Davis, Banned

imgresBanned: A History of Pesticides and the Science of Toxicology. By Frederick Rowe Davis. Yale University Press, 2014. 284 pp.

Review by Jacob Darwin Hamblin. Originally published as “Pick your poison: how getting rid of DDT opened the door for more dangerous pesticides” in Science 347:6227 (Mar 13, 2015), 1208.

The sacred success story in environmental literature is that of Rachel Carson, who awakened America to the dangers of indiscriminate pesticide use, and led the charge to ban the sale of DDT and other chlorinated hydrocarbons in the United States. In her best-selling 1962 book Silent Spring, Carson introduced many readers to the concept of ecology, warning that persistent pesticides might accumulate and magnify at unexpected intersections of the web of life. Those opposed to this legislation typically argue that DDT saved more lives by preventing mosquito-borne illnesses than it harmed, but there is another reason to be wary of the vilification of DDT. In Banned, historian of science Frederick Rowe Davis argues that doing so actually diverted attention away from the most toxic pesticides.

The science of toxicology itself was born from crises in consumer confidence. It began to pull away from pharmacology in the early twentieth century, maturing in the 1930s after a wave of deaths from Elixir sulfanilamide, an improperly prepared medicine that had been provided to consumers without first being tested for safety. Recognizing the need for standardized safety studies, the Food and Drug Administration devised statistical approaches and benchmarks (such as identifying the lethal dose to fifty percent of animal test subjects) that shaped the science for years to come. Toxicological studies expanded during the Second World War. With its high toxicity to insects and seemingly low toxicity to mammals, DDT seemed an ideal means to control mosquito-borne malaria among American troops.

When the Environmental Protection Agency ultimately banned DDT in 1972, the nightmare scenario of leading toxicologists became reality. Farmers turned to alternative pesticides that would-be regulators had already failed to keep from consumers, including cast-offs from chemical weapons laboratories. Ironically, Rachel Carson had done such a good job of drawing attention to hidden dangers, such as chronic exposure to small quantities and persistence in the environment, that chemicals with acute, direct effects went relatively unnoticed.

When Rachel Carson criticized indiscriminate use of pesticides, she identified not only DDT but also organophosphates as potentially dangerous. However, her readers focused on the troubling ecological implications of persistent pesticides. Organophosphates appeared to break down within days, acquitting them of long-term environmental impact.

Among toxicologists, however, organophosphates were considered far more troubling. Organophosphates are especially dangerous because they inhibit cholinesterase, an enzyme crucial for neural communication, leading to muscle spasms, defecation, drooling, and asphyxiation. As weapons, these compounds were called “nerve gas” but in the hands of farmers and household gardeners, they were dubbed pesticides. Davis reveals that in 19XX, one of the scientists studying them, Kenneth DuBois, expressed concern that if DDT ever was banned, the market would be flooded with these dangerous neurotoxins.

One might ask: if organophosphates were so terrible, why weren’t they banned along with DDT? Davis reveals that under pressure from corporations, Congress took the path of least resistance and simply required labeling. Thus, organophosphate insecticides “passed through the screen,” or “slipped through the cracks,” as Davis variously puts it, despite the fact that everyone from Rachel Carson to Monsanto acknowledged they were the worst of the bunch. In fact, their use did not diminish at all, but instead expanded to “a degree that would have shocked and disappointed Carson” (209, 213). By 1989 only three heaviest-use pesticides (more than half a million pounds applied) were not organophosphates.

Many organophosphates were banned eventually, some as recently as 2006, but not because of their acute toxicity. The EPA found that like other pesticides before them, they too could be banned based on environmental persistence and links to cancer. This took a very long time, however, and in the meantime, neurotoxins once imagined for wartime use filled the agricultural and gardening void left by the departure of DDT.

Although Davis is an admirer of Rachel Carson, Banned offers a provocative counter-narrative to the triumphal story of Silent Spring. Reading it should convince anyone to be wary of such success stories, and above all, to read labels carefully.