Keywords
pesticide exposure, insecticide effect, herbicide effect, fungicide effect, rhinitis, farmer health
This article is included in the Agriculture, Food and Nutrition gateway.
This article is included in the Global Public Health gateway.
Pesticide exposure has been suspected as a cause of rhinitis, a common disease that affects the health and well-being of millions of people around the world. This cross-sectional study aimed to examine the association between pesticide use and rhinitis prevalence among farmers in Phitsanulok province, Thailand.
Data on historical pesticide use and rhinitis were collected by an in-person interview questionnaire. Data from 9,649 participants were included in the analysis. The association between pesticide exposure and rhinitis was determined by multiple variable logistic regression, adjusted for potential confounding factors.
The study found an association between pesticide exposure and the prevalence of rhinitis. The association was consistent across various types of pesticides (insecticides, herbicides, fungicides, rodenticides, and molluscicides) and individual pesticides. Some of the relationships were in a dose-response pattern. This finding was new as previous studies often reported the association of only a few specific pesticides.
The results from this large cross-sectional study supports existing literature on the potential effects of pesticides on rhinitis. In addition, the analysis showed that the rhinitis effect might be in fact related to the properties of the types of pesticides rather than individual chemical toxicity. The impact of pesticides on rhinitis should receive more attention from public health and other organizations responsible for the farmers’ health.
pesticide exposure, insecticide effect, herbicide effect, fungicide effect, rhinitis, farmer health
In the Introduction, a statement on rational of study was added to justify the study objective.
The Methods section is updated with more detailed information on participants selection and data collection.
The discussion section is updated with more information on study limitations and strengths. Potential bias due to multiple testing, and common method bias has been discussed. In addition, statements on study strength and importance of study rhinitis were also added.
The conclusion statement was revised to precisely reflect the actual results of the study.
There were no changes made in tables, title, author list and order.
See the authors' detailed response to the review by Bente Elisabeth Moen
See the authors' detailed response to the review by Patricia Segura-Medina
Rhinitis is a common disease that affects general health, and quality of life. Approximately, 10% to 30% of the different populations worldwide suffer from this disease1. One study in Bangkok, Thailand, has reported a prevalence of chronic rhinitis to be approximately 13%2. In clinical terms, rhinitis refers to the inflammatory disease of the nasal mucosa, which can cause the following symptoms: nasal congestion, rhinorrhea, and sneezing3. Although rhinitis does not have a strict classification criterion, it can be classified into allergic rhinitis (AR), and nonallergic rhinitis (NAR). Both have the same nasal symptoms, with the difference that AR is triggered by allergens. Several factors can trigger NAR, including cold air, climate change, cooking smells, chemical odour, cigarette smoke, volatile organic chemicals, exercise, alcohol ingestion4, and cooking fumes5. NAR can be further classified by their pathological mechanisms into several subtypes, including occupation rhinitis, hormonal rhinitis, drug-induced rhinitis, food-induced rhinitis, emotion-induced rhinitis, etc6. Approximately 43% of all rhinitis cases are AR, and 23% are NAR, while 34% of the cases are a mixture of both4.
Studies found pesticide exposure to increase the risk of several respiratory problems, e.g., asthma, chronic bronchitis7, and rhinitis8. A study among grape farmers in Greece reported a higher prevalence of AR among those who used pesticides9. Another study in France found that children living in areas surrounding vineyards had a higher rate of rhinitis symptoms (OR=3.56; 95% CI 1.04–12.12)10. In an occupational setting, a study found number of hours working in the greenhouse per day to be associated with rhinitis (OR, 1.85; 95% CI, 1.05–3.23)11. A large survey of farmworkers in the United States of America (U.S.A) found that insecticide and herbicide use has significantly increased the risk of allergic rhinitis and asthma12.
A recent systematic review by Rodrigues et al.13 found pesticides exposure to associate with only asthma in children and adolescents but not allergic rhinitis. In addition, so far there were only a few individual pesticides identified as potential risk factors for rhinitis. Pesticides that were found to have a positive association with rhinitis were bipyridyl herbicides such as paraquat, and the broad-spectrum herbicides 2,4-D, glyphosate, dithiocarbamate fungicides including benomyl, and insecticide diazinon9,14,15. It has been suggested that exposure to OP insecticides might exaggerated nasal glandular response resulting in increased rhinitis16.
Currently, evidence on the effects of pesticides on rhinitis is limited. Rhinitis might be caused by allergens or irritants and there is no logic that all pesticides will equally affect the disease. The main objective of this cross-sectional study was to determine the association between pesticide use and rhinitis among farmers in Phitsanulok, Thailand. The use of a large sample size in this study has provided the opportunity to assess the risks that different groups and subgroups of pesticide exposure have had on these individuals. The study results would be useful for disease prevention, and comparison with other studies.
This study was a cross-sectional study. Participants were farmers in Phitsanulok province, located about 370 km north of Bangkok, Thailand. In 2019, the province had approximately 865,368 people (342,787 households) from nine districts. The major crops in the province are rice, sugarcane, and maize17,18.
