ε-caprolactam

Carcinogenicity

Additional information

Caprolactam (CAP) was tested for its carcinogenic potential in 2 species (rats and mice; NTP, 1982).

50 male and 50 female Fischer-344 rats per dose group were fed diets containing 187.5 mg/kg bw and 375 mg/kg bw CAP for 103 weeks. A dietary control group was also included.

Similarly B6C3F1 mice were fed with 2143 mg/kg bw and 1071 mg/kg bw CAP for 103 weeks. Survival in both species was similar to that of controls. The various types of neoplasms occurring in dosed groups and control group in both species were comparable and did not appear to be related to CAP administration.

Summarized, no carcinogenic potential was detected by feeding maximal dose levels of 187.5 mg/kg bw to rats or 2143 mg/kg bw to mice. Besides a decrease in body weight gain no further signs of systemic toxicity were observed.

Inconsistent results were reported in various cell transformation assays.

In one cell transformation assay CAP failed to transform Hamster Embryo cells at dose levels up to 10000 µg/ml (ACC, 1979).

In an interlaboratory comparison treatment of Syrian hamster embryo (SHE) cells with CAP dose levels up to 1000 µg/ml resulted in consistently higher transformation rates compared to non-treated control cells (Jones et al., 1988).

However, in a second interlaboratory comparison, results were negative with SHE cells at doses of 1-1000 µg/ml (LeBoeuf et al., 1989). In both interlaboratory validations significant cyotoxicity was observed with and above 1000 µg/ml. An apparent variance between both was the use of a slightly lower pH value by LeBoeuf et al., resulting in higher transformation efficiencies. Furthermore in this assay known carcinogens were consistently positive and non-carcinogens consistently negative, assigning a certain level of reliability to the test design chosen.

In a weight of evidence approach no indications for a carcinogenic potential can be deduced from these cell transformation assays and based on the 2-years carcinocenicity bioassays, CAP does not require any classification according to EU and GHS standards. 

Justification for classification or non-classification

No indication for a carcinogenic potential was identified in carcinogenicity studies in rodents.