OSHA formerly had no specific permissible exposure limit for aluminum metal dust, although the Agency's generic 15 mg/m3 TWA limit for total particulate applied. The ACGIH has an 8-hour TWA limit of 10 mg/m3 as total dust for this substance. OSHA proposed a PEL of 10 mg/m3 (total particulate) and 5 mg/m3 (respirable fraction) for aluminum metal dust; however, in the final rule, OSHA is retaining its former 15-mg/m3 total particulate limit for this substance. In its elemental form, aluminum is a white, malleable, ductile metal.
Aluminum metal dust has been shown to present a minimal health hazard, according to results from the McIntyre Foundation's 27-year study of aluminum oxide dust (discussed in Stokinger 1981a, in Patty's Industrial Hygiene and Toxicology, 3rd rev. ed., Vol. 2A, pp. 1500-1503). No deleterious lung or systemic effects were observed as a result of exposure to aluminum metal dust having a particle size of 1.2 um at calculated concentrations equivalent to 2 mg/m3 over an 8-hour workshift. Even much higher concentrations (not further specified) over 10- or 20-minute periods produced no adverse effects (ACGIH 1986/Ex. 1-3, p. 22). A comment submitted by the Reynolds Aluminum Company endorses OSHA's classification of aluminum metal dust under the general dust and particulate heading (Ex. 3-135). NIOSH (Ex. 8-47, Table N4) did not conduct an in-depth review of the health evidence for this substance. OSHA has concluded that aluminum metal dusts are appropriately controlled by retaining the Agency's PELs of 15 mg/m3 TWA, as total particulate, and 5 mg/m3, as the respirable fraction. OSHA has determined that these limits will provide protection against the significant risk of physical irritation.