Multistage sampling was used for the random selection of participants. The three districts were randomly selected from the nine districts of Phitsanulok province. From all the selected districts, 18 out of 26 (69.2%) sub-districts were further selected. In each sub-district, all local hospitals participated in the study and provided support for data collection. In each sub-district, farmers were selected by village health volunteers (VHV), who were working in the hospitals. In Thailand, VHVs are trained volunteers who provide primary healthcare service, including data survey, and they are familiar with villagers. By using the data from the local authority and personal contacts, the VHV selected the farmers and set up the interviewing plan. To collect the data, they visited the target household and conducted the interview. After finishing, they moved on to the next one, until the target number of participants was reached. By using this snowball sampling technique, the study collected data from 9,649 participants. In each family, only one adult aged 20 years or older who does agricultural work, was interviewed. The interview mostly took place in the participant’s home. However, sometimes it was done at a local temple or hospital. In these situations, an interview was conducted in a privated circumstance. In the data collection protocol of the study, a group interview was not allowed. Data was collected from October 2020 to February 2021, by 210 VHV. Before data collection, these volunteers had to attend a one-day training program to be informed on the purpose of the study and to learn how to properly interview and collect data by using an online questionnaire.
The minimum sample size was calculated to be 10,002, based on the following assumptions: significance level = 95%; power of detection = 80%; ratio of unexposed/exposed = 1; percent of unexposed with outcome = 10%2; odds ratio = 1.29.
Data were collected by using an in-person interview questionnaire (provided as Extended data in English and Thai)19. Data on rhinitis was collected by using a modified form of SFAR (Score For Allergic Rhinitis) questionnaire which is recommended for population studies, where medical diagnosis and objective measurements were absent or difficult to obtain20. The SFAR encompasses questions regarding the eight features of AR. Each of the items can be quantitatively scored and yield a maximum score of 16. AR refers to those with a score of 7 or more. Self-reported rhinitis was defined as the participant answering “yes” to the question: “during the last 12 months, have you ever had symptoms such as sneezing, or a runny, or blocked nose when you did not have a cold or the flu?”.
For pesticide exposure, the data was collected by a questionnaire used in our previous study21. Data on the long-term use of pesticides, either by types of pesticides (insecticide, herbicide, fungicide, rodenticide, and molluscicide), or by specific individual pesticides, were collected. A list of 39 individual pesticides were chosen from those that were commonly used in Thailand and were reported to cause adverse health effects15,21. Participants were asked whether they have ever used pesticides, defined as a mixture, or spray pesticides, in their lifetime. To help them recall better and distinguish the individual pesticide, either chemical name, common name, or trade name of individual pesticide were included in the question, and the interviewer had to read all of them to the participants when asking the question. Participants were also asked to provide data on the duration (days/year and total years) of pesticide use. This information was used to calculate total days, and quartiles of days using each pesticide in the farmers’ lifetime.
Lifetime pesticide use measured in days = [Number of days per year] × [total years]
The individual pesticides were six organochlorine insecticides (Aldrin, Chlordane, DDT, Dieldrin, Endosulfan, and Heptachlor); eleven organophosphate insecticides (Abamectin, Chlorpyrifos, Dicrotophos, Dichlorvos, EPN, Imidacloprid, Methamidophos, Mevinphos, Monocrotophos, Parathion/Folidol, and Profenofos); four carbamate insecticides (Carbaryl/sevin, Carbofuran, Carbosulfan, and Methomyl); and one pyrethroid insecticide Permethrin. The study also included eight herbicides (2,4 D, Acetrochlor, Alachlor, Ametryn, Butachlor, Diuron, Glyphosate, and Paraquat) and nine fungicides (Benomyl, Bordeaux mixture, Carbendazim, Copper sulphate, Mancozeb, Maneb, Metalaxyl, Propineb, and Thiophanate).
Demographic data were analysed using descriptive statistics. Comparison of categorical data was analysed using the Chi-square test. The association between pesticide exposure and rhinitis prevalence was analysed using multivariable logistic regression, and both crude and adjusted odds ratios (OR) and 95% confidence interval (CI) were reported. Adjusted variables were gender (male, female), age (continuous), marital status (married, single, divorced/widow/separated), education (non-educated, primary school, secondary school, college degree or higher), family income (<5000 THB, 5001–10000 THB, 10001–3000 THB, >30000 THB), cigarette smoking (non-smoker, ex-smoker, current smoker), alcohol consumption (non- drinker, ex- drinker, regular- drinker).
To control a potential confounding effect of the use of other pesticides, correlation matrices of types and individual pesticides were developed. Those pesticides with highly correlation (Spearman coefficient ≥0.30) were identified and included the regression model. A list of potential confounding pesticides was presented in Table S1 and Table S2. The dose-response relationship was analysed using chi-squared tests for trend using an ordinal term for the quartile days as a category. This statistical analysis was available only when there was sufficient frequency of exposure and disease. Data analysis was performed using IBM SPSS version 26, and OpenEpi (online version 3.01). All statistical values were two-tailed, and a p-value <0.05, was considered as statistically significant.
It was found that the proportion of female participants was slightly higher than that of the male participants (Table 1 and the underlying data22). Most of these individuals were aged 40 years and older with an average age of 55 (±12 years), married (78.0%), finished primary school or with lower education (77.2), and had an average family income of 10,000 THB or less. A total of 8.7% of these females are cigarette smokers, and 13.7% consume alcohol.
