EPA Administrator Scott Pruitt answers questions from reporters and members of the media during the daily briefing at the White House on June 2, 2017. (Photo by Jabin Botsford/The Washington Post)
Frederick Rowe Davis is professor of history and the R. Mark Lubbers Chair in the History of Science at Purdue University and author of "Banned: A History of Pesticides and the Science of Toxicology."

EPA Administrator Scott Pruitt has made headlines for huddling in first class to avoid public anger. But if the Environmental Protection Agency continues to ignore its main purpose — protecting the environment — by making concessions to pesticide companies, the public might not just be angry. They could be in danger.

This month, the EPA drastically reduced $4.8 million in penalties leveled against a major chemical producer for pesticide exposures in 2016, dropping the fine to $150,000 and a commitment to spend $400,000 in worker training. This followed a late December announcement that the EPA would reevaluate a 2015 rule that prohibited anyone under 18 from using “restricted use” pesticides. These rules were already inadequate: The historical and scientific evidence is overwhelming — and still growing — that these pesticides pose dire threats to the environment, wildlife and even humans.

Instead of relaxing restrictions on pesticides, the EPA ought to ban them altogether.

The history of synthetic insecticides dates to the early years of World War II. A Swiss chemist named Paul Mueller discovered the insecticidal properties of the solid form of DDT (the chemical was synthesized in 1873). Neutral Switzerland released samples of DDT to Germany, Great Britain and the United States.

When initial testing showed impressive effectiveness against many types of insect pests, the United States began DDT production, and the U.S. armed forces deployed DDT in the ongoing fight against the mosquitoes that carried malaria in the Pacific theater. By the end of the war, chemical corporations were producing millions of pounds of DDT, and they found an enthusiastic domestic market among farmers. In short order, farmers nationwide were using DDT on crops. In addition, cities and towns adopted the insecticide to control numerous insects.

In 1962, Rachel Carson’s exposé “Silent Spring” revealed to the public the dangerous downsides of DDT. This best-selling book dramatized the risks posed by DDT and other insecticides to ecosystems, wildlife and even humans — spawning the creation of the modern environmental movement in the process.

To pick but one of many examples, the book exposed how DDT was decimating populations of bald eagles, as the chemical disrupted their ability to reproduce successfully. Carson described two classes of synthetic insecticides: chlorinated hydrocarbons (including DDT) and organic phosphate insecticides — or the class of chemicals that the EPA is reassessing today. Although the popularity of DDT made the former more widespread, the latter chemicals were many times more toxic.

A decade of congressional hearings and lawsuits in Michigan, Wisconsin and New York compelled the newly established EPA to take action. By the end of 1972 the agency moved to effectively ban DDT by canceling the registration for most of its uses. Environmentalists rightly celebrated the DDT ban as a great achievement: A widely used pesticide that contaminated soil and water, and poisoned fish and birds, would no longer be used in the United States.

Many Americans have some familiarity with the DDT story, but there is a parallel story of the organophosphate insecticides — the second class of pesticides exposed by “Silent Spring” — that remains largely unknown.

Like DDT, the first of these chemicals were developed during World War II. Before the war, a brilliant chemist named Gerhard Schrader studied these compounds for potential use as insecticides in the research laboratory of a major German chemical company. When Schrader synthesized tabun and sarin in 1937 and 1938 respectively, however, he realized he had stumbled upon a potentially valuable military weapon and alerted the relevant authorities, who saw potential for these chemicals to serve as nerve agents and initiated research and development (the chemicals were not deployed in combat during the war).

Schrader returned to his original insecticide project in 1938. Four years later, in 1942, he made a breakthrough, synthesizing the first organophosphate insecticide: HETP (hexaethyl tetraphosphate). Two years later he uncovered a second such pesticide. In the years that followed, Schrader laid the foundation for the commercial development of many organophosphate insecticides.

After the war, toxicological assessments at the University of Chicago revealed each of the organophosphates to be highly toxic, not just to the insects they were designed to kill, but to animals and humans, as well. Despite high toxicity, toxicologists at the time believed that the environmental impact and risk to humans of organophosphates would be relatively low, because they underwent rapid hydrolysis and disintegration when they came into contact with moisture. For this reason, toxicologists believed that pesticides in this class would not persist or bioaccumulate (build up) in organisms and the environment.

Carson’s research revealed the flaws in this thinking. Her introduction to the chemicals was as succinct as it was disturbing: “The second major group of insecticides, the alkyl, or organic phosphates, are among the most poisonous chemicals in the world.” She went on to describe a case in which two children died after repairing a swing with an empty bag that had contained parathion and another in which 65,000 blackbirds died after an ill-timed bout of spraying with that insecticide.

Based on high toxicity and potential risk to humans and wildlife, it would stand to reason that the organophosphates would have been banned alongside DDT and other chlorinated hydrocarbons beginning in 1972.

This did not occur.

In fact, the ban on DDT increased their popularity among farmers still eager to protect their crops from insects. Organophosphates slipped through the regulatory net because they did not persist in the environment like DDT and the chlorinated hydrocarbons. U.S. farmers relied heavily on organophosphates until the Food Quality Protection Act of 1996 required EPA reassessment. In 2001, the EPA banned many organophosphates, but not all: Four of these pesticides remained available for agricultural applications because they demonstrated the lowest toxicities in a class of highly toxic chemicals.

Even the least toxic organophosphates carry serious risks, however.

The recent National Marine Fisheries Service report showed that pesticides containing chlorpyrifos or malathion were likely to jeopardize nearly half of 77 species listed under the Endangered Species Act and “adversely modify” more than 60 percent of designated critical habitats. Other related pesticides had similar effects. In 2016, under the headline “Like it’s been nuked,” The Washington Post reported widespread deaths of bees after South Carolina sprayed naled for Zika mosquitoes.

And risks are not confined to wildlife and ecosystems. In 2017, a team of American and Chinese researchers found an association between prenatal exposure to two of these pesticides and deficits in infant motor function in a cohort of Chinese infants.

In light of the historical legacy of the highly toxic organophosphates and recent findings showing significant risks to wildlife and humans, this is not the time for the EPA to reduce penalties or relax regulations that prohibit children under 18 from using these and other restricted-use pesticides. A more prudent course of action would be to ban the organophosphate insecticides altogether.