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Table 2.
Summary of epidemiologic studies used in quantitative risk assessment for
mesothelioma
Study
Cohort
Occupation
Selikoff et al. Insulation
(1979)
Peto (1980) Textile
manufacturing.
Seidman et al. Insulation
(1979) manufacturing.
Finkelstein Asbestos
(1983) Cement
manufacturing.
F/U = Follow-up
Fiber type Cohort
Number
Sex F/U No. Mesotheliomas
Pleural Peritoneal
Chrysotile, 17,800 M 1967-76 63 112
Amosite
Chrysotile 822 M 1933-74 9 0
Amosite 820 M 1961-76 7 7
Chrysotile,
Crocidolite
241 M 1963-80 6 5
Animal Studies
Many studies using laboratory animals have been conducted to investigate the carcinogenic potential of
various forms of asbestos administered by inhalation, by ingestion (in food or drinking water), and via
intraperitoneal and intrapleural injection or deposition. The animal studies have been reviewed by
Condie (1983), NRC (1984), and Nicholson (1985).
Gross et al. (1967) exposed male rats to airborne chrysotile to a mean concentration of 86 mg/m 3 , 30
hours/week for their lifetime and found that a large number of treated animals developed malignant lung
tumors (24/72; adenocarcinomas, squamous cell carcinomas and fibrosarcomas, compared to 0/39 for
controls) and one developed mesothelioma. Reeves et al. (1971) exposed rats, rabbits, mice and
hamsters to amosite, crocidolite or chrysotile at a concentration of approximately 48 mg/m 3 , 16
hours/week for up to two years. No lung tumors were reported in control or treated hamsters, mice or
rabbits. Lung tumors were found in 2/31 rats exposed to crocidolite; no lung tumors were reported for
the controls or other fiber exposure groups. In a similar study, Reeves et al. (1974) found that gerbils,
guinea pigs, hamsters and rabbits exposed to amosite, crocidolite or chrysotile at a concentration of
approximately 49 mg/m 3 , 16 hours/week for up to two years did not develop lung tumors. Lung tumor
incidences in rats exposed to chrysotile, amosite or crocidolite were 3/43, 4/46 and 3/36, respectively;
no lung tumors were noted in the 12 controls. Lung tumors were noted in the chrysotile-exposed mice
(2/18), but this incidence was not significantly increased compared to controls (1/6).
Wagner et al. (1974) compared the carcinogenic effect of five different Union Internationale contre le
Cancer (UICC) asbestos samples, amosite, anthophyllite, crocidolite, chrysotile (Canadian), and
chrysotile (Rhodesian). Exposure varied from 9.7 to 14.7 mg/m 3 from one day to 24 months, although
all animals were followed for their lifetimes. Malignant lung tumors (adenocarcinoma and squamous cell
carcinoma) were found in rats from all five asbestos exposure groups (11/146, 16/145, 16/141,
17/137, and 30/144, for the respective fiber types). All but the group exposed to Rhodesian chrysotile
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