The prevalence of rhinitis was found to be 6.3% (609/9649) (Table 2). Based on SFAR scoring, only about 36% of them had allergic rhinitis (SFAR score ≥7). Of the three symptoms, sneezing was found to be the most common (4.0%), followed by nasal congestion (3.0%), and runny nose (2.9%). Only 16.3% had eye irritations together with rhinitis symptoms. The months with the highest frequency of symptoms were March to July (summer season in Thailand), and November to February (winter season). The prevalence of rhinitis was significantly associated with marital status, education, family income, cigarette smoking, and alcohol consumption (Table 3).
N (%), N = 9649 | |
---|---|
Having symptoms in the past year | |
Sneezing | 390 (4.0) |
Stuffy nose | 294 (3.0) |
Runny nose | 282 (2.9) |
Rhinitis (having one of the above three symptoms) | 609 (6.3) |
Types of rhinitis (N=411) | |
Allergic rhnitis* | 147 (35.8) |
Non allergic rhnitis | 264 (64.2) |
SFAR score (N=411) | |
1-3 | 49 (11.9) |
3-6 | 215 (52.3) |
7-9 | 107 (26.0) |
10+ | 40 (9.7) |
Having eyes irritation while having rhinitis | 99 (16.3) |
Month of having the symptoms (n=609) | |
January | 177 (29.3) |
February | 103 (17.0) |
March | 76 (12.6) |
April | 100 (16.5) |
May | 258 (42.6) |
June | 272 (44.9) |
July | 245 (40.5) |
August | 95 (15.7) |
September | 61 (10.1) |
October | 53 (8.8) |
November | 99 (16.4) |
December | 137 (22.6) |
Allergens activated the symptoms (n=609) | |
Dust | 467 (76.7) |
Mites | 282 (46.3) |
Smoke | 275 (45.2) |
Cooking fume | 190 (31.4) |
Straw or grass | 101 (16.6) |
Pet | 33 (5.4) |
Pollen | 34 (5.6) |
Patients who believed they have allergy | 104 (17.1) |
Patients that had allergic testing | 36 (5.9) |
Patients with positive result | 24 (3.9) |
Patients who were diagnosed with asthma or allergy | 39 (6.7) |
Not rhinitis | Rhinitis | P-valuea | |
---|---|---|---|
Gender | 0.176 | ||
Male | 3884 (93.3) | 279 (6.7) | |
Female | 5156 (94.0) | 330 (6.0) | |
Age | 0.488 | ||
20–30 | 285 (93.1) | 21 (6.9) | |
31–40 | 777 (92.5) | 63 (7.5) | |
41–50 | 1867 (93.4) | 133 (6.7) | |
51–60 | 2983 (94.0) | 191 (6.0) | |
>60 | 3128 (94.0) | 201 (6.0) | |
Marital status | 0.010* | ||
Married | 7021 (93.3) | 502 (6.7) | |
Single | 693 (94.0) | 44 (6.0) | |
Divorce/widow/separated | 1326 (95.5) | 63 (4.5) | |
Education complete | <0.001* | ||
Non-educated | 381 (94.8) | 21 (5.2) | |
Primary school | 6655 (94.5) | 391 (5.5) | |
Secondary school | 1877 (91.0) | 186 (9.0) | |
College degree or higher | 127 (92.0) | 11 (8.0) | |
Family income, THB/month | <0.001* | ||
<5000 | 3067 (96.8) | 101 (3.2) | |
5001–10000 | 5330 (92.9) | 409 (7.1) | |
10001–30000 | 576 (86.2) | 92 (13.8) | |
>30000 | 67 (90.5) | 7 (9.5) | |
Cigarette smoking | 0.001* | ||
Non-smoker | 7997 (94.0) | 514 (6.0) | |
Ex-smoker | 269 (88.8) | 34 (11.2) | |
Current smoker | 774 (92.7) | 61 (7.3) | |
Alcohol consumption | <0.001* | ||
Non-drinker | 7415 (94.3) | 450 (5.7) | |
Ex-drinker | 406 (88.1) | 55 (11.9) | |
Regular-drinker | 1219 (92.1) | 104 (7.9) |
All five types of pesticides included in the study were found to be significantly related to rhinitis prevalence. Fungicides were significant until adjustments for using other pesticides were made, then it was shown to be not significant (Table 4). Any pesticide use increased rhinitis risk by 1.79 folds (95% CI 1.09-2.94). The lowest OR value was 1.67 (95% CI 1.41-1.99) for fungicide and 7.19 (95% CI 4.67-11.06) for insecticide. Many of the associations were in a dose-response pattern. The association remained significant after adjusting for use of other types of pesticides.
