Today the mutagenic potential of chemicals is considered in evaluating the mutagenic risks posed by chemical exposure. Many new methods have been developed to determine if chemicals to which people will be exposed, such as new drugs, food additives, and pesticides, are mutagens. Since mutations can occur in any organism, and because there are many different kinds of mutations, there are a correspondingly wide variety of tests to detect them. No one test detects them all.
The Ames test was the first and remains the only test to be almost universally required by regulatory agencies as a minimum standard for determining if a chemical is mutagenic. The test is conducted in Salmonella bacteria. Since bacteria have only one chromosome, recessive mutations can be detected readily. Rare mutations are easily detected because mutants can be selected very simply. Several variants have been added to the original test, allowing for detection of many types of mutations. In an effort to make the test more relevant to human risk, one variant uses an extract of liver to mimic the biochemical modifications of chemicals that occur in the human liver.