Study Links Parkinson's to Pesticide

ATLANTA (Cox News Service) -- People who were exposed to a common pesticide

while in the womb or during breast-feeding decades ago may be at increased risk

of developing Parkinson's disease after age 50 than contemporaries who

weren't, according to Emory University scientists whose studies on pregnant and

nursing mice demonstrated the link.

The pesticide dieldrin was commonly used for insect control in crops and as a

termite killer in home foundations, said researcher Gary Miller, a

neurotoxicologist at Emory's Center for Neurodegenerative Disease. Environmental

exposures have long been thought to trigger Parkinson's in adults, but this is the

first study to suggest that exposure to fetuses and breast-feeding babies could

be harmful, Miller said.

"Although most people are diagnosed in mid to late life with Parkinson's,

experimental evidence suggests that neurodegeneration begins long before clinical

diagnosis," Miller said.

Dieldrin, developed in 1940 as an alternative to DDT, is a probable human

carcinogen, Miller said. The Environmental Protection Agency banned the pesticide

for all uses except termite control in 1974 and that use was banned in 1987.

Defining Parkinson's

Parkinson's disease involves the death of brain cells that produce the

chemical messenger dopamine, a neurotransmitter that sends information to parts of

the brain that control movement and coordination. Victims are left incapable of

initiating and controlling movements normally.

Though Parkinson's is usually considered a disease of aging, 5 percent of its

victims are thought to inherit a mutated gene that causes it, Miller said.

Fifteen percent of Americans diagnosed with Parkinson's annually are under 50.

All told, about 1.5 million Americans have the disease.

Miller said the incidence of Parkinson's is highest in the South and in rural

areas. Emory sees about 2,000 patients with Parkinson's a year.

Dieldrin is still detectable in the environment -- in the ground, in home

foundations, and many food sources, including shellfish, meat, dairy and root

crops -- but levels of the pesticide have decreased dramatically in recent

decades, Miller said.

Because it and similar chemicals persist in the food chain, exposure by

pregnant women now could still pose a risk to their babies, he added.

But Miller said his research should not discourage women from breast-feeding.

"The pesticides currently in use do not accumulate in mother's milk the way

these older compounds did," Miller said. "The risk of potential pesticide

exposure via breast-feeding today is far outweighed by the beneficial effects of

breast-feeding."

In the Emory study, pregnant mice were given a dose of dieldrin, or a

placebo, every three days throughout gestation and lactation.

Then, when the mice were three months old, they were killed and their brains

examined for abnormalities that in humans lead to Parkinson's. In the

offspring of mice treated with dieldrin, the researchers found an elevation of the

dopamine transporter, a regulator of the brain system that in humans is affected

by Parkinson's, said Miller. Mice, he added, "don't typically get Parkinson's

disease."

"The fact that we saw these molecular changes in animals ? that had never

been directly exposed to the pesticide indicated the importance of the

developmental exposure," he said.

The study also found that male rodent offspring were more vulnerable than

females. Among humans, men are much more likely to get Parkinson's than women, he

added.

What can be done

Miller said the study's results "provide a potential molecular mechanism

responsible for the association between dieldrin exposure and increased risk of PD

and suggests that greater attention should be focused on the role of early

life exposures and the development of PD."

He said the study suggests that people born between 1940 and 1960 -- when

dieldrin was widely used -- who were breast-fed are likely at increased risk for

developing Parkinson's. He said he does not know of any registry that links

the disease in humans to possible exposure to chemicals.

The study should encourage scientists to look "at where mothers of PD

patients lived, whether they breast-fed, lived in rural areas where pesticides were

more likely to have been used," Miller said.

"We have banned these compounds in the United States," he said. "The better

we understand what causes the disease, it might suggest a better option for

treatment."

Link long suspected

A relationship between pesticides and Parkinson's has been thought to exist

for years. Just two weeks ago, researchers at the Harvard School of Public

Health reported anew that people with exposure to pesticides had a 70 percent

higher incidence of Parkinson's than those who hadn't.

Dr. Michael S. Okun, co-director of the Movement Disorders Center at the

University of Florida, said the Emory study should be interpreted "with caution as

it is unclear at this time whether dieldrin is important in the human form of

the disease."

But Okun, also medical director of the National Parkinson Foundation, added

that "the emerging information on the effects of pesticides and environmental

exposures on the development of neurodegenerative diseases represents an

important emerging area of research."

The Emory study, funded by the National Institute of Environmental Health

Science, was published June 29 in the Federation of American Societies for

Experimental Biology Journal.

Copyright 2006 The Cox News Service. All rights reserved.