Ames Test - Ames Test and Carcinogens

Ames Test and Carcinogens

Mutagens identified via Ames test are also possible carcinogens, and early studies by Ames showed that 90% of known carcinogens may be identified via this test. Later studies however showed identification of 50–70% of known carcinogens. The test was used to identify a number of compounds previously used in commercial products as potential carcinogens. Examples include tris(2,3-dibromopropyl)phosphate, which was used as a flame retardant in plastic and textiles as such children's sleepware, and furylfuramide which was used as an antibacterial additive in food in Japan in 1960s and 1970s. Furylfuramide in fact had previously passed animal test, but more vigorous tests after its identification in the Ames test showed it to be carcinogenic. Their positive tests resulted in those chemicals being withdrawn from use in consumer products.

One interesting result from the Ames test is that the dose response curve using varying concentrations of chemical is almost always linear, indicating that there is no threshold concentration for mutagenesis, therefore suggesting that, as with radiations, there may be no safe threshold for chemical mutagens or carcinogens. However some proposed that organisms can tolerate low level of mutagens due to protective mechanisms such as DNA repair, and threshold may exist for certain chemical mutagens. Bruce Ames himself argued against linear dose-response extrapolation from the high dose used in carcinogenesis tests in animal systems to the lower dose of chemicals normally encountered in human exposure, as the results may be false positives due to mitogenic response caused by the artificially high dose of chemicals used in such tests. He also cautioned against the "hysteria over tiny traces of chemicals that may or may not cause cancer", that "completely drives out the major risks you should be aware of."

The Ames test is often used as one of the initial screens for potential drugs to weed out possible carcinogens, and it is one of the eight tests required under the Pesticide Act (USA) and one of six tests required under the Toxic Substances Control Act (USA).