Pesticide | Not rhinitis | Rhinitis | OR (Crude) | OR (Model1)a | OR (Model2)b |
---|---|---|---|---|---|
Any pesticide | |||||
Yes | 8575 (93.5) | 592 (6.5) | 1.88 (1.15-3.07)c | 1.79 (1.09-2.94) | NA |
No | 463 (96.5) | 17 (3.5) | 1.0 | 1.0 | |
Insecticide | |||||
Yes | 7044 (92.3) | 587 (7.7) | 7.56 (4.93-11.61) | 7.19 (4.67-11.06) | 5.48 (3.47-8.67) |
No | 1996 (98.9) | 22 (1.1) | 1.0 | 1.0 | 1.0 |
Q1 | 1837 (95.1) | 94 (4.9) | 4.64 (2.91-7.42) | 4.22 (2.63-6.77) | 3.33 (2.03-5.47) |
Q2 | 2009 (93.7) | 136 (6.3) | 6.14 (3.90-9.68) | 5.76 (3.64-9.11) | 4.51 (2.78-7.32) |
Q3 | 2048 (90.5) | 215(9.5) | 9.53 (6.12-14.83) | 9.27 (5.92-14.49) | 7.16 (4.45-11.54) |
Q4 | 1150 (89.0) | 142 (11.0) | 11.20 (7.11-17.66) | 11.31 (7.14-17.92) | 8.85 (5.44-14.39) |
P for trend | <0.001 | ||||
Herbicide | |||||
Yes | 7786 (93.0) | 586 (7.0) | 4.74 (3.03-7.44) | 4.25 (2.71-6.69) | 3.64 (2.30-5.77) |
No | 1254 (98.4) | 20 (1.6) | 1.0 | 1.0 | 1.0 |
Q1 | 2227 (95.2) | 112 (4.8) | 3.15 (1.95-5.10) | 2.71 (1.67-4.41) | 2.28 (1.40-3.74) |
Q2 | 1864 (93.9) | 122 (6.1) | 4.10 (2.54-6.62) | 3.65 (2.26-5.91) | 3.09 (1.90-5.04) |
Q3 | 2555 (92.0) | 221 (8.0) | 5.42 (3.42-8.61) | 4.83 (3.03-7.70) | 4.09 (2.55-6.57) |
Q4 | 1140 (89.5) | 134 (10.5) | 7.37 (4.58-11.87) | 6.98 (4.31-11.28) | 5.99 (3.69-9.75) |
P for trend | <0.001 | ||||
Fungicide | |||||
Yes | 3933 (91.8) | 353 (8.2) | 1.79 (1.52-2.11) | 1.67 (1.41-1.99) | 1.03 (0.83-1.27) |
No | 5107 (95.2) | 256 (4.8) | 1.0 | 1.0 | 1.0 |
Q1 | 1006 (93.7) | 68 (6.3) | 1.35 (1.02-1.78) | 1.25 (0.94-1.66) | 0.80 (0.59-1.09) |
Q2 | 1020 (92.3) | 100 (7.7) | 1.66 (1.31-2.11) | 1.57 (1.22-2.01) | 1.01 (0.77-1.32) |
Q3 | 766 (90.7) | 79 (9.3) | 2.06 (1.58-2.68) | 1.94 (1.48-2.55) | 1.14 (0.84-1.55) |
Q4 | 959 (90.0) | 106 (10.0) | 2.21 (1.74-2.79) | 2.03 (1.59-2.60) | 1.22 (0.92-1.61) |
P for trend | <0.001 | ||||
Rodenticide | |||||
Yes | 1669 (87.9) | 230 (12.1) | 2.68 (2.26-3.18) | 2.63 (2.20-3.14) | 2.04 (1.63-2.55) |
No | 7371 (95.1) | 379 (4.9) | 1.0 | 1.0 | 1.0 |
Q1 | 514 (88.9) | 64 (11.1) | 2.42 (1.83-3.20) | 2.40 (1.80-3.20) | 1.86 (1.35-2.56) |
Q2 | 319 (83.5) | 63 (16.5) | 3.84 (2.88-5.13) | 3.71 (2.76-5.01) | 2.92 (2.11-4.04) |
Q3 | 448 (90.3) | 48 (9.7) | 2.08 (1.52-2.86) | 2.13 (1.54-2.94) | 1.69 (1.20-2.39) |
Q4 | 388 (87.6) | 55 (12.4) | 2.76 (2.04-3.72) | 2.58 (1.90-3.52) | 1.94 (1.38-2.74) |
P for trend | <0.001 | ||||
Molluscicide | |||||
Yes | 1944 (889.1) | 238 (10.9) | 2.34 (1.98-2.78) | 2.29 (1.92-2.73) | NA |
No | 7096 (95.0) | 371 (5.0) | 1.0 | 1.0 | |
Q1 | 573 (86.6) | 89 (13.4) | 2.97 (2.32-3.80) | 2.98 (2.31-3.85) | NA |
Q2 | 404 (87.6) | 57 (12.4) | 2.70 (2.01-3.63) | 2.62 (1.93-3.55) | NA |
Q3 | 544 (92.5) | 44 (7.5) | 1.55 (1.12-2.14) | 1.51 (1.08-2.10) | NA |
Q4 | 423 (89.8) | 48 (10.2) | 2.17 (1.58-2.98) | 2.06 (1.49-2.85) | NA |
P for trend | <0.001 |
a Model1: Adjusted variables were gender (male, female), age (continuous), marital status (married, single, divorce/willow/separated), education (non-educated, primary school, secondary school, college degree or higher), family income (<5000 THB, 5001-10000 THB, 10001-30000 THB, >30000 THB), cigarette smoking (non-smoker, ex-smoker, current smoker), alcohol consumption (non-drinker, ex-drinker, regular-drinker).
b Model2: Adjusted for all factors in the model1 and using other types of pesticide.
c Significant OR were indicated in bold numbers.
