Tenth Interim Report of the Subcommittee on Acute Exposure Guideline Levels (2004)

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TENTH INTERIM REPORT OF THE SUBCOMMITTEE ON ACUTE EXPOSURE GUIDELINE LEVELS 17 is proposed is speculative and does account for the toxicity of boric acid or the interaction of boric acid and HCl. The argument presented here is less than convincing and not supported by the comparison of LC50 values shown in Table 3 (that is meant to be supportive). Table 3 shows LC50 values for boron trichloride that are higher than would be predicted given the mole equivalent to HCl. However, this is based on data from only one study using one species (Vernot et al., 1977). Using the proposed surrogate approach appears to provide conservative AEGLs, but the data are not convincing. This approach assumes that boric acid is not responsible for the observed toxicity or has a negligible contribution relative to HCl; there is no discussion to support or refute this. Page 7, lines 23–24. Delete. One cannot conclude that male animals are “more sensitive” than female animals from the LC50 values listed in Vernot et al. (1977) report. Note that the LC50 values for boron trifluoride are nearly identical for both genders under identical conditions used for the Vernot BCl 3 study. Only if a true difference in “sensitivity” of the sexes can be demonstrated for HCl—which is considered by NAC as the active entity—can this argument be considered consistent with the weight-of-evidence for boron trichloride on this point. Page 11, Section 8.2. Given that no TLVs or other values are available for BCl 3 but that occupational limits have been developed for other boron halides and HCl and AEGLs have been finalized for HCl, it is worthwhile to insert and compare that information here. It is noteworthy that the TLV ceiling values for BBr3 and BFl3 are identical (1 ppm) and are both based on avoidance of “even transient irritation and complaints.” Routine control of these materials at ~1/3 the TLV ceiling results in values not dissimilar from the AEGL-1 values presented in Table. 7. Pages A-3 to C-3. Delete. Refer the reader to the published AEGL volume of HCl documentation that contains the (AEGLs Volume 4, in preparation). Reduce the text and eliminate the reproduction of the HCl documentation. Condense the BCl3 documentation to address the parent material, its decomposition to HCl and boric acid, the issues surrounding boron, and refer the reader to the derivation of the AEGL values for HCl. Indicate clearly that the AEGL values for BCl3 were developed by analogy to HCl, just as was done by the TLV committee in the case of BBr3 on page 145 of the TLV 6th edition. The NAC should reproduce one copy of the final summary AEGL table for HCl for all time points, since these values were all utilized for BrCl3. COMMENTS ON CHLORINE TRIFLUORIDE At its July 21–23, 2003 meeting, the subcommittee reviewed the AEGL document on chlorine trifluoride. The document was presented by Sylvia Talmage of Oak Ridge National Laboratory. The subcommittee recommends one minor revision. The document can be finalized if the recommended revision is made appropriately.