Local attributable burden disease to PM_2.5 ambient air pollution in Medellín, Colombia, 2010–2016

Introduction

Air pollution is one of the main concerns surrounding public health worldwide due to its impacts on human health and ecosystem (Dominici et al., 2006). According to the Environmental Performance Index of Yale University, poor air quality is the greatest environmental threat and the most difficult challenge for public policies in middle- and low-income countries (Wendling et al., 2020). The attributable disease burden to ambient air pollution at a global, regional, and local level has been widely documented, this involves the measurement of disability-adjusted life years (DALYs), an aggregate value of years of life lost (YLLs) due to premature death and years lived with disability (YLDs) (HEI, 2019). Globally, the Institute for Health Metrics and Evaluation (IHME) has identified to air pollution as the fifth main health risk factor for the population, and it is estimated that the exposure to PM_2.5 contributes to 4.9 million deaths (8.7% of all deaths worldwide), and the loss of 147 million of healthy life years (5.9% of all DALYs). The main causes of mortality worldwide due to air pollution are ischemic heart disease (35.9%), stroke (21.1%), chronic obstructive pulmonary disease (COPD; 20.4%), acute respiratory infections (15.9%), and lung and respiratory tract cancer (6.9%) (Cohen et al., 2017). Additionally, a wide list of events is evidenced beside to lung and respiratory cancer, which includes neoplasms in different organs and systems (Turner et al., 2020).

The World Health Organization (WHO) considers air pollution to be the main environmental health risk factor for the population in the Americas (Prüss-Ustün et al., 2016) due to its impact in susceptible populations, such as children younger than 5 years old, pregnant women, and elderly people (Piñeros-Jiménez et al., 2018). For Latin America and the Caribbean, it has been estimated that around 35,000 persons die annually to urban air pollution and 276,000 annual healthy life years are lost (Romieu et al., 2012).

In Colombia, few studies on ambient air pollution epidemiology have been carried out: a review of literature between 2008 and 2016 (Piñeros-Jiménez et al., 2018), 19 works were identified, which were mainly focused on the population-based analysis of the risk associated with the exposure to air pollutant on morbidity and mortality due to cardiovascular and respiratory events (Blanco-Becerra et al., 2014; Rodríguez-Villamizar et al., 2010; Salazar-Ceballos & Álvarez-Miño, 2011; Gaviria et al., 2011). Recently Rodríguez-Villamizar et al. (2018) conducted a multicity ecological time-series analysis with data from four major cities in the country. This analysis found for NO₂, PM₁₀, and PM_2.5, statistically significant percentage increases in emergency department visits for respiratory diseases in children between 5 and 9 years old, and for circulatory diseases in persons over 60 years of age.

Regarding studies of burden of disease attributable to ambient particulate matter pollution, few robust studies have been conducted (Romieu et al., 2012). In 2016, the Colombian National Health Institute estimated that 8% of 200,000 annual deaths in the country could be attributed to environmental risk factors, and calculated that 13.9% of ischemic heart disease deaths and 17.6% of chronic obstructive pulmonary disease deaths could be associated to ambient particulate matter pollution (INS, 2018). Also, the World Bank (WB) estimated 5,000 premature deaths and 69 million DALYs annually between 2002 and 2010 (Golub et al., 2014). These studies provided meaningful results of impact of air pollution in health in Colombia; however, they did not determine the magnitude of burden disease at the municipal levels where environmental phenomenon presents different magnitudes and particular local dynamics.

Medellín is the second largest city in Colombia and one the most polluted in Latin America. Since 2016, Piñeros-Jiménez et al., have conducted several researches about health impacts associated with short-term exposure to PM₁₀, PM_2.5 and ozone (Piñeros-Jiménez et al., 2018; Piñeros-Jiménez et al., 2019). They developed traceability techniques based on analytical methods to identify health events from the records of different sources of health information, which allowed them to have a more precise epidemiological baseline for the measurement of health impacts. For Medellín, an ecological time series study found that a 10 μg/m³ increase in PM_2.5 was associated with increase of 25.2% in the risk of respiratory diseases for children younger than 5 years old, and of 29.7% for adults of 65 years of age and over (Piñeros-Jiménez et al., 2018). Furthermore, they could establish the increases in the risk percentage of emergency room visits for asthma (2.8%), acute respiratory infection (2.0%) and pneumonia (2.2%) due to population exposure to critical air pollution episodes occurred in February and March 2015 (Nieto-López et al., 2020).

