The former OSHA limit for the terphenyls was 1.0 ppm as a ceiling limit. The ACGIH has a 0.5-ppm ceiling limit for these substances. The proposed PEL for the terphenyls was 0.5 ppm as a ceiling; NIOSH (Ex. 8-47, Table N1) concurs with, and the final rule establishes, this limit. Terphenyls are colorless or light yellow solids and are used as coolants in nuclear reactors. Commercial preparations contain mixtures of ortho-, meta-, and para-terphenyls.
The terphenyls are primary irritants that cause eye, skin, and respiratory tract irritation. Haley, Detrick, Komesu et al. (1959/Ex. 1-326) reported that mixtures of terphenyls caused conjunctival irritation when instilled into the eyes of rabbits, and damaged guinea pig skin following intracutaneous injection. Cornish, Bahor, and Ryan (1962/Ex. 1-410) determined LD(50) values of 1900, 2400, and greater than 10,000 mg/kg for the ortho-, meta-, and para-terphenyls, respectively. These authors also conducted 30-day feeding studies of rats involving doses of 250 or 500 mg/kg/day of the individual terphenyl isomers. Rats fed ortho-terphenyl showed elevated liver and kidney weight ratios; rats fed meta-terphenyl displayed elevated kidney weight ratios only; and rats fed para-terphenyl showed no elevation in liver or kidney weight ratios. Two studies by Petkau and Hoogstraaten (1965/Ex. 1-432) and Young, Petkau, and Hoogstraaten (1969/Ex. 1-459) have shown that the terphenyls have nephrotoxic effects and cause hepatic damage in rats fed 33 mg/kg/day. Adamson, Bowden, and Wyatt (1969/Ex. 1-293) published a study in which rats exposed to terphenyl aerosols for seven hours per day at a concentration of 50 mg/m3(approximately 5 ppm), for a period of eight days, developed morphological changes in their pulmonary cell mitochondria; the number of vacuolated mitochondria was directly related to duration of exposure.
Weeks (1971/Ex. 1-580) and Weeks and Lentle (1970/Ex. 1-682) conducted a clinical survey of 47 workers with ongoing exposure to terphenyl coolant in a nuclear facility. The study represented 122 man-years of occupational exposure, with durations of exposure ranging from six months to seven years. The airborne concentrations of terphenyl varied, measuring 0.094 mg/m3 in general working areas and up to 0.89 mg/m3 in areas with organic piping equipment. The terphenyl coolant was determined to be a primary irritant, even in those workers wearing protective clothing, because skin moistness increased dermal sensitivity to the terphenyls (Weeks 1971/Ex. 1-580; Weeks and Lentle 1970/Ex. 1-682). Testa and Masi (1964/Ex. 1-578) reported that, at concentrations above 10 mg/m3 (approximately 1 ppm, the former OSHA ceiling limit), workers reported both eye and respiratory irritation.
The Motor Vehicle Manufacturers Association (MVMA) recommended generally that OSHA delay rulemaking on a number of substances, including the terphenyls, on the grounds that the MVMA did not have sufficient time to review and evaluate the impacts of this rulemaking (Ex. 3-902). The MVMA did not provide any data or report any problems specific to the health effects or feasibility of the limit proposed for the terphenyls; instead, the MVMA merely listed these substances and many others in its submission. In response to the MVMA, OSHA notes that hundreds of commenters were able to provide detailed information to OSHA in the time allotted. In addition, no other comments were received on the subject of the terphenyls.
In the final rule, OSHA is establishing a ceiling limit of 0.5 ppm for the terphenyls. The Agency concludes that this limit will protect exposed workers against the significant risk of primary irritation of the eyes, skin, and upper respiratory tract and of mitochondrial changes potentially associated with exposure to very low airborne levels of the terphenyls. The Agency has determined that this limit will substantially reduce these significant risks and that primary irritation and metabolic effects constitute material health impairments.