From 1962 to 1971, US military sprayed herbicides over Vietnam to strip the thick jungle canopy that could conceal opposition forces, to destroy crops that those forces might depend on, and to clear tall grasses and bushes from the perimeters of US base camps and outlying fire-support bases. Because of continuing uncertainty about the long term health effects of the sprayed herbicides on Vietnam veterans, Congress passed the Agent Orange Act of 1991. The legislation directed the Secretary of Veterans Affairs to request the IOM to perform a comprehensive evaluation of scientific and medical information regarding the health effects of exposure to Agent Orange and other herbicides used in Vietnam. Veterans and Agent Orange: Update 2012 is the ninth congressionally mandated biennial update.
The committee reviewed all relevant literature published between October 2010 and September 2011 and integrated the new findings with the previously assembled epidemiological data on each health outcome assessed with respect to exposure to the chemicals constituting the herbicides used in Vietnam, including the dioxin contaminant 2,3,7,8-TCDD. The single new conclusion was that there is limited or suggestive evidence of a scientifically meaningful association of stroke with exposure to the chemicals in question.