OSHA previously had no limit for ethylene glycol and proposed a ceiling limit of 50 ppm (approximately 125 mg/m3) for this clear, colorless, odorless, hygroscopic liquid. The final rule establishes a limit of 50 ppm as a ceiling, which is consistent with the limit recommended by the ACGIH for ethylene glycol. Ethylene glycol poses virtually no exposure risk at room temperature because of its low vapor pressure; at elevated temperatures, however, exposures are possible and adverse effects have been reported as a result of exposure to mists.
In studies of rats, guinea pigs, rabbits, dogs, and monkeys, Coon and colleagues (1970/Ex. 1-84) reported that animals exposed over a 30-day period to concentrations of 10 or 57 mg/m3 for eight hours daily, five days per week, showed no adverse effects. Moderate to severe eye irritation did occur in rats and rabbits exposed at 12 mg/m3 for 24 hours per day for 90 days (Coon, Jones, Jenkins, and Siegel 1970/Ex. 1-84). Wiley and co-workers (1936/Ex. 1-600) reported no ill effects in animals exposed to approximately 350 to 400 mg/m3, eight hours per day, for 16 weeks (Wiley, Hueper, and von Oettingen 1936/Ex. 1-600).
Rowe (1963/Ex. 1-865) concluded that daily exposure to 100 ppm of the vapor did not cause systemic or eye injuries, although Troisi (1949/Ex. 1-598) described nystagmus in overexposed workers (concentrations not reported). In a human inhalation study, Wills and colleagues (1974/Ex. 1-582) reported that volunteers exposed to the aerosol from 20 to 22 hours per day for four weeks, at an average concentration of 12 ppm, complained of throat irritation, mild headache, and lower back pain. Complaints were more pronounced when the concentration was raised to 140 mg/m3 (50 ppm) for part of a day. Average concentrations of 80 ppm were found intolerable by the subjects, who reported a burning sensation in the throat and respiratory passages; irritation was also common at 60 ppm (Wills, Coulston, Harris et al. 1974/Ex. 1-582). Based primarily on this study, NIOSH (Ex. 8-47, p. 6; Tr. p. 3-86) suggested that OSHA reconsider its proposed 50-ppm ceiling limit; however, NIOSH acknowledged that the exposure concentrations used by Wills et al. (1974/Ex. 1-582) were "significantly erratic." NIOSH also described recent evidence that ethylene glycol may be a potential teratogen. OSHA will continue to monitor the toxicologic literature on this substance to evaluate ethylene glycol's potential teratogenicity.
Gary L. Melampy, counsel for the Independent Lubricant Manufacturers Association (ILMA)(Ex. 3-830), commented that OSHA should apply the 50-ppm ceiling limit only to those workplaces where ethylene glycol is used at elevated temperatures. In the final rule, OSHA has not restricted the application of any new or revised PEL to a particular industry segment or industrial process. OSHA recognizes that industrial processes vary in characteristics that affect the degree of risk to which workers are exposed; these characteristics include the amount of material processed or handled, the frequency with which a substance is present, the extent to which a process is open or closed, and the temperatures and pressures at which materials are used. OSHA's policy, which is reflected in all of its previous health standards, has been to base its permissible exposure limits on scientific evidence that exposure to a substance at a given concentration or dose is associated with a health risk and that promulgating a PEL will reduce that risk. Thus, a relationship between exposure level and degree of risk is established and is deemed applicable in all situations where a substance is present. If the characteristics of a process are such that employee exposure to a substance is nonexistent or is well below the levels associated with a health risk, the promulgation of a limit on employee exposure will have little or no effect on the operation or process and imposes no additional burden on the employer. Therefore, in the specific case of ethylene glycol, OSHA sees no reason to limit application of the 50-ppm ceiling limit to those processes where exposure to airborne ethylene glycol is most likely.
Based on evidence of an occupational risk of severe throat and respiratory irritation associated with exposure to the vapor and mist, OSHA is promulgating a ceiling limit of 50 ppm for ethylene glycol; this level is just below the level at which clinical symptoms have been noted in humans. OSHA considers these symptoms, which include throat and respiratory irritation and headache, to be material impairments of health. The Agency concludes that this limit will substantially reduce the significant risk associated with exposures to higher levels that would be permitted in the absence of a PEL.