chapter  40
Human Risk Assessment of Chemical Warfare Agents from Skin Exposure
ByRonald C. Wester, Hanafi Tanojo, Xiao-Ying Hui, Hongbo Zhai, Howard I. Maibach, Eugene Olajos, Harry Salem
Pages 32

The objective was to perform analysis on existent dermal absorption data on selected organophosphorus (OP) compounds including chemical warfare agents (CWA)— sarin (GB), soman (GD), and VX-and develop a postulate of critical factors in observed regional differences in toxicant uptake/absorption by human skin. Body contours for skin absorption and lethality were developed. Parathion and malathion exposed head and neck region (4), trunk (3) and genital area (12) absorb more chemical than arms and hands, and legs and feet. In field userparathion has caused human death, while malathion is considered safe. Human skin is more permeable to parathion than malathion. Permeability constants (Kp) (potential chemical absorbed through human skin per unit area and time) indexed to regional variation gives the mass of chemical absorbed through all regions of the human body. Further overlap of toxicity data to the constant showed lethality with parathion but not for malathion. VX has a high Kp and is also the most toxic; 50% lethality is reached when exposure is to any single region of the body. Sarin and soman are less toxic percutaneously than VX and they have the same toxicity level. However, soman has greater skin absorption than sarin. Estimate of 50% lethality is only reached for sarin at the 24-hour exposure level, whereas the 50% lethality estimate for soman is reached in the first hour.