High Pesticide Exposure Events and Olfactory Impairment among U.S. Farmers

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.

We aimed to examine high pesticide exposure events (HPEEs) in relation to self-reported OI in participants in the Agricultural Health Study (AHS).

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.

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 [Formula: see text] [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 [Formula: see text] delay between HPEE and washing with soap and water [e.g., [Formula: see text] (95% CI: 1.48, 2.89) for 4-6 h vs. [Formula: see text] (95% CI: 1.11, 1.75) for [Formula: see text]]. Further, significant associations were observed both for HPEEs involving the respiratory or digestive tract [[Formula: see text] (95% CI: 1.22, 1.92)] and dermal contact [[Formula: see text] (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.

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.