DDT's Long Tail in the Arkansas Delta

Why did traces of DDT show up in a southeastern bat colony more than 40 years after the pesticide was banned—and what could it mean for humans and wildlife?

• By Brontë Pearson // Photos by Rory Doyle
• Conservation
• Mar 26, 2025

The 359-mile-long Bayou Bartholomew runs adjacent to Arkansas farmland that was crop-dusted with DDT and other pesticides for decades.

BACK IN 2014, THE TAYLOR HOUSE had been vacant of human residents for years, pine straw littering the floor and wooden slats nailed across the exterior. But the two-story dogtrot—located between a cornfield and the world’s longest bayou, Bayou Bartholomew, in rural Drew County, Arkansas—wasn’t devoid of all life. Inside nested a maternal colony of about 200 Rafinesque’s big-eared bats, a species native to the southeastern United States.

After learning about the Taylor House, John Hunt, a mammalogist at the University of Arkansas at Monticello, and two fellow scientists—Chris Sims, an ecologist at Monticello, and Matthew Grilliot, a physiologist at Alabama’s Auburn University at Montgomery—got permission to collect samples in an effort to study the bats’ susceptibility to white-nose syndrome (WNS). The emerging fatal fungal disease has plagued hibernating bats in North America since the early 2000s, when it likely was introduced by transatlantic travelers, resulting in the federal listing of several species of bats as threatened or endangered, including gray bats and Indiana bats.

One day, while carefully collecting hair and fecal samples from the delicate creatures—which measure about 4 inches long and weigh less than half an ounce each—before releasing them unharmed, Grilliot remarked on the agricultural fields surrounding the Taylor House. “I made a snide comment about all the crop-dusting and the number of insects and told John maybe we were testing for the wrong thing and should test for pesticides,” he says.

Intrigued, the team sent samples to the University of Connecticut’s Center for Environmental Sciences and Engineering for a broad-spectrum analysis. Results revealed the samples did not have the detectable hormone levels needed for WNS research. But they did have something else: high levels of agricultural pesticides and the metabolites left behind when those pesticides break down. Some traces found, such as 1,2,4,5-tetrachlorobenzene, are used in a number of pesticides and could have come from the crop-dusting of local corn, rice and soybean fields. But others, such as DDT, have been illegal for decades.

“I was absolutely shocked by the results,” Grilliot says.

On land, in water, in wildlife

First synthesized in 1874, DDT’s popularity took off in the 1940s, when the artificial compound was used to combat insect-borne diseases such as malaria and typhus during World War II. Relatively inexpensive to produce, DDT became a staple of the U.S. agricultural industry. It was widely used as an insecticide in public, commercial and residential spaces until the U.S. Environmental Protection Agency (EPA) banned it in 1972, 10 years after the publication of Silent Spring, the seminal book by biologist and conservationist Rachel Carson documenting environmental damage caused by DDT.

Numerous studies since have proven DDT to be detrimental to humans and wildlife alike due to its carcinogenic and nerve-damaging effects. For decades, scientific consensus has held DDT largely responsible for the near extinction of several raptor species, including bald eagles. The pesticide not only ran off agricultural fields, washing into waterways and contaminating the fish that eagles eat; in one well-documented case, the manufacturer Montrose Chemical Corporation of California dumped DDT acid waste into the Pacific Ocean, causing reduced fertility, improper egg production and formation, sex organ abnormalities, skewed sex ratios and hormone disruptions in fish and seabirds.

The eagle made its comeback once DDT was banned, and the Endangered Species Act was signed into law in 1973. In humans, studies over the last 30 years have linked DDT exposure to breast, lung and liver cancers; diabetes; fertility issues; premature births and miscarriages; and neurodevelopmental problems.

Given that DDT was outlawed more than 40 years before his team encountered it, Hunt and his colleagues were at a loss as to why traces of it were still registering in Arkansas. DDT has a half-life of two to 15 years in soil, meaning at least 50 percent of it should have broken down by 1988, 15 years after the EPA banned it, and all of it by 2003. And yet, DDT was present in bats with a lifespan of 10 years in 2014.

“We considered the idea that where we were working is heavily agricultural and has been since before the Civil War, so DDT would have been used heavily as a pesticide there,” Hunt says of Drew County, located 100 miles south of Little Rock. “Southeast Arkansas was also part of the malaria belt, so there have been really intensive mosquito control programs here.” In the mid-1940s, a federally funded program sprayed around 45,000 acres of standing water in Arkansas each year, as well as nearly half a million homes between 1947 and 1953.

“One would think it would have all broken down but apparently not,” Hunt says.

In searching for data, the team encountered little scientific research on DDT conducted after 1972 in the Arkansas Delta or elsewhere. One of the few studies, by University of Mississippi biologists, found DDT present in fish in Tennessee and Mississippi—but that data came from samples analyzed between 1978 and 1981, less than 10 years after DDT was banned. On the other side of the country, a 2015 study of California’s Newport Bay watershed recorded DDT and other illegal pesticides.