Despite the advances in air pollution epidemiology research in Latin America, it has been recognized that establishing the attributable burden of disease to this environmental risk factor at the municipal level is a challenge for the academy and local management of environmental health, which requires updated information of the best quality to guide political decision-making and public planning with a territorial perspective. The aim of this study was to determine the local burden of disease to PM_2.5 (LBD_PM2.5) for Medellín, for which an updated epidemiological baseline focused on respiratory and circulatory events.

Methods

Results

Ambient PM_2.5 pollution in Medellín

Between 2010 and 2016, daily concentrations of PM_2.5 were 35.8 μg/m³ (min–max: 13.6–123.1 μg/m³). with important variations at each year, we could observe that, in 2016, there was an annual increase of the average PM_2.5 of 21.9%, compared with the base year, 2010. Interestingly, at all years, the annually average values of PM_2.5 were higher than the 25 μg/m³ value established by the Environmental National Authority (i.e., Resolution No. 610 of 2010).

On February and March of each year the highest averages were presented during the study years, except for 2012. Likewise, there is a greater tendency to increase the monthly average for PM_2.5 for these months during the study period. In March 2016, the highest mean value of the entire time series of data were identified.

On the other hand, the months of October and November from 2010 to 2016 presented monthly averages with slight increases, except for 2011 (Figure 1A–G).

Figure 1. Monthly average of PM_2.5, 2010–2016.

Local attributable burden of disease

During the seven-year period there was a premature YLLs of 536,772 (95% UI 524,048–549,495) due to events related to air pollution in Medellín; 13.0% (n = 71,590 (95% UI 69,843–73,339)) corresponded to LBD_PM2.5 (Table 3). The attributable YLLs to PM_2.5 pollution (YLLs_PM2.5) showed little variation throughout the period, with an annual average of attributable mortality burden calculated in 10,227 (95% UI 9,950–10,505) of YLLs. The Figure 2A–B shows annual YLLs_PM2.5 rates for males and females between 2010 and 2016. In both genders, stable losses were observed in the YLLPs_PM2.5 rates with a tendency to decrease. The highest concentration of YLLs_PM2.5 were presented in 2016, with annual rates for this year of 496.9 per 100,000 inhabitants for males and 378.6 cases per 100,000 inhabitants for females.

Table 3. Attributable local burden disease to ambient PM_2.5 pollution by type of event and gender, 2010-2016.

Type of event	Gender	LBDa	LBDPM2.5b	% LBDPM2.5	Average LBDPM2.5 rate	Average LDBPM2.5 (UI 95%)c
A C U T E E V E N T S	Male
	YLLs	197,533	25,795	13.1	323.8	3,685 (3,609 – 3,761)
	YLDs	55,016	7,838	14.2	688.8	1,120 (1,030 – 1,209)
	DALYs	252,550	33,633	13.3	422.2	4,806 (4,684 – 4,925)
	Female
	YLLs	156,458	20,201	12.9	225.6	2,886 (2,820 – 2,952)
	YLDs	57,124	8,286	14.5	647.6	1,183 (1,095 – 1,273)
	DALYs	213,582	28,487	13.3	318.1	4,070 (4,027 – 4,113)
	Total
	YLLs	353,991	45,996	13.0	271.8	6,570 (6,454 – 6,688)
	YLDs	112,140	16,124	14.4	422.2	2,302 (2,129 – 2,477)
	DALYs	466,132	62,120	13.3	367.1	8,873 (8,716 – 9,032)
C H R O N I C E V E N T S	Male
	YLLs	91,173	12,600	13.8	158.2	1,799 (1,694 – 1,906)
	YLDs	38,125	6,147	16.1	540.1	879 (719 – 1,038)
	DALYs	129,298	18,747	14.5	235.3	2,679 (2,537 – 2,819)
	Female
	YLLs	91,608	12,994	14.2	145.1	1,857 (1,768 – 1,945)
	YLDs	39,315	6,347	16.1	496.1	906 (753 – 1,060)
	DALYs	130,923	19,341	14.8	216.0	2,763 (2,669 – 2,857)
	Total
	YLLs	182,781	25,594	14.0	151.3	3,656 (3,496 – 3,817)
	YLDs	77,440	12,494	16.1	516.9	1,783 (1,484 – 2,085)
	DALYs	260,221	38,089	14.6	225.1	5,441 (5,262 – 5,621)

a LBD: Local Burden Disease.

b LBD_PM2.5: Attributable Local Burden Disease to ambient PM_2.5 pollution.

c UI 95%: Uncertainty Interval of 95% In relation to the attributable total per each event.

