HealthDay News  [Printer-friendly version]
June 26, 2006


[Rachel's introduction: A new study reconfirms earlier findings, that
pesticide exposure is linked to Parkinson's disease.]

By Alan Mozes

Exposure to pesticides, but not other environmental contaminants, may
boost the long-term risk for developing Parkinson's disease by 70%, a
new study suggests.

The researchers did not assess the length, frequency, or strength of
pesticide exposure, and they stressed that the absolute risk of
developing Parkinson's remains relatively small.

However, their finding does back up earlier animal studies linking
pesticide exposure to motor function abnormalities and lower levels of
the brain neurotransmitter dopamine. Declines in dopamine have long
been associated with Parkinson's.

"This is the first large human study that shows that exposure to
pesticide is associated with a higher incidence of Parkinson's," said
study lead author Dr. Alberto Ascherio, associate professor of
nutrition and epidemiology at the Harvard School of Public Health in

"It is, of course, a relative increase," emphasized Ascherio. "So,
whereas normally the lifetime risk for developing Parkinson's is three
percent, pesticide exposure will bring the risk to five percent."

Ascherio and his colleagues discussed their work in the July issue of
the Annals of Neurology.

The authors reviewed lifestyle surveys completed in both 1982 and in
2001 by over 143,000 participants in the U.S. "Cancer Prevention Study
II Nutrition Cohort," launched in 1982.

In addition to pesticide exposure, participants were asked about
exposure to a host of chemicals and dusts, such as: asbestos, acids,
solvents, coal and stone dust, coal tar, asphalt, diesel engine
exhaust, dyes, formaldehyde, gasoline exhaust, herbicides, textile
fibers, wood dust, and x-ray or radioactive materials. Nearly all the
patients were white, with an average age just of over 60.

In total, 413 participants went on to develop Parkinson's disease.

The surveys revealed that just over eight percent of the men and just
over three percent of the women reported exposure to pesticides.

Exposed patients were twice as likely to be blue-collar workers and 14
times more likely to work as either a farmer, rancher, or fisherman.

However, no differences were found in terms of risk increase between
patients who experienced exposure because of their work, such as
farmers, and those who came into contact with the chemicals because of
home or garden use.

The Harvard team found that, regardless of occupation, pesticide
exposure boosted long-term Parkinson's risk by 70% over the long-term.

Ascherio stressed that although the association found in his study was
stronger than any previously documented, more work is needed to
pinpoint what exactly it is about pesticides that may help spur

"The key point would be to identify which chemicals cause
Parkinson's," he said. "It's not very practical to tell people to
avoid pesticides, because many people find it very useful. So this
will require more detailed study," he added.

Robin Elliot, executive director for the Parkinson's Disease
Foundation in New York City, described the findings as "important and

"This is certainly the biggest and most serious populations study on
people, and it appears to be the best proof today that there is a
general association between pesticide and Parkinson's among people,"
said Elliot. "It merits further investigation," he said.

In a separate smaller study, published in the June issue of Movement
Disorders, a team of researchers from the Mayo Clinic in Olmsted
County, Minnesota, found that pesticide exposure seemed to increase
Parkinson's risk for men, but not women.

Telephone interviews were conducted with 149 men and women, all local-
area Parkinson's patients who developed the illness between 1976 and
1995. The Mayo team also interviewed 129 healthy individuals.

They found that male patients were 2.4 times more likely than healthy
individuals to have been exposed to pesticides. No such increased risk
was evident among the female patients.