CHROMIUM METAL

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: 7440-47-3; Chemical Formula: Cr

OSHA formerly had an 8-hour TWA of 1 mg/m³ for chromium metal. The proposed PEL was 0.5 mg/m³; NIOSH (Ex. 8-47, Table N1) concurred with the proposed limit. The ACGIH has established an 8-hour TWA of 0.5 mg/m³ for chromium, which is a steel-grey metal. In the final rule, OSHA is retaining the former 8-hour TWA PEL of 1 mg/m³ for chromium metal.

According to the ACGIH, a 0.5 mg/m³ TLV-TWA for chromium “should be adequate to prevent pulmonary disease or other toxic effects” (ACGIH 1986/Ex. 1-3, p. 139). Many commenters objected to the proposed 0.5 mg/m³ PEL for chromium metal (Exs. 3-236, 3-829, 3-902, 3-1095, 3-1123, 129, 145, and 188; Tr. pp. 11-136 to 11-137). These commenters argued that there was no health basis for lowering the PEL for chromium metal and questioned the studies described in the health effects discussion for this substance. For example, Peter Hernandez, Vice President for Employee Relations at the American Iron and Steel Institute (AISI), commented in several submissions that one of the studies (Mancuso and Hueper 1951/Ex. 1-215) relied on by OSHA, which was performed for the Indian government in 1951, found “exaggerated pulmonary markings” on the X-rays of exposed workers but failed to demonstrate that these markings constituted a health risk to these workers (Ex. 188, p. 18). The AISI also criticized the results of another study relied on by OSHA, the work of Princi et al. (1962, as cited in ACGIH 1986/Ex. 1-3, p. 139), which detected pulmonary disease in workers exposed to chromium at levels of 0.27 mg/m³ (Princi, Miller, Davis, and Cholak 1962, as cited in ACGIH 1986/Ex. 1-3, p. 139). According to the AISI, “the results of this study are highly questionable…because other dust and fumes besides chromium were present, including 36.7 percent silica” (Ex. 188, p. 19).

In response to these comments, OSHA has further reviewed the toxicological literature on chromium metal. The Agency finds that the metallic form of chromium, in its pure state, does not present a significant risk to exposed workers at levels below 1 mg/m³, OSHA’s former 8-hour TWA PEL for this substance. This view of chromium metal’s toxicity is shared by several toxicologists. For example, Proctor, Hughes, and Fischman (Chemical Hazards of the Workplace, 2nd ed., 1988, p. 155) state, “Chromium metal is relatively nontoxic….” OSHA finds that the markings associated with exposure to chromium metal (which were not suggestive of alteration of the architecture of the lung) and reported in the Mancuso and Hueper (1951/Ex. 1-215) study do not present a risk of material impairment of health because they do not presage any decrement in pulmonary function or interfere with the functional capacity of exposed workers.

OSHA also agrees with the AISI that [A] major problem [in] defining the health effects which may be associated with exposure to metallic chromium is the frequent co-existence of the metallic form with both trivalent and hexavalent salts (Tr. p. 11-136). The Princi et al. study (1962, as cited in ACGIH 1986/Ex. 1-3, p. 139) reflects the problem of confounding exposures to which the AISI alludes. In this study, ferrochrome alloy workers were exposed to several toxic contaminants simultaneously, including chromium salts, silica, iron oxide, and chromium metal. OSHA believes it likely that exposure to the other contaminants present, which included a high percentage of silica, accounts for the development of pulmonary disease in these workers. The ACGIH (1986/Ex. 1-3, p. 139) stated, after reviewing the Mancuso and Hueper (1951/Ex. 1-215) and the Princi et al. (1962, as cited in ACGIH 1986/Ex. 1-3, p. 139) studies, that “[e]xposure to chromium metal does not give rise to pulmonary fibrosis or pneumoconiosis.”

Thus, after a reanalysis of the toxicological data and the record evidence, OSHA concludes that there is no health basis for reducing the Agency’s former limit of 1 mg/m³ for chromium metal. OSHA finds that the 1 mg/m³ PEL provides appropriate worker protection from the toxic effects of exposure to chromium metal.

Accordingly, in the final rule, OSHA is retaining the former 8-hour TWA limit of 1.0 mg/m³ for chromium metal. The Agency concludes that this limit protects workers against the significant risk of pulmonary effects potentially associated with exposure to the metallic form of chromium.