Figure 2. Attributable local burden disease to ambient PM_2.5 pollution by gender, 2010-2016.

YLLs_PM2.5: Attributable years of life lost to ambient PM_2.5 pollution.

YLDs_PM2.5: Attributable years lived with disability to ambient PM_2.5 pollution.

DALYs_PM2.5: Attributable disability adjusted life years to ambient PM_2.5 pollution.

The highest attributable mortality burden was found for acute events with 45,996 (95% UI 45,175-46,817) YLLs_PM2.5, on the other hand, chronic events presented 25,594 (95% UI 24,454-26,734) YLLs_PM2.5 for chronic events. Males had a greater contribution to the attributable mortality burden for acute events (56.1%), while females showed a slightly higher frequency of this for chronic events (50.8%). No large fluctuations were observed in the distribution of the attributable burden during period; although, in 2016 there was a slightly higher concentration of mortality due to the two types of events for both genders.

When viewed in term of disability, a loss of 189,580 (95% UI 168,455–210,703) YLDs due to respiratory and circulatory events related to air pollution was observed. 15.1% (n = 28,618 (95% UI 25,280–31,956)) corresponded to LBD_PM2.5, with an annual average of 4,086 (95% UI 3,619–4,565) YLDs. The highest proportion of attributable disability loss to PM2.5 pollution (YLDs_PM2.5) occurred in 2011 and 2012, when 32,6% of YLDs_PM2.5 were concentrated. Compared with 2010, in 2016 the rate of YLDs_PM2.5 decreased by 36.4%, with a more marked decrease in males (Figure 2C–D). Acute events constituted 56.3% of YLDs_PM2.5 (n = 16,124 (95% UI 14,902–17,346)). Females had a higher percentage contribution, both for YLDs_PM2.5 due to acute events (51.4%) and YLDs_PM2.5 due to chronic events (50.8%). However, throughout the study period the highest rates occurred in men.

Of total LBDs associated with pollution (n = 726,353 DALYs, 95% UI 715,045-737,659), 73.9% corresponded to YLLs and the remaining to YLDs. The premature mortality due to acute events was higher than that estimated for chronic events, with 33 percentage points of difference, with a slightly greater magnitude in the male burden than the female burden (Table 3). Of total estimated DALYs, 13.8% (95% UI 13.7%–13.9%) was attributed to PM_2.5 pollution (DALYs_PM2.5), with an average of 14,315 DALYs_PM2.5 per year (95% UI 14,005–14,626), equivalent to rate of 592.2 DALYs_PM2.5 per 100,000 cases. Compared with the initial year of study in 2016, a decrease of 8.3% in total DALYs_PM2.5 was observed, with decreases of 8.1%in DALYs_PM2.5 due to acute events and 8.6% due to chronic events. According to the gender, distribution of DALYs_PM2.5 had variations by type of event; while DALYs_PM2.5 due to acute events was higher in males (54.1%), the DALYs due to chronic events were slightly concentrated in females (50.8%) (Table 3) (Figure 2E–F).

Attributable burden to PM_2.5 pollution by age group and type of event

LBD_PM2.5 showed a positive gradient from 35 years of age, with significant differences among the five-year age groups. Those over 65 years of age contributed with 61.7% of the total burden, with the highest rates in the group of 80 years and older. In all the five-year age groups, LBD_PM2.5 for acute events was higher than for chronic events, with considerable differences that were more marked until the age of 59 years. After 60 years of age, the differences were smaller although maintaining the trend. LBD_PM2.5 for chronic events was comparable in the age groups between 15 years and 44 years; but after 45 years of age, it gradually increased until the age of 79 years, when it slowly decreases in the last age group. Only 10.3% of the total attributable burden was in the population younger than 39 years old (Table 4). Male showed the highest prevalence of LBD_PM2.5, with the highest difference in the 40–44 and 55–59 age groups, and an approximate ratio of 2 to 1.

Table 4. Attributable local burden disease to ambient PM_2.5 pollution by age group, 2010-2016.

