More evidence suggests pesticides cause Parkinson's disease

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Agri. & Environ.

More evidence suggests pesticides cause Parkinson's disease

By Ben Wasserman

http://www.foodconsumer.org/777/8/More_evidence_suggests_pe

sticides_cause_Parkinson_s_disease.shtml

Jun 26, 2006, 17:06

 

June 26 (foodconsumer.org) - People who use pesticides on their farms or

backyards or homes should take note that exposure to pesticides is likely to

raise

their risk of developing Parkinson's disease later in life, suggests a new

study.

 

The study reported in the July issue of the Annals of Neurology found that

the risk of Parkinson's disease in those who reported being exposed to

pesticides and herbicides increased by about 70 percent, ten to 20 years after

initial

exposure.

 

The finding resulted from data extracted from surveys of more than 140,000

men and women who took part in the Cancer Prevention Study II Nutrition cohort

that began in 1992.

 

The team led by Alberto Ascherio, M.D., Dr.Ph., of the Harvard School of

Public Health found that the risk of Parkinson's disease is highest among people

with occupational exposure to pesticides such as farmers. The risk was also

found in those who were exposed to pesticides used in gardens and backyards.

 

However, the risk of Parkinson’s was not associated with exposure to other

occupational exposures such as asbestos and dust, according to the study.

 

The risk of Parkinson's disease associated with exposure to pesticides has

been reported in many studies. One recent study was reported by Mayo Clinic

researchers who published their finding in the online June issue of Movement

Disorders.

 

In the study, they found that men who had ever been exposed to pesticides on

their farms or gardens were more than twice as likely to develop Parkinson's

disease compared to men who was not exposed to the toxic chemicals.

 

However, Walter A. Rocca, M.D., M.P.H. and colleagues who conducted the study

were unable to figure out the effect of intensity and duration of pesticide

exposure on the risk of Parkinson's disease because complete data on the dosage

and exposure duration were not available.

 

Both studies found high risk of Parkinson's disease in both farmers and

non-farmers who were exposed to pesticides. But other occupational risk factors

were not associated with the disease.

 

In the Harvard study, among 143,325 who responded to study surveys in 2001

and who were not diagnosed with Parkinson's disease or symptoms at the time the

survey began, 5.7 percent or a total of 7,864 participants including 5,203 men

and 2,661 women reported exposure to pesticides.

 

Researchers found that 1,956 farmers, ranchers, or fishermen were fourteen

times more likely to be exposed to pesticides compared with people in other

occupations. Blue collar workers had a two-fold higher risk of exposure to

pesticides.

 

Even after adjustment of other risk factors including age, gender, and

smoking status, the risk of Parkinson's disease was still significant among

those

who were exposed to pesticides, 1.7 times higher than that for those who were

not exposed.

 

The duration of pesticide exposure did not seem to change the risk. Among

those who did report the duration, the risk of Parkinson's disease was not

significantly different between those who had been exposed to pesticides for

more

than a decade and those for less than ten years, with the relative risk 2.3 for

the former and 2.1 for the latter.

 

Although the study was based on the statistical correlations and a

cause-effect association could not be established, exposure to pesticides is

likely to

harm the brain as the pesticides commonly used in the U.S. have been shown to

cause degeneration of dopaminergic neurons in the brain, causing neurologic

adnormalities in animals who received high doses of pesticides, according to the

authors.

 

Also in postmortem studies, other researchers have found that high levels of

organochlorine pesticides were present in the substantia nigra or striatum of

patients with Parkinson's disease, indicating that these pesticides are

persistent in tissues years or even decades after exposure.

 

Evidence that organochlorines damage the brain of patients with Parkinson's

disease were also found in autopsy studies as cited by the authors. The

presence of these pesticides in Parkinson's patients seems to be unique as they

were

not detected in other similar degeneration diseases such as Alzheimer’s

disease.

 

Organochlorine pesticides such as DDT, chlordane, lindane and toxaphene are

persistent in the environment. Some of such pesticides such as DDT have been

banned in many countries, but they are still polluting the environment.

 

Other than biochemical evidence, many epidemiologic studies have linked

exposure to pesticides to Parkinson’s disease.

 

One early study carried out by scientists at Stanford University in

California also fond that people who were exposed to pesticides were more than

two

times as likely to develop Parkinson's disease as those who were not exposed to

the chemicals. The results were reported in 2000 at the annual meeting of the

American Academy of Neurobiology in San Diego, California.

 

However, Lorene Nelson, lead author of the study and colleagues found

exposure to pesticides in the home environment was linked to the highest risk of

developing Parkinson’s disease. People who used pesticides in their gardens

were

not found to be at greater risk for the disease.

 

The current study, supported by a grant from the Michael J. Fox Foundation

and Kinetic Foundation, was unable to reveal the association between a

particular pesticide and risk of Parkinson’s disease. How the duration,

frequency and

level of exposure to pesticides affect the risk of the disease remains unknown.

 

 

Parkinson's disease is a progressive neurological disorder that results from

degeneration of neurons in a region of the brain that controls movement. It

remains unclear why pesticides may increase the risk of Parkinson's disease. But

scientists say toxic pesticides may target and kill cells in some parts of

the brain. Such damage to nerve cells leads to signs of Parkinson's disease.

 

 

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