home edit2 whole TSD November 2002 PDF format - OEHHA

were exposed to a continuous (23.5 hours/day) airborne concentration of 13.4, 25.7, or 50.8 µg of
cadmium/m 3 of air for 18 months. A control group of 41 rats was exposed to filtered room air. The
aerodynamic mass median diameter of the aerosol particles was 0.55 µm with a arithmetic standard
deviation of 0.48 µm and a geometric standard deviation of 1.8 µm. The rats were followed for an
additional 13 months before surviving rats were sacrificed.
There were no statistically significant differences seen in body weight or survival between exposed and
control groups. The incidence of lung carcinomas was significantly increased (p > 0.014, Fisher's exact
test) in all exposure groups. Three lung tumor types were identified, adenocarcinoma, epidermoid
carcinoma, and mucoepidermoid carcinoma. The numbers of animals in each group that had these
tumor types are given in Table 5. The first lung tumor was observed at 20 months. In the high-dose
group, the first tumors were observed at 23 months and 23 out of 25 animals in this group dying or
sacrificed after 27 months had lung tumors. Therefore, these appear to be late-developing tumors.
Table 5: Lung tumors in rats exposed to cadmium chloride aerosols (Takenaka et al., 1983)
Exposure
Group
# rats with tumors
# rats Adenocarcinoma
examined
histologically
Epidermoid
Carcinoma
Mucoepidermoid
Carcinoma
Total
Carcinomas
Control 38 0 0 0 0
13.4 µg/m 3 39 4 2 0 6
25.7 µg/m 3 38 16 5 0 20 b
50.8 µg/m 3 35 15 8 3 25 b
a Airborne exposure concentrations are based on the cadmium, not cadmium chloride,
concentration.
b
One rat had both an adenocarcinoma and an epidermoid carcinoma.
IV.
DERIVATION OF CANCER POTENCY
Basis for Cancer Potency
A quantitative cancer risk assessment for cadmium using the data from the occupational mortality study
by Thun et al. (1985) and extrapolating to ambient levels in California was done by DHS staff. The
exposure data in this study were based on industrial hygiene measurements and individual work
histories. These measurements consisted of historical area monitoring samples and, when appropriate,
were adjusted to reflect respirator protection in departments where respirators had been worn. For
workers employed 6 months or longer in production areas of the plant the person-years of follow-up
were divided into 3 categories according to cumulative exposure in mg-days/m 3 (see Table 6). The risk
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