Age group	Chronic Events			Acute Events			Total
	DALYsPM2.5	% DALYsPM2.5a	DALYsPM2.5 Rate	DALYsPM2.5	% DALYsPM2.5	DALYsPM2.5 Rate	DALYsPM2.5	% DALYsPM2.5b	DALYsPM2.5 Rate
0-4	123	3.2	12.0	3769	96.8	368.3	3892	3.9	380.3
5-9	26	2.6	2.5	973	97.4	92.9	999	1.0	95.4
10-14	19	4.1	1.7	442	95.9	39.5	461	0.5	41.2
15-19	105	13.5	8.3	670	86.5	53.1	775	0.8	61.5
20-24	72	11.1	5.1	579	88.9	41.2	651	0.6	46.3
25-29	110	10.1	7.8	980	89.9	69.5	1090	1.1	77.3
30-34	131	13.1	10.5	867	86.9	69.5	998	1.0	80.0
35-39	234	15.9	21.6	1,236	84.1	114.0	1,470	1.5	135.6
40-44	299	15.9	26.5	1,580	84.1	139.7	1,879	1.9	166.2
45-49	702	20.7	51.5	2,690	79.3	197.4	3,392	3.4	248.9
50-54	1,541	28.9	116.9	3,789	71.1	287.6	5,330	5.3	404.5
55-59	2,773	35.2	258.2	5,095	64.8	474.5	7,868	7.9	732.7
60-64	3,983	41.5	481.9	5,625	58.5	680.6	9,607	9.6	1,162.5
65-69	4,785	45.5	804.5	5,720	54.5	961.8	10,505	10.5	1,766.4
70-74	5,521	47.7	1,395.3	6,065	52.3	1,532.8	11,586	11.6	2,928.0
75-79	5,962	48.8	1,932.0	6,248	51.2	2,024.6	12,211	12.2	3,956.6
80 and older	11,704	42.6	3,671.5	15,790	57.4	4,953.3	27,495	27.4	8,624.8

a % in relation to the total per age group.

b % in relation to the total.

Five groups provided the highest contribution to attributable premature mortality and disability according to the type of event by diagnosis group (chapter) of the seven groups analyzed (Table 5). 80.6% of premature deaths were caused by ischemic heart disease (40.1% of YLL_PM2.5), chronic lower respiratory tract diseases (23.4% of YLL_PM2.5) and acute infections of the lower respiratory tract (16.9% of YLL_PM2.5). On the other hand, among the causes that most contributed to attributable disability were chronic lower respiratory tract diseases (43.3% of YLD_PM2.5), other acute infections of the lower respiratory tract (24.3%) and influenza and pneumonia (20.1% of YLD_PM2.5). In contrast, the group of neoplasms had a relatively lower contribution to LBD_PM2.5, explaining 8.8% of DALYs_PM2.5 (12.2% of YLL_PM2.5 and 0.3% of YLD_PM2.5).

Table 5. Disability adjusted life years and disease burden attributable to ambient PM_2.5 pollution according to each group and sub-group of events, Medellín, 2010-2016.

Group of Event (CIE-10 codes)	YLLsPM2.5	YLLsPM2.5 Rate	% LBDPM2.5a	YLDsPM2.5	YLDsPM2.5 Rate	% LBDPM2.5a	DALYsPM2.5	DALYsPM2.5 Rate	± DALYsPM2.5 (95% UI)b
ACUTE EVENTS
Respiratory system diseases
Influenza and pneumonia (J09–J18)	12,101	71.5	67.8	5,738	237.4	32.2	17,839	105.4	2,548 (1,148 – 3,948)
Other acute lower respiratory tract infection (J20–J22)	395	2.3	5.4	6,942	287.2	94.6	7,336	43.4	1,948 (594 – 2,594)
Circulatory system diseases
Ischemic heart diseases (I20-I25)	28,717	169.7	93.4	2,031	84.0	6.6	30,748	181.7	4,393 (1,771 – 7,014)
Cerebrovascular diseases (I60–I69)	4,784	28.3	77.2	1,413	58.4	22.8	6,197	36.6	885 (369 – 1,401)
CHRONIC EVENTS
Respiratory system diseases
Chronic lower respiratory tract diseases (J40–J47)	16,852	99.6	57.6	12,400	512.9	42.4	29,252	172.9	4,179 (756 – 7.602)
Neoplasms
in situ neoplasms (D00–D09)	0	0.0	0.0	0.2	0.0	100.0	0.2	0.0	0.032 (0.009 – 0.06)
Malignant neoplasms of respiratory and intrathoracic organs (C30–C39)	8,742	51.7	98.9	94	3.9	1.1	8,836	52.2	1,262 (552 – 1,972)

a % in relation to the total LBD_PM2.5 by group of event.

b Period 2010-2016, Uncertainty ranges of 95% calculated using the bootstrap method for n = 10,000 samples.

