Monday, July 10, 2006

Linking Parkinson's to everyday pesticides

Whittier Daily News
Linking Parkinson's to everyday pesticides

San Gabriel Valley Tribune

HERE'S an idea for a box-office blockbuster:

Evil chemist finds undetectable way to modify household products to cause debilitating, incurable, frequently fatal nerve disease. But - he doesn't want to set off a big epidemic, stirring up FBI, NIH, FEMA, etc. So he tweaks, making weapon work only sometimes, randomly, and escapes detection for years while keeping a steady 1 million Americans disabled - until hero chemist stumbles on scheme by accident.

A chilling tale? Subtract the mad scientist, and this nightmarish scenario of chemically induced disease could be, as they say in Hollywood, "inspired by real events" - the probable link between pesticides and Parkinson's disease, for which evidence has been mounting since a lucky discovery in 1982.

Last week, a team from the Harvard School of Public Health published some of the strongest findings to date, based on analysis of pesticide exposure and Parkinson's among 143,000 Americans whose case histories have been gathered by cancer researchers for a quarter-century. More than 400 people in that pool developed Parkinson's in the 1990s, and the data show that those with histories of pesticide exposure were 70percent more likely to develop the disease.

Especially horrifying is a finding that the risk was unrelated to degree of exposure: Weekend gardeners were in as much danger as lifelong farmers.

The database didn't allow the Harvard team to examine individual pesticides, but earlier studies have found that lots of insecticides, herbicides and fungicides, alone or in combination, show up in the histories of Parkinson's victims. Often a genetic factor is involved, too, but having the wrong DNA isn't enough - some trigger is necessary.

Far less mysterious is the mechanism of Parkinson's disease. It is simple brain damage, destruction of cells in an area called the substantia nigra. Kill enough of these and the body begins to ignore the brain, muscles stiffening and shaking uncontrollably. Pesticides first came under suspicion through a fluke - an observant neurologist noting Parkinson's-like symptoms in a heroin addict who shot up with herbicide.

But in most people with Parkinson's, it is probably that the triggering exposure was not only unnoticed but also well within long-established safety limits for these poisons.

Those limits are based on testing that looks at the short-term, high-dose toxicity in lab rats of one chemical after another - exactly the opposite of real life, which consists of long-term, variable-dose exposure to chemicals whose ingredients have never been tested in combination.

This is a scenario that has moved many sane scientists to call for realistic testing protocols on the 80,000 man-made chemicals floating all around us. Perhaps the example of Parkinson's will finally help their views gain the respect they deserve.

Star Tribune (Minneapolis)

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