A new study confirms the link between on-the-job pesticide exposure and Parkinson's disease, and suggests that certain insecticides may be particularly risky.

Parkinson's disease is a degenerative brain condition in which dopamine-producing cells in the brain gradually die off or malfunction.

Dopamine helps regulate movement, and as Parkinson's progresses, people have increasing difficulty walking, talking and performing simple tasks.

The exact cause of Parkinson's is unknown, but research indicates that a combination of genetics and environmental triggers – such as certain chemicals or viral infections – may be at work.

This latest study, published in the Annals of Neurology, bolsters evidence that occupational pesticide exposure may be one of those environmental triggers. French researchers found that among nearly 800 adults with and without Parkinson's, agricultural workers exposed to pesticides – including insecticides, weed killers and fungicides – were at greater risk of the disease.