Table Talk : Opinion Breaker : The Ames Test

In 1972, when Bruce Ames developed a simple method to test for mutagens, it changed the way chemicals were tested for cancer-causing potential. He started with a strain of bacteria that couldn’t grow because of a mutation in a particular gene; in order for them to grow, that gene would have to be mutated back. If you added a chemical to a Petri dish full of these bacteria and a few started to grow, that was prima facie evidence that the chemical was mutagenic.

Since it was known that some chemicals that didn’t themselves mutate genes might give rise to mutagens in the body, Ames refined this test by adding ground liver. The liver is the body’s chief metabolizing organ; if the chemical is going to turn into something else in the body, liver cells are what will change it. This worked the same as the earlier test: Add the chemical and watch for bacterial growth.

This method became known as the Ames mutagenicity test. Federal regulations might still require slow, expensive animal tests before a substance can be declared non-carcinogenic, but the Ames test provides a quick way to weed out obvious carcinogens.