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: 144-62-7; Chemical Formula: H2C2O4

OSHA formerly had a limit of 1 mg/m3 for oxalic acid. The ACGIH has a TLV-TWA of 1 mg/m3 and a TLV-STEL of 2 mg/m3. The proposal retained the 1-mg/m3 8-hour TWA limit but added a STEL of 2 mg/m3; NIOSH (Ex. 8-47, Table N1) concurs with these limits. The final rule retains the 8-hour TWA PEL of 1 mg/m3 for oxalic acid and adds a STEL of 2 mg/m3. Anhydrous oxalic acid usually occurs in the form of a white powder; the dihydrate form is a colorless, odorless, crystalline substance.

Oxalic acid is known to produce severe burns of the eyes, mucous membranes, and skin (Windholz 1983d/Ex. 1-835, p. 991). There have been human fatalities from ingesting as little as 5 grams of oxalic acid. It appears that these deaths were caused by oxalic acid’s ability to disturb the calcium-potassium balance in critical tissues (Klauder, Shelanski, and Gabriel 1955/Ex. 1-1057). Solutions of 5- to 10-percent oxalic acid have also been reported to irritate the skin on prolonged exposure. NIOSH was the only commenter on oxalic acid.

Because of oxalic acid’s severe acute toxicity, OSHA is retaining the 8-hour TWA limit of 1 mg/m3 PEL and adding a STEL of 2 mg/m3 in the final rule. The Agency concludes that both of these limits are required to protect exposed workers from the significant risk of severe eye and skin burns and respiratory tract irritation, which are material health impairments associated with elevated short-term exposures at levels above the TWA limit.

Page last reviewed: September 28, 2011