Figure 3 shows the relationship of the rates of YLL_PM2.5 and YLD_PM2.5 for each diagnosis group studied. The groups of causes were classified into four categories according to the relationship between the two rates: A (low mortality and low disability), B (low mortality and high disability), C (high mortality and low disability) and D (high mortality and high disability). Four of the seven groups of events studied (ischemic heart disease, cerebrovascular disease, influenza and pneumonia, and chronic lower respiratory tract diseases) were included in category D, due to their contribution to both mortality and disability. On the other hand, in situ neoplasms were included in category A, other acute lower respiratory tract infections in category B, and malignant neoplasms of respiratory and intrathoracic organs in category C.

Figure 3. Relation of YLL_PM2.5 and YLD_PM2.5 rates per group of events, 2010–2016.

YLLs_PM2.5: Attributable years of life lost to ambient PM_2.5 pollution. YLDs_PM2.5: Attributable years lived with disability to ambient PM_2.5 pollution.

^a Logarithmic scale.

Table 6 shows the ranking of the diagnostic events according to their contribution to the LBD_PM2.5. Comparing the years of beginning and end of the study period, there were no changes in the order of the groups of events. In both years, the three highest DALY_PM2.5 rates were found to be due to ischemic heart disease, chronic lower respiratory tract disease, and influenza and pneumonia. Cerebrovascular diseases, chronic lower respiratory tract diseases and in situ neoplasms showed a reduction of more than 10% in the rates of DALY_PM2.5 by 2016 in relation to the year of initiation of the study. The opposite occurred with malignant neoplasms of respiratory and intrathoracic organs, which showed an increase of 22.3% in DALY_PM2.5 rate.

Table 6. Leading of diagnosis group by attributable DALYs ambient PM_2.5 pollution in Medellín, 2010 and 2016.

2010				Diagnosis Group	Change	2016
Local DALYs	DALYs PM2.5	DALYs PM2.5 Ratea	Attribution percentageb			Local DALYs	DALYsPM2.5	DALYsPM2.5 Ratea	Attribution percentageb
33,561	4,420	188.6	30.6	Ischemic heart diseases	-8.6	32,584	4,288	172.4	30.5
25,924	4,287	183.0	29.6	Chronic lower respiratory tract diseases	-16.7	22,844	3,792	152.5	27.0
17,447	2,652	113.2	18.3	Influenza and pneumonia	-4.1	17,753	2,698	108.5	19.2
10,527	1,116	47.6	7.7	Malignant neoplasms of respiratory and intrathoracic organs	+22.3	13,660	1,448	58.2	10.3
6,808	1,035	44.2	7.2	Other acute lower respiratory tract infections	-8.9	6,579	1,000	40.2	7.1
10,314	951	40.6	6.6	Cerebrovascular diseases	-16.4	9,129	844	33.9	6.0
0.2	0.02	0.001	0.0	In situ neoplasms	-75.1	0.1	0.01	0.0002	0.0

a per 100,000 inhabitants.

b % in relation to the total attributable local burden.

Discussion

Nowadays, ambient air pollution by the criteria pollutant PM_2.5 is considered one of the biggest environmental problems at the global and local level due to the impact it causes on the health of populations (Apte et al., 2018). Although cities in Latin America and the Caribbean region have shown annual average PM_2.5 values that could be considered moderate if compared to cities located in Southeastern Asia and India, most of these have reported annual average higher than the levels recommended by WHO of 10 μg/m³ (Riojas, 2016). For Medellín, one of the most polluted cities of the region, the annual average PM_2.5 levels during the seven years of study was 35.6 μg/m³, where more than 90% of the days had daily averages above 25 μg/m³ (Piñeros-Jiménez et al., 2018), risk factor to which approximately 3 million people are exposed. Under these conditions, in the last five years, some studies have been carried out to establish the health impacts of criteria pollutants (PM₁₀, PM_2.5, ozone and nitrogenous) with population models of a single and multiple pollutants at a local level (Piñeros-Jiménez et al. 2018, Piñeros-Jiménez et al. 2019, Rodríguez-Villamizar et al. 2018). This is the first study that seeks to establish the magnitude of such an impact by using a holistic indicator.

Since the 1990s, multiple strategies have been used to gather knowledge about the burden disease caused by different risk factors. These strategies offer a holistic view of the joint effects of morbidity and mortality in the number of healthy life years lost. Environmental risk factors, mainly air pollutants, have had a growing interest among decision makers and the community at the local and global level, and have been prioritized in the political agendas promoted by research in environmental epidemiology in recent decades. Among the advances in research, the studies that analyze the magnitude of the impacts based on holistic indicators at the global and national level, supported by exposure-response functions and relative risk analysis, with the data available in the health and environmental information systems, stand out. All of which may help in transcending towards causality (Burnett et al., 2014).

