VM & P NAPHTHA
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: 8032-32-4; Chemical Formula: none
OSHA formerly had no PEL for VM & P (Varnish Makers’ and Printers’) naphtha. The Agency proposed to establish an 8-hour TWA of 300 ppm and a STEL of 400 ppm for this substance. NIOSH (Ex. 8-47, Table N1) concurred with these limits, which are based on the ACGIH TLVs. These limits are established in the final rule. VM & P naphtha, also known as ligroin, is a colorless, flammable liquid.
A study in which rats and beagles received inhalation doses of 500 ppm VM & P naphtha for 30 hours per week for 13 weeks resulted in no chronic or latent effects (Carpenter, Kinkead, Geary et al. 1975a/Ex. 1-302). These authors also noted that the acute toxicity of VM & P naphtha for rats and other species was four times greater than that of rubber solvent naphtha, which has a limit of 400 ppm. Carpenter and associates (1975a/Ex. 1-302) also reported on an experiment in which rats lost coordination and went into convulsions within 15 minutes during exposures to saturation concentrations at ambient room temperature. The 4-hour inhalation LC(50) was 3400 ppm, and the acclimated rats survived 5800 ppm for six hours.
Seven human volunteers exposed to 880 ppm VM & P naphtha for 15 minutes reported upper respiratory tract, eye, and nose irritation, in addition to olfactory fatigue (ACGIH 1986/ Ex. 1-3, p. 631). Elkins (1959d, as cited in ACGIH 1986/ Ex. 1-3, p. 631) noted one case of a worker, exposed to levels of VM & P naphtha averaging 800 ppm, who developed unspecified chronic effects. Elkins also reported that the VM & P naphtha level producing significant irritation in human volunteers was about half as great for this form of naphtha as for rubber solvent naphtha.
The Agency concludes that the 300-ppm TWA is necessary to protect workers against the risk of possible chronic effects associated with naphtha exposure. In addition, OSHA finds that a STEL is necessary to prevent upper respiratory tract and eye irritation, which are considered by OSHA to be material impairments of health that have been demonstrated to occur on short-term exposure to 880 ppm VM & P naphtha (ACGIH 1986/Ex. 1-3, p. 631); the proposed 300-ppm TWA limit alone would permit such excursions. Therefore, OSHA is establishing both a 300-ppm 8-hour TWA and a 400-ppm STEL for VM & P naphtha in the final rule.