Rodent cancer bioassays are currently required by regulatory authorities for the carcinogenicity assessment of industrial chemicals, agrochemicals, food additives, pharmaceuticals, and environmental pollutants. In these tests, at least 480 rats and 400 mice are forced to ingest or inhale chemicals every day for 18 to 24 months and then killed to assess the effects of chemical exposure.

Over the past 50 years, we have learned a great deal about cancer biology, but our approach to testing chemicals for carcinogenic potential in humans has not kept up. Rodent cancer bioassays are expensive, time-consuming, and of questionable relevance to humans and require the use of many animals. Fortunately, scientists are now modernising carcinogenicity assessment through mechanistic approaches that reduce testing on animals and provide information that is more relevant to protecting human health.


The Rethinking Carcinogenicity Assessment for Agrochemicals Project (ReCAAP) is led by experts from the PETA Science Consortium International, government, and industry who are developing a strategy to move away from a “check-box” approach that includes bioassays to one based on human-relevant mechanisms of disease and other sources of information.

Details about this project are available in our 2022 publication in Regulatory Toxicology and Pharmacology, as well as a poster we presented at the 11th World Congress on Alternatives and Animal Use in the Life Sciences and the EuroTox2021 Congress.

The revised approach will provide a safe carcinogenicity assessment while sparing countless animals immense suffering.

In addition to the above project, there are many others aiming to help make the transition away from the bioassay, including those led by the following groups and initiatives:

For more information on carcinogenicity, see here.