In wartime DDT had saved lives, and it had done so by inflicting easily accepted collateral damage. In peacetime, however, DDT’s negative effects on beneficial insects, birds, and fish warranted renewed consideration. National Geographic merely alluded to this; others were more direct. When the War Production Board first released DDT for sale to the public, it cautioned against “use of it to upset the balance of nature” and added that if applied to crops, DDT would leave residues that might also cause harm to humans.

What kind of harm? The problem was that no one really knew. Testing at the National Institutes of Health (NIH) and at the Food and Drug Administration (FDA) had shown that in lab animals DDT could cause tremors, liver damage, and death. Of the variety of animals tested in 1943 and 1944, monkeys seemed most resistant to DDT’s effects, mice the least. DDT suspended in oil proved more toxic than DDT dust, and the liquids DDT was dissolved in (like kerosene) often seemed more toxic than DDT itself. What was worrisome, according to FDA pharmacologist Herbert O. Calvery, was that the amount of DDT it took to produce symptoms of toxicity had no clear correlation across species; in some species it took very little, while in others it took a lot. The problem was complicated even further by the fact that when small animals ate small amounts of DDT over time, they developed poisoning symptoms normally associated with a single, large dose. Calvery concluded that although it was extremely difficult to say just how much DDT was safe for animals or humans to ingest, the safe “chronic”—or ongoing—level of DDT exposure “would be very low indeed.”

Calvery’s concerns appeared at the very end of a long, “restricted” report on insecticides issued by the Office of Scientific Research and Development in 1944. A War Department bulletin released the same month warned against spraying DDT on cattle, fowl, and fish and on waters that might be used for human consumption. It also cautioned soldiers against getting DDT-infused oil on their skin or DDT dust in their lungs, and strongly urged them not to let the pesticide “mingle” with kitchen supplies. At the same time, the insecticide in every recruit’s aerosol bomb was swapped out for DDT, and soldiers were instructed to spray or dust their mattresses and mess halls, latrines and barracks, dugouts, infirmaries, and even their uniforms. The warnings and cautions attached to army memos about DDT did yield some measures of self-protection: soldiers charged with DDT detail were given the protective gear Materi later saw on the team that entered her home. DDT was a poison, but it was safe enough for war. Any person harmed by DDT would be an accepted casualty of combat.

If DDT was harmful to humans, the methods by which it worked its harm were no clearer in peace than in combat. If anything, as time passed, DDT’s safety seemed to be unprecedented. By the fall of 1945 millions of people had come in direct contact with DDT—in Naples, North Africa, the Pacific, even throughout the southeastern United States where the chemical was sprayed in homes in an attempt to rout the last vestiges of malaria. No one displayed ill effects. The few human DDT poisonings seemed to be isolated cases associated with massive ingestion, like that among a group of starving Formosan prisoners of war who mistook DDT for flour and used it to bake bread. Not one died, though those who ate the most bread suffered lasting neurological damage.

But such cases caused little alarm. DDT was released for public sale in late 1945, at a time when insecticides were commonly known as “poisons” (or by professionals as “economic poisons” for their ability to preserve agricultural profits). Insecticides introduced in the latter half of the 19th century for commercial agriculture often contained copper, lead, and arsenic, and by the first half of the 20th century it was well known that insecticide residues on fruits and vegetables could sicken and even kill hapless consumers. This reputation was regularly reinforced by publicized cases of poisoning: Illinois women sickened by sprayed asparagus; the Montana girl poisoned by sprayed fruit; poisonings in Los Angeles traced back to excessive residues of arsenic on cabbage, pears, spinach, broccoli, and celery. There were also the tragic accidents associated with the increased presence of pest poisons in everyday life, such as the death of 47 patients at an Oregon hospital where roach powder was confused for powdered milk.

Instead of distancing themselves from poison sprays, however, by World War II more and more American consumers were bringing them home from the corner store. As Americans planted victory gardens to grow their own food, they amassed household-sized collections of agricultural poisons, including lead arsenate, calcium arsenate, nicotine sulfate, bichloride of mercury, and Bordeaux powder, a mixture of copper sulfate and lime. “Every gardener with more than a month’s experience,” noted a magazine writer in the spring of 1945, now has “a combination of powders and solutions as lethal as an arsenal.”