For individual pesticides, the study found 32 out of 39 to be significantly associated with rhinitis after adjusted for demographic factors. Those pesticides were six herbicides, nine organophosphates (OP) insecticides, four carbamate insecticides, one pyrethroid insecticide, five OC insecticides, and seven fungicides (Table 5). Most of the OR decreased but remained significant after the adjustment for using other potential confounding pesticides. The association of some pesticides were in a dose-response pattern (Table 6).
Not rhinitis | Rhinitis | OR (Crude) | OR (Model1)a | OR (Model2)b | |
---|---|---|---|---|---|
Insecticides | |||||
Organochlorine | |||||
Aldrin | 6.1 | 29.4 | 6.36 (3.75-10.79) | 4.83 (2.78-8.39) | 2.02 (0.97-4.19) |
Chlordane | 6.1 | 20.0 | 3.82 (2.40-6.07) | 3.43 (2.11-5.58) | 1.95 (1.07-3.55) |
Dieldrin | 6.1 | 28.2 | 6.04 (3.74-9.76) | 5.15 (3.11-8.53) | 2.70 (1.41-5.14) |
DDT | 5.6 | 23.2 | 5.05 (3.91-6.55) | 4.57 (3.43-5.99) | NA |
Endosulfan | 5.4 | 11.7 | 2.31 (1.91-2.79) | 2.17 (1.78-2.64) | 1.60 (1.26-2.03) |
Heptachlor | 6.1 | 20.2 | 3.87 (2.47-6.04) | 3.29 (2.07-5.24) | 1.83 (1.02-3.29) |
Organophosphate | |||||
Abamectin | 6.8 | 5.9 | 0.85 (0.73-1.01) | 0.82 (0.69-0.97) | 0.68 (0.56-0.81) |
Chlorpyrifos | 5.5 | 9.0 | 1.71 (1.43-2.04) | 1.53 (1.28-1.84) | 1.08 (0.85-1.37) |
Dicrotophos | 6.2 | 11.3 | 1.93 (1.23-3.04) | 1.70 (1.07-2.71) | 0.93 (0.52-1.63) |
Dichlorvos | 6.2 | 16.8 | 3.06 (1.83-5.12) | 2.77 (1.63-4.70) | 2.57 (1.40-4.71) |
EPN | 5.8 | 24.0 | 5.11 (3.81-6.86) | 4.15 (3.06-5.62) | NA |
Imidacloprid | 6.1 | 11.9 | 2.08 (1.52-2.85) | 1.88 (1.36-2.61) | 1.55 (1.09-2.20) |
Methamidophos | 6.0 | 12.8 | 2.30 (1.71-3.08) | 2.06 (1.522-2.79) | NA |
Mevinphos | 6.2 | 14.9 | 2.64 (1.59-4.39) | 2.32 (1.36-3.94) | 2.04 (1.14-3.62) |
Monocrotophos | 6.1 | 15.6 | 2.85 (1.96-4.13) | 2.46 (1.66-3.63) | 2.31 (1.52-3.52) |
Parathion/ Folidol | 4.7 | 17.6 | 4.37 (3.66-5.22) | 3.95 (3.29-4.74) | NA |
Profenofos | 6.3 | 8.0 | 1.30 (0.81-2.10) | 1.30 (0.80-2.12) | 0.96 (0.57-1.65) |
Carbamate | |||||
Carbaryl/ Sevin | 5.7 | 13.6 | 2.58 (2.05-3.23) | 2.31 (1.82-2.93) | NA |
Carbosulfan | 5.6 | 11.5 | 2.21 (1.81-2.69) | 2.09 (1.70-2.56) | 1.44 (1.13-1.85) |
Carbofuran | 5.6 | 13.7 | 2.67 (2.14-3.32) | 2.34 (1.86-2.93) | 1.84 (1.44-2.35) |
Methomyl | 5.9 | 12.7 | 2.31 (1.76-3.03) | 2.02 (1.53-2.68) | NA |
Pyrethroid | |||||
Permethrin | 6.0 | 8.9 | 1.54 (1.23-1.94) | 1.60 (1.27-2.03) | 1.15 (0.88-1.49) |
Herbicides | |||||
2,4-D | 5.1 | 7.4 | 1.48 (1.25-1.75) | 1.38 (1.61-1.63) | NA |
Acetrochlor | 6.3 | 6.3 | 0.99 (0.59-1.65) | 0.96 (0.57-1.62) | NA |
Alachlor | 6.1 | 8.2 | 1.37 (1.06-1.77) | 1.30 (1.00-1.69) | 1.47 (1.08-2.03) |
Ametryn | 6.3 | 7.0 | 1.13 (0.69-1.83) | 0.94 (0.57-1.54) | NA |
Butachlor | 5.2 | 9.8 | 1.99 (1.68-2.36) | 1.82 (1.52-2.17) | 1.44 (1.17-1.77) |
Diuron | 6.2 | 12.8 | 2.21 (1.30-3.76) | 1.73 (1.00-2.99) | 2.33 (1.14-4.76) |
Glyphosate | 2.7 | 6.8 | 2.59 (1.80-3.74) | 2.43 (1.68-3.52) | NA |
Paraquat | 4.4 | 7.5 | 1.78 (1.48-2.14) | 1.54 (1.28-1.87) | NA |
Fungicide | |||||
Benomyl | 6.2 | 13.3 | 2.32 (1.42-3.78) | 2.03 (1.22-3.36) | NA |
Bordeaux mixture | 6.2 | 29.0 | 6.23 (34.58-10.84) | 5.67 (3.16-10.16) | 3.44 (1.78-6.65) |
Carbendazim | 5.8 | 9.5 | 1.71 (1.40-2.11) | 1.57 (1.27-1.94) | 1.43 (1.14-1.79) |
Copper sulfate | 6.3 | 6.1 | 0.97 (0.68-1.38) | 0.82 (0.57-1.17) | NA |
Mancozeb | 5.9 | 11.7 | 2.13 (1.67-2.71) | 1.99 (1.55-2.55) | NA |
