2,6-Di-tert-butyl-pcresol

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: 128-37-0; Chemical Formula: C₁₅H₂₄O

OSHA previously had no limit for 2,6-di-tert-butyl-pcresol (DBPD). The Agency proposed an 8-hour TWA of 10 mg/m³ for DBPD, and this limit is adopted in the final rule. NIOSH (Ex. 8-47, Table N1) concurred with the selection of this limit. The ACGIH has a TLV-TWA of 10 mg/m³ for this white crystalline compound, which is prepared from p-cresol and isobutylene. DBPD is widely used as a food preservative.

DBPD has a low order of toxicity; in extensive animal studies, ingestion has not been associated with toxic effects (ACGIH 1986/Ex. 1-3, p. 227). Deichmann and associates (1955/Ex. 1-505) reported oral LD(50) values of 10.7 g/kg for guinea pigs, 1.7 and 1.97 g/kg for male and female rats, respectively, and ranges of between 0.94 and 2.1 g/kg for cats and between 2.1 and 3.2 g/kg for rabbits. One year of daily oral administration of 0.17 to 0.9 g/kg in dogs produced no effects, nor did a 24-month oral administration of 0.2, 0.5, or 0.8 percent DBPD in rats (Deichmann, Clemmer, Rakoczy, Bianchine et al. 1955/Ex. 1-505). Other studies have confirmed these overall results, although some growth rate decreases and liver weight increases were demonstrated in rats fed 0.01 to 0.5 percent DBPD, total daily diet (Brown, Johnson, and O’Halloran 1959/Ex. 1-621; Creaven, Davies, and Williams 1966/Ex. 1-547).

The estimated human intake of DBPD in the United States does not exceed a few milligrams daily (perhaps no more than 0.2 mg/kg body weight) (Gilbert and Golberg 1965/Ex. 1-902). These authors also observed that the no-effect dietary level for DBPD in rats is 25 mg/kg.

OSHA is establishing an 8-hour TWA limit of 10 mg/m³ for 2,6-di-tert-butyl-p-cresol. The Agency concludes that this limit will protect workers against the significant risk of material health impairments in the form of acute or chronic effects that may potentially be associated with occupational exposure to this substance at the levels permitted by the absence of any OSHA PEL.