(Beyond Pesticides, August 7, 2009) A recent study published in the journal Environmental Health Perspectives has added to evidence that certain pesticides significantly increase one’s risk of developing Parkinson’s disease (PD). Researchers found that rural residents who drank private well water within 500 meters of fields sprayed with certain pesticides had an increased – up to 90 percent – risk of developing PD, and those with Parkinson’s “were more likely to have consumed private well water, and had consumed it on average 4.3 years longer.”
The study evaluated more than 700 people, including carefully chosen controls, in Fresno, Kent, and Tulare counties. 17 percent reported drinking private well water between 1974 and 1999. Researchers focused on wells’ proximity to agricultural fields sprayed with pesticides, since private wells are not regulated, and many are shallow enough to be contaminated by pesticides seeping into groundwater.
Researchers looked at 26 pesticides and six in particular, “selected for their potential to pollute groundwater or because they are of interest for PD, and to which at least 10% of our population were exposed.” Those are: diazinon, chlorpyrifos, propargite, paraquat, dimethoate, and methomyl.
Propargite exposure was most closely correlated with incidence of PD, with a 90 percent increase in risk. It is still used in California, mostly on nuts, corn, and grapes. Chlorpyrifos, once a common household chemical, was linked to an 87 percent higher risk of PD. While it was banned for residential use in 2001, it is stilled commonly used on California crops. Methomyl also increased risk by 67 percent.
One strength of the study is its focus on subjects’ proximity to pesticide application. Researchers used California’s pesticide use data to estimate exposure. Pesticide use reporting elsewhere is not widespread, and in some states, has been cut from budgets. Full reporting would make broader research of this kind possible. Although proximity data is helpful in evaluating risk, the researchers did not know what chemicals each subject was exposed to, since private wells are not tested.
This study is the latest in a growing body of research linking PD and pesticides. Elevated risk of the disease has been found from exposure to Agent Orange to residential exposure to agricultural chemicals. For a review of this research, read Beyond Pesticides’ report, “Pesticides Trigger Parkinson’s Disease.”
Sources: Environmental Health News, LA Times