International Agency for Research on Cancer (IARC) - Summaries & Evaluations


VOL.: 35 (1985) (p. 219)

5. Summary of Data Reported and Evaluation

5.1 Exposures

Humans (primarily chimney-sweeps) are exposed to chimney soots in the course of chimney maintenance. Exposures occur to a limited extent in horticultural uses and in other occupations. The general public may be exposed to the particulates emitted from chimneys when domestic heating fuels are burned.

5.2 Experimental data

Coal soot was tested in two experiments in mice by whole-body exposure, but the studies were inadequate for evaluation.

Coal-soot extracts applied to the skin of mice produced skin tumours in two studies.

A wood-soot extract applied to the skin of mice was inadequately tested. In limited studies, subcutaneous implants of wood soot in female rats produced a few local sarcomas; similar implants in the scrotal sac of rats did not produce local tumours.

An extract of fuel-oil soot was inadequately tested by application to the skin of mice.

Extracts of soot from the combustion of oil shale produced skin tumours in mice after dermal application and lung tumours in rats after intratracheal instillation. Extracts of soot from the combustion of a heating oil produced from shale-oil produced skin tumours in mice in two experiments when applied to the skin.

In one study, extracts of soot samples from domestic sources were mutagenic in Salmonella typhimurium. Extracts of an experimentally-derived soot were mutagenic in forward mutation assays in S. typhimurium and in cultured human lymphoblasts.

5.3 Human data

The carcinogenicity of soot is demonstrated by numerous case reports, dating back over 200 years, of skin cancer, particularly of the scrotum, among chimney-sweeps.

Cohort studies of mortality among chimney-sweeps in Sweden and Denmark have shown a significantly increased risk of lung cancer. Supporting evidence for an association with lung cancer was provided by two earlier epidemiological studies in the German Democratic Republic and the UK. The potentially confounding and interactive effects of smoking could not be evaluated; however, cigarette smoking is not believed to have seriously biased these estimates.

In addition to lung cancer, statistically significant excess mortality from oesophageal cancer, primary liver cancer and leukaemia was found among chimney-sweeps in one study.

5.4 Evaluation

There is sufficient evidence for the carcinogenicity of coal-soot extract and of oil-shale soot extract in experimental animals.

There is limited evidence for the carcinogenicity of implanted wood soot and for that of an extract of a soot from heating oil produced from oil shale in experimental animals.

There is inadequate evidence for the carcinogenicity of coal soot, of an extract of wood soot and of an extract of a fuel-oil soot in experimental animals.

There is sufficient evidence that soot is carcinogenic to humans.

For definition of the italicized terms, see Preamble Evaluation.

Subsequent evaluation: Suppl. 7 (1987)

Last updated: 20 April 1998

    See Also:
       Toxicological Abbreviations
       Soots  (IARC Summary & Evaluation, Supplement7, 1987)