help the reader if this rather long section were subdivided, as it currently presents the two rather different topics of CKD prevalence and then the PM-CKD association. Secondly, I believe that it would lend more strength to the authors’ recommendations, if the authors would present a little more extensively the rapidly growing literature supporting an air pollution-CKD association, with particular note to any previous studies in similar settings. Thirdly, I think the authors should reconsider the currently rather technical discussion on regression analyses and statistical methodologies, given that this is presumably of little use to a policy-maker who is not themselves trained in quantitative analysis; possibly, it suffice to say that the prevalence of CKD was higher closer to the refineries adjusting for age, sex, BMI, if this is in line with how the authors interpret their results.

Turning to the second concern, relating to the policy recommendations. The conclusions bullet-pointed under “Implications for policy” are substantive, well-written, and supported by literature and empirical findings. However, I have concerns with multiple recommendations provided as actionable recommendations in table 1. In the following, I will for practical reasons refer to them as numbers, with recommendation 1 as the first recommendation in the table.

For recommendation 1, the call for CKD screening is a charitable one. However, the decision on initiating screening is a difficult one, and should include a cost-benefit analysis as well as strategies to accurately identify individuals with false-positive screening results. Furthermore, this analysis needs to account for the availability of treatment options.
Similarly, the subsidy reintroduction mentioned in recommendation 5 would need some cost-benefit analysis, or if such is available elsewhere, as a reference.
The suggestion of a medical fitness certificate before international passport renewals in recommendation 9 might not be compatible with the UN’s Universal Human Rights (article 13, section 2). However, this is beyond my area of expertise.
The National Renal Care Policy referred to in recommendation 11 is not mentioned or detailed in the policy brief, and for the non-Nigerian it might be difficult to know what the authors refer to here.
Including environmental risk factors in NCD prevention plans, as suggested in recommendation 13, could be supported by an attributable fraction calculation, illustrating the magnitude of these risk factors in comparison to other relevant, traditional risk factors.

Minor comments:

The air pollutant levels, measured during 4 weeks, are compared to the annual WHO limits. While this is presumably necessary due to lack of more extensive data, it would be recommended to mention this.
Hazard quotients (HQ) are presented for PM_2.5, PM₁₀, VOC and CO₂, no concentration or WHO limit is presented for VOC. Furthermore, CO₂, while central to global warming, is not a criteria pollutant and there is little literature to support adverse health effect of direct CO₂ exposure. It also seems, purely from the figures themselves, that HQs for the pollutants have been summarised to a combined HQ, and it is questionable whether this method can capture magnitudes of and synergies between health effects in any meaningful way.
The in-text link is missing for a key reference in the Introduction (Chukwuonye et al., 2018). Furthermore, the “Publisher Full Text” link in the first author’s thesis redirects not to the thesis but to a conference abstract.
The authors report using “R studios” for statistical analyses, yet it should be noted that the RStudio software is merely a front-end for R, which is the statistical programme used. If the authors wish to state their choice of statistical software in this policy brief (see the first major concern outlined above), I would recommend stating it more correctly as R.

Does the paper provide a comprehensive overview of the policy and the context of its implementation in a way which is accessible to a general reader?

Partly
Is the discussion on the implications clearly and accurately presented and does it cite the current literature?

Partly
Are the recommendations made clear, balanced, and justified on the basis of the presented arguments?

Partly

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Environmental epidemiology

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Responses (1)

Author Response

31 Dec 2024

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

We appreciate your review and useful critique.
We acknowledge your main concerns and wish to respond here. However, we will revise our manuscript where needed.

1) Regarding the inclusion of considerable empirical data and analysis: The original manuscript submitted had minimal empirical data as expected for a policy brief. However, we included more data in response to two of the previous reviewers. We agree that the intended audience may find some aspects of the manuscript too technical and we will make some adjustments to minimise the data and complexity.

Although the empirical data has not been published in any journal, we included a link to the Thesis underlying this study. We agree that our data serves to support the existing literature on PM and kidney disease, although these studies are mostly from the global north. While we note the study limitations, we agree that our findings are a strong validation that air pollution associated health effects noted elsewhere also applies to the Niger Delta.

