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Another Study Links Pesticides to Parkinson's Disease
(Beyond Pesticides, November 8, 2004)
Researchers at Emory University and the University of Washington have shown for the first time that chronic exposure to the insecticide rotenone can cause Parkinson's-like pathology in monkeys, according to a press release from the Society for Neuroscience.This finding builds upon their previous study in which they demonstrated that rotenone, a commonly used agricultural pesticide made from the extracts of tropical plants, can reproduce parkinsonian features in rats. The researchers developed a new nonhuman primate model of this disorder.

This research also builds on epidemiologic research that finds elevated numbers of Parkinson's cases in household that use home and garden pesticides.Other researchers have documented low-dose effects of the insecticide permethrin, doses below one-one thousandth of a lethal dose for a mouse, with effects on those brain pathways involved in Parkinson's disease. The effects are consistent with a pre-parkinsonsian condition, but not yet full-blown parkinsonism.See previous Daily News article and other articles in the Daily News archives.

In 2000, researchers at a meeting of the American Academy of Neurology's 52nd annual meeting announced their findings that link Parkinson's disease to pesticide use and exposure in the home and garden, based on a study of almost 500 people newly diagnosed with the disease.

The new research into Parkinson's disease is helping scientists better understand some of the mechanisms of this serious and disabling brain disorder, which affects about 1 million people in the United States. Knowledge of the environmental factors and genetics of this illness has allowed investigators to create models of disease that are being used to examine potential causes of neuron disease and to test experimental therapeutics in animals. The researchers hope that their work will eventually lead to the development of more effective treatments of this human illness. Activists want to see the scientific knowledge support the banning of the chemicals associated with these effects.

The second most common neurodegenerative disease (after Alzheimer's disease), Parkinson's occurs when certain groups of nerve cells are damaged and destroyed. For example, neurons in the substantia nigra, an area of the brain that is important for normal voluntary movements, are invariably damaged. These abnormalities result in a variety of signs, including tremor, muscle stiffness, and slowness of movement. People with Parkinson's may also experience depression, anxiety, dementia, constipation, urinary difficulties, and sleep disturbances. Symptoms tend to worsen over time.

"Monkeys have a brain structure that is much more similar to humans than rats," notes J. Timothy Greenamyre, MD, PhD, of Emory University. "These studies on monkeys, therefore, support our previous findings that chronic pesticide exposure may be capable of causing parkinsonian pathology in humans."
In this pilot study, two monkeys were treated with rotenone-one at Dr. Greenamyre's laboratory at Emory University and the other at the University of Washington laboratory of Marjorie Anderson, PhD. The rotenone was administered subcutaneously to the animals over a period of 18 months in one case and 19 months in the other before the Parkinson's-like pathology developed. When the monkeys' brains were later examined, the scientists found anatomical and biochemical changes virtually identical to the major abnormalities seen in Parkinson's disease, including degeneration of the nigrostriatal dopaminergic pathway and synuclein positive cytoplasmic inclusions in nerve cells in the substantia nigra.

Although this study does not prove that rotenone causes Parkinson's disease, it adds to previous questions about the pesticide's safety and that of similar environmental toxins. "We think this is an important proof of the concept that what we eat, drink, breathe, or are otherwise exposed to can predispose us to Parkinson's disease," says Dr. Greenamyre.

TAKE ACTION: Write U.S.EPA Administrator Michael Leavitt and EPA Deputy Administrator Stephen Johnson and let them know that they have a duty to alert the public to the scientific findings (laboratory and epidemiologic) that link pesticides with Parkinson's disease. In addition, urge these EPA officials to initiate an urgent and expedited review of pesticides' link to Parkinson's.