OSHA's former Z tables included an exposure limit of 5 ppm as an 8-hour TWA for xylidine, with a skin notation. In 1982, the ACGIH reduced its TLV to 2 ppm as an 8-hour TWA and retained the skin notation. The proposed PEL was 2 ppm as an 8-hour TWA, and the skin notation was retained. NIOSH (Ex. 8-47, Table N1) concurs with these limits, and they are established by the final rule. Xylidine is a pale yellow to brown liquid. Commercial xylidine is a mixture of isomers.
Several studies indicate that the former OSHA PEL for xylidine is insufficient to protect workers against hepatotoxic and other adverse effects. A paper by von Oettingen, Neal, Sievers et al. (1947, as cited in ACGIH 1986/Ex. 1-3, p. 639) reported liver damage in dogs, rats, cats, and mice repeatedly exposed to 45 ppm xylidine for seven hours per day for a period of 20 to 40 weeks; these exposures also caused death in dogs, cats, and mice. Treon, Sigmon, Wright et al. (1950/Ex. 1-533) noted cardiac, liver, and kidney damage in animals fatally exposed at the following doses: cats, 17 ppm; guinea pigs, 50 ppm; and rabbits, 60 ppm; cyanosis was also observed in these animals. Only NIOSH commented on xylidine.
In the final rule, OSHA is reducing the existing 8-hour TWA to 2 ppm and retaining the skin notation for xylidene. The Agency concludes that these limits will protect workers from the significant risk of exposure-related cardiac, kidney, and liver damage, all of which constitute material health impairments.