Pesticide Exposure Tied To Parkinson's Risk

Date: May-28-2013Two researchers in Italy suggest exposure to pesticides, herbicides and solvents is linked to a higher risk of developing Parkinson's
disease. They came to this conclusion after analyzing over 100 studies from around the world.

Parkinson's is a progressive degenerative disease that affects a person's ability to control and coordinate their muscle movement.

What can begin as a tremor in a little finger eventually leads to problems with speech and writing, and one day, inability to walk without
help.

This deterioration is caused by the gradual reduction in brain levels of dopamine, a chemical messenger that carries signals to brain regions that
control movement and coordination.

Exactly why Parkinson's develops and how this affects dopamine production and maintenance is not known. But there is increasing evidence
of an inherited component, and there is also a possibility that the cause, in a small proportion of cases, is genetic.

One view that is gaining ground is that inflammation likely has a role in the
development of Parkinson's disease.

Dopamine is produced by a special type of brain cell, the dopaminergic neuron.

There is also a suggestion that certain toxins in the environment cause Parkinson's by selectively destroying dopaminergic neurons. This latest
analysis from Italy appears to add some weight to that view.

Emanuele Cereda from the IRCCS University Hospital San Matteo Foundation in Pavia, and Gianni Pezzoli of the Parkinson Institute - ICP in Milan,
write about their findings in the 28 May print issue of the journal Neurology.

For their meta-analysis, a type of study that pools data from several studies of similar design, Cereda and Pezzoli reviewed results of 104 cohort
and case-control studies that examined links between exposure to bug, weed, fungus and rodent killers, and solvents, and risk for developing
Parkinson's disease.

They found that exposure to these chemicals is linked to a higher risk of developing Parkinson's by between 33% and 80%.

And results from high quality case-controlled studies shows that exposure to paraquat (a herbicide) and maneb and mancozeb (fungicides), is tied
to around a two-fold increase in risk of developing Parkinson's.

The analysis also included studies that took into account how close people lived to the site of exposure (for instance urban or rural settings), their
jobs, and whether their drinking water came from wells.

In a statement, Cereda says they also found "a link between farming or country living and developing Parkinson's in some of the
studies".

And while they did not look at whether type of exposure, such as through the skin or inhaled, and type of application, such as spraying or mixing,
affects the risk, Cereda says it appears that the risk "increases in a dose response manner as the length of exposure to these chemicals
increases".

The authors call for further prospective and high-quality case-control studies to prove whether these chemicals actually cause the higher risk of
Parkinson's disease.

They suggest these studies should also concentrate on specific chemicals.

Funds from the Grigioni Foundation for Parkinson's Disease and the IRCCS University Hospital San Matteo Foundation helped finance the
analysis.

In another recently published study, neurologists in Calofornia added the
pesticide, benomyl, whose toxic effects still linger a decade after being banned by the US Environmental Protection Agency, to the list of
pesticides linked to Parkinson's.

Written by Catharine Paddock PhD

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