High-level pesticide exposure may harm farm workers’ sense of smell down the road: study

East Lansing, MI — Farm workers exposed to an unusually high level of pesticides may be 50% more likely to lose, either partially or completely, their sense of smell later in life – an early symptom of Parkinson’s disease and dementia, results of a recent Michigan State University study show.

Researchers surveyed 11,323 farm workers over a 20-year period as part of the Agricultural Health Study. Participants were asked at the beginning of the study whether they had experienced a high pesticide exposure event such as a large amount of pesticides spilling onto them. In a follow-up two decades later, the workers were asked if they had noticed any decreased sense of smell.

Between 1993 and 1997, 1,588 (15.8%) of the workers reported that they had experienced a high pesticide exposure event. During the follow-up from 2013 to 2015, 1,186 (10.6%) confirmed an impairment in their sense of smell.

Researchers found that washing with soap and water immediately after a high pesticide exposure event lessened the potential impairment. In contrast, those who washed within three hours had a 40% higher risk of future problems with smell, and exposed workers who waited four or more hours to wash saw their risk potentially double.

“Studying farmers gives us more reliable data on pesticide exposures than if we had studied the general population,” lead study author Honglei Chen, professor of epidemiology at MSU, said in a press release. “Because they use pesticides more and it’s part of their job, they’re more likely to remember what pesticides they used and, in cases of high exposures, report the specific events.”

The researchers identified two insecticides – DDT and lindane – and four weed killers – alachlor; metolachlor; 2,4-D; and pendimethalin – that showed greater association with poor sense of smell.

The study was published online Jan. 16 in the journal Environmental Health Perspectives.