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In 1988, Travis and Arms reviewed the literature and collected data to develop a relationship between the octanol-water partition coefficient (Kow) and the uptake of organic compounds into milk and beef (Travis and Arms, 1988). These equations have been utilized for predicting biotransfer factors for organic chemicals when empirical data are lacking. During the external peer review of the draft US Environmental Protection Agency (EPA) guidance entitled Human Health Risk Assessment Protocol for Hazardous Waste Combustion Facilities (US EPA, 1998) and the development of Superfund's Ecological Soil Screening Levels (US EPA, 2000b), questions challenging the derivation and use of these equations were raised. The primary questions raised were: 1) Are the equations presented in Travis and Arms (1988) for the estimation of transfer of organic compounds from contaminated feed to beef and milk technically valid and reproducible? If so, (2) are the equations appropriate across the entire log Kow range? For these reasons, this study was undertaken to validate the original Travis and Arms equations, to review more recent literature, and. if appropriate, to add to the original Travis and Arms data set to obtain updated equations. This paper presents an evaluation of the original Travis and Arms equations, limitations to their use, and steps to reduce uncertainties associated with their use by updating with more current literature.

Provisional Advisory Levels (PALs) are concentrations in air and drinking water for priority toxic chemicals. This article summarizes the Standing Operating Procedure (SOP) currently in place for the data-driven development of chemical-specific PALs. To provide consistency and transparency, and to avoid faults of arbitrariness, the SOP was developed for guidance in deriving PAL values. Three levels (PAL 1, PAL 2, and PAL 3), distinguished by severity of toxic effects, are developed for 24-hour, 30-day, 90-day, and 2-year durations of potential drinking water and inhalation exposures for the general public. The SOP for PAL development focuses on (1) data acquisition and analysis, (2) identification of a chemical-specific critical effect, (3) selection of a quantitative point-of-departure (POD), (4) uncertainty analysis and adjustments, (5) exposure duration adjustment and extrapolation, (6) identification of special concerns and issues, and (7) verification, documentation, and dissemination of PALs. To avoid uncompromising rigidity in deriving PAL values and to allow for incorporation of new or refined methodologies, the overall procedure is fluid and subject to modification. The purpose of this publication is to provide a summary of this SOP.