Maneb | 6.3 | 7.6 | 1.23 (0.86-1.76) | 1.24 (0.86-1.80) | NA |
Metalaxyl | 6.1 | 8.2 | 1.37 (1.05-1.79) | 1.35 (1.03-1.78) | NA |
Propineb | 6.1 | 11.0 | 1.90 (1.40-2.59) | 1.84 (1.34-2.53) | NA |
Thiophanate | 6.2 | 11.3 | 1.93 (1.28-2.91) | 1.90 (1.25-2.90) | NA |
a Model1: Adjusted variables were gender (male, female), age (continuous), marital status (married, single, divorce/willow/separated), education (non-educated, primary school, secondary school, college degree or higher), family income (<5,000 THB, 5,001-10,000 THB, 10,001-30,000 THB, >30,000 THB), cigarette smoking (non-smoker, ex-smoker, current smoker), alcohol consumption (non-drinker, ex-drinker, regular-drinker).
b Model2: Adjusting for all the factors in the model1 and using of other pesticides.
Pesticide | Exposure | Rhinitis | OR | P for trend* |
---|---|---|---|---|
Herbicide | ||||
2,4-D | Not use | 5.1 | 1.0 | 0.01 |
Q1 | 7.7 | 1.40 (1.10-1.78) | ||
Q2 | 8.5 | 1.60 (1.26-2.03) | ||
Q3 | 7.6 | 1.42 (1.10-1.83) | ||
Q4 | 5.6 | 1.07 (.80-1.42) | ||
Alachlor | Not use | 6.1 | 1.0 | 0.01 |
Q1 | 7.2 | 1.10 (.69-1.76) | ||
Q2 | 12.5 | 2.08 (1.29-3.35) | ||
Q3 | 4.7 | 0.76 (.45-1.30) | ||
Q4 | 13.4 | 2.11 (1.24-3.59) | ||
Butachlor | Not use | 5.2 | 1.0 | <0.001 |
Q1 | 9.7 | 1.85 (1.38-2.48) | ||
Q2 | 9.9 | 1.94 (1.47-2.55) | ||
Q3 | 10.1 | 1.80 (1.34-2.42) | ||
Q4 | 9.2 | 1.63 (1.16-2.27) | ||
Glyphosate | Not use | 2.7 | 1.0 | <0.001 |
Q1 | 5.4 | 1.84 (1.23-2.74) | ||
Q2 | 6.5 | 2.35 (1.57-3.53) | ||
Q3 | 8.4 | 3.07 (2.07-4.55) | ||
Q4 | 7.3 | 2.69 (1.80-4.03) | ||
Paraquat | Not use | 4.4 | 1.0 | <0.001 |
Q1 | 6.6 | 1.28 (1.00-1.64) | ||
Q2 | 6.9 | 1.43 (1.09-1.87) | ||
Q3 | 9.6 | 2.04 (1.61-2.60) | ||
Q4 | 7.2 | 1.51 (1.16-1.97) | ||
Organophosphate | ||||
Monocrotophos | Not use | 1.0 | <0.001 | |
Q1 | 11.9 | 1.80 (.80-4.07) | ||
Q2 | 15.5 | 2.51 (1.20-5.25) | ||
Q3 | 3.4 | 0.49 (.12-2.05) | ||
Q4 | 38.1 | 7.57 (3.88-14.77) | ||
Parathion/Folidol | Not use | 4.7 | 1.0 | <0.001 |
Q1 | 10.8 | 2.19 (1.52-3.16) | ||
Q2 | 13.2 | 2.92 (2.06-4.13) | ||
Q3 | 20.6 | 4.70 (3.44-6.42) | ||
Q4 | 26.8 | 6.91 (5.21-9.18) | ||
Carbamate | ||||
Carbaryl/Sevin | Not use | 5.7 | 1.0 | <0.001 |
Q1 | 10.1 | 1.63 (1.0-2.66) | ||
Q2 | 13.8 | 2.46 (1.57-3.87) | ||
Q3 | 11.9 | 1.84 (1.16-2.90) | ||
Q4 | 19.3 | 3.73 (2.48-5.63) | ||
Organochlorine | ||||
DDT | Not use | 5.6 | 1.0 | <0.001 |
Q1 | 21.3 | 3.70 (2.20-6.24) | ||
Q2 | 21.1 | 4.72 (2.91- 7.66) | ||
Q3 | 16.3 | 3.07 (1.78-5.29) | ||
Q4 | 42.4 | 9.50 (5.47-16.50) | ||
Endosulfan | Not use | 5.4 | 1.0 | <0.001 |
Q1 | 15.6 | 2.93 (2.21-3.89) | ||
Q2 | 6.5 | 1.23 (0.78-1.95) | ||
Q3 | 11.5 | 2.06 (1.41-3.00) | ||
Q4 | 11.4 | 2.20 (1.53-3.17) | ||
Fungicide | ||||
Carbendazim | Not use | 5.8 | 1.0 | <0.001 |
Q1 | 12.0 | 1.94 (1.38-2.73) | ||
Q2 | 8.4 | 1.50 (1.01-2.21) | ||
Q3 | 10.4 | 1.70 (1.18-2.45) | ||
Q4 | 6.5 | 0.98 (0.58-1.66) | ||
Metalaxyl | Not use | 6.1 | 1.0 | <0.001 |
Q1 | 7.1 | 1.18 (0.70-2.01) | ||
Q2 | 4.6 | 0.72 (0.37-1.43) | ||
Q3 | 7.7 | 1.23 (0.74-2.04) | ||
Q4 | 15.6 | 2.80 (1.75-4.49) | ||
Propineb | Not use | 6.1 | 1.0 | <0.001 |
Q1 | 18.4 | 1.05 (0.52-2.09) | ||
Q2 | 11.1 | 1.76 (0.89-3.46) | ||
Q3 | 12.1 | 2.27 (1.29-3.98) | ||
Q4 | 15.2 | 2.55 (1.44-4.54) | ||
Thiophanate | Not use | 6.2 | 1.0 | <0.001 |
Q1 | 13.3 | 2.07 (0.97-4.44) | ||
Q2 | 4.8 | 0.66 (0.20-2.15) | ||
Q3 | 8.6 | 1.71 (0.67-4.39) | ||
Q4 | 19.0 | 3.68 (1.84-7.34) |
