OSHA comments from the January 19, 1989 Final Rule on Air Contaminants Project extracted from 54FR2332 et. seq. This rule was remanded by the U.S. Circuit Court of Appeals and the limits are not currently in force.
CAS: 460-19-5; Chemical Formula: (CN)2
OSHA previously had no limit for cyanogen. The Agency proposed a limit of 10 ppm as an 8-hour TWA for this colorless gas, which has a pungent, almond-like odor. NIOSH (Ex. 8-47, Table N1) concurred with this proposal, and the final rule establishes the 10 ppm TWA limit, which is the same as that recommended by the ACGIH (1986/Ex. 1-3).
The acute toxicity for cyanogen in various animal species is high (Flury and Zernik 1931d, as cited in ACGIH 1986/Ex. 1-3, p. 154). One hundred ppm was fatal to cats in two to three hours, and 400 ppm was fatal to rabbits in less than two hours. However, rabbits exposed to 100 ppm for four hours showed practically no effects. Cats exposed to 50 ppm were severely affected but recovered (Flury and Zernik 1931d, as cited in ACGIH 1986/Ex. 1-3, p. 154). Investigations in the rat suggest that cyanogen is approximately 10 times less acutely toxic than is hydrogen cyanide (McNerney and Schrenk 1960/Ex. 1-426).
Human tests showed that subjects experienced almost immediate eye and nasal irritation at exposures of 16 ppm (McNerney and Schrenk 1960/Ex. 1-426).
The New Jersey Department of Public Health (Exs. 144, 144A) urged OSHA to set a limit for cyanogen on the basis of EPA's IRIS data. The use of such an approach is discussed in Section VI.A of the preamble.
In the final rule, OSHA is establishing an 8-hour TWA limit for cyanogen. The Agency concludes that this limit is necessary to protect against the significant risk of irritation and systemic effects associated with exposure at the levels permitted in the absence of any OSHA limit. OSHA considers the irritant and systemic effects caused by exposure to cyanogen to be material impairments of health.
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