home edit2 whole TSD November 2002 PDF format - OEHHA

Table 1.
Ethylene thiourea (ETU)-induced tumor incidence in (C57BL/6×C3H/Anf)F 1 and
(C57BL/6×AKR)F 1 mice (Innes et al., 1969)
Sex/strain Dose group Tumor type Tumor incidence
Male (C57BL/6×C3H/Anf)F 1 control liver tumors 8/79
treated 14/16
Female (C57BL/6×C3H/Anf)F 1 control liver tumors 0/87
treated 18/18
Male (C57BL/6×AKR)F 1 control liver tumors 5/90
lymphomas 1/90
treated liver tumors 18/18
lymphomas 3/18
Female (C57BL/6×AKR)F 1 control liver tumors 1/82
lymphomas 4/82
treated liver tumors 9/16
lymphomas 4/16
Graham et al. (1973, 1975) exposed male and female Charles River CD rats (initial group sizes 68
animals/sex/group) to diets containing ETU at levels of 5, 25, 125, 250 or 500 mg/kg diet. An
untreated control group was included. Interim sacrifices were conducted at 2, 6, 12 and 18 months; the
study was terminated at 24 months. An increased incidence of thyroid tumors (adenomas and
carcinomas) was noted in males and females (combined). Tumor incidence data is listed in Table 2.
Table 2.
Ethylene thiourea-induced thyroid tumor incidence in male and female
(combined) Charles River CD rats (Graham et al., 1973, 1975)
Ethylene thiourea dietary level
(mg/kg diet)
Average dose 1
(mg/kg-day)
Tumor incidence 2
0 0 2/72
5 0.225 2/75
25 1.13 1/73
125 5.63 2/73
250 11.3 16/69
500 22.5 62/70
1. Doses as reported by Gold et al. (1984).
2. Tumor incidences as reported by Gold et al. (1984)
Male and female Charles River CD rats were exposed to diet containing 0, 175 or 350 mg/kg ETU for
78 weeks, then switched to control diet for an additional observation period of 26 weeks (Weisburger
et al., 1981). A significantly increased incidence of thyroid follicular-cell carcinomas was noted in both
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