2) The section on "High prevalence of CKD and risk factors" will be split to improve clarity.
3) Response to concerns about some 'actionable recommendations:
a)We agree that whole population screening may be cost-intensive and require cost-benefit analysis. However, screening of high-risk populations is currently recommended in Nigeria and globally. (KDIGO).
Treatment options for early CKD mostly entails addressing identified risks to slow progression of the disease. These treatment measures are widely available.

b)We agree that the subsidy re-introduction would need a cost-benefit-analysis, which we consider a great suggestion for further studies.
c) Thank you for drawing our attention to the possible Human Rights implication of requiring a medical fitness certificate before issuing international passport. We will explore the feasibility and revise this accordingly.

d) Regarding the calculated Hazard Quotients and Total HQ, we stated that the figures do not necessarily represent a statistical probability of harm occurring. However, we have included a further statement that 'the Total HQs do not represent synergies or magnitude of health effect'.

e) The concentration for VOC was not included in Figure 1, for simplicity of presentation as the values were less than 1. However, the HQs for VOC were included in the calculation of total HQ. Again, for simplicity, we have not included these details in the text. All information is available in the underlying Thesis.

f) The two references highlighted will be sorted. Thank you.
g) We will replace 'R studios' with 'R'. Thank you

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Competing Interests

No competing interests were disclosed.

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Reviewer Report

18 Views

14 Sep 2024 | for Version 1

Nicholas Osborne, The University of Queensland, Saint Lucia, Queensland, Australia

18 Views Cite this report Responses(1)

Not Approved

Does the paper provide a comprehensive overview of the policy and the context of its implementation in a way which is accessible to a general reader?

No
Is the discussion on the implications clearly and accurately presented and does it cite the current literature?

No
Are the recommendations made clear, balanced, and justified on the basis of the presented arguments?

No

Competing Interests

Dr Nicholas Osborne received an honorarium for speakers’ fees from Reckitt, an honorarium from Taylor and Francis Publishing, and payment for assisting the Federal Court of Australia.

Reviewer Expertise

Environmental epidemiology

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Responses (1)

Author Response

21 Nov 2024

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript.

Comment: This study proposes to discover association between air pollution and CKD. Unfortunately, an accurate measure of air pollution was not available.
Consequently, attempts to examine the relationship do not have data of sufficient quality to make the linkage.
Response: Extensive methodological and statistical details were deliberately omitted as this document was targeted at policymakers. However, we have provided additional information in the text to describe how air pollution was measured and other details are available in the link to the underlying study. Page 4

Comment: Similarly, an accurate measure of the health outcome, kidney function was not available.
Diagnosis of CKD requires two measures of kidney function (usually by eGRF) at least 3 months apart.
Response: We agree with your observation. The authors initially set out to obtain at least two measurements from participants who have abnormalities but encountered challenges with participant retention. This limitation has been highlighted in more detail.
However, all biological samples were handled and processed by a reputable independent laboratory with documented standard operating procedures to ensure accuracy and reliability. Page 11

Comment: The paper was not conducted as a policy brief. Large amounts of extant literature were missing from the evidence base presented.
Response: Thank you for your valid observation. We structured the paper according to the journal's template for a policy brief. Our intention was to provide a brief summary of the underlying study before delving into the policy implications and recommendations. We deliberately excluded excessive statistical information to enhance readability for the non-academic audience. However, we have now included more data in the text figures and supplementary files.

