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Table 4.
Epichlorohydrin-induced forestomach tumor incidence in male and female Wistar rats
(Wester et al., 1985)
Sex
Dose level
(mg/kg body weight)
Tumor type
Tumor incidence
male 0 papilloma 1/50
2 6/49
10 4/49
0 squamous cell carcinoma 0/50
2 6/49
10 35/49
female 0 papilloma 2/47
2 3/44
10 0/39
0 squamous cell carcinoma 0/47
2 2/44
10 24/39
IV.
DERIVATION OF CANCER POTENCY
Basis for Cancer Potency
Cancer potency values are based on the most sensitive site, species and study demonstrating
carcinogenicity of a particular chemical, unless other evidence indicates that a value derived from that
data set would not be appropriate (CDHS, 1985). Several studies describe ECH-induced tumor
incidence data which can be used to generate a cancer potency factor (male Wistar rat forestomach
papilloma and squamous cell carcinoma data, Konishi et al. (1980); male Sprague-Dawley rat nasal
tumor data, Laskin et al. (1980); male and female ICR/HA Swiss mouse forestomach squamous cell
carcinoma data, Henschler et al. (1984); male and female Wistar rat papilloma and squamous cell
carcinoma data, Wester et al. (1985). The data from the study by Konishi et al. (1980) was chosen
by CDHS (1988) as the basis for a cancer potency factor for ECH. Data from the Laskin et al. (1980)
study was considered to be less suitable for generating a cancer potency factor than data from the
Konishi et al. (1980) study because of the poor survival of the study animals. The studies by Henschler
et al. (1984) and Wester et al., (1985) contained potential confounding factors. The ECH-exposed
animals in the Henschler et al. (1984) study were also exposed to trichloroethylene. The animals used
in the Wester et al. (1985) study exhibited trichobezoar-induced intestinal obstructions early in the
study due to the diet composition; CDHS (1988) noted that those obstructions could have been a
contributing factor to the observed forestomach carcinogenesis.
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