n-BUTYL ALCOHOL

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: 71-36-3; Chemical Formula: CH₃CH₂CH₂CH₂OH

OSHA’s former PEL for n-butyl-alcohol was a 100-ppm 8-hour TWA; the ACGIH limit is a 50-ppm ceiling, with a skin notation. The proposed and final rule PEL is a 50-ppm ceiling, with a skin notation. NIOSH (Ex. 8-47, Table N1) concurs that these limits are appropriate. n-Butyl alcohol is a colorless, highly refractive liquid with a mild vinous odor that has long been known to cause irritation of the eyes and headaches in occupational settings.

Systemic effects in the form of vestibular and auditory nerve injuries have been reported in workers in France and Mexico (Seitz 1972 and Velasquez 1964, both as cited in ACGIH 1986/Ex. 1-3, p. 76; Velasquez, Escobar, and Almaraz 1969/Ex. 1-1174). Contact dermatitis of the hands may occur due to the defatting action of liquid n-butyl alcohol, and toxic amounts can be absorbed through the skin. Based on data describing the rate of n-butyl alcohol uptake through the skin of dogs, DiVincenzo and Hamilton (1979, as cited in Patty’s Industrial Hygiene and Toxicology, 3rd rev. ed., Vol. 2C, pp. 4571-78, Clayton and Clayton 1982) suggested that direct contact of human hands with n-butyl alcohol for one hour results in an absorbed dose that is four times that resulting from inhalation of 50 ppm for one hour.

The former OSHA limit of 100 ppm (TWA) was based on the studies of Tabershaw, Fahy, and Skinner (1944, as cited in ACGIH 1986/Ex. 1-3, p. 76) and of Smyth (1956/Ex. 1-759). These studies indicated that workers experienced no narcotic or systemic effects at levels lower than 100 ppm. However, irritation has been reported in humans exposed to 24 ppm; this irritation became uncomfortable and was followed by headaches at 50 ppm (Nelson, Enge, Ross et al. 1943/Ex. 1-66).

More recent data reported by Seitz (1972, as cited in ACGIH 1986/Ex. 1-3, p. 76), Velasquez (1964, as cited in ACGIH 1986/Ex. 1-3, p. 76), and Velasquez, Escobar, and Almaraz (1969/Ex. 1-1174) indicate serious exposure-related long-term systemic effects on the auditory nerve and hearing loss (hypoacusia); the magnitude of the hearing loss was related to length of exposure. Nine of 11 workers exposed without hearing protection to 80 ppm for periods of from 3 to 11 years displayed impaired hearing. This phenomenon was particularly evident in younger workers (Velasquez 1964, as cited in ACGIH 1986/Ex. 1-3, p. 76; Velasquez, Escobar, and Almaraz 1969/Ex. 1-1174).

Three commenters, ConAgra (Ex. 3-635), the Motor Vehicle Manufacturers Association (MVMA) (Ex. 3-902), and ARCO (Tr. p. 3-237) submitted comments on n-butyl alcohol. ConAgra (Ex. 3-635) misinterpreted OSHA’s discussion of a 1964 study (Velasquez, as cited in ACGIH 1986/Ex. 1-3, p. 76) to mean that OSHA attributed all hearing loss found in the workers in this study to n-butyl alcohol exposure. ARCO (Tr. p. 3-237) also questioned n-butyl alcohol’s effect on hearing. In response to these commenters, OSHA notes that n-butyl alcohol has been shown in many studies to damage the auditory nerve and further, that workplace noise may also have contributed to the hearing loss observed in these studies. The MVMA comment (Ex. 3-902) lists n-butyl alcohol as a substance for which rulemaking should be delayed, but provides no other details.

OSHA finds that the former PEL of 100 ppm is not sufficiently protective against the acute effects associated with exposure to n-butyl alcohol; in addition, the possibility of auditory nerve damage from exposures below the 100-ppm level makes the former PEL inadequate. A skin notation is necessary because data in beagle dogs suggest that dermal contact with n-butyl alcohol can result in a systemic dose greater than that obtained by inhalation (DiVincenzo and Hamilton 1979). The Agency is establishing a permissible exposure limit of 50 ppm as a ceiling, with a skin notation, for n-butyl alcohol. OSHA concludes that this limit will protect workers against the significant risks of possible vestibular and auditory nerve injury as well as of headaches and irritation, which constitute material impairments of health and are associated with exposure to this substance at levels above the new limit.