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: 7429-90-5; Chemical Formula: Al
OSHA formerly had no permissible exposure limits for either the soluble salts of aluminum or the aluminum alkyls. The ACGIH has an 8-hour TLV-TWA limit of 2 mg/m3 for aluminum (soluble salts) and 2 mg/m3 for the aluminum alkyls. The proposed PELs were 2 mg/m3 for both groups of aluminum compounds, and NIOSH (Ex. 8-47, Table N1) concurred that these limits were appropriate. The final rule establishes a 2-mg/m3 8-hour TWA PEL for the aluminum alkyls and the soluble salts of aluminum.
The ACGIH’s limits for aluminum soluble salts have been set on the basis of the amount of hydrolized acid, such as hydrochloric acid or sulphuric acid, in their acid compounds. For example, three mols of hydrogen chloride (HCl) hydrolize from one mol of aluminum chloride; since HCl has a PEL of 5 ppm, a PEL of 2 mg/m3 for aluminum chloride (which is a soluble salt of aluminum) would provide the same degree of protection from irritation as that provided by this limit for HCl. The acute toxicity of aluminum chloride is generally representative of the toxicity of all of the soluble salts of aluminum. For the aluminum alkyls, toxicity data are sparse. However, all of the nonhalo- genated alkyls decompose into aluminum oxide fume, and the halogenated alkyls are even more irritating because of acid hydrolysis.
In the final rule, OSHA is establishing an 8-hour TWA limit of 2 mg/m3, for both the soluble salts of aluminum and the aluminum alkyls. The Agency concludes that these limits will protect against the significant risk of irritation and skin burns, which constitute material health impairments that are associated with exposures at levels above the new PEL.