Insecticides, by definition, were poisons, and consumers were used to thinking of them as such despite their growing ubiquity. DDT thus posed an unparalleled paradox. It seemed to avoid so many of the downsides of the old insecticides: insects didn’t have to eat it to die but merely had to come into contact with it; it kept on killing for months after it was applied; and it killed an extraordinary range of insects at very low doses, all without causing any detectable harm to people. But for every feature that set it apart from the earlier insecticides, it was still a substance meant to kill. So how were consumers to receive reassurances of DDT’s safety in the government brochures, news articles, and ads that sang its praises?

One answer was to reject such claims, as a number of journalists and lawmakers did in DDT’s first year on the consumer market. When the pesticide was first released for sale, state officials in Missouri issued a formal warning against it, citing unknown hazards to plants, animals, and humans. Minnesota banned its sale, New Jersey restricted it, and California and New York issued decrees requiring that DDT-containing products bear the skull and crossbones indicating a dangerous poison. This last approach worried officials at the FDA and NIH. If people learned through experience that DDT could be handled with less caution than such bona-fide poisons as strychnine and bichloride of mercury—which it certainly could—they would lose their respect for the skull and crossbones as a signifier of danger.

As states struggled to regulate DDT, journalists struggled to reconcile warnings and promises. “Make no mistake about it. DDT in sufficient quantity is a poison,” announced one homemaking magazine. Sure, it slaughtered cockroaches, but “DDT presumably could send you on a death jag too,” reported another. “DDT: Handle with Care,” announced yet another publication, which went on to tell readers that DDT in substantial amounts would “attack nerve centers and the liver” and that small amounts consumed over time might “build up in the body to a fatal dose.” After all, noted one writer, that’s exactly what consuming lead and arsenic could do. DDT, “that storm center of pros and cons,” needed to be treated “as respectfully as arsenate of lead,” wrote another. DDT’s purported safety was one of the most exciting things about it, but it was also one of the hardest to believe.

So when Dorothy Colson saw planes spraying DDT over land adjacent to her family farm, it was easy for her to connect the pesticide to the problems that suddenly wouldn’t let up. In the years just after the war Colson launched a dogged investigation into DDT, writing to state agencies, manufacturers, and organizations far and wide. The literature she amassed on the pesticide indicated that it might be harmful to humans but offered no conclusive proof that it was. And the more experts she questioned, the more she was told that DDT had above all saved countless lives around the globe, all while never harming a person.

But Colson’s research turned up plenty of evidence that DDT was harmful to other living things, especially bees. To her this was reason enough to worry. As she wrote to a state health officer, “Any poison strong enough to kill or damage honey bees is surely strong enough to affect people.” The pesticide’s effects on bees and other beneficial insects had in fact worried federal scientists since DDT’s introduction. They noted early on (as National Geographic had reported) that DDT was deadly to honeybees, butterflies, small fish and reptiles, and, in high enough concentrations, birds and small mammals. Death to pollinators would lead to fruitless orchards and barren crop fields. As a report by the U.S. Public Health Service noted, “A delicate balance exists in the biota of every environment, and it is essential to determine the extent to which DDT upsets this balance.” The American Association of Economic Entomologists concurred that DDT’s “large scale use might create problems which do not now exist.” Even DDT maker Monsanto warned that “the danger inherent in the indiscriminate use of DDT as a cure-all is very real.”

Such expert worries were no secret. Newspapers far and wide reported that the new chemical was a threat to nature. (Older agricultural chemicals, such as lead and arsenic, typically got press space only when they poisoned people.) DDT killed off beneficial bugs and had the potential to “eliminate ducks and geese,” “paralyze” sheep, “burn” plants, and spark population explosions of some pests by wiping out their natural predators. In Colson’s home state, Atlanta Constitution farm editor and radio-show host Channing Cope wrote of his experience testing DDT on his property.

