ZINC STEARATE

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: 557-05-1; Chemical Formula: Zn(C₁₈H₃₅O₂)₂

OSHA formerly regulated zinc stearate under its generic total particulate limit of 15 mg/m³ TWA. The proposed PEL was 10 mg/m³ (total particulate), and the final rule promulgates this limit. NIOSH (Ex. 8-47, Table N4) agrees that this PEL is appropriate. The ACGIH has established an 8-hour TWA of 10 mg/m 3 for zinc stearate, measured as total dust. Zinc stearate is a white hydrophobic powder.

A report in Folia Medica (Volita and Noro 1957, as cited in ACGIH 1986/Ex. 1-3, p. 646) documented the case of a worker exposed to zinc stearate dust for 30 years who died from extensive fibrosis of the lungs. More recent studies have revealed incidences of pulmonary fibrosis associated with encephalopathy that stemmed directly from exposure to aluminum dust, which is frequently coated with stearic acid (British Journal of Industrial Medicine 1962, as cited in ACGIH 1986/Ex. 1-3, p. 646); the ACGIH (1986/Ex. 1-3, p. 646) is uncertain of the relevance of this report to zinc stearate exposures.

Observations of long-term worker exposures to this dust in the rubber industry revealed no adverse effects of exposure (B.F. Goodrich Rubber Company, private communication, as cited in the ACGIH 1986/Ex. 1-3, p. 646). NIOSH was the only commenter on zinc stearate.

OSHA is establishing a 10-mg/m³ TWA limit for this particulate (measured as total particulate) and is retaining the 5-mg/m³ TWA limit for the respirable fraction. The Agency concludes that these limits will prevent the significant health risks associated with workplace exposures to zinc stearate dust at higher levels. OSHA finds that the pulmonary effects potentially associated with exposure to zinc stearate constitute material impairments of health within the meaning of the Act.