SODIUM METABISULFITE

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: 7681-57-4; Chemical Formula: Na₂S₂O₅

OSHA previously had no exposure limit for sodium metabisulfite. The Agency proposed a 5-mg/m³ limit as an 8-hour TWA, based on the ACGIH recommendation, and is establishing this limit in the final rule. NIOSH (Ex. 8-47, Table N1) concurred with the selection of this limit. Sodium metabisulfite can occur either in the form of a solid or as white crystals; this substance smells like sulfur dioxide.

A two-year study at the Dow Chemical Company (1977e, as cited in ACGIH 1986/Ex. 1-3, p. 535), in which rats ingested 0.215 percent sodium metabisulfite, demonstrated no adverse effects in the rats. Other animal studies show a median lethal dose of 192 mg/kg for rabbits and 115 mg/kg for rats when sodium metabisulfite is injected intravenously (NIOSH 1973c, as cited in ACGIH 1986/Ex. 1-3, p. 535). Inhalation of sodium metabisulfite dust is irritating to the lungs, nose, and throat (ACGIH 1986/Ex. 1-3, p. 535).

Dr. Grace Ziem, an independent physician (Ex. 46), expressed concern that sensitized individuals may experience severe allergic reactions on exposure to sodium metabisulfite dust. Cases of severe, and even fatal, reactions have ben documented in individuals exposed by consuming food items containing metabisulfite additive. At this time, OSHA believes there is insufficient data on oral toxicity to use as a basis to extra-polate to the airborne concentration likely to cause sensitization.

OSHA proposed an 8-hour TWA of 5 mg/m³ for sodium metabisulfite. The Agency concludes that establishing this limit is necessary to reduce the risk of skin and eye irritation associated with exposure to high concentrations of sodium metabisulfite dust. OSHA has determined that these effects constitute material impairments of health. Accordingly, OSHA is promulgating a 5-mg/m³ limit as an 8-hour TWA for this substance.