“DDT will kill the bees and that means that it will kill the clover, which means, too, that it will kill off our livestock,” he warned. “It will destroy the fruit crops which are dependent on bees for pollenization! It will kill most of the flowers for the same reason and will wipe out many of our vegetables.” He concluded, ominously, that DDT “has the power to ruin us.”

But Cope had other observations to share as well. The pesticide had eliminated the bugs pestering his mules, dairy cows, Scottish terrier, cat, and pig; and it seemed to be keeping the bugs from coming in through cracks and crevices in his windows and walls. Although its downside was undeniable, he wrote that DDT was also a “great tool for our betterment.”

Cope’s ambivalence captured that of the nation as a whole. Despite their trepidation Americans were enamored with the ways in which DDT promised to improve life on the farm and at home. Unmolested by insects, dairy cattle produced more milk and steers yielded more meat. Cockroaches disappeared from cupboards, ants from the sugar, bedbugs from mattresses, and moths from rugs. Even the flies then suspected of carrying polio seemed to take the disease with them as they disappeared. DDT sales continued to climb—even as the Colsons and the Copes struggled to make sense of the chemical’s harms. And so the nation moved forward, still ambivalent: DDT production increased tenfold to more than 100 million pounds by the beginning of the 1950s (the vast majority of it used in agriculture).

But the fears didn’t fade away. In the spring of 1949 headlines across the country carried the news that DDT had found its way into the nation’s dairy supply and that the “slow, insidious poison” was building up in human bodies. The following year, and for the rest of the 1950s, DDT became a focus of congressional hearings about the safety of the food supply. FDA scientist Arnold J. Lehman testified that small amounts of DDT were being stored in human fat and accumulating over time and that, unlike with the older poisons, no one knew what the consequences would be. Physician Morton Biskind shared his concern that DDT was behind a new epidemic, so-called virus X (an epidemic later attributed to chlorinated naphthalene, a chemical in farm machinery lubricants). Pesticide-eschewing farmers, such as Louis Bromfield, testified they simply could not meet the demand for spray-free crops from Heinz, Campbell’s, A&P, and other companies—all of which were themselves trying to meet the demands of consumers worried about pesticides generally, and specifically the ubiquitous and well-publicized DDT.

By the time Rachel Carson detailed DDT’s harm to falcons, salmon, eagles, and other forms of wildlife in Silent Spring, a good number of Americans had been demanding more information about the insecticide’s ill effects for the better part of two decades. And yet to this day that’s not how we talk about DDT’s past. Instead, we tell the story of a chemical whose powers were so awe-inspiring that no one gave any thought to its downsides—at least not until they were brought to light by one renegade scientist. It’s a narrative that gave Americans a hero for the latter part of the 20th century, a female scientist and writer smart enough and brave enough to take on the establishment and win. It’s a story about the power of social movements to remake society for the better. And it’s a story of a nation reformed, able to set aside hubris for reason.

As a society we use narratives to organize our shared past into a beginning, middle, and end. The stories we tell over and over again, like that of DDT, explain how we arrived at the present, and they point to a hoped-for future. DDT was banned in the United States in 1972, a development largely credited to Carson and the environmental movement she helped inspire. But in recent reports on Zika—and in less-recent debates about malaria in developing nations—a new ending to DDT’s story took shape. In this version of events there is a responsible way to use the pesticide and a potential need for it when it comes to controlling the most intractable insect-borne diseases. In this version our considered deployment of DDT would never repeat the mistakes of the past, especially the overuse of the pesticide in agriculture. In this new ending today’s experts are more enlightened than their historical counterparts; their expertise stems in part from learning from past mistakes, and with this wisdom they determine the appropriate limits in using powerful technologies.

Maybe so. I can’t predict the future, but I can say that these competing DDT narratives neatly illustrate a problem with the past: when we as a collective remember our shared history, we pick and choose from what happened in order to build our great narratives of nation and identity. In so doing we throw out the pieces that don’t fit and come to believe there is only one true past. If this manner of storytelling is a human inevitability, then perhaps we should learn to recognize the ways selective memory shapes so many of the narratives that tell us who we think we are.