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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: 8052-41-3; Chemical Formula: C9H20

OSHA's former limit for Stoddard solvent was 500 ppm as an 8-hour TWA. The ACGIH has established a TLV-TWA of 100 ppm, and NIOSH (1977g, as cited in ACGIH 1986/Ex. 1-3, p. 537) recommends limits of 350 mg/m3 as a 10-hour TWA and 1800 mg/m3 as a 15-minute ceiling for all refined petroleum solvents; these limits correspond approximately to a 60-ppm TWA and a 310-ppm STEL, respectively. Stoddard solvent is a refined petroleum solvent having a flash point in the range of 102 to 110 deg. F, a boiling point in the range of 154 to 202 deg. C, and containing 65 percent or more C10 and higher-molecular-weight hydrocarbons. OSHA proposed to reduce its 8-hour TWA to 100 ppm, and the final rule promulgates this limit. NIOSH (Ex. 8-47, Table N1) agreed with the Agency's selection of this PEL.

The former OSHA limit of 500 ppm (equivalent to the limit in the 1968 ACGIH TLV list) was based largely on analogy to the irritant and narcotic effects of gasoline vapor in humans (ACGIH 1966/Ex. 1-13, pp. 176-177). The revised ACGIH limit of 100 ppm was based on a report by Carpenter, Geary, Myers et al. (1978/Ex. 1-301), which found slight kidney damage among rats exposed to 330 ppm Stoddard solvent for 65 days. The ACGIH TLV for Stoddard solvent was calculated from the TLVs for nonane and trimethyl benzene, the major components of Stoddard solvent (ACGIH 1986/Ex. 1-3); the TLV for nonane is 200 ppm, based on the Carpenter, Geary, Myers et al. (1978/Ex. 1-301) study's findings of a no-effect level for nonane in rats of 590 ppm, while the TLV for trimethyl benzene is 25 ppm, because there is evidence that humans exposed to the isomers of trimethyl benzene exhibited central nervous system effects (ACGIH 1986/Ex. 1-3).

The ACGIH (1986/Ex. 1-3, p. 537) notes that guinea pigs exposed for 30 eight-hour days to 290 ppm Stoddard solvent developed congestion and emphysema of the lungs. The eye irritation threshold in humans is approximately 150 ppm for 15 minutes (ACGIH 1986/Ex. 1-3, p. 537).

The NIOSH limits of a 350-mg/m3 (60-ppm) TWA and an 1800-mg/m3 (310-ppm) 15-minute short-term limit are derived from NIOSH's recommended limits for all of the C(5)-C(8) alkanes; NIOSH recommended the same limit for Stoddard solvent as for all C(5)-C(8) alkanes both because of the lack of scientific data on Stoddard solvent's chronic effects and because of a report of polyneuropathy occurring among workers exposed to jet fuels containing mixtures of kerosene and gasoline. NIOSH reasoned that, although the C(5)-C(8) alkanes present in jet fuel may have been implicated, it was possible that the heavier hydrocarbon components may also have been responsible. Thus, the NIOSH recommended limits for Stoddard solvent reflect a concern that higher-molecular-weight hydrocarbons may be neuropathic. However, no evidence exists that the C(10) and higher molecular weight hydrocarbons cause neuropathies. NIOSH has re-examined the health evidence for Stoddard solvent in this rulemaking and concurs with OSHA that the 100-ppm 8-hour TWA limit is appropriate for this substance (Ex. 8-47, Table N1). Several commenters (Tr. 7-70 to 7-95; Exs. 46, 116, 194, 197) urged OSHA to reevaluate the final rule's limits for this substance because recent evidence points to hepatic and hematopoietic effects. OSHA is aware of the emerging literature and will monitor developments in the future. In the final rule, OSHA is establishing an 8-hour TWA of 100 ppm to reduce the significant risk of eye irritation, narcosis, polyneuropathy, and kidney damage, all of which constitute material health impairments that have been demonstrated to occur in either humans or animals at levels well below the former PEL. OSHA finds that the study of Carpenter and co-workers (1978/Ex. 1-301) in animals and the study reported by the ACGIH showing that exposed workers develop eye irritation at levels of 150 ppm and above clearly indicate that a reduced PEL is needed for Stoddard solvent to diminish these significant occupational risks.