Relevance of short-term carcinogenicity tests to the study of the carcinogenic potential of urban air.

It is now accepted that screening for carcinogens in animals is expensive and demonstrates carcinogenic potential rather than actual carcinogenicity in man. A number of short-term tests which depend on mutagenicity, stimulation of DNA repair, ability to produce chromosome damage or other actions, and which correlate at least to some extent with carcinogenic potential, have been devised. These have the advantages of being rapid and cheap. Some can be carried out by using human cells. They may have advantages in the context of air pollution since they are sensitive down to very low dose levels and since they can deal with complex mixtures. Combinations of such tests may be of more value than any single test. Their particular value may be as a preliminary screening procedure in a tiered testing programme which may have high predictive efficiency.