Travis and Arms revisited: a second look at a widely used bioconcentration algorithm

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.