Technical Basis
The current review and analysis included hydrated forms of magnesium silicate, of which, Talc is defined as magnesium silicate with an unspecified amount of water. A review of available data source identified the following: an IDLH and REL-TWA for hydrous magnesium silicate (Talc; CASRN: 14807-96-6). The IDLH for Talc was selected as the TEEL-3 basis, as the most preferred source (Table 3.1). Note that the 1990 and 1994 IDLH reported by NIOSH are equivalent. A TEEL-2 value was calculated from the TEEL-3 according to Table 3.5 of the handbook. The REL-TWA (respirable dust) was selected as the TEEL-1 basis.
• TEEL-1 = REL-TWA (2 mg/m3) x 3
• TEEL-2 = TEEL-3/6
• TEEL-3 = IDLH, 1990/1994 (1000 mg/m3)
This review generated TEEL values that are more conservative than those published in Rev. 29A. The basis for Rev. 29A was an HHR=1, which is less preferred than an IDLH, even when considering the ambiguity of the chemical of interest.