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Parkinson’s research paints a grim picture

Wednesday December 28, 2005

December 27, 2005(StarTribune.com) - Research on Parkinson’s disease is converging toward a grim conclusion -- that it is almost always an environmental illness, caused by pesticides and other industrial chemicals.

Worse, it seems in some cases to result from long-term, low-dose exposure to multiple products, each of which may have been used within safety guidelines. This is the nightmare scenario of chemically induced disease.

Scientists have long pointed out that the 80,000 or so industrial chemicals released into the environment have been certified as safe based on short-term, one-at-a-time testing in animal labs. But in real life we acquire multiple toxins, even before birth, and many accumulate in our bodies.

What kind of damage might that do? Parkinson’s appears to offer an especially credible example, according to a powerful summary of research recently published in the Los Angeles Times.

This disease, in which the brain gradually loses control over the body, follows damage to a structure called the substantia nigra, whose cells produce the neurotransmitter dopamine. Usually it develops gradually, and in people older than 55; only one case in 20 can be explained by physical injury (Muhammad Ali, for example) or genetic abnormality.

Pesticides have long been linked, at least loosely, to neurological damage in people who use them. The specific connection to Parkinson’s has been researched since the early 1980s, after a California neurologist saw the disease develop virtually overnight in a 42-year-old heroin addict who, it turned out, had wrecked his substantia nigra by injecting a chemical cousin of the weedkiller paraquat.

Subsequent animal studies have associated similar damage with several specific pesticides, as well as with polychlorinated biphenyls (PCBs).

But the most chilling possibilities are raised by findings that pesticides which may be safe individually can be devastating when administered together or in sequence, in ways that mimic routine human exposure -- even at very low doses.

Pesticide companies and government regulators defend the current practice of testing each chemical product in isolation, arguing that it’s impossible to check out all the possible combinations that arise in the environment. True enough, but the Parkinson’s findings suggest that a much more manageable task -- examining the combined impact of pesticides routinely used together -- is long overdue.