High pesticide exposure events and olfactory impairment among U.S. farmers

Abstract

BACKGROUND: Olfactory impairment (OI) is common among older adults and independently predicts all-cause mortality and the risk of several major neurodegenerative diseases. Pesticide exposure may impair olfaction, but empirical evidence is lacking. OBJECTIVE: We aimed to examine high pesticide exposure events (HPEEs) in relation to self-reported OI in participants in the Agricultural Health Study (AHS). METHODS: We conducted multivariable logistic regression to examine the associations between HPEEs reported at enrollment (1993–1997) and self-reported OI at the latest AHS follow-up (2013–2015) among 11,232 farmers, using farmers without HPEEs as the reference or unexposed group. RESULTS: A total of 1,186 (10.6%) farmers reported OI. A history of HPEEs reported at enrollment was associated with a higher likelihood of reporting OI two decades later {odds ratio (OR) =1:49 [95% confidence interval (CI): 1.28, 1.73]}. In the analyses on the HPEE involving the highest exposure, the association appears to be stronger when there was a >4-h delay between HPEE and washing with soap and water [e.g., OR = 2:07 (95% CI: 1.48, 2.89) for 4–6 h vs. OR = 1:39 (95% CI: 1.11, 1.75) for <30 min]. Further, significant associations were observed both for HPEEs involving the respiratory or digestive tract [OR = 1:53 (95% CI: 1.22, 1.92)] and dermal contact [OR = 1:47 (95% CI: 1.22, 1.78)]. Finally, we found significant associations with several specific pesticides involved in the highest exposed HPEEs, including two organochlorine insecticides (DDT and lindane) and four herbicides (alachlor, metolachlor, 2,4-D, and pendimethalin). HPEEs that occurred after enrollment were also associated with OI development. CONCLUSIONS: HPEEs may cause long-lasting olfactory deficit. Future studies should confirm these findings with objectively assessed OI and also investigate potential mechanisms. https://doi.org/10.1289/EHP3713.