CAPROLACTAM DUST

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: 105-60-2; Chemical Formula: C₆H₁₁NO

OSHA had no previous permissible exposure limit for caprolactam dust; however, a 1-mg/m³ 8-hour TWA and a 3-mg/m³ STEL were proposed, based on the recommended limits adopted by the ACGIH, and NIOSH (Ex. 8-47, Table N1) concurred with these limits. The final rule establishes these limits. Caprolactam is a white crystalline solid with an unpleasant odor.

In humans, caprolactam has been shown to be a convulsant, a dermal and respiratory irritant, and a dermal sensitizer; however, dosage levels in humans are ill-defined (Ferguson and Wheeler 1973/Ex. 1-1108; Tuma, Orson, Fossella, and Waidhofer 1981/Ex. 1-1071). In animals, exposure to caprolactam by several routes can cause convulsions, tremors, mydriasis, opisthotonus (Elison, Lien, Zinger et al. 1971/Ex. 1-1050; Lien, Lien, and Tong 1971/Ex. 1-1089) and salivation (Goldblatt, Farquharson, Bennett, and Askew 1954/Ex. 1-1044). Cardiovascular and respiratory effects have been reported in rabbits and cats, with an initial increase in blood pressure followed by a decrease in blood pressure and an increased respiratory rate (Goldblatt, Farquharson, Bennett, and Askew 1954/Ex. 1-1044). Weight loss and initial growth depression occurred in rats and mice (Morrison, Ross, and Ruth 1980/Ex. 1-1062).

One animal study observed that caprolactam’s convulsant effects on rats, rabbits, and cats occur at injection doses above 100 mg/kg (Goldblatt, Farquharson, Bennett, and Askew 1954/Ex. 1-1044). Results of studies in guinea pigs were consistent with these findings (Hohensee 1951, as cited in ACGIH 1986/Ex. 1-3, p. 95). In a 90-day feeding study of dogs, Burdock, Kolwick, Alsakor, and Marshall (1984, as cited in ACGIH 1986/Ex. 1-3, p. 95) reported that dogs given dietary dose levels of 0.1, 0.5, or 1.0 percent caprolactam showed weight losses at both the 1.0-percent and 0.5-percent levels. Hematologic and ophthalmologic changes did not occur. In a two-year bioassay of rats and mice, caprolactam was not observed to be carcinogenic (NCI/NTP 1982, as cited in ACGIH 1986/Ex. 1-3, p. 95). A Polish study observed hematologic and systemic changes, increased mortality, kidney and liver damage, and growth inhibition in animals given daily doses of 50 or 100 mg/kg (Zwierzchowski, Kowalski, Szendzikowski, and Slusarczyk-Zalobna 1967, as cited in ACGIH 1986/Ex. 1-3, p. 96.1). The results of early studies of caprolactam’s teratogenicity in rats and rabbits indicate that it is not teratogenic even at doses as high as 1000 mg/kg/day (Gad, Powers, Robinson et al. 1984, as cited in ACGIH 1986/Ex. 1-3, p. 96.1).

Studies of industrial exposures to caprolactam dust in Germany report severe irritation on inhalation of 10 percent caprolactam in dust (Hohensee 1951, as cited in ACGIH 1986/Ex. 1-3, p. 95). Workers experienced a bitter taste, nervousness, epistaxis, upper respiratory tract irritation, and dry and splitting skin on the lips and nose (Hohensee 1951, as cited in ACGIH 1986/Ex. 1-3, p. 95). Direct contact with the solid form of caprolactam produces primary skin irritation (Ferguson 1972, as cited in ACGIH 1986/Ex. 1-3, p. 96.1). Brief (1972, as cited in ACGIH 1986/Ex. 1-3, p. 96.1) also reports that the dust produces skin irritation.

OSHA received no comments, other than NIOSH’s, on its proposed limits for caprolactam dust. Based on its review of the health evidence, OSHA concludes that, in the absence of any limit on employee exposure to caprolactam dust, workers are at significant risk of respiratory irritation, adverse nervous system effects, and possible cardiovascular effects; the Agency considers these effects to be material impairments of health. OSHA finds that promulgation of the 1-mg/m³ TWA and 3-mg/m³ STEL limits for caprolactam dust will substantially reduce this risk.