An example of a chemical teratogen is the drug thalidomide which caused birth defects in children when their mothers used it during their pregnancy. Measles virus infection during pregnancy also has teratogenic effects. Mutagenesis Mutagenesis is the production of changes in genetic structure. A mutagen is a substance which causes a genetic change. Many mutagenic substances are oncogenic, meaning they also produce tumors.
Many oncogenic substances are also mutagens.
Some chemicals have effects on the fertility or reproductive rates of animals. Males or females can be affected. Chronic Toxicity Testing Chronic toxicity testing is both lengthy and expensive. EPA and regulatory agencies in other countries require an extensive battery of tests to identify and evaluate the chronic effects of pesticides. These studies, which may last up to 2 years, utilize several species of animals to evaluate toxicity from multiple exposures or continuous long-term exposure.