Air pollution epidemiological research in Latin America and Colombia has been characterized by ecological studies of time series and some panel studies, which have confirmed the short-term effects associated to criteria pollutants (Romieu et al., 2012; Piñeros-Jiménez et al., 2018). Very few studies have been carried out at the local level to document the local burden of disease attributable to air pollution (Golub et al., 2014; INS, 2018). No one has evaluated the long-term effects.

In this study, we provided a detailed view of the local burden of disease attributable to air pollution, for Medellín, one of most development cities of the country and region. Which recognizes the local character of the epidemiological phenomenon associated to air pollution, and the need for updated information to influence public environmental policy in the city. It was focused on using a synthetic indicator: DALYs, an aggregate value YLLs due to premature death and YLDs, based on up-to-date methodologies validated by experts and international organizations (Cohen et al., 2017; World Bank, 2016; WHO 2016). In the absence of local cohort studies, the PAF estimates made in the GBD study were used, which assumed a non-linear relationship between the incidence of health events and short- and long-term exposure to particulate matter and developed the integrated exposure–response curve to estimate the long-term PM_2.5 exposure–response association from low exposure level to concentration as high as 1000 μg/m³ to avoid overestimating the magnitude of health effects (Burnett et al., 2014)

We found that the attributable burden disease PM_2.5 pollution constituted 13.8% of the total local burden of DALYs for all the selected pollution-related events (100,208 DALYs_PM2.5 out of 726,352 total DALYs,). In the study on environmental burden disease in Colombia carried out by National Health Institute of Colombia (INS), for 2016, 19% of the total national burden disease was associated to environmental risk factors (air, water, and other similar factors) (INS, 2018). Regarding air pollution, YLLs_PM2.5 was calculated in 619.8 per 100,000 inhabitants. In our study, for the same year, 434.3 YLLs_PM2.5 per 100,000 inhabitants was estimated. This difference can be considered reasonable, since the study cited above was carried out in a higher geographical area (national level), and it is possible that cities with a greater air pollution problem such as the capital of the country (Bogota D.C.) had a greater weight in the total estimate.

Acute diseases contributed with 62.0% of DALY_PM2.5, this is explained by the higher contribution of YLLs_PM2.5 (74.0%) in the burden health index, mainly by ischemic heart disease, that constitute 30.5% of DALY_PM2.5 for 2016 in contrast to the estimation of 15.8% from the study on the environmental burden disease in Colombia for this year (INS, 2018). Our results are consistent with the results of the study by Cohen et al. (2017) regarding the events but not the magnitudes. The number of DALYs associated to ischemic heart disease was the highest in this study, similar results was found in India State-Level Disease Burden Initiative Air Pollution Collaborators study for 2017 (2019). There is more and more evidence from prospective studies that PM_2.5 exerts adverse effects particularly on the cardiovascular system, contributing substantially (mainly through mechanisms of atherosclerosis, thrombosis and inflammation) to coronary artery disease, but also to heart failure, hypertension, diabetes and cardiac arrhythmias (Hu, et al., 2018; Hajat, et al., 2019; Franklin, et al., 2015; Kauffman, et al., 2016a; Kauffman, et al., 2016b; Song, et al., 2020), which can help to explain the findings regarding this type of event in relation to the attributable burden disease.

In the case of the burden of disease attributable to acute respiratory diseases, our result differs from other studies conducted with national data. This can be observed in the estimated proportion of DALY_PM2.5 for acute lower respiratory tract disease in the INS study was of 13.7% (INS, 2018), which contrasts with the 7.1% reported by us for the events of the diagnostic group of other acute lower respiratory tract infection events (J20–J22) in Medellín. Regarding the study by Golub et al. (2014), we found more approximate results, although the basis for calculating the attributable DALYs in the case of acute respiratory disease was the proxy for the reports of respiratory symptoms. These differences could be explained by the methodology used to identify the cases and calculate the indicators. In our study we used a data mining-based traceability strategy to select health events that was constructed based on the natural history of the disease. Which established that the duration of acute respiratory events was 15 days, and with this criterion grouped the records of each source of information into a data set that made up each case (Piñeros-Jiménez et al., 2018). This strategy allowed a more precise approach to the number of events and the calculation of the study indicators. This strategy allowed a more precise approach to the number of events and the calculation of the study indicators.

