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


VOL.: 41 (1986) (p. 319)

5. Summary of Data Reported and Evaluation

5.1 Exposure data

Several chlorophenols and their salts have been widely produced since the 1950s and used as wood preservatives, fungicides, slimicides, weed-killers and as precursors for chlorophenoxy herbicides. Widespread occupational exposure to chlorophenols and their chlorinated dibenzodioxin and dibenzofuran impurities is known to have occurred, especially in manufacturing plants and in wood-treatment applications. Increased urinary levels of chlorophenols and increased concentrations in adipose tissue of some chlorinated dibenzodioxins and dibenzofurans have been measured in workers exposed in sawmills and tanneries and in the textile industry. Skin absorption is believed to be a major route of exposure in these occupations. Burning of chlorophenol-containing materials in industrial or municipal incinerators may lead to the formation of various dibenzodioxin and dibenzofuran congeners.

5.2 Experimental data

Previous IARC evaluations of the carcinogenicity to experimental animals of several individual chlorophenols and of their impurity, 2,3,7,8-tetrachloro-para-dibenzodioxin (TCDD), are summarized in section 3.1, in this volume.

5.3 Human data

Two studies among the wives of the workers at two chemical plants did not show an association between pregnancy outcomes and paternal exposure to 2,4,5-trichlorophenol, pentachlorophenol and TCDD and other dioxins.

Three studies have been published in which cytogenetic effects were investigated in workers exposed occupationally to chlorophenols. In two of the studies, no difference was seen between exposed and control subjects; but in one of these studies the persons were examined ten years after exposure. The other study showed increased incidences of dicentric and acentric chromosomal aberrations, but not of gaps, chromatid breaks or sister chromatid exchanges.

Several cohort studies have been conducted among chemical industry workers with potential exposure to 2,4,5-trichlorophenol, TCDD and other chemicals. Mortality rates for all cancers combined were not elevated. In a Danish cohort study, there may have been exposure to chlorophenols, present as intermediates in the production of chlorophenoxy herbicides. No increase in the incidence of cancers at all sites combined was observed, but there were statistically significantly increased risks of soft-tissue sarcoma and lung cancer in different subcohorts.

Two case-control studies conducted in different regions of Sweden showed a statistically significant association between exposure to chlorophenols and soft-tissue sarcoma; a study from New Zealand did not.

A statistically significant association between malignant lymphoma and exposure to chlorophenols was identified in a Swedish case-control study. A case-control study of non-Hodgkin's lymphoma in New Zealand suggested a possible association with fencing work, but not with other occupational exposures to chlorophenols.

A case-control study in Sweden detected a significant association between nasal and nasopharyngeal cancer and exposure to chlorophenols, independent of exposure to wood dust.

4.4 Evaluation

There is limited evidence for the carcinogenicity of occupational exposure to chlorophenols to humans.

For definition of the italicized terms, see Preamble Evaluation.

Subsequent evaluation: Suppl. 7 (1987)

Last updated: 23 April 1998

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