A large epidemiologic study shows that individuals reporting regular
exposure to pesticides had a 70 percent higher incidence of
Parkinson's disease than those reporting no exposure. The study,
funded by NIEHS and conducted by researchers at the Harvard School of
Public Health, is the first large­scale prospective study to examine
the possible links between chronic pesticide exposure and Parkinson's
disease.

Previous studies suggested pesticide exposure as a risk factor for
the dreaded neurological disorder; however, the results were
inconclusive probably because of the relatively small number of
participants. The current study included more than 143,000 subjects;
7,800 reported exposure to pesticides. No increased risk for
Parkinson's disease was found from other occupational hazards
including exposure to other chemicals or solvents.

Research utilizing twins has established that genetics probably plays
a minor role in Parkinson's disease and thus has made environmental
exposures the focus of much interest. A compound known as MPTP, a by­
product of the production of a heroin­like illicit drug and
structurally similar to the herbicide paraquat, causes death of
neurons in the substantia nigra, the part of the brain affected by
Parkinsons's disease. For that reason pesticides and herbicides
exposures are considered likely to cause or contribute to the
development of Parkinson's disease.
Michael A. Schwarzschild, MD, Ph.D.
Department of Neurology, Massachusetts General Hospital