Chronic diseases of the lower respiratory tract constituted the chronic events with the greatest weight in the total of DALYs_PM2.5 (38%) in our study. This result is consistent with estimations of DALYs due to chronic respiratory diseases in relation to the IHME reports. Between 2010 and 2016, the average rate of DALYs due to chronic diseases of the respiratory tract and ischemic heart diseases in Medellín, was of 172.9 and 181.7 per 100,000 inhabitants, respectively. Estimations published by the IHME show that, in 2016, around 112.2 DALYs due to chronic respiratory diseases were calculated per 100,000 inhabitants in Colombia. Also, in this period, 165.32 (106.5–217.9) DALYs due to ischemic heart disease were calculated per 100,000 inhabitants, which were associated to air pollution (Cohen et al., 2017).

Among the events included in the diagnosis group of chronic lower respiratory tract diseases were asthma (J45) and COPD (J40–J42), two of the most relevant events in relation to the attributable burden disease to exposure to air pollution, specifically for the pollutants PM_2.5, NO₂ and ozone (Achakulwisut et al., 2019; Anenberg et al., 2018, Cohen et al., 2017). In the case of COPD, although its impact on GBD has been established with a global point prevalence of 3.918% (95% UI (3.5111–4.3201) and a mortality rate of 41.9 deaths per 100,000 people (5.7% of all deaths from all causes) (GBD Chronic Respiratory Disease Collaborators, 2020), its risk association with some air pollutants has had a positive sign but of low magnitude and in some cases without statistical significance (Schikowski et al., 2005, 2014), including its specific association with ambient PM_2.5 pollution (Atkinson RW et al., 2015; Dany Doiron et al., 2019). Globally, seven million deaths were attributed to the joint effects of environmental and domestic air pollution (Cohen et al., 2017). And it is recognized that the effects can be divided into short and long-term effects, ranging from exacerbation of existing symptoms, impaired lung function and increase in hospitalization and mortality rates. Prolonged exposure to air with a high concentration of pollutants can also increase the incidence of COPD.

Air pollution can induce the development of asthma, increasing respiratory morbidity and mortality, particularly in minority groups (Nishimura et al., 2013). Annually, it is estimated that 40 million (95% UI 18–52) of new cases of pediatric asthma could be attributable to NO₂ contamination, with a higher burden of new asthma cases associated with NO₂ exposure per 100,000 children for the Latin American region (340 cases per year, 95% UI 150–440) (Achakulwisut et al., 2019). Likewise, it is estimated that 9–23 million and 5–10 million annual asthma emergency room visits globally could be attributable to ozone and PM_2.5, respectively (Anenberg et al., 2018). Our results demonstrate an important impact of ambient PM_2.5 pollution on chronic respiratory diseases that should be analyzed in more detail, with the aim of generating useful knowledge for the design of interventions and decision-making in specific groups, especially taking into account, age groups where asthma and COPD are more frequent.

In contrast with other reports, the contribution of lung and airway cancer to local DALYs_PM2.5 was relatively low (8.8%), and it was explained almost exclusively by YLLs_PM2.5. The Cohen study found that lung and airway cancer accounted for 16.5% of the global burden attributable to PM_2.5, while recently Yin et al. reported for China that 16.6% of deaths attributed to ambient particulate matters at the national level were due to this this cause (Cohen et al., 2017; Yin et al., 2020). This difference of more than double the DALYs_PM2.5 could be due to the level of analysis carried out in the different studies, but it is mainly explained by the coverage of high-cost disease care in our country, where there is a health system with great inequalities in access, which makes these types of diseases often go undiagnosed and unattended, so they are not reported to health information systems. This situation is especially worrying in the economically most vulnerable sectors of the population, there is a hidden burden of the disease that makes difficult to carry out targeted interventions according to equity criteria.

The highest proportion of DALYs_PM2 was related to YLL_PM2.5, at 71.4%. This apparent paradoxical effect of a significant premature mortality burden attributable to PM_2.5 pollution could be explained using the protracted polarized model, which is predominant in Latin America and other regions of the world sharing the same development features. Here we find a superposition of transmissible acute diseases and non-transmissible chronic diseases, along with the reappearance of emergent diseases, which affect vulnerable human groups discriminately and disparately, as observed in the population of Medellín. Despite the improvements in the control of childhood diseases, as well as demographic changes and the increased life expectancy, conditions of inequality, poverty and extreme poverty persist, which add to the new risk factors, such as PM_2.5 pollution caused by transportation and urbanization (GBD 2019 Risk Factors Collaborators, 2020). This new risk factor generates a negative impact on air quality, affecting the exposed population, accelerating disease and increasing mortality, and resulting in an unbalanced pattern of death and disability.

