Previously, OSHA had no limit for cyhexatin. The ACGIH has a TLV-TWA of 5 mg/m3. The proposed PEL was an 8-hour TWA of 5 mg/m3. NIOSH (Ex. 8-47) concurred with the proposed limit and this is the limit established by the final rule. At room temperature, cyhexatin exists in the form of white crystals.
Cyhexatin has oral LD(50)s of 500, 700, and 654 mg/kg for rabbits, guinea pigs, and chickens, respectively. The intraperitoneal LD(50) for the rat is 13 mg/kg (NIOSH 1977i/ Ex. 1-1182), and the oral LD(50) for rats has been reported to be 190 mg/kg (ACGIH 1974, as cited in ACGIH 1986/Ex. 1-3, p. 165). Skin exposure to a 1- to 2-percent solution of cyhexatin in goats and cattle caused mild effects; sheep showed mild effects after application of a 0.5-percent solution. One of five sheep died from multiple skin applications of a 1-percent suspension (Johnson, Younger, Witzel, and Radeleff 1975/Ex. 1-336).
The toxicity of cyhexatin is considered to be moderate, although it is greater than the toxicity of most other organic tin compounds. Long-term feeding in rats produced no behavioral changes, mortality, tissue changes, or hematologic or biochemical changes in response to two years of dosing at 12 mg/kg per day; however, dosed animals were smaller than controls. After daily doses by gavage of 24 mg/kg per day for two weeks, rats showed microscopic changes in the liver, kidneys, and adrenal glands at autopsy. Six mg/kg is considered to be the no-effect level in rats, and in dogs, the no-effect feeding level is reported to be 3 mg/kg. Rats fed 4 to 6 mg/kg, and rabbits fed 3 mg/kg, showed no ill effects on indices for fertility, gestation, viability, or lactation (Dow Chemical Company 1973d, as cited in ACGIH 1986/Ex. 1-3, p. 165). No inhalation data on animals are available, and there are no human data. Other than the comment by NIOSH (Ex. 8-47), no comments were received on this substance.
In the final rule, OSHA is establishing an 8-hour TWA limit of 5 mg/m3 for cyhexatin. OSHA concludes that a PEL of 5 mg/m3 will protect workers against the significant risk of skin and respiratory irritation, as well as other possible adverse effects associated with exposure to this tin compound in the absence of a current limit. The Agency considers eye and respiratory irritation to be material health impairments within the meaning of the Act.