Pesticides Linked to Parkinson's

Sept. 16 -- TUESDAY, Sept. 15 (HealthDay News) -- People whose jobs bring them in regular contact with pesticides may be at increased risk for Parkinson's disease, a U.S. study finds.

Researchers asked 519 Parkinson's patients and 511 people without the disease about their work history and exposure to toxins, including pesticides and solvents. Working in agriculture, education, health care or welding wasn't associated with Parkinson's disease, nor was any other specific occupation after the researchers adjusted for other factors.

But the study found that 44 (8.5 percent) of Parkinson's patients reported pesticide exposure, compared with 27 (5.3 percent) of those without the disease. The finding suggests an association between work-related pesticide exposure and increased risk of Parkinson's.

"Growing evidence suggests a causal association between pesticide use and parkinsonism. However, the term 'pesticide' is broad and includes chemicals with varied mechanisms," wrote Dr. Caroline M. Tanner of the Parkinson's Institute in Sunnyvale, Calif., and colleagues. "Because few investigations have identified specific pesticides, we studied eight pesticides with high neurotoxic plausibility based on laboratory findings. Use of these pesticides was associated with higher risk of parkinsonism, more than double that in those not exposed."

Three compounds -- an organic (2,4-dichlorophenoxyacetic acid), an herbicide (paraquat), and an insecticide (permethrin) -- were associated with a more than threefold increased risk of Parkinson's, the study found. Laboratory tests have shown that all three compounds have effects on dopaminergic neurons, which are affected by Parkinson's disease.

"This convergence of epidemiologic and laboratory data from experimental models of Parkinson's disease lends credence to a causative role of certain pesticides in the neurodegenerative process," Tanner and colleagues concluded. "Other pesticide exposures, such as hobby gardening, residential exposure, wearing treated garments or dietary intake, were not assessed. Because these exposures may affect more subjects, future attention is warranted."

The study appears in the September issue of the Archives of Neurology.

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SOURCE: JAMA/Archives journals, news release, Sept. 14, 2009