Exposure to Pesticide Ziram Associated with Higher Risk of Parkinson's DiseaseMay 31, 2011 | Parker Waichman LLP
A group of UCLA researchers who were the first scientist to link exposure to the pesticides maneb and paraquat to Parkinson's disease have now connected a third – ziram - to the neurological disorder. The same team also found that combined exposure to ziram, maneb and paraquat near any workplace - farm or nonfarm - increased the risk of Parkinson's disease threefold.
Parkinson’s disease, a brain disorder common after the age of 50, leads to shaking and difficulty with walking, movement and coordination. The disease has been reported to occur at high rates among farmers and in rural populations, contributing to the hypothesis that agricultural pesticides may be partially responsible.
The UCLA researchers first discovered the connection between maneb and paraquat and Parkinson's disease in a study published in 2009. That study found that the risk for Parkinson's disease for people who lived near farm fields that were sprayed with the two pesticides increased by 75 percent.
For this study, the same group of researchers evaluated 703 people, including 362 with Parkinson’s, who lived in California’s heavily agricultural Central Valley from 1974 to 1999. They found that that the combined exposure to ziram, maneb and paraquat near any workplace increased the risk of Parkinson's disease (PD) threefold, while combined exposure to ziram and paraquat alone was associated with an 80 percent increase in risk.
This is the first study that provides strong evidence in humans that the combination of the three chemicals confers a greater risk of Parkinson's than exposure to the individual chemicals alone, according to the study authors.
"Our estimates of risk for ambient exposure in the workplaces were actually greater than for exposure at residences," Dr. Beate Ritz, senior author and a professor of epidemiology at the UCLA School of Public Health, said in a UCLA press release. "And, of course, people who both live and work near these fields experience the greatest PD risk. These workplace results give us independent confirmation of our earlier work that focused only on residences, and of the damage these chemicals are doing."
In animal studies conducted as part of the research, the team found that ziram was especially destructive to neurons that use the transmitter chemical dopamine to send messages. They die off in regions of the brain that govern motor function, causing symptoms, such a tremor, that are typical in Parkinson's patients. When ziram was given systemically to rodents, it reproduced many of the features of Parkinson's disease.