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

PROPYLENE
(Group 3)

For definition of Groups, see Preamble Evaluation.

VOL.: 60 (1994) (p. 161)
CAS No.: 115-07-1
Chem. Abstr. Name: 1-Propene

5. Summary of Data Reported and Evaluation

5.1 Exposure data

Propylene is a major chemical intermediate, produced by catalytic or thermal cracking of hydrocarbons or as a by-product of petroleum refining. It is used mainly in the preparation of alkylates for gasoline and in the production of polypropylene, acrylonitrile, propylene oxide and a number of other industrial chemicals. Propylene is introduced into the atmosphere from natural and man-made sources, including emissions from vegetation, burning of organic material and incomplete combustion of fossil fuels, and from its production and use. Few data are available on levels of occupational exposure.

5.2 Human carcinogenicity data

No relevant data were available to the Working Group.

5.3 Animal carcinogenicity data

Propylene was tested by inhalation in two studies in mice and in two studies in rats. A slight increase in the incidence of vascular tumours was observed in female mice in one study. In one study in rats, no treatment-related increase in tumour incidence was observed. In two studies in mice and rats exposed by inhalation, insufficient information was provided to allow an assessment of carcinogenicity.

5.4 Other relevant data

In rats exposed to 50 ppm propylene, about one-sixth of the inhaled material is absorbed, of which almost one-half is exhaled again, unchanged. The remainder is eliminated metabolically, through oxidation to propylene oxide, which is subsequently either conjugated with glutathione or, to a smaller extent, hydrated by epoxide hydrolase. Oxidation is a saturable reaction mediated by cytochrome P450 enzymes, whereas no saturation concentration has been identified for the hydration of propylene oxide. There is, therefore, a maximal attainable tissue concentration of propylene oxide in rats. Oxidation of propylene can occur in the rat nasal epithelium, where irritation, hyperplasia and metaplasia have been described after chronic exposure.

No data were available on the genetic and related effects of propylene in humans.

Alkylation products of the metabolite, propylene oxide, were found in haemoglobin and in DNA from mice exposed to propylene by inhalation. Although insufficient data are available to evaluate the genetic and related effects of propylene, its major metabolite, propylene oxide, is genotoxic in a broad range of assays.

5.5 Evaluation

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

There is inadequate evidence in experimental animals for the carcinogenicity of propylene.

Overall evaluation

Propylene is not classifiable as to its carcinogenicity to humans (Group 3).

For definition of Groups, see Preamble Evaluation.

Previous evaluation: Suppl. 7 (1987) (p. 71)

Synonyms


Last updated 08/26/1997























    See Also:
       Toxicological Abbreviations
       Propylene (ICSC)