It is worth mentioning that the effects of air pollution on health are not directly proportional to the intensity of exposure in individuals, but it is clear that such effects exist and are dependent on other variables as well as the time and level of exposure. Air quality in high-income countries has improved in recent decades, however, adverse effects of external air pollution on health due to particulate matter continue to be a public health problem worldwide, even if levels are low (Cohen et al., 2017; Liu et al., 2021).

We can conclude that 71.4% of DALYs_PM2.5 between 2010 and 2016 was due to premature death; especially YLLs_PM2.5 due to acute events. A proportion of 28.6% was YLDs_PM2.5. The greatest concentration of YLLs_PM2.5 was associated to ischemic heart diseases and chronic lower respiratory tract diseases with a high proportion of COPD, particularly in male older than 80 years of age. Considering YLDs_PM2.5, these were caused mainly by chronic lower respiratory tract diseases, influenza and pneumonia, and other acute lower respiratory tract infection which were more prevalent among the population older than 60 years of age, in both genders.

One of the greatest strengths of this study is that it was pioneers in Colombia and region in the use of the new proposed methodology to calculate the burden of disease indicators, as it uses the new GBD study (GBD 2019 Risk Factors Collaborators, 2020), which gives a higher importance to prevalence over incidence as epidemiological indicators for disability calculations, this allows establishing the basis for future studies based on our findings. The quality assessment of data from the information sources we used exhaustive and included protocols that have been previously validated (Piñeros-Jiménez et al., 2018; Piñeros-Jiménez et al., 2019), in contrast with the majority of GBD studies where it has been shown to be one of the greatest obstacles in the application of the disease burden methodology. We obtained consistency percentages of more than 90% in morbidity aspects and more than 82% in mortality aspects, which are comparable to the results of INS and Ribotta studies (INS, 2018; Ribotta et al., 2019).

Since the first study of the global burden of disease in 1993, constant updates have been made. In 2010 they introduced significant changes in the methodology for the measurement of the base metric of the Years of Life Adjusted for Disability, which were supported by the experience of around 40 working groups in the area of epidemiology, several of them providing support to the public health programs of the WHO. Thus, over more than two decades this methodology has been refined and validated in national and international health analysis scenarios.

In this study, the latest theoretical and methodological criteria defined by the WHO since 2013 were taken into account, omitting economic and social evaluations in the metric. In addition, to identify the disability weights associated with each of the events related to air pollution, the lists of the study of the global burden of diseases 1990-2017 updated by the IHME were used and the Attributable Fractions were considered. Population-based (FAP) associated with PM_2.5 contamination standardized by age that were estimated for Colombia in a study carried out by the IHME (Cohen et al., 2017).

Among the limitations, we can mention that the multiple sources we used respond in an unarticulated way to events follow-up, which does not allow for an optimal traceability. The effects of migration could not be considered, and it was impossible to make an adjustment of results according to the coverage of morbidity information. The underreporting of the RIPS corresponds to a reality inherent to the reporting dynamics of morbidity of Colombia’s information system, as this is recognized in some previous publications (Castañeda-Orjuela et al., 2015; Rosselli & Rueda, 2012). However, the advances in the timeliness of information that have been achieved during the last decade due to the efforts made by the health system at the local level, particularly Medellín has achieved less underreporting than other cities in the country. It should be noted that the estimation of underreporting considers the clinical history as a source of comparison for the RIPS, which as the primary document would allow comparison with the diagnoses of interest of the RIPS (capture-recapture method). However, this procedure requires access to data that is under the habeas data considerations.

We do not consider the National Demographic and Health Survey as a source of comparison with the RIPS, due to the temporal differences between the RIPS used in the present study (2010-2016) and the information from the survey, whose most current version is that of the year 2015. Added to this is the difficulty in accessing to its anonymized database.

Also, estimations of the Population Attributable Fraction proposed by the GBD methodology, which were used for a list of specific events, could not be representative for Medellín’s population. The prevalence values that we used in this study were related only with those people who visited medical services; therefore, stating that this information can be extrapolated to obtain the actual prevalence of the diseases we examined may be risky.

We recommend developing cohort studies for the local context, which can help in the documentation of the actual attribution (attributable risk estimation) of morbidity and mortality to air pollution due to the environmental risk factors that have been explained by literature. Morbidity studies should be conducted with a focus on disability analysis at a local level, to improve the estimation of the disease burden attributable to environmental pollution, based on data that accurately show those events associated to environmental factors.