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Pesticides Drifting from Farms to Workplaces Increase Parkinsonís Risk

A new study reports that people whose workplaces and homes were near fields sprayed with the pesticides ziram, maneb and paraquat, have an increased risk of developing Parkinson’s disease (PD).  The research is the first to link ziram, a fungicide, to people with PD.  The results appear in the April 20 online edition of the European Journal of Epidemiology.

For several years evidence has mounted that pesticide exposure increases Parkinson’s risk, in particular for farmers and others who use pesticides in the workplace.  But these chemicals can drift from the fields where they are applied to surrounding areas.  Two years ago a team of researchers led by Beate Ritz, M.D., Ph.D., at the University of California, Los Angeles (UCLA), found that people who lived near fields sprayed with the fungicide maneb and the herbicide paraquat had an increased risk of Parkinson’s.

The same epidemiology research team, in a follow-up study authored by Anthony Wang, investigated a broad range of occupations who worked and lived near farm fields in California’s Central Valley.  They recruited 362 study participants with Parkinson’s and 341 people of similar age who had no Parkinson’s symptoms.  In order to estimate study participants’ exposure to pesticides, Mr. Wang and colleagues, recorded, among other data, the addresses where study participants had lived and worked between 1974 and 1999.  Then they combined land-use maps and pesticide-use reporting data from the state of California to determine which pesticides were applied, where, by what method, and in what amount, during the same period of time near these addresses.


  • People exposed at their workplaces to all three pesticides studied—ziram, maneb and paraquat—tripled their risk of Parkinson’s.
  • Workplace exposure to both ziram and paraquat nearly doubled Parkinson’s risk.
  • Pesticide exposure in workplaces was higher than in homes near the pesticide-sprayed fields.
  • People who both lived and worked near fields sprayed with pesticides had the highest Parkinson’s risk.
  • People with younger onset PD had higher exposures to pesticides both at work and at home.


What Does it Mean?

Parkinson’s is a complex disorder that is caused by an interaction between genetic and environmental exposures. While researchers estimate that environmental exposures have a key role in Parkinson’s, studies of the environment are very complicated to conduct and are often inherently biased.

For instance, estimating a person’s exposure to pesticides decades after the fact is a difficult task.  A strength of this study is its methodology for making these estimates, by use of land-use maps and pesticide-use reporting data from the state of California. 

This study provides the first evidence in humans that exposure to the combination of the three chemicals studied – ziram, maneb and paraquat – increases Parkinson’s risk more than any one individually.  It also validated prior epidemiological and laboratory research implicating some pesticides as a risk factor for Parkinson’s.

Of note, based on this study, most of the people who reportedly were exposed to high pesticide levels will never develop Parkinson’s. Yet this study may have important implications for the public health, perhaps leading to reevaluation of the safety of using some of these agents and assessment of whether guidelines on how to decrease exposure are warranted.

While epidemiology studies like this one cannot establish concrete links like cause and effect, only correlations, this study is part of the accumulating evidence suggesting that substantial exposure to pesticides is a strong environmental influence that places people at risk of Parkinson’s disease.


Learn More

Dr. Caroline Tanner recently wrote an overview about, "Environmental Factors and Parkinson's" for PDF's newsletter.

Read Dr. Tanner's Article

Source Date: Jun 10 2011