UNUSUALLY high pesticide exposure is linked to a poor sense of smell among aging farmers in a 20-year American study,
At the start of the study of 11,200 farmers over 20 years, Michigan State University researchers found 16 per cent reported experiencing a high pesticide exposure event (HPEE), such as a large amount of pesticide spilling on their body.
Two decades later, they were asked if they suffered olfactory impairment, a partial to complete loss of sense of smell.
Farmers reporting an HPEE were 50 per cent more likely to have a poor sense of smell at the end of the study.
The research also showed immediate washing with soap and water might mitigate risk. Compared to farmers who never experienced an HPEE, those who did and washed within three hours had about a 40 per cent higher risk of having problems with smell.
Professor of epidemiology Honglei Chen says those who waited four or more hours saw their risk potentially double.
“Studying farmers gives us more reliable data on pesticide exposures than if we had studied the general population,” Chen says.
“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.”
Chen identified two insecticides, DDT and lindane, and four weed killers – alachlor, metolachlor, 2,4-D and pendimethalin – that showed a greater association with poor sense of smell.
“Farmers reporting incidents involving unusually high exposures to certain organochlorine insecticides such as DDT and herbicides, including 2,4-D, were more likely to have a poor sense of smell,” he said.
“More research needs to be done, but some studies have linked these chemicals to Parkinson’s and possibly dementia too.”
While poor sense of smell has been shown to be an early symptom of Parkinson’s and dementia, Chen said his study only addresses an association between pesticide exposure and impaired smell, not to neurodegenerative diseases.
“Olfactory impairment affects up to 25 per cent of our older population, and our understanding of what the consequences are is still very limited,” he said.