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 19 Clarify the comment on Section 8.3 that “potential unidentified reactive intermediates…may be involved in the toxicity…” If other toxic decomposition products could result, then this reduces the confidence one can place in the AEGL derivations based on analogy to HCl. Page 26, lines 9–13. What are the details of the study? What strain of rats were used and what gross and microscopic pathology was observed? Were the lungs properly prepared for fixation and sectioning? Were any special studies on the tissues performed? AEGL-2. Delete the sentence on page 8, lines 39–40. “The modifying factor of 3 is considered insufficient due to the steepness of the concentration-response curve.” This is not needed as there are two other mentioned reasons; further, the slope of the curve can be argued as a reason for a larger uncertainty factor. The AEGL-2 and AEGL-3 were derived using the HCl data for time scaling, but in each case a different approach was taken with the same data. This is inconsistent. As the HCl document is being finalized, it may be necessary to make these two documents consistent. COMMENTS ON TRICHLOROMETHYL SILANE At its July 21–23, 2003 meeting, the subcommittee reviewed the AEGL document on trichloromethyl silane. The document was presented by Cheryl Bast of Oak Ridge National Laboratory. The subcommittee recommends the following revisions. A revised draft should be reviewed by the subcommittee at its next meeting. General Comment The AEGL for the chlorosilanes should not be finalized until the AEGL document for HCl is finalized. The AEGL document on HCl should be added as a reference and cited at several key places where the AEGL derivation for trichloromethyl silane is dependent on the AEGL document for HCl. Specific Comments Clarify the comment in Section 8.3 on page 12 that “potential unidentified reactive intermediate…may be involved in the toxicity…” If the toxic decomposition products could result, this undermines the AEGL derivations based on an analogy to HCl. Page 3, Table 2. Add the time to death for the one female that died when exposed to 1047 ppm. Page 4. The death of one of two animals is formated incorrectly as the fraction 1/2. Page 6, lines 10–12. See the statement above about dichlorodimethyl silane combustion/decomposition products, as this applies to trichloromethyl silane as well.