Exposure to high levels of pesticides may cause farmers over time to lose their sense of smell, according to a study published recently in Environmental Health Perspectives. The study examined high pesticide exposure events (HPEEs) in relation to self-reported olfactory impairment (OI) in participants in the long running, multi-generational Agricultural Health Study (AHS) conducted by the National Institutes of Health (NIH).

About the study

A little more than ten percent of the farmers surveyed reported OI. A history of HPEEs reported at enrollment was associated with a higher likelihood of reporting OI two decades later. The study found higher exposure rates when there was a delay between HPEE and washing with soap and water. Significant associations were observed both for HPEEs involving the respiratory or digestive tract and dermal contact.

Additionally, associations were found with several specific pesticides involved in the highest exposed HPEE,sincluding two organochlorine insecticides (DDT and lindane) and four herbicides (alachlormetolachlor2,4-Dand pendimethalin).

“Future studies should confirm these findings with objectively assessed OI and also investigate potential mechanisms,” notes the study.

Why it matters

The human sense of smell decreases with age. OI is a significant health factor because it “independently predicts all-cause mortality and the risk of several major neurodegenerative diseases,” according to the study. Existing research suggests that OI may be an early symptom for Parkinson’s disease and Alzheimer’s disease. “OI research,” say the study’s authors,“ could have major implications for understanding the pathophysiology of early stages of neurodegeneration.”

Beyond that, OI also adversely affects nutritionmood and behaviorsexualityemotional and physical well-being and the ability to detect environmental hazards.

The study's authors are: Srishti Shrestha, Freya Kamel, David M. Umbach, Laura E. Beane Freeman, Stella Koutros, Michael Alavanja, Aaron Blair, Dale P. Sandler, and Honglei Chen.