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