ε-Caprolactam

Abstract

The German Senate Commission for the Investigation of Health Hazards of Chemical Compounds in the Work Area (MAK Commission) summarized and re-evaluated the data for ε-caprolactam [105-60-2] to derive an occupational exposure limit value (maximum concentration at the workplace, MAK value) considering all toxicological end points. Relevant studies were identified from a literature search. ε-Caprolactam is used mainly for the manufacture of synthetic fibres (especially Nylon 6). In two double-blind studies with male and female volunteers, a NOAEC of 5 mg/m3 was derived for chemosensory irritation. In a 13-week inhalation study with whole-body exposure of male and female rats to an aerosol, moderately severe goblet cell hyperplasia was observed in the respiratory mucosa at the lowest concentrations of 24 to 37 mg/m3 and above. From the human and animal data, a MAK value of 2 mg/m3 was determined. The findings from animal studies suggest that the MAK value derived based on local effects also protects against systemic effects. Peak Limitation Category I with an excursion factor of 2 has been set to prevent chemosensory irritation. In prenatal developmental toxicity studies, ε-caprolactam caused skeletal variations in rats at 500 mg/kg body weight (bw) and day and decreased foetal body weights in rabbits at 150 mg/kg bw and day and above with concurrent maternal toxicity. The NOAELs were 100 and 50 mg/kg bw and day, respectively. The substance is not teratogenic. Damage to the embryo or foetus is unlikely if the MAK value is not exceeded (Pregnancy Risk Group C). ε-Caprolactam is not regarded as genotoxic. The substance did not show carcinogenic potential in studies with rats and mice. Although occupational exposure frequently occurs, only one case of contact sensitization has been reported. Overall, animal studies have not revealed a pronounced sensitizing potential for ε-caprolactam. The substance has been designated with “H” because, according to skin absorption models, skin contact is expected to contribute significantly to systemic toxicity