BARIUM SULFATE

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: 7727-43-7; Chemical Formula: BaSO₄

OSHA formerly had no specific limit for barium sulfate, although OSHA’s generic 15-mg/m³ total particulate limit previously applied; the ACGIH has a TLV-TWA of 10 mg/m³, total dust, for this substance. The proposal included a 10-mg/m³ TWA PEL for barium sulfate (total particulate), and the final rule establishes this limit and additionally retains the 5-mg/m³ PEL for the respirable fraction. Barium sulfate is a white or yellowish, odorless, tasteless powder.

Einbrodt, Wobker, and Klippel (1972/Ex. 1-1020) exposed rats to a concentration of 40 mg/m³ for two months and concluded that barium sulfate is not toxic. As an inert dust of the noncollagenous type, however, barium sulfate has the potential to cause pneumoconiosis through tissue reactions to accumulated dust in the lung (Anonymous, British Medical Journal 1972, as cited in ACGIH 1986/Ex. 1-3, p. 48). Barium sulfate has not been known to cause adverse effects in industrial workers exposed over periods of several years (Doig 1976/Ex. 1-551). NIOSH did not conduct an in-depth review of the health evidence for barium sulfate (Ex. 8-47, Table N4); no other comments on this substance were submitted to the record.

In the final rule, OSHA is establishing a 8-hour TWA PEL for barium sulfate of 10 mg/m³ (total particulate) and retaining the 5-mg/m³ 8-hour TWA (respirable particulate). The Agency concludes that these limits will protect workers against the significant risks of material health impairment in the form of eye, nose, and upper-respiratory-tract irritation and, perhaps, of pneumoconiosis that are associated with exposure to barium sulfate.