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Table 1.
Liver tumor incidence data in Colworth rats exposed to NDMA in drinking water (Peto
et al., 1982).
dose level fatal liver tumor incidence
(ppm) * male female
0 1/240 1/240
0.033 1/60 1/60
0.066 3/60 0/60
0.132 3/60 2/60
0.264 3/60 3/60
0.528 3/60 5/60
1.056 5/60 5/60
1.584 3/60 27/60
2.112 13/60 33/60
2.640 27/60 44/60
3.168 33/60 48/60
4.224 36/60 53/60
5.280 46/60 52/60
6.336 49/60 51/60
8.448 55/60 55/60
16.896 59/60 58/60
* Colworth rats (48/sex/group) were exposed to NDMA in drinking water for life.
Druckrey et al.(1967) exposed BD rats (sex unspecified) to NDMA by inhalation twice per week for
30 minutes. One group of 6 rats received 100 ppm NDMA and a group of 12 rats received 50 ppm
NDMA. No information on a control group was reported. Tumors of the nasal turbinates were
reported at the time of death in 4/6 and 8/12 of the high- and low-dose groups, respectively. Three
animals in the low-dose group died prematurely (time unspecified). No liver tumors were reported in
either group.
Moiseev and Benemansky (1975; reviewed in IARC, 1978) exposed Balb/c mice and Wistar rats to
NDMA by inhalation at concentrations of 0.005 and 0.2 mg/m 3 . Exposure duration was 17 months for
mice and 25 months for rats. At 0.2 mg/m 3 NDMA, tumors of the lung, liver, and kidney were
reported to arise earlier and in greater numbers than in control animals (IARC, 1978). Exposures to the
lower concentration did not result in significantly increased incidence in tumors over controls.
IV.
DERIVATION OF CANCER POTENCY
Basis for Cancer Potency
Five studies showing tumor induction in animals by NDMA have been deemed appropriate by CDHS
(1988) for the development of cancer potency values. The values derived from the studies are
presented in Table 2. The methodologies used to derive the values are described below as well as the
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