Comment: The paper has a limited data reference list.
Response: The short reference list was to adhere to the limits of a policy brief. More references have been included in specific sections. Pages 3,5,6,7,14

Comment: Abstract mentions CKDu in passing without mentioning its prevalence in certain LMIC settings. The disease CKDu in Sri Lankan and Mesoamerican settings.
Response: Thank you for your comment. There may have been a mix up. CKDu was not mentioned in the abstract.
-

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Competing Interests

None

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Reviewer Report

15 Views

11 Sep 2024 | for Version 1

Nikola M Pavlović, University of Niš, Niš, Serbia

15 Views Cite this report Responses(1)

Approved

Ambient Air Pollution and Chronic kidney disease risk in Deltan communities: A Policy Brief, 2023.
Abstract

Comments:
- The abstract effectively highlights the importance of the study by addressing an issue that is often overlooked: CKD in developing countries. However, it could refine its focus on the study's objectives, methods, key findings, and specific policy recommendations.
Suggestions:
- Objective Clarification: Include a brief statement that clearly outlines the study's objective.
- Methodology Mention: Explicitly mention that a mixed-methods approach was used.
- Specific Findings: Highlight specific data points, such as the exact levels of pollutants that exceed WHO limits.
- Policy Recommendations: Summarize one or two key policy recommendations for a clear takeaway.

Introduction

Comments:
- The introduction is comprehensive, providing a strong background on CKD and air pollution, particularly in the context of developing countries. However, it somewhat repeats itself by discussing traditional CKD risk factors.
Suggestions:
- Streamlining: Consider consolidating the discussion on traditional CKD risk factors to avoid redundancy.
- Focused Transition: Ensure a smooth transition from discussing CKD globally to the specific context of the Niger Delta.
- Identification of Gap: Introduce the research gap on the link between air pollution and CKD in the Niger Delta earlier in the section.

Policy Outcomes and Implications

Comments:
- This section succinctly outlines the critical issue of lacking renal care policies in Nigeria. However, the link between CKD and air pollution could be articulated more forcefully to emphasize urgency.
Suggestions:
- Direct Link: Explicitly connect the absence of CKD in national health policy to the study’s findings on air pollution and CKD prevalence.
- Broader Implications: Discuss the broader public health implications if this policy gap continues, including potential long-term consequences.

Evidence of High Ambient Air Pollutant Levels in Warri

Comments:
- This section is rich in data and provides a clear picture of pollution levels. The use of a table to present hazard quotients is effective, but the narrative could be enhanced for better flow and readability.
Suggestions:
- Narrative Flow: Integrate the table with the narrative by referencing key figures directly in the text.
- Benchmark Against Global Standards: Briefly compare the findings with global or regional averages for context.
- Graphical Representation: Consider using a graph to visualize the levels of pollutants across communities for greater impact.

High Prevalence of CKD and the Risk Factors

Comments:
- This section effectively presents prevalence data and associated risk factors. The statistical significance is clearly noted, strengthening the findings.
Suggestions:
- Risk Factor Hierarchy: Present the risk factors in order of their strength of association with CKD.
- Visual Aids: While the current figure is useful, additional visual aids, such as bar charts or scatter plots, could further clarify the distribution of CKD stages across communities.
- Contextualization: Briefly contextualize the CKD prevalence data with national or regional statistics to highlight the severity.

Social Determinants of CKD Risk

Comments:
- The social determinants are well-captured, providing a comprehensive picture of contributing factors. However, the section could benefit from a more concise presentation.
Suggestions:
- Condensation: Consider condensing the list of behavioral factors by grouping similar items, such as unhealthy dietary habits.
- Clearer Connections: Draw clearer connections between these social determinants and the higher CKD prevalence, emphasizing the compounding effect of multiple risk factors.
- Implications: Discuss the potential public health implications of these social determinants in more depth.

Low Air Pollution Health Risk Literacy in Warri

Comments:
- This section addresses an important issue but could be more impactful if it connected low health literacy directly with CKD prevalence.
Suggestions:
- Direct Linkage: Explicitly link low literacy levels to poor health outcomes, particularly in the context of CKD and air pollution.
- Awareness Campaigns: Suggest potential public health campaigns or educational interventions to improve awareness based on the findings.

Implications for Policy

Comments:
- This section provides a strong call to action. The identified policy gaps are critical and well-presented.
Suggestions:
- Structured Recommendations: Present the policy implications in a more structured format, possibly using bullet points or numbered lists for clarity.
- Evidence Integration: Integrate specific study findings more directly into the policy recommendations to strengthen the argument for immediate action.