The study found an association between the history of pesticide exposure and the prevalence of rhinitis. However, the results must be interpreted with caution due to serveral methodological weaknesses. The association was consistent across various types of pesticides, including insecticides, herbicides, fungicides, rodenticides, and molluscicide (Table 4). For individual pesticides, 32 out of 39 showed a significant relation with the disease and some with a dose-response pattern (Table 5, Table 6). The relationship exists after adjustment by potential confounding factors including the use of other pesticides. This finding was new as previous studies often reported the association of only a few specific pesticides. In addition, the OR in this study was higher. For instance, a study among grape farmers in Crete, Greece reported the highest risks for a lifetime exposure to paraquat and other bipyridyl herbicide, (OR, 2.2; 95% CI, 1.0 to 4.8), dithiocarbamate fungicides (OR, 2.5; 95% CI, 1.1 to 5.3) and carbamate insecticides (OR, 3.0; 95% CI, 1.4 to 6.5)9. In Agricultural Health Study, an elevated risk of rhinitis was observed among those who had a previous year exposure to herbicides (glyphosate, petroleum oil, 2,4-D), organophosphates insecticide (chlorpyrifos, diazinon, dichlorvos, malathion), carbamate insecticide (carbaryl/savin, carbofuran), fungicide (benomyl, captain)15,16.
The difference might be explained by the fact that most of the rhinitis cases were NAR and the exposure was chronic. The study results also implied that the rhinitic effect might be related to the general characteristics of pesticide types, rather than individual properties. Pesticides can affect AR and NAR by several biomechanisms, involving immune and nonimmune pathways, after acute and chronic exposure. For acute high dose exposure, pesticides and the solvent composition of the mixture that contains them can directly irritate the nose and throat23. Organophosphate and carbamate can cause cholinergic stimulation of the nasal mucosa and inhibit acetylcholinesterase thus causing more secretion of mucus in the nose and airway system24. Organochlorines and pyrethroids are another type of insecticides designed to target the nervous system of insects. Exposure to the compounds can cause hyperexcitability of nerve cells by interacting with the sodium channel and keeping it open longer25. Pyrethroid like other insecticides can irritate the respiratory tract, nose, and throat26. For herbicides, evidence from both animal and human studies showed that it can cause airway inflammation27. An experimental study found that acute exposure to herbicide 2,4-D increases the mast cells in the nasal epithelium of mice28. Paraquat was another herbicide with high toxicity to the respiratory system, and previous studies reported a positive association of it and several respiratory illnesses, including rhinitis9 and wheezing29. In an experimental study, it was found that fungicides have cytotoxic effects on bronchial epithelial cells30.
For chronic exposure, pesticide exposure can lead to exaggerated responses that increase the risk of rhinitis16. This continual response had been involved in the development of other chronic diseases, e.g., asthma, and bronchitis31. In a respiratory health study, OPs affect the bronchial lining and increase susceptibility to allergens or other stimuli32. OP can also induce airway hyperreactivity at doses lower than those required to cause acetylcholinesterase inhibition33,34.
