A rapid screening of hazard method (RASH) is presented for deriving relative potency estimates for hazardous substances. The method utilizes data from any available toxicological database such as the Registry of Toxic Effects of Chemical Substances (RTECS) or EPA's GENE-TOX database on genetic activity profiles. The method has been applied to derive relative potency values and permissible environmental concentrations for 278 chemicals. The derived values have been compared with recommendations of expert committees where possible, and substantial agreement is found.

Food-chain transport of Pb-210 and Po-210 from soil to edible plant parts and from animal feed to meat and milk were evaluated from a review of literature. The degree of transfer was characterized by estimating concentration factors (unweighted arithmetic means) as well as the transfer coefficients B v , B r (unweighted geometric means), f m and f f (unweighted arithmetic means). Global dietary intake of Pb-210 and Po-210 was also summarized, and 50-year dose estimates to target organs calculated. The greatest estimated ingestion doses were those to populations with large dietary complements of animal protein in the form of seafood (Japan) or caribou/reindeer muscle and organ meats (Arctic Eskimos and Lapps). The magnitude of this latter source illustrates the importance of simple food chains in generating significant exposures to populations dependent upon them. The origin and magnitude of inhalation exposure and dose from tobacco products was also assessed. For the majority of internal organs evaluated, the dose resulting from smoking commercially available tobacco products is comparable to or greater than the dose estimates for ingestion of naturally occurring dietary Pb-210 and Po-210. vii distance from supposed sites of release due to the extreme mobility of the noble gas Rn-222 [T ½ = 3.8 d (Kocher, 1977)], an intermediate product of Ra-226 decay. The rapid decay of Rn-222 in the atmosphere generates Pb-210 and Po-210, which are adsorbed by aerosols and returned to earth as surficial deposition or rainout. The degree of potential long-range atmospheric transport in North America has been previously demonstrated for Rn-222 (Travis et al., 1979). Other intermediates in the decay

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NOTICE This document contains information of a preliminary nature. It is subject to revision or correction and therefore does not represent a final report.

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