International Agency for Research on Cancer (IARC) - Summaries & Evaluations
ASBESTOS
VOL.: 14 (1977)
5. Summary of Data Reported and Evaluation
5.1 Animal data
All commercial forms of asbestos tested are carcinogenic in mice,
rats, hamsters and rabbits. In mice, mesotheliomas were induced
following intraperitoneal injection of asbestos fibres. In rats,
various types of asbestos produced lung carcinomas and mesotheliomas
following their inhalation and mesotheliomas and sarcomas following
their intrapleural or intraperitoneal injection. The oral
administration of asbestos filter material to rats also resulted in an
increased incidence of tumours. Mesotheliomas were produced in
hamsters and rabbits after intrapleural injection of a number of types
of asbestos fibre.
The size and shape of the fibres influence the incidence of tumours;
fibres less than 0.5 mm in diameter are more active in
producing tumours. Glass fibres and nemalite of a similar size can
also produce mesotheliomas following their intrapleural or
intraperitoneal injection in rats.
5.2 Human data
In humans, occupational exposure to chrysotile, amosite, anthophyllite
and mixed fibres containing crocidolite has resulted in a high
incidence of lung cancer; a predominantly tremolitic material mixed
with anthophyllite and small amounts of chrysotile has also caused an
increased incidence of lung cancer. Many pleural and peritoneal
mesotheliomas have been observed after occupational exposure to
crocidolite, amosite and chrysotile. An excess risk of
gastrointestinal tract cancers has been demonstrated in groups exposed
occupationally to amosite, chrysotile or mixed fibres containing
crocidolite. An excess of cancers of the larynx was also observed in
exposed workers. Mesotheliomas also occur in individuals living in the
neighbourhood of asbestos factories and crocidolite mines and in
household contacts of asbestos workers.
Occupational exposure to asbestos may occur during the mining of
fibrous minerals, as well as of minerals embodied in rocks, which may
contain asbestiform fibres as a contaminant.
Both cigarette smoking and occupational exposure to asbestos fibres
independently increase lung cancer incidence, but when they are
present together they act in a multiplicative fashion.
The general population may also be exposed to asbestos fibres in
air, beverages, drinking-water, food and pharmaceutical and dental
preparations and by consumer use of asbestos-containing products. The
presence of asbestos and asbestiform minerals from natural sources in
the environment, other than mines or quarries, has only recently shown
itself to be a further potential problem.
At present, it is not possible to assess whether there is a level of
exposure in humans below which an increased risk of cancer would not
occur.
Previous evaluation: Vol. 2 (1973)
Subsequent evaluation: Suppl. 7 (1987)
Last updated: 26 March 1998
See Also:
Toxicological Abbreviations
Asbestos (WHO Food Additives Series 13)
ASBESTOS (JECFA Evaluation)
Asbestos (IARC Summary & Evaluation, Supplement7, 1987)
Asbestos (IARC Summary & Evaluation, Volume 2, 1973)