Herbicide Exposure Could Increase Vietnam Vets' Risk for Parkinson's

A report from the Institute of Medicine finds suggestive but limited evidence that exposure to Agent Orange and other herbicides used during the Vietnam War is associated with an increased chance of developing Parkinson's disease for Vietnam veterans.

The report is the latest in a congressionally mandated series by the IOM that every two years reviews the evidence about the health effects of these herbicides and a type of dioxin (TCDD) that contaminated some of the defoliants.

A finding of "limited or suggestive evidence of an association" means that the evidence indicates there could be a link between exposure to a chemical and increased risk for a particular health effect, though conflicting results from studies, problems with how the studies were conducted, or other confounding factors limit the certainty of the evidence. Until now, the cumulative evidence had been inadequate to draw conclusions about whether Parkinson's disease may be associated with veterans' exposures to herbicides or TCDD.

The conclusion that there may be a relationship between Parkinson's disease and Agent Orange exposure stems from the review of 16 studies that looked at herbicide exposures among people with Parkinson's disease or Parkinson's disease like symptoms. The finding was bolstered by several studies that have identified exposure to certain compounds similar to those in the herbicides used in the war as potential risk factors for the development of Parkinson's disease.

The review was hampered by the lack of studies investigating the occurrence of Parkinson's disease in Vietnam veterans specifically and the lack of animal studies testing the chemical components of Agent Orange for their potential to cause Parkinson's disease like symptoms. The report strongly recommends that studies examining the relationship between Parkinson's disease incidence and exposures in the veteran population be performed. Parkinson's disease affects approximately 1 percent of people over age 60, some 5 million people worldwide.

U.S. forces sprayed Agent Orange and other defoliants over parts of southern Vietnam and surrounding areas from 1962 to 1970. Most large-scale sprayings were conducted from airplanes and helicopters, but herbicides were also dispersed from boats and ground vehicles and by soldiers wearing back-mounted equipment.
References:
1. Herbicide Exposure May Increase Vietnam Vets' Risk for Heart Disease, Parkinson's. National Academy of Sciences.

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