OSHA had no former limit for iodoform. The ACGIH has an 8-hour TWA limit of 0.6 ppm for this yellow-green powder or crystalline solid with a pungent odor. The proposed PEL was 0.6 ppm as an 8-hour TWA; NIOSH (Ex. 8-47, Table N1) concurred with this limit, which is established by the final rule.
The subcutaneous LD(50) for rabbits is 50 mg/kg, and the oral LD(Lo) for iodoform in dogs is 1000 mg/kg (Kutob and Plaa 1962/Ex. 1-61). These authors also report that, on a molar basis, iodoform has an acute toxicity in mice similar to that of methyl iodide; this conclusion is based on parameters of lethality, barbiturate sleeping time, and bromsulphalein (BSP) retention time. An NCI bioassay (1978c/Ex. 1-1117) of iodoform indicates that the substance is not carcinogenic nor of high systemic toxicity, although histopathological examination of laboratory animals in this bioassay was judged by NCI to be inadequate.
No human data are available for this compound, and OSHA received no comments on this substance, other than those from NIOSH.
In the final rule, OSHA is establishing an 8-hour TWA limit of 0.6 ppm for iodoform, based on the limit being established for methyl iodide (2 ppm TWA); these limits are comparable on a molar iodine basis. OSHA concludes that this limit will protect workers from the significant risks of irritation and hepatotoxicity, both material impairments of health that are associated with exposure to iodoform. The Agency has determined that this limit will substantially reduce these significant risks.