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Table 2.
Tumor induction in F344 rats and B6C3F 1 mice fed diet containing 4-chloro-ophenylenediamine
(NCI, 1978)
Sex/species
Dose
group
Average
dose 1
(mg/kg-day)
Tumor type Tumor incidence 2
Male rats control 0 urinary bladder tumors 0/50
low-dose 149 15/49
high-dose 294 25/50
Female rats control 0 urinary bladder tumors 0/50
low-dose 184 5/50
high-dose 368 22/50
Male mice control 0 liver tumors 15/50
low-dose 701 28/50
high-dose 1390 34/50
Female mice control 0 liver tumors 0/50
low-dose 752 11/50
high-dose 1500 10/50
1. Doses as reported by Gold et al. (1984).
2. Tumor incidences as reported by Gold et al. (1984).
IV.
DERIVATION OF CANCER POTENCY
Basis for Cancer Potency
Gold et al. (1984) list results of the NCI (1978) feeding study in male and female B6C3F 1 mice and
F344 rats. Benign and malignant neoplasms of the liver were elevated in treated male and female mice.
Forestomach tumors were also observed in treated rats; these tumors are relatively uncommon in this
strain. In addition, substantial increases in the incidences of urinary bladder cancers were seen in rats of
both sexes. Dose-response data are given in Table 2. Rats appear to be more sensitive than mice.
Quantitative analysis of dose-response data for urinary bladder tumors indicate that male and female
rats have nearly the same sensitivity. The upper confidence bound on potency for data on male rats is
slightly higher, and this is the value used as a cancer potency for 4-chloro-o-phenylenediamine
(Cal/EPA, 1992).
Methodology
Expedited Proposition 65 methodology (with cross-route extrapolation) was used to derive a cancer
potency factor. A unit risk factor was then calculated by OEHHA/ATES from the cancer potency
factor using a reference human body weight of 70 kg and an inspiration rate of 20 m 3 /day.
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