For most people in the sciences, the only –ist they will ever admit to being is a scientist. In a direct challenge to his peers, however, Barry Commoner admitted early in his career, without reservation, that he was an environmentalist. He was, in fact, one of the foremost enviros of his time, close on the heels of Rachel Carson. But Commoner, who died September 30, did not come to environmentalism through a love of wilderness, bird song and wildlife. “The Atomic Energy Commission turned me into an environmentalist,” he said. More specifically, it was the aboveground testing of atomic bombs, which the AEC oversaw, that drew him into the fray.

Commoner played a key role in early efforts to protect the public from the dangers of nuclear tests. In 1958 he encouraged thousands of scientists to sign a petition to stop atmospheric weapons testing. His research on the subject was simple and brilliant. He pursued radiation epidemiology through a single fallout chemical, strontium 90, the radioactive isotope of an otherwise harmless substance. Because he knew that radiation eventually finds its way into children’s bones, Commoner was able to trace the spread of strontium 90 through baby teeth, which he asked thousands of parents to send him instead of selling them to the tooth fairy. The results were conclusive and unassailable. Almost every tooth he received contained strontium 90. The evidence that radioactive fallout from atomic testing in Nevada was poisoning the population as far away as St. Louis, where the study was conducted, became the scientific underpinning for the Nuclear Test Ban Treaty, which was signed in 1963.

In 1970, Time magazine dubbed Commoner “the Paul Revere of ecology”—a title well deserved. He made the arcane science of ecology clear and accessible. But while describing the impact of toxins on sensitive ecosystems, he remained sharply focused on their production. It was here, he said, that man-made ecological damage began and could best be prevented. He also touted solar power and organic agriculture, and called for equal pay for women even before most feminists demanded it. And all the while he taught biology, first at Washington University in St. Louis and later at Queens College in New York City. But it was to the world at large that he offered his best teachings.

No other scientist of the past century did more than Commoner to defend our right to know and understand the risks and hazards of modern life. “In order to avoid a poison,” he once told me in an interview, “one has to know what is poisoning him.” That simple precept drove Commoner to expose everything he learned about the impact of radiation, pesticides, lead and other pollutants on biological systems. And he did so in a way that almost any person could understand, in a body of literature that will long survive him.

In his private, professional and political life, Commoner appeared to be as human as the rest of us. Unlike most of us, however, and certainly unlike every other scientist of his time, he took a run at the presidency. In 1980, he represented a party of his own creation, the Citizens’ Party, which disappeared shortly after the election of a candidate who opposed and set out to repudiate just about everything Commoner believed in.

But even an anti-environment gunslinger like Ronald Reagan couldn’t stop Commoner from campaigning against the toxicity of our diet or the abuse of scientific research for private gain. And in that regard, his last assault may have been one of his greatest. In 2002, shortly after the Human Genome Project released its initial findings, Commoner published a long, complex article in Harper’s challenging what Francis Crick had declared to be the “central dogma” of molecular biology. Crick proposed the “dogma” in 1958, five years after he and James Watson discovered the double-helix structure of the DNA molecule. The hypothesis states that an organism’s genetic makeup totally accounts for its inherited traits. To reduce it further: “DNA makes RNA makes protein.”

Commoner wasn’t questioning the existence or function of DNA, which he acknowledged “clearly exerts an important influence on inheritance.” But he believed that geneticists’ focus on DNA had become too rigid and narrow, discounting the significance of other processes (such as alternative splicing, in which gene sequences are split into fragments and recombined) that cause variations of gene expression. “Biological replication does include the precise duplication of DNA,” he wrote, “but this is accomplished by the living cell, not by the DNA molecule alone.” In other words, to understand what separates humans from roundworms, the double helix is not the only place to look.

Molecular biologists already knew this, but Commoner’s article served as a warning that the funding priorities in this field were misplaced. Commoner was alarmed at the unchecked rise of the biotechnology industry, which had grown into a multibillion-dollar juggernaut with significant support from the government and the scientific community. Without providing sufficient evidence to back the claim, the industry had promised that “its methods of genetically modifying food crops are ‘specific, precise, and predictable’ and therefore safe.” As Commoner concluded, “Billions of transgenic plants are now being grown with only the most rudimentary knowledge about the resulting changes in their composition. Without detailed, ongoing analyses of the transgenic crops, there is no way of knowing if hazardous consequences might arise.”

One of the best measures of a scientist’s impact on the world is the intensity of the forces that attack his or her ideas. After the Harper’s article was published, pro-corporate organizations like the Heartland Institute didn’t waste a minute before doing just that. Their rants were ignored by all but a few industry-backed scientists. But what endures—and will surely be remembered as one of Commoner’s overriding concerns—is the need to keep the public interest at the heart of scientific pursuit.

The Lived History section on this site features remembrances of other recently departed iconic figures, including Tom Hayden on Russell Means and Eric Foner on Eric Hobsbawm.