Why are farm residents more likely to get Parkinson’s disease? That question, writes Robin Marantz Henig in the National Resources Defense Council’s magazine On Earth, is one epidemiologists started asking in the 1970s.

Today, scientific evidence is mounting that common pesticides are linked to Parkinson’s, Robin writes. An Agricultural Health Study by the National Cancer Institute and the National Institute for Environmental Health Sciences found some scary links:
People who had been exposed to pesticides sporadically over a lifetime were 1.2 times more likely to develop Parkinson’s than those who had not been. And when the exposure was heavy — the kind of lifetime exposure seen in career pesticide applicators, or a single massive exposure as the result of a spill — that increased risk jumped to 2.3 times.
The pesticides, which include Paraquat and Trifluralin, are commonly used in American agriculture. And while scientists have found more and more correlations between pesticides and Parkinson’s, causation is difficult to prove. Writes Robin:
As with many other scientific efforts to establish disease causation through population studies, there will probably never be a smoking gun that settles things once and for all. Population studies can detect associations between certain suspected agents and diseases such as cancer, but it’s hard to draw conclusions about what causes a disease from studies that can register only correlations.
Find out more about the link between pesticides and Parkinson’s by reading Robin’s feature article, which tells the plight of Jackie Christensen, a woman who worked at pesticide-sprayed farms as a teen, then was diagnosed with early-onset Parkinson’s when she was just 32. Jackie has since written a book — The First Year: Parkinson’s Disease: An Essential Guide for the Newly Diagnosed — and become an environmental activist.

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