CALCIUM CYANAMIDE

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: 156-62-7; Chemical Formula: CaNC=N

OSHA formerly had no limit for calcium cyanamide. The ACGIH has a TLV-TWA of 0.5 mg/m³ for this crystalline gray material. The proposed PEL was an 8-hour TWA of 0.5 mg/m(3, and NIOSH (Ex. 8-47, Table N1) concurs with this limit, which is established in the final rule.

Data regarding the acute toxicity of calcium cyanamide are sparse. The oral LD(50) in rabbits is 1400 mg/kg, and that for rats is 1000 mg/kg (Spencer 1973, as cited in ACGIH 1986/Ex. 1-3, p. 91).

Skin and eye irritation have been reported in rats and rabbits, with significant irritation occurring when 100 mg of calcium cyanamide is placed directly into the eyes of rabbits (Martin 1975, as cited in ACGIH 1986/Ex. 1-3, p. 91). Severe skin irritation developed in rabbits when a paste of this substance was applied to the shaved abdominal skin for 24 hours (Martin 1975, as cited in ACGIH 1986/Ex. 1-3, p. 91). Two of five animals died when the dose was 10 g/kg, but all survived a dose of 5 g/kg.

Most cases of industrial calcium cyanamide poisoning involve primary skin irritation or sensitizing dermatitis. Skin irritation develops in the form of an erythematous rash over the surfaces of the body that are exposed to the substance or those body surfaces irritated by clothing or perspiration. Some individuals develop a macular rash on exposure, and this may progress to the weeping stage. In addition, exposed workers may develop temporary vasomotor disturbances of the upper body, with susceptibility increasing with alcohol intake (Fassett 1963d, as cited in ACGIH 1986/Ex. 1-3, p. 91). Calcium cyanamide is used medically for its Antabuse-like effect, and the maintenance dose in adults is between 50 and 100 mg/day (Hald, Jacobsen, and Larson 1952/Ex. 1-905). No comments, other than NIOSH’s, were received on this substance.

In the final rule, OSHA is establishing an 8-hour TWA PEL of 0.5 mg/m³ for calcium cyanamide. The Agency concludes that this limit will substantially reduce the significant risks of material health impairment in the form of eye and skin irritation, sensitizing dermatitis, and the occurrence of Antabuse-like effects, which were possible at the levels of exposure formerly permitted by the absence of an OSHA limit.