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al., 1983). Histopathology of all organs was not performed on all animals; therefore, tumors not grossly
observable or palpable could have been missed. Because of the shortcomings of the study, its utility for
the evaluation of carcinogenic risk is limited.
Several researchers have investigated the potential carcinogenicity of VC administered by inhalation
(Viola, 1977; Caputo et al., 1974; Keplinger et al., 1975; Lee et al., 1977; Hong et al., 1981;
Suzuki, 1981; Groth et al., 1981; Drew et al., 1983; Maltoni et al., 1984; Bi et al., 1985). All
experiments confirm the carcinogenicity of VC, although only a few of the studies are adequate for a
quantitative evaluation of carcinogenic risk. This summary will concentrate on the studies (Drew et al.,
1983; Maltoni et al., 1984; Bi et al., 1985) used by CDHS (1990) for quantitative risk assessment
purposes.
Table 2: Tumor incidences in male and female Wistar rats exposed to dietary vinyl chloride
(Feron et al., 1981).
Incidence 1
Vinyl chloride (mg/kg-day)
Tumor type/Sex 0 1.7 5.0 14.1
Liver angiosarcoma
male 0/55 0/58 6/56 *2 27/59 ***
female 0/57 0/58 2/59 9/57 **
Hepatocellular carcinoma
male 0/55 1/58 2/56 8/59 **
female 0/57 4/58 19/59 *** 29/57 ***
Neoplastic nodules
male 0/55 1/58 7/56 ** 23/59 ***
female 2/57 26/58 *** 39/59 *** 44/57 ***
Lung angiosarcoma
male 0/55 0/58 4/56 * 19/59 ***
female 0/57 0/58 1/59 5/57 *
Abdominal mesotheliomas
male 3/55 1/58 7/56 8/59
female 1/57 6/58 * 3/59 3/57
Mammary tumors 3
female 3/57 2/58 5/59 9/57
1
Number in denominator = number of animals necropsied.
2 values marked with asterisks differ significantly from controls as determined using the Chi-square test.
* = p < 0.05; ** = p < 0.01; *** = p < 0.001.
3 Including mammary adenomas, adenocarcinomas and anaplastic carcinomas.
Bi et al. (1985) evaluated the tumorigenic potential of VC in male Wistar rats following inhalation
exposure to 0, 10, 100 or 3000 ppm (six hours/day, six days/week) for up to 12 months. The incidence
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