The volunteers in thece tests are enlisted US Army personnel. These tests are governed by the principles, policies, and rules for medical volunteers as established in AR 70-25. DIGESTThis report summarizes information on the physiological and toxicological effects of three riot control agents: CS, o-chlorobenzalmalononitrile; CN, chloroacetophenone; and DM, dimethyl aminochloroarsine. Included in the report is a review of the toxicity tests conducted on the old compounds CN and DM by various organizations from 1918 to the present, and on CS from 1958 to the present. Detailed results of experiments conducted by the Toxicology Department, Medical Research Laboratory, by various methods on animals of several species are given. Based on the animal experiments, estimates are given for lethal doses in man. Incapacitating doses P.e determined and reported on the basis of tolerance times of volunteers exposed to aerosols of th[e three compounds. Safety fac..ors, dern ed from ratios of estir, ated lethal doses to bncapacitatipg dimes, are reported for the three compour•ds, P CONTENTS

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JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The National Institute of Environmental Health Sciences (NIEHS) andBrogan & Partners are collaborating with JSTOR to digitize, preserve and extend access to Environmental Health Perspectives.Vinyl chloride monomer (VCM), already identified as a human animal carcinogen, was selected as a model agent to explore an area of concern for single and intermittent low level exposure. In traditional cancer bioassay, animals are repeatedly exposed over their lifespan to a dose of suspected chemical.In the current studies rats and mice were exposed in an inhalation chamber to single one-hour doses of VCM ranging from 50 to 50,000 ppm.A second group was given 10 one-hour exposures to 500 ppm or 100 one-hour exposures to 50 ppm of the same chemical. All animals were then observed for the remainder of their lives, generally 18-24 months. Moribund animals were euthanized, and survivors were sacrificed on schedule and their tissues examined for pathological changes. Specifically, the oncogenic study demonstrated dose related effects for single one-hour exposure of VCM at high levels, i.e., 5,000 and 50,000 ppm. These concentrations increased the incidence of pulmonary adenomas and carcinomas in mice.