For definition of Groups, see Preamble Evaluation.
Supplement 7: (1987) (p. 106)
Asbestos fibre
CAS No.: 1332-21-4
Actinolite
CAS No.: 13768-00-8
Amosite
CAS No.: 12172-73-5
Anthophyllite
CAS No.: 17068-78-9
Chrysotile
CAS No.: 12001-29-5
Crocidolite
CAS No.: 12001-28-4
Tremolite
CAS No.: 14567-73-8
A. Evidence for carcinogenicity to humans (sufficient)
Numerous reports from several countries have described cases or series of pleural and peritoneal mesotheliomas in relation to occupational exposure to various types and mixtures of asbestos (including talc containing asbestos), although occupational exposures have not been identified in all cases [ref: 1-21]. Mesotheliomas of the tunica vaginalis testis and of the pericardium have been reported in persons occupationally exposed to asbestos [ref: 22-24].
Environmental exposure either in the houses of asbestos workers or in the neighbourhood of asbestos mines or factories has been noted in some of the cases [ref: 1,2,4-6,9,11,25,26]. It has been estimated that a third of the mesotheliomas occurring in the USA may be due to nonoccupational exposure [ref: 27]. In a study from Israel, the incidence of mesothelioma was found to be higher among those born in the USA or in Europe relative to those born in Israel [ref: 9].
In some of these case reports and in other studies, asbestos fibres have been identified in the lung [ref: 5,6,11,28-32]. Amphibole fibres have usually predominated, but in a few cases mainly or only chrysotile fibres were found [ref: 6,28].
The long latency required for mesothelioma to develop after asbestos exposure has been documented in a number of publications [ref: 11,13,26,28,33-37]. An increasing proportion of cases has been seen with increasing duration of exposure [ref: 36].
A number of epidemiological studies of respiratory cancer and mesothelioma have been reported in relation to exposure to unspecified or complex mixtures of asbestos in shipyard work [ref: 38-45]. The risk ratio for lung cancer has usually been moderately increased, both in these studies and in studies on various other occupational groups with similarly job-related but unspecified or complex asbestos exposures [ref: 35,46-54]. Risk ratios of about 2-5 have been reported in some studies, but the ratio was considerably higher in one rather small study [ref: 55] and did not exceed unity in another [ref: 42]. In one study, individuals suffering from asbestosis had a considerably greater risk for lung cancer, with a risk ratio of 9.0 [ref: 56]. In some of the studies referred to, a number of mesotheliomas were also observed [ref: 41,42,44,47,51,53,55]. Abdominal mesotheliomas have sometimes been mistaken for pancreatic cancer [ref: 57]. Mesothelioma cases have been observed to have a relatively lower fibre content in the lungs than lung cancer cases [ref: 32].