Respiratory and allergic outcomes among farmworkers exposed to pesticides in Costa Rica.

Aim: We examined the association of exposure to a pesticide mixture with respiratory and allergic outcomes among farmworkers from Costa Rica.

Methods: We conducted a cross-sectional study of 299 farmworkers between May and August 2016. We collected information on sociodemographic factors, pesticide use, and the presence of respiratory and allergic symptoms during the last 12 months via questionnaire. We calculated specific gravity-adjusted average concentrations of 15 pesticide biomarkers measured in urine samples collected during two visits (4-5 weeks apart). We fitted "traditional" Bayesian and Bayesian Weighted Quantile Sum (BWQS) regression models to assess the association of exposure to independent and summed pesticide mixture components with the outcomes of interest. We adjusted all models for age and smoking status.

Results: In "traditional" Bayesian analyses, higher urinary concentrations of 2-isopropyl-4-methyl-6-hydroxypyrimidine (IMPY, metabolite of organophosphate insecticide diazinon) were associated with increased odds of a higher asthma symptom score [adjusted OR per two-fold increase in concentrations = 1.15; 95 % credible interval (CrI): 1.04, 1.27)], asthma symptoms or medication use (aOR = 1.37; 95 % CrI: 1.13, 1.67), and rhinitis (aOR = 1.34; 95 % CrI: 1.15, 1.56). Higher urinary concentrations of boscalid-5-hydroxy (metabolite of fungicide boscalid) were associated with increased odds of asthma symptoms or medication use (aOR = 1.24; 95 % CrI: 1.00, 1.55), whereas higher concentrations of 4-hydroxypyrimethanil (metabolite of the fungicide pyrimethanil) were associated with increased odds of eczema (aOR = 1.11; 95 % CrI: 0.99, 1.24). Several inverse associations of herbicide concentrations with respiratory and allergic outcomes were observed. In BWQS analyses, a positive association was found between exposure to the pesticide mixture and increased odds of rhinitis (aOR = 1.96; 95 % CrI: 1.14, 3.20), with IMPY being the largest contributor.

Conclusion: Our findings indicate that exposure to pesticides may have both independent and summed mixture effects on respiratory and allergic health among farmworkers.