A review of available sources identified animal and human acute toxicity data (LD50, TDLo) for several routes. In addition, there are exposure limits for aryl and inorganic mercury compounds (inorganic mercury, CASRN: 7439-97-6; ceiling limits, TWAs, ERPG-3/ERPG-2, and IDLH). Data sources were selected according to the hierarchy listed in Table 3.1. Toxicity data were selected according to type of exposure, species, and route according to the hierarchies stated in Sections 3.3.1, 3.3.2, and evaluated using factors in Tables 3.2, 3.3, and 3.4. The mercury aryl and inorganic compounds ERPG-3 and ERPG-2 were selected as the TEEL-3 and TEEL-2, respectively. Note that mercuric cyanide animal toxicity doses evaluated resulted in TEEL-3 values comparable in magnitude to these exposure limits while the human TDLo resulted in values several orders of magnitude greater than ceiling limits. The mercury TLV-TWA was selected as the TEEL-1 basis and a compound adjustment factor was applied (Section 3.2.2).
• TEEL-1 = MW-adjusted TLV-TWA (mercury, aryl and inorganic compounds, CASRN: 7439-97-6, 0.025 mg/m3) x 3
• TEEL-2 = ERPG-2 (mercury, aryl and inorganic compounds, CASRN: 7439-97-6, 0.25 ppm)
• TEEL-3 = ERPG-3 (mercury, aryl and inorganic compounds, CASRN: 7439-97-6, 0.5 ppm)
This review generated TEEL-3 and TEEL-2 values inconsistent with Rev. 29A. The Rev. 29A TEEL-3 basis was the mercury 1990 IDLH (CASRN: 7439-97-6) and the Rev. 29A TEEL-2 basis was a mercury PEL-C; compound adjustment factors were applied to both limits. The current TEEL-3 and TEEL-2 are unadjusted ERPGs for mercury aryl and inorganic compounds (CASRN: 7439-97-6), a higher priority source (Section 1). The Rev. 29A and current TEEL-1 values, methodology, and source are consistent.