Pesticide Exposure and Parkinson's Risk

Pesticides and related lifestyle factors, exposure to well water containing ground run-off, farming using pesticides, rural living are repeatedly reported risk factors for Parkinson's disease. There are few family-based studies looked at those relationships. Is there a genetic connection?

In 1992 the results of a study conducted at the University of Calgary were published. It involved 130 residents with neurologist-diagnosed ideopathic Parkinson's and 260 controls to determine whether agricultural or occupational use of pesticides had an association with increased PD risk. The study looked at field crop farming, grain farming, herbicide or insecticide usage and exposure variables. The ultimate conclusions were that there was a dose-response relation to the PD risk through field and grain crop farming and also occupational use of herbicides.

In 1998 the results of a study by the Department of Neurology at the Henry Ford Health System in Detroit performed a similar study adding cigarette smoking to the mix. The conclusions were similar: a significant association of occupation-exposure (farming) and herbicides and insecticides but no increased risk of PD with rural or farm residence or well water usage. They concluded that farming or pesticide exposure alone did not appear to be a risk factor.

A study was published in the June 2006 issue of Movement Disorders by Dr Demetrius "Jim" Maraganore, Mayo Clinic Professor of Neurology whose principle research interest is to identify the causes of Parkinson's disease, through molecular genetic and epidemiologic approaches. That study confirmed conclusions of prior studies, "What we think may be happening is that pesticide use combines with other risk factors in mens environment or genetic makeup, causing them to cross over the threshold into developiing the disease." Moreover, "One possibility is that to get Parkinson's disease, you not only have to be exposed to pesticides, but you have to be genetically predisposed" He also noted that pesticide exposure accounts for only 10-15% of Parkinson's cases.

In the Mayo Clinic study, investigators contacted all of the Olmsted County, MN residents who had been diagnosed with PD between 1976 and 1995. They were then assigned control matches. The phone interview was to determine the exposure to chemical products: farming, non-farming work or hobbies. Although unable to determine the exact exposure levels the study did conclude that men with PD had 2-4 times more exposure to pesticides than the controls.

In 2006 research at the University of North Dakota, at Emory University and at Harvard University had similar conclusions that pesticide exposure appears to cause a loss of neurons in particular areas of the brain.

Researcher's at Duke University Medical Center and the University of Miami Miller School of Medicine examined 319 cases and 296 relative and other controls. They recorded associations of direct pesticide application, well-water consumption, and farming residences/occupations. They controled for age at examination, sex, cigarette smoking and caffeine consumption.

Individuals with PD were significantly more likely to report direct pesticide application than their unaffected relatives. Associations of direct pesticide application did not vary by gender.
When classifying pesticides by a functional type, both insecticides and herbicides were found to significantly increase the risk of PD: Two specific classes of insecticides, organochlorines and organophosphorus, were significantly associated with PD.

Sources:
Pesticide exposure and risk of Parkinson's disease:
A family-based case-control study
Hancock,Martin,Mayhew etal 8 March, 2008
Duke University Medical Center
University of Miami Milleer school of Medicine

http://www.voanews.com/english/archive/2006-06/2006-06-24-voa21.cfm
http://www.ncbi.nlm.nih.gov/pibmed/9595985
http://www.ncbi.nlh.gov/pubmed/17708091?ordinalpos=1&tool=EntrezSystem2.PEnt
http://www.ncbi.nlm.nih.gov/sites/entrez

To view Purple Haze, Pesticides, Big Brother and the Migrant Farm Worker as referenced in the comment section:
http://www.phf.org/infrastructure/resources/marphli/purple.pdf