A review of available sources identified the following: a LOC, and numerous acute toxicity data (LCLo, LD50, TDLo) for various routes and species. Additionally, available exposure limits (TLV-TWA, IDLH, AEGLs) for mercury (CASRN: 7439-97-6) were also evaluated. Data sources were selected according to the hierarchy listed in Table 3.1. Toxicity data were selected based on the 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. Inhalation exposures were scaled to 60-minute equivalents using the ten Berge equation (Section 3.3.4). Mercury(II) chloride was determined to be both hazardous and corrosive; mercury exposure limits did not accurately capture these effects, so use of mercury exposure limits was determined inappropriate for TEEL development. The source of the LOC could not be determined; these were historically derived from IDLH values, which was not identified during review. Considering this, and the lack of conservatism in the LOC value, this source was determined inappropriate for TEEL development. Available human TDLo data was reviewed, however these 1) did not list appropriate toxicity endpoints for TEEL development or 2) were based on general exposure to inorganic mercury, not mercury(II) chloride. Of remaining available acute toxicity data, the most preferred source, a rat oral LD50, was selected as the TEEL-3 basis. TEEL-2 and TEEL-1 values were derived according to Table 3.5.
• TEEL-1 = TEEL-2/11
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat oral LD50 (35 mg/kg)
This review generated TEEL values more conservative than those in Rev. 29A. The Rev. 29A TEEL-3 values were derived from molecular weight adjusted mercury exposure limits (TVL-TWA, REL-C, IDLH). The current review determined that this is not an appropriate analog for mercury(II) chloride because it does not account for its corrosivity. Instead, a rat oral LD50 was selected as the TEEL-3 basis, with TEEL-2 and TEEL-1 values derived from this TEEL-3.