Bruce Ames - Ames On Synthetic Carcinogens

Ames On Synthetic Carcinogens

Bruce Ames developed the Ames test, described in series of papers in the 1970s, which is a cheap and convenient assay for mutagens and therefore potential carcinogens. The Ames test uses the bacteria Salmonella typhimurium to test for mutagens. Previous carcinogenic testing used live animals, and are therefore expensive and time-consuming. This made animal testing impractical for use in screening on a wide scale, and reduced the number of compounds that could be tested. The Ames test is widely used as an initial screen for possible carcinogens and has been used to identify potential carcinogens previously used in commercial products, and their identification led to some of those formulations, such as chemicals used in hair dye, being withdrawn from commercial use. The ease with which Ames test allows widely-used chemicals to be identified as possible carcinogens made him an early hero of environmentalism.

Subsequent work in Ames' lab involved looking at an overview of what was mutagenic or carcinogenic, and to what degree. Previously, scientists tended to only look for positive or negative results without considering the magnitude of the effect, which meant that as more and more items were shown to be potentially mutagenic, there was no system for evaluating the relative dangers. He also continued to test various natural and man-made compounds, and discovered that, despite what he and others had assumed, naturally occurring compounds were not turning out to be benign as compared to man-made ones. His continued work eventually led to his falling out of favor with many environmentalists. As natural chemicals turned out to also be frequently mutagenic, he argued that environmental exposure to manufactured chemicals may be of limited relevance to human cancer, even when such chemicals are mutagenic in an Ames test and carcinogenic in rodent assays. He contended that most human genetic damage arises from the oxidation of DNA during normal metabolism, and that the most important environmental carcinogens may include some whose chief effect is to cause the chronic division of stem cells whereby the normal protective mechanisms of a cell become less effective.

He argued against the banning of synthetic pesticides and other chemicals such as Alar which have been shown to be carcinogenic. He was concerned that overzealous attention to the relatively minor health effects of trace quantities of carcinogens may divert scarce financial resources away from major health risks, and cause public confusion about the relative importance of different hazards. Ames considered himself a leading “contrarian in the hysteria over tiny traces of chemicals that may or may not cause cancer", and said that "if you have thousands of hypothetical risks that you are supposed to pay attention to, that completely drives out the major risks you should be aware of."