Human Exposure to TCDD from Aerial Spraying of Agent Orange

Abstract

AbstractThe prospect of exposure to TCDD from Agent Orange to ground troops in Vietnam seemed unlikely because of the environmental dissipation of TCDD, little bioavailability, and the properties of the herbicides and circumstances of application that occurred. Photochemical degradation of TCDD and limited bioavailability of any residual TCDD present in soil or on vegetation suggested that dioxin concentrations in ground troops who served in Vietnam would have been small and indistinguishable from background levels even if they had been in recently treated areas. Laboratory and field data reported in the literature provided compelling evidence on the fate of the herbicide and TCDD in the environment. The evidence of the environmental fate and poor bioavailability of TCDD from the spraying of Agent Orange was consistent with the observation of little or no exposure in the veterans who served in Vietnam. Appreciable accumulation of TCDD in veterans would have required repeated long-term direct skin contact of the type experienced by the US Air Force RANCH HAND and US Army Chemical Corps personnel who handled or otherwise had direct contact with liquid herbicide, not from incidental environmental exposure under field conditions where Agent Orange had been sprayed.