Actionable Recommendations

Comments:
- The recommendations are comprehensive and relevant but could be more prioritized or categorized.
Suggestions:
- Prioritization: Consider categorizing the recommendations into short-term, medium-term, and long-term actions.
- Stakeholder Engagement: Emphasize the role of specific stakeholders (e.g., government, NGOs, the public) in implementing these recommendations.
- Feasibility: Briefly discuss the feasibility of these recommendations, particularly in the context of existing infrastructure and resources.

Limitations of the Study

Comments:
- The limitations are transparently discussed, which is commendable. However, there is a risk that some of these might overshadow the study's strengths.
Suggestions:
- Strengths Emphasis: Counterbalance the limitations with a brief discussion of the study’s strengths, particularly its novel approach and the involvement of citizen scientists.
- Future Directions: Suggest specific areas for future research that could address these limitations, enhancing the study's impact.

Conclusion

Comments:
- The conclusion effectively summarizes the key points but could be more emphatic in calling for urgent action.
Suggestions:
- Stronger Call to Action: End with a more forceful call to action directed at policymakers, highlighting the urgency of addressing CKD in the Niger Delta.
- Summary of Key Points: Briefly summarize the most critical findings and recommendations to leave a lasting impression.

Overall Document Comments:

Consistency: Ensure consistency in the use of terms (e.g., CKD vs. chronic kidney disease) throughout the document.
Clarity: While the document is generally clear, some sections, particularly those with dense data, could benefit from simpler language and clearer transitions.
Visual Aids: Consider the strategic use of additional visual aids to break up text-heavy sections and improve reader engagement.
Proofreading: A thorough proofreading is recommended to correct any minor grammatical errors and ensure a polished final submission.

Does the paper provide a comprehensive overview of the policy and the context of its implementation in a way which is accessible to a general reader?

Yes
Is the discussion on the implications clearly and accurately presented and does it cite the current literature?

Yes
Are the recommendations made clear, balanced, and justified on the basis of the presented arguments?

Yes

Competing Interests

No competing interests were disclosed.

I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

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Responses (1)

Author Response

31 Jan 2025

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

We are grateful for your detailed and constructive critique which has helped to improve the merit and quality of our manuscript.

ABSTRACT
Reviewer comment: Objective Clarification: Include a brief statement that clearly outlines the study's objective.
Author response: The objective has been clarified as follows:
“This brief is based on a mixed-methods study conducted in four communities situated near an oil and gas refinery in Warri, Nigeria to explore perceived and actual air pollution risk and determine whether long-term exposure to AAP increases NCD risk” (Page 2)

Reviewer comment: Methodology Mention: Explicitly mention that a mixed-methods approach was used.
Author response: Done as stated above

Reviewer comment: Specific Findings: Highlight specific data points, such as the exact levels of pollutants that exceed WHO limits.
Author response: Included as follows:
“Measured PM_2.5 ranged from 22.8 – 28.0 μg/m3, PM₁₀, 40.6 - 55.5 μg/m3, and CO₂, 584-652ppm”. 2

Reviewer comment: Policy Recommendations: Summarise one or two key policy recommendations for a clear takeaway.
Author response: Included as follows:
“The government needs to urgently invest in air monitoring services and data, cleaner technologies and environmental risk communication through various media channels. We strongly recommend public inclusion in planning, designing and implementing future environmental interventions. Lastly, environmental risk factors such as air pollution should feature prominently in strategic plans for NCD prevention”. (Page 2)

Introduction
Reviewer comment: Streamlining: Consider consolidating the discussion on traditional CKD risk factors to avoid redundancy.
Focused Transition: Ensure a smooth transition from discussing CKD globally to the specific context of the Niger Delta.
Identification of Gap: Introduce the research gap on the link between air pollution and CKD in the Niger Delta earlier in the section.
Author response: Thank you for your suggestions. We have reviewed this section accordingly. (Page 3)

