A review of available sources identified the following: a TLV-STEL, an IDLH (1990, 1994,) and LD50 acute toxicity data. The chemical health hazard rating (NFPA=2,) and LD50 for a similar chemical (phthalic acid, CASRN: 88-9-3) were also evaluated. 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 1990 IDLH is based on LD25 animal toxicity, while the 1994 IDLH is ten times a NIOSH REL-TWA. When this IDLH is compared with TEELs from acute animal toxicity and an HHR between 1 and 2 (estimated from an NFPA=2), the 1990 IDLH is not conservative enough and the 1994 IDLH is overly conservative. Given these conflicting results and considering reports that phthalic anhydride is likely be hydrated when inhaled, a rat oral LD50 for phthalic acid (CASRN: 88-99-3) was selected as the TEEL-3 basis. The TEEL-2 was derived according to Table 3.5. The TLV-STEL for phthalic anhydride was selected as the TEEL-1.
• TEEL-1 = TLV-STEL (0.005 mg/m3)
• TEEL-2 = TEEL-3/6
• TEEL-3 = Rat oral LD50 (phthalic acid, CASRN: 88-99-3) (7.9 g/kg)
This review generated TEEL values that are less conservative than Rev. 29A. The Rev. 29A basis was a 1990 IDLH, which is based on LD25 data. The current TEEL-3 basis is a rat LD50 of a similar compound which is more conservative, but not overly restrictive. The Rev. 29A TEEL-2 basis was a rat oral TDLo not found during current research, while the current TEEL-2 is derived from the TEEL-3 (Table 3.5). The Rev. 29A TEEL-1 basis was a TLV-TWA, while the current basis is a higher priority TLV-STEL (Table 3.1).