(Group 2B)

For definition of Groups, see Preamble Evaluation.

VOL.: 53 (1991) (p. 371)

CAS No.: 87-86-5

Chem. Abstr. Name: Pentachlorophenol


5. Summary of Data Reported and Evaluation

5.1 Exposure data

Since its introduction in the 1930s, pentachlorophenol has been used in large quantities, mainly as a wood preservative. It has also found minor use as a herbicide, defoliant, bactericide and molluscicide. In recent years, its use in agriculture has been restricted in many countries.

Pentachlorophenol is usually formulated and applied to wood with a hydrocarbon diluant. Technical-grade pentachlorophenol has been shown to contain a large number of impurities, including tetrachlorophenols and, to a much lesser extent, polychloro-dibenzodioxins, polychlorodibenzofurans, polychlorodiphenyl ethers, polychlorophenoxy phenols and chlorinated hydrocarbons.

Pentachlorophenol has been detected in fruits, vegetables, meats, water and soils. It has been detected in the urine of the general population in several countries and at higher levels in the urine of workers in wood treatment plants.

Exposure to pentachlorophenol can occur during its production and use; from contact with pentachlorophenol-treated wood; at lower levels, from consumption of foods and water containing residues; and as a result of its ubiquitous presence as an environmental contaminant.

5.2 Carcinogenicity in humans

Two population-based case-control studies of soft-tissue sarcoma and non-Hodgkin’s lymphoma in New Zealand found no increased risk associated with potential exposure to sodium pentachlorophenate through work in a sawmill or timber company. A similar study of multiple myeloma showed a slightly increased risk. A Swedish population-based case-control study found an increased risk for soft-tissue sarcoma associated with self-reported exposure to pentachlorophenol.

Excess incidences of cancers of the skin and of the lip, mouth and pharynx and of leukaemia were found in a cohort study of sawmill workers in Finland. Pentachlorophenol constituted only a minor proportion of the chlorophenols to which the workers were exposed.

5.3 Carcinogenicity in experimental animals

Two different pentachlorophenol formulations were tested for carcinogenicity by oral administration in two separate experiments in mice. A dose-related increase in the incidence of hepatocellular adenomas and carcinomas was observed in males exposed to either formulation and of hepatocellular adenomas in females exposed to one of the formulations. A dose-related increase in the incidence of adrenal phaeochromocytomas was observed in male mice exposed to either formulation, and an increase was also seen in females exposed to one of the formulations at the highest dose. A dose-related increase in the incidence of malignant vascular tumours of the liver and spleen was seen in female mice exposed to either formulation.

5.4 Other relevant data

Pentachlorophenol was embryotoxic and embryolethal and caused a slight increase in the number of malformations in rats.

Significant increases in the incidence of dicentric chromosomes and acentric fragments were detected in the peripheral lymphocytes of workers exposed occupationally to penta-chlorophenol in one study, but no increase in the frequency of sister chromatid exchange was observed.

Pentachlorophenol gave negative results in most tests for genetic and related effects. It gave weakly positive results for somatic gene mutation in a mouse spot test. It induced chromosomal aberrations in cultured rodent cells but not in human cells and caused gene conversion in yeast.

5.5 Evaluation

There is inadequate evidence in humans for the carcinogenicity of pentachlorophenol.

There is sufficient evidence in experimental animals for the carcinogenicity of penta-chlorophenol.

Overall evaluation

Pentachlorophenol is possibly carcinogenic to humans (Group 2B).

For definition of the italicized terms, see Preamble Evaluation.


    See Also:
       Toxicological Abbreviations
       Pentachlorophenol (EHC 71, 1987)
       Pentachlorophenol (HSG 19, 1989)
       Pentachlorophenol (ICSC)
       Pentachlorophenol (PIM 405)