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


VOL.: 40 (1986) (p. 327)

5. Summary of Data Reported and Evaluation

5.1 Exposure

5-Methoxypsoralen is found in a variety of plant species, including parsnips and celery, in bergamot and lime oils, and in derivative products. Use of foods, beverages, perfumes and sunscreen preparations containing these products results in human exposure. Exposure also occurs when 5-methoxypsoralen is used as a drug, in conjunction with ultraviolet A radiation, for the treatment of skin disorders. Occupational exposure occurs during the extraction of this compound from bergamot oil and its preparation into foods and consumer goods.

5.2 Experimental data

5-Methoxypsoralen was tested in combination with ultraviolet A or solar-simulated radiation for skin carcinogenicity in two experiments in two strains of mice by skin application. It produced papillomas and squamous-cell carcinomas of the skin.

The studies were inadequate to evaluate the systemic carcinogenicity of 5-methoxypsoralen.

Maternally toxic doses of 5-methoxypsoralen did not increase the number of anomalies in surviving fetuses of treated rats.

5-Methoxypsoralen in the presence of ultraviolet A radiation bound covalently to isolated DNA and to DNA in yeast and cultured mammalian cells, and induced prophage expression in bacteria. In the presence of ultraviolet A radiation, it was mutagenic to bacteria, green algae and yeast and induced mutations, sister chromatid exchanges and chromosomal aberrations in mammalian cells in vitro. Studies of 5-methoxypsoralen in the absence of ultraviolet A radiation were inadequate for evaluation.

5.3 Human data

One small survey showed no excess prevalence of skin tumours in workers in the bergamot oil production industry, but this study had methodological weaknesses.

5.4 Evaluation

On the basis of experiments designed to test only the carcinogenicity to mouse skin of 5-methoxypsoralen in combination with ultraviolet A radiation or solar-simulated radiation, there is sufficient evidence of carcinogenicity to experimental animals.

There is inadequate evidence for the carcinogenicity of 5-methoxypsoralen to experimental animals in the absence of ultraviolet A radiation.

There is inadequate evidence for the carcinogenicity of 5-methoxypsoralen to humans.

For definition of the italicized terms, see Preamble Evaluation.

Subsequent evaluation: Suppl. 7 (1987)

Last updated: 22 April 1998

    See Also:
       Toxicological Abbreviations
       Methoxypsoralen, 5-  (IARC Summary & Evaluation, Supplement7, 1987)