Previously, OSHA had no limit for nonane. The ACGIH has a TLV-TWA of 200 ppm for this colorless liquid. The proposed PEL was 200 ppm; NIOSH concurs that this limit is appropriate (Ex. 8-47, Table N1). The final rule promulgates an 8-hour TWA PEL for nonane of 200 ppm.
The toxicity of nonane is approximately equal to that of VM&P naphtha. Naphtha has a 4-hour inhalation LC(50) for rats of 3400 ppm, while nonane has an LC(50) of 3200 ppm (Carpenter, Kinkead, Geary et al. 1975a/Ex. 1-302; Carpenter, Geary, Myers et al. 1978/Ex. 1-301). These investigators found a no-effect level of 590 ppm nonane for rats exposed six hours/day, five days/week for a 65-day period; under the same exposure conditions, a no-effect level of 560 ppm was reported for rats exposed to VM&P naphtha (Carpenter, Kinkead, Geary et al. 1975a/Ex. 1-302; Carpenter, Geary, Myers et al. 1978/Ex. 1-301). Earlier studies of octane and heptane have resulted in much higher LC(50) values for mice, i.e., 13,500 ppm and 16,000 ppm, respectively, for 30- to 60-minute exposures (Flury and Zernik 1931j/Ex. 1-994). Swann and associates (1974/Ex. 1-124) have reported similarly high LD(50) values in mice for octane and hexane; mice died from respiratory arrest after 3 to 5 minutes of exposure to 16,000 ppm of octane or to 48,000 ppm of hexane (Swann, Kwon, and Hogan 1974/Ex. 1-124). The AFL-CIO (Ex. 194) and the United Auto Workers (Ex. 197) favor a 10 ppm PEL for all petroleum solvents and urge OSHA to consider a lower PEL.
In the final rule, OSHA establishes an 8-hour TWA limit of 200 ppm for nonane. The Agency concludes that this limit will protect workers against the significant risk of narcosis, a material impairment of health that is associated with exposure to nonane at levels above the new PEL.