REVIEW OF GRAZING STUDIES ON PLUTONIUM-CONTAMINATED RANGELANDS Donald D. Smith Environmental Monitoring and Support Laboratory--Las Vegas U.S. Environmental Protection Agency, Las Vegas, Nevada ABSTRACT Literature is cited that has provided data on tissue actinide concentrations in grazing animals when the actinide dosages resulted from artificial administration or from periodic exposure. Only one longterm study is known where a reproducing beef herd was restricted to a plutonium-contaminated environment. Highlights of this study that are reviewed and discussed include: relationship of ingesta concentrations to food habits; tissue concentration related to length of exposure and level of exposure; and the concentration range in various tissues. Emphasis is given to the gonadal concentration which is approximately 25 times that of muscle and blood. Future study plans are also discussed. INTRODUCTION In recent years, there have been several reports published that listed data on actinide levels in the tissues of grazing or browsing animals that periodically ranged over plutonium-contaminated areas or were exposed to worldwide fallout (Fountain, 1961; Brechbill, 1969; Hakonson et al., 1973; Smith and Giles, 1974; Smith and Giles, 1975; Smith and Black, 1975: Smith et al., 1976a; Smith et al., 1976b; and Brown et al., 1976). Other studies have been conducted in which actinides were administered either orally, intravenously, or by inhalation (McClellan et al., 1962; Moskalev et al,, 1969; Stanley et al., 1974; Stanley ‘et al., 1975; and Sutton, 1976). However, only one study has been conducted in which reproducing beef cattle were restricted for an extended period of time to a plutonium-contaminated range whose native vegetation supplied all subsistence. This study, conducted under the auspices of the Nevada Applied Ecology Group, took place within the fenced compounds of the Project 57 site in Area 13 of the Nevada Test Site and extended from May 1973 to April 1976. During this time, tissue samples were collected from 20 cattle, 4 fetuses, 2 goats, and selected wildlife. In addition to the tissue samples collected from the sacrificed animals, ingesta samples were collected from the rumen-fistulated steers (steers with a capped tube inserted into a permanent surgical opening into the stomach) which periodically grazed the most highly contaminated areas. 407