The effects of pesticides that have leached into the water supply may explain why some groups are more susceptible to the neurological condition, say scientists from UT Southwestern Medical Center.

The researchers say that while a body of research has developed supporting the idea that pesticides can cause disease in the brain later in life, which chemicals are the cause and why is still unclear.

In examining beta-HCH, they found that patients at the medical center were more likely to suffer from Parkinson’s disease if they had higher levels of the chemical in their bloodstream.

They added that 76 percent of those with the condition were found to have the pesticide in blood samples, compared to 40 percent of healthier people used as controls and 30 percent of patients who suffer from Alzheimer’s disease.

Beta-HCH was transmitted through the air and water supplies, the scientists note, and while genetic factors also come into play they are hopeful that more studies will strengthen the link between the chemical and its effect on older minds.