Summary
This study examined whether pesticide exposure is associated with the development of inflammatory bowel disease (IBD) among participants in the Agricultural Health Study, which included 68,480 pesticide applicators and their spouses. Researchers tracked self-reported IBD cases from 1993–2022 and evaluated associations with the use of 50 different pesticides.
A total of 454 IBD cases were identified. The analysis found that exposure to several pesticides—particularly organochlorine and organophosphate insecticides, one fungicide, and several herbicides—was associated with higher risks of developing IBD. The strongest associations were observed for dieldrin, toxaphene, parathion, and terbufos, which showed significantly increased hazard ratios compared with people who never used them.
When examining cumulative exposure levels among male applicators, the study did not find clear dose–response trends for most pesticides, though terbufos exposure consistently showed elevated risk across all exposure levels.
Overall, the findings suggest that exposure to certain pesticides may increase the risk of inflammatory bowel disease, highlighting a potential environmental risk factor for this autoimmune condition and underscoring the importance of further research given the widespread use of pesticides.
PMID: 38354883
PMCID: PMC11065595
DOI: 10.1016/j.envres.2024.118464
Abstract
Background: Pesticide exposure has been linked to some autoimmune diseases and colorectal cancer, possibly via alteration of gut microbiota or other mechanisms. While pesticides have been linked to gut dysbiosis and inflammation in animal models, few epidemiologic studies have examined pesticides in relation to inflammatory bowel disease (IBD).
Objectives: We evaluated use of pesticides and incident IBD in 68,480 eligible pesticide applicators and spouses enrolled in the Agricultural Health Study.
Methods: Self-reported IBD cases were identified from follow-up questionnaires between enrollment (1993-1997) and 2022. We evaluated IBD incidence in relation to self-reported ever use of 50 pesticides among applicators and spouses. We also explored associations with intensity-weighted lifetime days (IWLD) of pesticide use among male applicators. Covariate-adjusted hazard ratios (HR) and 95% confidence intervals (CI) were calculated using Cox regression.
Results: We identified 454 IBD cases, including 227 among male applicators. In analyses with applicators and spouses combined, associations were positive (HR > 1.2) for ever vs. never use of five organochlorine insecticides, three organophosphate insecticides, one fungicide, and five herbicides. HRs were highest for dieldrin (HR = 1.59, 95%CI: 1.03, 2.44), toxaphene (HR = 1.61, 95%CI: 1.17, 2.21), parathion (HR = 1.42, 95%CI: 1.03, 1.95), and terbufos (HR = 1.53, 95%CI: 1.19, 1.96). We had limited power in many IWLD of pesticide use analyses and did not find clear evidence of exposure-response trends; however, we observed elevated HRs in all tertiles of IWLD use of terbufos compared to never use (T1 vs. never use HR = 1.52, 95%CI: 1.03, 2.24; T2 vs. never use HR = 1.53, 95%CI: 1.04, 2.26; T3 vs. never use HR = 1.51, 95%CI: 1.03, 2.23).
Conclusions: Exposure to specific pesticides was associated with elevated hazards of IBD. These findings may have public health importance given the widespread use of pesticides and the limited number of known modifiable environmental risk factors for IBD.