OSHA formerly had a limit of 0.1 mg/m3 TWA, with a skin notation, for octachloronaphthalene. The Agency proposed to obtain the 8-hour TWA and to add a STEL of 0.3 mg/m3, also with a skin notation, for this substance, and NIOSH (Ex. 8-47, Table N1) concurred. These limits are established in the final rule. Octachloronaphthalene is a nonflammable, pale yellow, waxy solid containing 70 percent chlorine.
Inhalation toxicity data for octachloronaphthalene fumes or dust are lacking, but exposure to the chloronaphthalenes causes acne-like lesions that itch severely. Repeated exposures to the fumes of molten chlorinated naphthalenes can cause severe and sometimes fatal systemic poisoning and are especially damaging to the liver (Patty 1963g/Ex. 1-845). Ingestion studies of cattle have shown different toxicities for different naphthalenes, with toxicity increasing with the compound's degree of chlorination (Sikes, Wise, and Bridges 1952/Ex. 1-804). However, these data are controverted by another report in which octachloronaphthalene was found to be less toxic than the hexachloro derivative (Bell 1953/Ex. 1-951). This divergence in the data may be due to differing methods of administration (suspension versus solution), or may reflect the soluble form's greater capacity for absorption (ACGIH 1986/ Ex. 1-3, p. 447). NIOSH was the only submitter of comments specifically relating to octachloronaphthalene.
In the final rule, OSHA is retaining the 8-hour TWA PEL of 0.1 mg/m3 and adding a STEL of 0.3 mg/m3, with a skin notation, for octachloronaphthalene. The Agency concludes that this combined limit will protect workers against the significant risks of serious liver damage and dermal lesions, which constitute material health impairments and are associated with exposure to this substance at the elevated levels permitted by an 8-hour limit alone. The skin notation is retained because of octachloronaphthalene's demonstrated ability to cause systemic toxicity by percutaneous absorption.