Reviewer comment: Policy Outcomes and Implications
Author response: This section has been improved accordingly

Reviewer comment: Direct Link: Explicitly connect the absence of CKD in national health policy to the study’s findings on air pollution and CKD prevalence.
Author response: This has been revised as follows: “This lack of recognition of CKD and the environmental risk factors important in the disease epidemiology, may explain why CKD and related NCDs are persistent.” (Page 4)

Reviewer comment: Broader Implications: Discuss the broader public health implications if this policy gap continues, including potential long-term consequences.
Author response: “The long-term consequences of continually neglecting CKD in health policies include the persistence of hypertension and CKD with associated considerable morbidity and mortality; high health care expenditure which further impoverishes the affected members of society and their families”. (Page 4)

Reviewer comment: Evidence of High Ambient Air Pollutant Levels in Warr
Narrative Flow: Integrate the table with the narrative by referencing key figures directly in the text.
Author response: This section has been improved accordingly and highlighted in the text (Page 4-5)

Reviewer comment: Benchmark Against Global Standards: Briefly compare the findings with global or regional averages for context.
Author response: This section has been improved as follows:
“The PM2.5 concentrations for three of the communities are higher than Nigeria’s 2023 average of 23.9 μg/m3 (IQAIR) and five times higher than the WHO acceptable limit. Furthermore, these levels are much higher than 7.8μg/m3 achieved in Angola, the least polluted African country which ranked 114th out of 134 countries, while Nigeria was ranked the 35th most polluted”.( Page 4-5)

Reviewer comment: Graphical Representation: Consider using a graph to visualize the levels of pollutants across communities for greater impact.
Author response: A bar chart showing air pollutant levels in the 4 communities have been included. (Figure 1)

Reviewer comment: High Prevalence of CKD and the Risk Factors
Risk Factor Hierarchy: Present the risk factors in order of their strength of association with CKD.
Author response: Included as follows:
“The independent risk factors for CKD were proximity to the refinery [OR=2.00 (1.43 – 2.81], increasing age [OR=1.02(1.005-1.04)], hypertension [OR=1.61(1.12-2.31)], and level of education [OR=0.63(0.44-0.91)]. In a further logistic mixed model, which accounted for clustering effects at household level, only increasing age was an independent risk factor for CKD [OR=1.16 (1.07-1.25)]”, (Page 6)

Reviewer comment: Visual Aids: While the current figure is useful, additional visual aids, such as bar charts or scatter plots, could further clarify the distribution of CKD stages across communities.
Author response: A new figure showing the information requested has been included. (Figure 3)

Reviewer comment: Contextualization: Briefly contextualize the CKD prevalence data with national or regional statistics to highlight the severity.
Author response: Revised as follows:
The prevalence of CKD reported across Nigeria and Sub-Saharan Africa varies greatly depending on the population studied, CKD definition and methodology; from as low as 2% to >20% (Abd ElHafeez et al., 2018; Chukwuonye et al., 2018). However, our findings demonstrate a higher CKD prevalence in the nearest/semiurban community A, compared with a pooled prevalence of 10% and 13.7% reported for Africa and Nigeria, respectively (Abd ElHafeez et al., 2018; Raji et al., 2024). (Page 5)

Social Determinants of CKD Risk
Reviewer comment: Condensation: Consider condensing the list of behavioral factors by grouping similar items, such as unhealthy dietary habits.
Author response: Revised as follows:
‘Behavioural factors included unhealthy dietary habits (70-90%), low physical activity (47.2%), habitual exposure to potential nephrotoxins (37-44%)’. (Page 6)

Reviewer comment: Clearer Connections: Draw clearer connections between these social determinants and the higher CKD prevalence, emphasizing the compounding effect of multiple risk factors.
Author response: Revised as follows:
“The concentration of multiple social and environmental risk factors in the studied population may explain the high prevalence of CKD and other NCDs. These findings support the multicasuation theory, drawing attention to the need for a multi-faceted approach to CKD prevention.” (Page 6)

