Study Links Exposure to Bug and Weed Killers to Higher Risk for Parkinson’s

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Who doesn’t want a pristine lawn free of annoying weeds and bugs? But some of those pest-fighting strategies may come with a price — to your health.

A new study published in the journal Neurology found that pesticides, which have already been linked to a range of health complications from allergies to lower IQ levels, may also play a role in the development of Parkinson’s.

Parkinson’s is a neurological disease in which motor nerves in the brain lose their ability to function, leading to uncontrolled movements, tremors and difficulty in walking and speaking. While genes play some role in the condition, more research is connecting lifestyle and environmental factors to a higher risk of disease.

In the latest review, the researchers reviewed 104 studies that analyzed exposure to pesticides and solvents that kill weeds, fungus, rodents and bugs, and the risk of Parkinson’s disease. The trials measured things such as whether the participants lived in close proximity to farms or other agricultural plots that use a higher volume of such chemicals, the likelihood of well-water consumption, rural living and various occupations that put an individual at a greater or lower risk of exposure.

(MORE: Study: Flavonoids May Help Protect Against Parkinson’s)

They found that exposure to bug and weed killers and solvents was linked to a 33% to 80% greater risk of developing Parkinson’s disease. In some studies, individuals who came in contact with the weed killer paraquat or the fungicides maneb and mancozeb were twice as likely to develop Parkinson’s.

Unfortunately, the trials did not all address how the participants were exposed, so the scientists could not determine if certain routes, like inhaling the chemicals, was more dangerous than absorbing them through the skin. The investigation did conclude, however, that risk appears to increase the longer people are exposed. But more studies are needed to figure out whether there is a threshold for when the chemicals become most harmful to the brain.

The scientists also acknowledge that some of the data is conflicting; while the studies they analyzed showed a strong association between solvents and well water and a higher risk of Parkinson’s, the same elevated risk didn’t appear for insecticides.

(MORE: How the Brain Chooses: Secrets From Parkinson’s Disease)

Despite that, the results add to growing research about how exposure to environmental factors may play a role in diseases like Parkinson’s. “I think the study is actually a big advance in our research knowledge of the relation between chemical exposures and the basic neurological injuries,” Dr. Arch Carson of the University of Texas School of Public Health in Houston told MedPage Today. “This report is the first to show that there is a positive relationship between not only insecticides and herbicides but also some other solvent chemicals to which many people are exposed and the development of Parkinson’s syndrome.”

Uncovering and understanding these links could not only help prevent some cases of disease, but also lead to more targeted ways of intervening with effective treatments.