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Bruce Nathan Ames, a biochemist who discovered a revolutionary method of detecting potential carcinogens, paving the way for the banning of many commonly used chemicals, died on Oct. 5 in Berkeley, Calif. He was 95.
His wife, Giovanna Ferro-Luzzi Ames, said his death, in a hospital, was from complications after a fall.
The so-called Ames Test, developed in the 1970s, is still used by drug manufacturers and pesticide companies to check the safety of their products. It involves exposing chemicals to a mutant strain of salmonella bacteria that Dr. Ames created; how the bacteria responds to a chemical makes it possible to determine whether that chemical caused DNA damage and therefore might lead to cancer in humans.
In an America increasingly concerned about the effects of pollution and industrial chemicals, the test offered a quick, inexpensive alternative to animal testing, which was so prohibitively expensive that regulators were able to test only a fraction of chemicals on the market.
“It changed the regulatory sphere,” said Angela Creager, a science historian at Princeton University who is writing a book about the Ames Test. “It showed that it was actually possible to get toxicity information on every chemical if we wanted to.”
After capturing the attention of the national press, Dr. Ames remained in the spotlight as he used the Ames Test to expose the toxicity of a number of commonplace chemicals.
He stumbled on one of his most publicized discoveries accidentally, when he asked his undergraduate students at the University of California, Berkeley, to bring in a chemical of their choosing to undergo testing. All of the chemicals tested negative, except for one: contained in a bottle of hair dye a student had borrowed from his girlfriend.
Dr. Ames sent a lab technician, Edith Yamasaki, to buy out every type of hair dye at a local drugstore, and after extensive testing concluded that the dyes — used by more than 20 million Americans at the time — were very likely linked to cancer and birth defects.
“I wrote a paper and, as I remember, sent it out to all the hair dye companies and said, ‘You guys better shape up,’” Dr. Ames said in an interview for the Berkeley Oral History Center. “And they did.”
A year later, his work made headlines again when he discovered that a chemical called Tris, used to make children’s pajamas flame-retardant, caused genetic mutations. By some estimates, 45 million children were wearing Tris-treated pajamas. The chemical was later banned from garment manufacturing.
As more scientists and companies began using the Ames Test, the list of chemicals linked to cancer grew to include Japanese food preservatives (banned in 1974), cigarette smoke condensate and many others.
The test was widely used in part because Dr. Ames did not patent his discovery, a decision almost “unheard-of” in biomedical research, said Randy Schekman, a Nobel laureate at Berkeley. Dr. Ames shipped out his mutant bacteria to governments, universities and businesses, asking only that private companies make small donations to help pay for his lab’s labor and the cost of delivery.
“He was sort of this archetypal absent-minded professor,” Dr. Schekman said. “He didn’t care about money.”
Later in his career, as Dr. Ames’s opinions about the dangers of man-made chemicals began to shift, his legacy in the environmental movement became more complicated.
He felt that some activists were overstating the risks of these chemicals and targeting chemical companies unfairly. He often said that he thought there was too much focus on substances that were technically mutagenic but that were no more likely to cause DNA damage than the “natural” chemicals found in fruits and vegetables.
“I don’t mean to suggest that there aren’t real problems with some synthetic chemicals, but the environmentalists are wildly exaggerating the risks,” he told The Times in 1994. “If our resources are diverted from important things to unimportant things, this doesn’t serve the public.”
That position endeared him to industry leaders, who wanted to delegitimize regulation efforts, and antagonized activists, who had viewed him as a champion of their cause, Dr. Creager said.
Bruce Nathan Ames was born on Dec. 16, 1928, in New York City to Maurice and Dorothy (Andres) Ames. His father was a high school chemistry teacher, his mother a secretary. He grew up in the Washington Heights neighborhood of Manhattan and attended the Bronx High School of Science, where he conducted his first science experiment: exposing a tomato root to hormones to stimulate growth.
Later, he studied chemistry and biology at Cornell University but “wasn’t a great student” because he often went folk dancing instead of studying, said his wife, Dr. Ferro-Luzzi Ames, who is also a scientist. Despite his study habits, he was accepted to the California Institute of Technology, where he earned a Ph.D. in biochemistry. He then spent several years doing research at the National Institutes of Health.
He met his future wife in 1958, when she, a postdoctoral fellow at Johns Hopkins University, attended one of his lectures. They married in 1960.
In addition to Dr. Ferro-Luzzi Ames, he is survived by their children, Sofia and Matteo Ames, and two grandchildren.
Dr. Ames and his wife moved to California in 1968. Joining the faculty at Berkeley, he remained there for more than three decades.
In his lab, Dr. Ames was known for generating a constant stream of ideas, convinced that each new one was the best he had ever had, said Graham Walker, a biologist at the Massachusetts Institute of Technology, who worked with him at Berkeley.
Dr. Ames came to these ideas unconventionally, sometimes by reading niche scientific journals with no obvious connection to his research.
Gerald Fink, an M.I.T. biologist who briefly shared an office with Dr. Ames at the N.I.H., remembered a heavily notated copy of the journal Indian Phytopathology on his desk. “It had nothing to do with what we were doing,” Dr. Fink said, “but somehow Bruce found some weird fact in there that he could align with everything.”
In 2000, Dr. Ames moved his research laboratory to the Children’s Hospital Oakland Research Institute, where he continued to tell friends that he was doing the best science of his life, Dr. Walker said, despite being well past the usual retirement age.
“Aging has not damaged my enthusiasm genes,” Dr. Ames wrote in 2002, “though I am not as certain about my neurons.”
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