Reviewer comment: Implications: Discuss the potential public health implications of these social determinants in more depth.
Author response: Done as above. These points were further discussed in the section on implications for policy. (Pages 6,7)

Reviewer comment: Low Air Pollution Health Risk Literacy in Warri
Direct Linkage: Explicitly link low literacy levels to poor health outcomes, particularly in the context of CKD and air pollution.
Author response: Revised as follows:
“This low literacy level suggests that the necessary preventive measures such as individual behavioral changes, are lacking and this may contribute to the high burden of air pollution associated NCDs in the community”. (Page 7)

Reviewer comment: Awareness Campaigns: Suggest potential public health campaigns or educational interventions to improve awareness based on the findings.
Author response: These have been suggested.
“The high prevalence of CKD risk factors and low awareness of CKD and NCD status among the study participants suggests low health literacy and poor health-seeking behavior which necessitates more persuasive and inclusive public health educational interventions.” (Page 7)

Implications for Policy
Reviewer comment: Structured Recommendations: Present the policy implications in a more structured format, possibly using bullet points or numbered lists for clarity.
Author response: This section has been reviewed accordingly. (Page 7,8)

Reviewer comment: Evidence Integration: Integrate specific study findings more directly into the policy recommendations to strengthen the argument for immediate action.
Prioritization: Consider categorizing the recommendations into short-term, medium-term, and long-term actions.
Author response: We appreciate your comments. This section has been improved as is shown in Table 1. (Page 8-11)

Reviewer comment: Stakeholder Engagement: Emphasize the role of specific stakeholders (e.g., government, NGOs, the public) in implementing these recommendations.
Feasibility: Briefly discuss the feasibility of these recommendations, particularly in the context of existing infrastructure and resources.
Author response: These points have all been considered in the revised table of recommendations. (Page 8-11)

Limitations of the Study
Reviewer comment: Strengths Emphasis: Counterbalance the limitations with a brief discussion of the study’s strengths, particularly its novel approach and the involvement of citizen scientists.
Author response: This has been included as follows:
“Despite the limitations, the strength of the underlying study lies in the relatively large sample size, the extensive consideration and adjustment for confounding factors, the innovative combination of multiple research methods and involving citizen scientists in addressing a public health problem”. (Page 11)

Reviewer comment: Future Directions: Suggest specific areas for future research that could address these limitations, enhancing the study's impact.
Author response: This has been included as follows:
“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”. (Page 110)

Conclusion
Reviewer comment: Stronger Call to Action: End with a more forceful call to action directed at policymakers, highlighting the urgency of addressing CKD in the Niger Delta.
Author response: Thank you for your suggestions. The section has been improved. (Page 11,12)

Reviewer comment: Summary of Key Points: Briefly summarize the most critical findings and recommendations to leave a lasting impression.
Author response: Thank you for your suggestions. The section has been improved. (Page 11, 12)

Overall
Reviewer comment: Consistency: Ensure consistency in the use of terms (e.g., CKD vs. chronic kidney disease) throughout the document.
Author response: CKD is now used consistently throughout the text, except for where it was first mentioned.

Reviewer comment: Clarity: While the document is generally clear, some sections, particularly those with dense data, could benefit from simpler language and clearer transitions.
Author response: Thank you. The authors have made significant efforts to improve the clarity and readability of the document using a proof reader.

Reviewer comment: Visual Aids: Consider the strategic use of additional visual aids to break up text-heavy sections and improve reader engagement.
Author response: Additional visual aids have been introduced. e.g., more figures and the recommendations have been tabulated.

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Competing Interests

None

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Reviewer Report

21 Views

08 May 2024 | for Version 1

Chao Yang, Peking University, Beijing, Beijing, China

21 Views Cite this report Responses(2)

Approved With Reservations

Does the paper provide a comprehensive overview of the policy and the context of its implementation in a way which is accessible to a general reader?

Partly
Is the discussion on the implications clearly and accurately presented and does it cite the current literature?

Partly
Are the recommendations made clear, balanced, and justified on the basis of the presented arguments?

Partly

Competing Interests

No competing interests were disclosed.

