ZINC OXIDE DUST

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: 1314-13-2; Chemical Formula: ZnO

OSHA formerly had no exposure limit specifically for zinc oxide dust. The ACGIH has a limit of 10 mg/m³ as an 8-hour TWA for zinc oxide, measured as total dust. The proposed PEL was 10 mg/m³, and this limit, measured as total particulate, is established by the final rule. Zinc oxide dust is a white or pale yellow powder.

According to Turner and Thompson (1926/Ex. 1-1124), exposure to finely divided zinc oxide dust can produce symptoms similar to those for metal fume fever. Beeckmans and Brown (1963/Ex. 1-775) reported that catalytically active zinc oxide dust is more toxic when treated with ultraviolet light. Aside from these considerations, the ACGIH considers zinc oxide dust to be a nuisance dust.

Two comments on zinc oxide were submitted to the rulemaking record (Exs. 3-673 and 3-675), but neither of these comments addressed the health effects associated with zinc oxide exposure. NIOSH does not concur with these limits; the NIOSH RELs for zinc oxide dust are 5 mg/m³ TWA (respirable fraction) and 15 mg/m³ (total dust) as 15-minute ceilings (Ex. 8-47, Table N4). NIOSH believes that exposure to zinc oxide dust causes respiratory effects and cites Gupta, Pandey, Misra, and Viswanathan (1986); Lam, Conner, Rogers et al. (1985); and NIOSH (1975d) in support of this view. OSHA will monitor developments on the toxicology of zinc oxide in the future to ensure that the PELs for this substance are protective .

In the final rule, OSHA is establishing limits of 10 mg/m³ TWA (total particulate) and 5 mg/m³ TWA (respirable particulate) for zinc oxide. The Agency concludes that these limits will protect workers from the significant risk of material health impairment in the form of physical irritation and, perhaps, of respiratory effects.