ESTIMATION OF A CHROMIUM INHALATION REFERENCE CONCENTRATION USING THEBENCHMARK DOSE METHOD - A CASE-STUDY

The benchmark dose (BD) method has been proposed as an alternative to the NOAEL/UF method for setting reference levels. The BD is the 95% lo wer confidence limit on a dose corresponding to a 10% increase (or rel ative change) in an adverse effect. A case study exploring the suitabi lity of the current Cr(III) and Cr(VI) inhalation toxicity data bases to the BD approach is presented. Because chromic acid mists, typical o f many occupational Cr(VI) exposures, present a toxicological profile different from that of Cr(VI) particulates, representative of environm ental exposures, Cr(VI) particulate data were evaluated separately fro m Cr(VI) acidic mist data. The current Cr(III) and Cr(VI) acidic mist data bases proved inadequate for BD analysis due to data and/or study quality limitations. Benchmark reference concentrations (RfCs) for par ticulate Cr(VI) ranging from 0.34 mu g/m(3) (for lactate dehydrogenase (LDH) in bronchoalveolar lavage fluid (BALF)) to 1.4 mu g/m(3) (for i ncreased lung weights) are derived from data taken from U. Glaser et a l. (Arch. Toxicol. 57, 250-256, 1985) and U. Glaser et al. (Environmen tal Hygiene II, Springer-Verlag, Berlin/New York, 1990). A Cr(VI) part iculate RfC of 0.34 mu g/m(3) based upon LDH in BALF as the critical e ffect is proposed. This value may be viewed as conservative since it r epresents the 95% lower confidence limit on the dose associated with a 10% increase in response for a sensitive endpoint and has appropriate dosimetric adjustments and uncertainty factors incorporated. (C) 1994 Academic Press, Inc.