Reviewer Expertise

Public health

Respond to this report

Responses (2)

Author Response

21 Nov 2024

Ogochukwu Okoye, Department of Medicine, Delta State University, Abraka, Nigeria

REVIEWER 1

We are grateful for your detailed and constructive critique which has helped to significantly improve the merit and quality of our manuscript

1) The authors should provide a more detailed description of the mixed-methods approach used in the study. Clarify the specific quantitative and qualitative methods employed, sample sizes, and data collection techniques.
Thank you for your observations. Extensive methodological and statistical details were deliberately omitted as the manuscript was targeted at policymakers. However, we have provided additional details in the text.
The underlying study was an exploratory mixed methods study with an embedded citizen science inquiry. Details of the first strand which was a focus group has been published and we have provided a reference to the article. In the current brief, we focus on findings from the other strands of the study.
(Pages 2,3,5)

2) The paper mentions that air pollutant concentrations were measured and compared to WHO limits. However, the analysis of these data and their statistical significance is lacking. The authors should include a more thorough analysis of the air pollution data.
For the reasons mentioned above, we omitted these details. However, some additional data have been provided in the text and as supplementary files.
(Page 5, suppl 1, Figure 1)

3) The paper discusses the association between ambient air pollution and CKD risk, but does not claim causality. The authors should clarify this distinction and discuss potential confounders or alternative explanations for the observed association.
We agree with your observations. We have provided details of confounding factors considered and a supplementary file containing updated results from a binary mixed effects logistic model conducted to account for clustering effects.

We report that long-term exposure to ambient air pollution is associated with CKD risk, but does not independently increase its risk, after adjusting for clustering effects and confounders (age, gender, hypertension, level of education and diabetes).
(Page 6, suppl 2)

4) The paper should acknowledge other limitations of the study, such as sample size, data availability, or methodological constraints. Additionally, the authors should discuss potential directions for future research to build upon the current findings.

The section on limitation of the study has been improved and suggestions for future research as follows:

“More research is required from under-served areas to explore: this exposure-effect relationship, the mechanism of air pollution associated CKD and potential interventions to reverse it; and to develop educational interventions that would effectively improve public awareness of environmental health risks”.
(Page 11)

5) The authors should discuss the generalizability of their findings to other communities and regions with similar industrial activities.

This has been included.
“…. our findings are generalisable to similar vulnerable populations across the globe who reside near point emission sources” (Page 7)

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Competing Interests

No competing interests were disclosed.

Alongside their report, reviewers assign a status to the article:

Approved - the paper is scientifically sound in its current form and only minor, if any, improvements are suggested

Approved with reservations - A number of small changes, sometimes more significant revisions are required to address specific details and improve the papers academic merit.

Not approved - fundamental flaws in the paper seriously undermine the findings and conclusions

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[2] Federal Ministry of Health: National Health Policy 2016: Promoting the Health of Nigerians to Accelerate Socio-economic Development.2016.Reference Source

[3] Garcia-Garcia G, Jha V; World Kidney Day Steering, C: Chronic kidney disease in disadvantaged populations: The case of Africa. Afr. J. Prim. Health Care Fam. Med. 2015, Apr 28; 7(1): e1–e2. PubMed Abstract | Publisher Full Text | Free Full Text

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Ambient Air Pollution and Chronic kidney disease risk in Deltan communities: A Policy Brief, 2023

Abstract

Keywords

Introduction

Policy outcomes and implications

Evidence of high ambient air pollutant levels in Warri

Table 1. Hazard Quotient of air pollutants exceeding WHO 2021 annual acceptable limits in the four communities.

High prevalence of CKD and the risk factors

Figure 1. Stages of CKD among participants (N=180).

Social determinants of CKD risk

Low air pollution health risk literacy in Warri

Figure 2. Participants’ perception of sources of air pollution (N=628).

Figure 3. Medical conditions the participants associated with air pollution (N=1460).

Implications for policy

Actionable recommendations

Limitations of the study

Conclusion

Data availability statement

Acknowledgements

References

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