Pesticides linked to Parkinson's disease

combination of two widely used agricultural pesticides--but neither one alone--creates in mice the exact pattern of brain damage that doctors see in patients with Parkinson's disease, according to Rochester research that offers the most compelling evidence yet that everyday environmental factors may play a role in the development of the disease.

The latest findings of the team led by Deborah Cory-Slechta, professor of environmental medicine and dean for research at the School of Medicine and Dentistry, appear in the December 15 issue of the Journal of Neuroscience.

The scientists caution that more studies are necessary to explain the link, since it's probable that many factors contribute to a complex disease like Parkinson's, and they say it's unlikely that the pesticides on their own actually cause the disease.

Cory-Slechta's team studied the effects of a mixture of two very common agrichemicals, the herbicide paraquat and the fungicide maneb.

Each is used by farmers on millions of acres in the United States alone. Maneb is applied widely on such crops as potatoes, tomatoes, lettuce, and corn, and paraquat is used on corn, soybeans, cotton, fruit, and a variety of other products.

In the experiment, mice exposed to either one had little or no brain damage, but mice exposed to both share a significant trait with people in the very early stages of the disease: Though they appear healthy, the mice exposed to the mixture carried nearly all of the molecular hallmarks of Parkinson's disease as seen in humans.

"The environmental reality is that several of these chemicals are used on the same crops and in the same geographical locations," said Cory-Slechta, who was joined in the research by graduate student Mona Thiruchelvam and faculty members Eric Richfield, Raymond Baggs, and A. William Tank.

The study is one of the first to examine the effects of such chemicals in tandem. Cory-Slechta noted that current regulations and determinations of safety levels are usually based on the effects of single chemicals.

Maneb, paraquat, and many other pesticides are used in the same agriculture-rich areas of the country, and the map of their use mirrors areas of the country where people are more likely to die of Parkinson's disease.

Several other epidemiological studies have hinted at a role for pesticides in the development of the disease.

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