home edit2 whole TSD November 2002 PDF format - OEHHA

control group of 79 females and 47 males was maintained on regular diet for three generations. During
880 days of observation, each generation was dosed for two years. Approximately two-thirds of the
animals in both the treatment and the control group died during months 8-11. Necropsies were
performed on 66 dosed females and 35 dosed males and on 79 female and 47 male controls. Two
carcinomas of the stomach were found in dosed females, but no stomach carcinomas were found in
dosed males or controls. In addition, benign stomach tumors (papillomas and hyperkeratomas) were
seen in 9 females and 2 males given chromium and in 2 females and 3 males in the control group. The
increased incidence of malignant stomach tumors was not significant when compared with controls, but
the incidence of malignant or benign stomach tumors in dosed females, 11/66, was significantly
increased above 2/79, the incidence in controls (p = 0.003).
IV.
DERIVATION OF CANCER POTENCY
Basis for Cancer Potency
Inhalation
A number of human occupational studies (relevant reviews listed above) have demonstrated that
inhalation exposure to chromium results in an increased risk of lung cancer mortality in humans. An
occupational exposure study by Mancuso (1975) was used by US EPA (1984) as the basis for an
inhalation cancer unit risk for chromium. This study demonstrated the carcinogenicity of chromium in a
cohort which was sufficiently large and which was followed for an adequate time period. Data from an
industrial hygiene study were used to derive weighted average exposures to insoluble, soluble and total
chromium which were then applied to the worker cohort. Table 1 lists the age, exposure and lung
cancer mortality study data.
Table 1
Age, chromium exposure concentrations, lung cancer mortality and person-years of
exposure for male chromate workers (Mancuso, 1975; as cited in US EPA, 1998).
Age Midrange Deaths from Person
(years) (µg/m 3 ) Lung Cancer Years
50 5.66 3 1345
25.27 6 931
46.83 6 299
60 4.68 4 1063
20.79 5 712
39.08 5 211
70 4.41 2 401
21.29 4 345
213