Parkinson's and Pesticides

by Priscilla Stevens

 

Parkinson's Disease, a degenerative neurological condition has been related to chronic, low-dose pesticide exposure of agricultural workers.

It is estimated that 60,000 people in the U. S. develop Parkinson's Disease (PD) each year and that number is expected to climb as the population grows older. ("chemicals called main cause of Parkinson's" L.A. Times 1-27-99) PD is a degenerative disorder affecting the central nervous system characterized by "brady and hypokinesia, resting tremor, rigidity, gait disorder and postural reflex impairment" (Veldman, et al, "Genetic and environmental risk factors in Parkinson's disease" Clinical Neurol. And Neruosurg., 100 (1998), 15-26. The lesion involves loss of the brain;s pigmented nigral dopamine cells from the substantia nigra. Nigral cells with mitochondrial respiratory chain dysfunction and diminished energy production are associated with lesion.

The cause of PD remains unknown, but appears to be multifactorial. The onset may involve both a genetic predisposition as well as exposure to environmental toxic triggers or promoters. Researchers have proposed that defects in the enzymes that detoxify neurotoxins, including certain pesticides, appear to increase susceptibility. The incidence of PD increases with age.

Epidemiological studies have given preliminary implications of pesticide (insecticide and herbicide) exposure as a risk factor for developing PD. The following chemicals have been suspected of inolvement with PD: 1) Insecticides - dieldrin, which acts as a mitochondrial poison and against dopaminergic cells, and has also been found in brain tissue (Sanchez-Ramos, J. "Association of organochlorine insecticide exposure with Parkinson's Disease," Abstract 14, Pesticide and Susceptible Populations, Who is at risk and when? Little Rock, AK, September 13-16, 1998), certain organochlorines and cholinesterase inhibitors (Seidler, et al., "Possible environmental, occupational, and other etiologic factors for Parkinson's disease: A case-control study in Germany,"May 1996, Neurology, 1275-1284); 2) herbicides - paraquat, diquat, and 2,4-D (DiMonte, DA, "Pesticides and Parkinson's Disease," A research proposal from the Parkinson's Institute, Sunnyvale, CA).

A very recent report from France's Toxicovigilance program has implicated fungicides as involved in Parkinson's Disease of grape pickers ("link established between fungicides and Parkinson's disease," World Food Chemical News, June 9 1999., p. 9)

A study in Montana (P. Butterfield, "Environment: Seeking clues to Parkinson's disease, "Reflections, p. 14-15 3rd Quarter 1996) foundÉ

  • "Five times the risk of Parkinson's Disease for people reporting direct exposure to insecticides more than 10 times a year."
  • "Three times the risk of Parkinson's Disease for people reporting direct exposure to herbicides more than 10 times a year."
  • "Two times the risk of Parkinson's disease for people ever living within on-quarter mile of agricultural spraying."
  • "Five times the risk for people ever living in a house that was commercially fumigated with a tent."

According to a recent report, researchers at Virginia Tech (VPI) in Blacksburg, VA are investigating the possible role played by combinations of insecticides in triggering or promoting Parkinson's Disease, specifically the synergistic effects of the organophosphate, chlorpyrifos, and the pyrethroid, permethrin. Military personnel serving in the Persian Gulf may have been exposed to such compounds since insecticides were used around field encampments and in housing areas. In addition, uniforms were impregnated with insecticides to protect against disease-carrying insects. ("Gulf war troop exposure to pesticides to examined by Virginia Tech researchers in CALS, VMRCVM" Virginia-Maryland, VPI Veterinary College Newsletter, Summer/Fall 98)

Another study underway exposes laboratory mice pretreated with a dopaminiergic toxicant to chemicals suspected of producing Parkinson's Disease including those mentioned above as well as the insecticide rotenone and a thiocarbamate fungicide. (DiMonte Study at Parkinson's Institute).

If, as seems possible based on preliminary data, there is a n increased risk of Parkinson's Disease from pesticide exposure, gardeners may want to reduce contacts with neurotoxic chemical pesticides in their own horticultural activities.

For more information, visit the Rachel Carson Council, Inc. website or e-mail them at: rccouncil@aol.com