ZINC OXIDE (FUM)
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’s former exposure limit for zinc oxide fume was 5 mg/m3 as an 8-hour TWA. The ACGIH recommends a 5 mg/m3 TWA and also has a STEL of 10 mg/m3. NIOSH recommends a 5 mg/m3 10-hour TWA limit with a 15-minute ceiling of 15 mg/m3. OSHA proposed to retain the 5 mg/m3 8-hour TWA and to add a STEL of 10 mg/m3, and NIOSH (Ex. 8-47, Table N1) concurs with this proposal. The final rule establishes these limits. When heated, zinc oxide produces a white fume.
The most prevalent toxic effect of zinc oxide fume is a condition known as “metal fume fever,” whose symptoms include chills, fever, muscular pain, nausea, and vomiting (Turner and Thompson 1926/Ex. 1-1124). Studies in the workplace have shown that welders exposed to zinc oxide fume at concentrations of 320 to 580 mg/m3 reported nausea, with the development of chills, shortness of breath, and severe chest pains 2 to 12 hours later. Most workers took approximately 4 days to recover, and some eventually developed pneumonia (Hammond 1944/Ex. 1-981). Other studies have reported the frequent occurrence of chills in workers exposed to zinc oxide at levels as low as 5 mg/m3 (Hickish 1963 and Wall 1970, both as cited in ACGIH 1986/Ex. 1-3, p. 645). Hammond (1944/Ex. 1-981) reported that workers exposed to 8 to 12 mg/m3 of zinc oxide fume did not suffer from metal fume fever.
Zinc oxide exposures of guinea pigs that lasted only an hour caused a drop in body temperature, followed 6 to 18 hours later by an increase above normal levels (Turner and Thompson 1926/Ex. 1-1124). The animals in the high-exposure group (2500 mg/m3 for three to four hours) died after exposure.
Early studies (Drinker, Thomson, and Finn 1927/Ex. 1-356) suggested that metal fume fever was unlikely to occur at concentrations below 15 mg/m3, but subsequent experience shows that exposures even at 5 mg/m3 can cause this syndrome (Hickish 1963 and Wall 1970, both as cited in ACGIH 1986/Ex. 1-3, p. 646).
NIOSH’s criteria document (1975d, as cited in ACGIH 1986/Ex. 1-3, p. 645) reported that the development of metal fume fever was unlikely at levels as low as 5 mg/m3, but the Institute stated that exposures to the fume at this level could cause chronic respiratory effects. Dr. Lawrence Hecker, representing Abbott Laboratories (Ex. 3-678), objected to a STEL for zinc oxide fume. However, in both its criteria document (1975d) and post-hearing testimony (Ex. 150, Comments on Zinc Oxide Fume), NIOSH indicated that a short-term limit is necessary to “prevent pathological tissue changes in the lung from acute exposure.” Therefore, OSHA finds that a STEL for zinc oxide fume is necessary to prevent or minimize these effects.
In the final rule, OSHA is retaining the 5 mg/m3 8-hour TWA and adding a STEL of 10 mg/m3. The Agency concludes that both of these limits will protect workers from the significant risk of metal fume fever, which constitutes a material health impairment that is associated with acute and chronic exposure to zinc oxide fumes.