OSHA's former PEL for titanium dioxide was 15 mg/m3 as an 8-hour TWA; this was the Agency's generic exposure limit for particulates. A 10-mg/m3 8-hour TWA, measured as total dust, has been established by the ACGIH. The Agency proposed a PEL of 10 mg/m3 (total particulate) for titaniom dioxide, and this limit is established in the final rule. Titanium dioxide is a white crystalline solid.
Miller and Sayers (1941/Ex. 1-595) reported that intraperitoneal injections of titanium dioxide in guinea pigs showed a tendency to remain in the injected tissues but not to produce a proliferative response. A study by Grandjean, Turrian, and Nicod (1956/Ex. 1-638), in which rats were administered 50 mg of titanium dioxide intratracheally, showed pigmented dust deposits in the lungs. In addition, evidence of infection appeared in the alveoli of one rat and diffuse fibrosis was found in the lungs of a separate test animal. No nodule formation was observed (Grandjean, Turrian, and Nicod 1956/Ex. 1-638). Another study by Dale (1973/Ex. 1-624) revealed thickening of the walls of the alveoli in the lungs of rabbits injected with titanium dioxide dust; however, lungs had returned to normal by three months post-treatment. Feeding studies of rats and mice at doses of 2.5 percent or 5 percent titanium dioxide for 103 weeks revealed no signs of carcinogenicity in either species (National Cancer Institute (NCI) 1979d/Ex. 1-947).
At the rulemaking hearing, NIOSH (Tr. p. 3-95) testified that exposure to this substance is associated with "a risk of cancer....The incidence of tumors in animals exposed to titanium dioxide (Lee, Trochimowicz, and Reinhardt 1985) meets the...criteria for...[a] potential occupational carcinogen." Accordingly, NIOSH (Ex. 8-47, Table N4) recommends a full 6(b) rulemaking for this substance. In response to NIOSH, OSHA notes that the Agency intends to monitor the developing literature on titanium dioxide to determine whether an additional reduction in the PEL is warranted. NIOSH was the only commenter on titanium dioxide.
OSHA is establishing 8-hour TWA of 10 mg/m3 (total particulate) for titanium dioxide in the final rule. OSHA concludes that the final rule's limits will protect workers from the significant health risks associated with exposure to titanium dioxide at higher levels. These risks include material impairments of health in the form of eye, skin, and other physical irritation, and, perhaps, of carcinogenicity.