NCJ Number
190892
Date Published
1999
Length
11 pages
Annotation
This document provides a health risk assessment of the chemical warfare agent VX an organophosphate nerve agent.
Abstract
VX is an organophosphate nerve agent found at several stockpile and nonstockpile munitions sites in the United States. At the request of the Army, Oak Ridge National Laboratory (ORNL) conducted a heath risk assessment of VX. The assessment included a detailed analysis of VX’s physical and chemical properties, environmental fate, mechanism of action, and animal and human toxicity. On the basis of that assessment, ORNL proposed a reference dose (RfD) of a number of milligrams/kilograms of body weight per day for noncancer health effects of VX exposure. Because there was no evidence that VX is carcinogenic, a slope factor was not derived. The Army’s Surgeon General accepted ORNL’s proposed RfD as an interim exposure value until the National Research Council conducted an independent evaluation of the proposed RfD. It was concluded that there were several weaknesses and uncertainties that undermined the confidence in this study. The data from human studies should be used to derive the RfD whenever possible. These studies also had a number of weaknesses, but it is preferable to be used rather than data from a questionable animal model. The major gap in the available information on VX is the lack of an oral subchronic or chronic toxicity study that demonstrates a clear dose-response relationship between VX exposure and inhibition. If further research reveals that significant toxic effects can be induced by any of the nerve agents evaluated at doses below those that cause significant inhibition, new studies should be conducted to reassess the safety of the recommended RfD for VX. 1 table and 22 references