At this stage, researchers have not been able to link a specific herbicide or pesticide component to the disease.

Nevertheless, current research indicates that people with lengthy exposure to certain herbicides and pesticides are more likely to develop Parkinson's than people who don't have this same level of exposure.

Researchers have also found a genetic variation that appears to make people more likely to develop Parkinson's if they are exposed to certain pesticides. A fairly strong and consistent finding of research is that the risk of Parkinson's is increased by rural living, exposure to well or ground water, and agricultural work, suggesting that pesticides or herbicides may cause or contribute to Parkinson's.

The normal CYP2D6 gene produces an enzyme that helps break-down pesticides, making them less toxic to the body. However, a variant of this gene produces an enzyme which is less effective against pesticides, causing an increase in the body’s sensitivity to pesticides and a corresponding increase in the risk of developing Parkinson's Disease. However, people with this genetic variation have nothing to fear and do not have an increased risk of developing Parkinson's unless they are exposed to pesticides.

In addition, exposure to certain toxic substances, such as manganese and carbon monoxide, has also been linked to Parkinson’s.

It is believed that the effects of these toxins may build up in the body, over many years or decades, and eventually lead to the development of Parkinson’s Disease.