Although it is hard to differentiate between AR and NAR, by using the SFAR questionnaire and its scoring method20, the study found that most of rhinitis cases in this study (64.2%) were NAR (Table 2). Further analysis by comparing the association of pesticides and types of rhinitis revealed that NAR had a stronger association (Table S3). This piece of information was often missed in the literature as most previous studies on rhinitis did not have enough data or focus on allergic types. The information helps explain why the results OR found in this study were higher than those previously reported.
This study has some limitations. The study did not have information and control for other potential confounding pollutants, such as grain and hay handling, and maintenance activities, e.g., repairing engines and pesticide equipment15. It was also very likely that participants were exposed to environmental pesticides. However, it is more likely that both the control and study groups will have a similar risk to those factors and the problems would bias toward the null. The information on pesticide exposure was dependent solely on the questionnaire method. However, as the study is focusing on long-term exposure, the questionnaire method was the best option35. This type of study could also be subject to recall bias as the case groups might be more aware of pesticide use than the control. However, the problem was less likely to occur because the information on the rhinitic effect of pesticides was not yet available in Thailand. In addition, the bias would only minimize but not increase the association36. Also, it was necessary to note that the questionnaire was first developed in France which has a different cultural background to Thailand, and this might affect the outcome. However, as most of the questions are of the “yes” or “no” type and ask about common symptoms, such as sneezing, runny, and blocked nose, application in a different cultural setting should not pose a serious problem. By using a cross-sectional design, the cause-effect association cannot be directly determined. In addition, the study collected data on pesticides used and rhinitis by using the same questionnaire method. This might cause common method bias which will affect the results and therefore the validity of the associations found. However, the bias was minimized to some extent by using a face-to-face interview instead of a self-administer questionnaire. The survey questionnaire was also designed so that exposure to information was collected before some of the health effects and rhinitis was noted. In addition, as the information is rather new, the workers were unlikely to be aware of the relationship between pesticide exposure and rhinitis. Lastly, as many statistical tests were performed to explore the association between various pesticides and rhinitis, the results were subjected to bias from multiple testing. The study results should be interpreted with caution.
The study is particularly strong in its design using a large sample size and many of the participants experienced using several pesticides in their lifetime. The survey also collected data regarding several individual chemicals from various types of pesticides. This posts a unique opportunity to study the effects of pesticides on rhinitis. The research is particularly important as rhinitis is an important public health issue and its prevalence is rising1. The disease not only affects quality of life and causes economic burden but also connected to other serious health problems, such as asthma and chronic bronchitis7. Understanding the effects of pesticides is crucial as the chemicals are widely used and almost everyone is at risk of exposure. The information is crucial for the development of effective prevention and control measurements of rhinitis.
The results from this large cross-sectional study supports existing literature on the potential effects of chronic exposure to pesticides on rhinitis. The effects of pesticides on rhinitis should receive more public attention, and the information be incorporated into the disease prevention program.
Figshare: Dataset for study on pesticide exposure and rhinitis in Phitsanulok Thailand https://doi.org/10.6084/m9.figshare.1452432622.
This project contains the following underlying data:
Figshare: Questionnaire-pesticide and rhinitis-Thailand. https://doi.org/10.6084/m9.figshare.14524335.v119.
This project contains the following extended data:
Questionnaire-pesticide and rhinitis-English (DOCX). (Study questionnaire in English.)
Questionnaire-pesticide and rhinitis-Thai (DOCX). (Study questionnaire in Thai.)
Data are available under the terms of the Creative Commons Zero “No right reserved” data waiver (CC0 1.0 Public domain dedication).
We would like to thank all study participants for the valuable information provided. Thanks also to the village health volunteers and local hospital staff for data collection. We would like also to thank Mr. Kevin Mark Roebl for language editing.
1 | 2 | 3 | 4 | 5 | ||
---|---|---|---|---|---|---|
1 | Insecticides | 1.00 | .50 | .42 | .24 | .26 |
2 | Herbicides | 1.00 | .30 | .17 | .19 | |
3 | Fungicides | 1.00 | .48 | .46 | ||
4 | Rodenticides | 1.00 | .55 | |||
5 | Molluscicides | 1.00 |
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Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Occupational health and neurotoxicology
Is the work clearly and accurately presented and does it cite the current literature?
Yes
Is the study design appropriate and is the work technically sound?
Yes
Are sufficient details of methods and analysis provided to allow replication by others?
Yes
If applicable, is the statistical analysis and its interpretation appropriate?
Yes
Are all the source data underlying the results available to ensure full reproducibility?
Yes
Are the conclusions drawn adequately supported by the results?
Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Asthma, COPD, Air pollution and health effects, Organophosphates and Asthma, Respiratory Toxicology
Is the work clearly and accurately presented and does it cite the current literature?
Yes
Is the study design appropriate and is the work technically sound?
Partly
Are sufficient details of methods and analysis provided to allow replication by others?
Partly
If applicable, is the statistical analysis and its interpretation appropriate?
Partly
Are all the source data underlying the results available to ensure full reproducibility?
Partly
Are the conclusions drawn adequately supported by the results?
Partly
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Occupational health and neurotoxicology
Alongside their report, reviewers assign a status to the article:
Invited Reviewers | ||
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Version 1 15 Jun 21 |
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