“Since DDT was widely used and is bioaccumulated in ecosystems, one would expect to find it everywhere. The important question is at what levels,” says James Byard, a toxicologist who worked on the Newport Bay study for the University of California, Davis. Byard’s research has found that, while DDT doesn’t dissolve easily in water—where its half-life extends up to 150 years—levels of the chemical counterintuitively tend to be higher on land, where the first 50 percent of DDT breaks down more quickly than the latter half.

In water, DDT settles into sediment, evaporates or is absorbed by fish and small organisms, according to the Agency for Toxic Substances and Disease Registry. DDT and other chemicals make their way up the food chain through biomagnification, which occurs when one organism eats others that have pesticides in their bodies. “The farther up the chain you go, the more of the toxins you find,” Hunt says. “Very small concentrations low in the food chain can become serious concentrations at the top.” DDT levels can register thousands of times higher in wildlife than in water.

In 2016, Hunt’s team began collecting samples from other wildlife species, all within 6 miles of the Taylor property: rodent hairs, a blue jay feather, hair from a coyote pup killed on the highway. “We were interested in finding out how widespread [DDT] was,” he says. “We chose those [species] because they were easy to get to, easy to catch, and they were in a similar habitat but in a different ecological niche.” Rats, for example, are ground-dwelling and, unlike bats, eat more seeds and plants than insects, providing new data points. The team’s research, published in the Journal of the Arkansas Academy of Science in 2018, found DDT present in at least one sample of every species tested, with the mammals registering higher levels of DDT and its metabolites than in studies conducted before the 1972 ban—as much as six times more.

“Agricultural runoff would run right into the bayou,” Hunt says of the 359-mile-long Bayou Bartholomew, on whose bank the Taylor House sits. “It’s the main drainage in this part of the state, so that’s my guess as to why we were finding higher levels than in years past.” He posits that DDT has been preserved “in the anaerobic muck at the bottom and that it is released into the general environment when the bayou gets low, as it does most years.”

Among the five water and soil sites where the team collected samples, also in 2016, none showed DDT present, but all five sites registered 4,4-DDE, and three contained 4,4-DDD—both DDT metabolites. Also present at one or more sites: heptachlor and cis-Nonachlor, insecticides banned in 1988 for causing carcinogenic, neurological and negative liver impacts on wildlife, plus gastrointestinal distress and neurological effects in humans; and aldrin, banned in 1974 for similar problems, including reproductive issues in animals. The pesticide hexachlorobenzene—banned in 1966 for causing liver disease in humans, as well as liver, kidney and thyroid cancers in animals—was present in the blue jay feather.

And then there’s white-nose syndrome, of which Hunt says, “You’re looking for one thing and accidentally discover something else.” The team believes exposure to agricultural chemicals in general, and DDT in particular, makes bats more susceptible to WNS by weakening their immune systems—an assertion supported by research published in the journal Chemosphere in 2010. That study showed high concentrations of DDT and its metabolites in adipose, or fatty tissue, samples from little brown bats with WNS in New York. While the study did not determine that DDT was causing WNS, it showed a correlation. “Adipose tissue plays a role in hair growth, so it makes sense why these levels would also be high in the fur samples we collected,” Grilliot explains.

Why is WNS such a cause for concern? While the disease does not kill bats directly, it interrupts their winter hibernation, leading them to wake up and deplete their energy looking for food when no insects are present. The bats eventually become exhausted and die. That means fewer bats consume fewer insects, including insects that eat crops, which can lead to increased pesticide use and pollinator die-off—a deadly domino effect that reverberates throughout ecosystems.

“Some populations are losing 90 to 95 percent [from WNS], so you go from a bat species that’s healthy and not considered threatened or endangered to being on the federal endangered species list nearly overnight,” Hunt says.

And among humans

Tanya Hagler, 55, grew up in Rector, Arkansas, a town of about 2,000 people in the state’s Delta region. She and at least 28 other local women in her age group have been diagnosed with multiple sclerosis (MS)—a neurological disease that, on average, affects 36 out of every 100,000 people worldwide. Hagler suspects pesticide exposure caused her MS and accounts for the area’s mind-boggling incidence.

“Rector is very tiny, and it’s surrounded by crops,” Hagler says. “They were spraying everywhere. Even if it wasn’t right on our little bit of land, it was close, always, and then there’s runoff everywhere.” While some insecticides were dropped by plane, some farmers sprayed by hand. “I’ve heard stories of men in Rector mixing the chemicals in a tank on the back of a tractor with their arm, ungloved,” she says. “They’d just stick their hand in and mix it up in the water to dilute it down. This was decades ago, but they didn’t think anything about it.”

To Hagler’s knowledge, Rector’s cluster of MS cases does not include anyone younger than the graduating class of 1987—meaning the youngest affected were born before DDT was banned. “My neurologist is aware of [the trend],” she says. “He believes it could have been from a nearby ditch that had been contaminated. He said, from what he understands, you don’t have to live on the ditch, you just have to live near it.” Representatives of the Arkansas Department of Health’s Environmental Health Protection program, as well as Hagler’s neurologist and the hospital with which he is affiliated, did not respond to requests for comment.

“DDT was ubiquitous in Arkansas [before 1972], especially from cotton farming in the Delta,” says Jay Gandy, a toxicologist retired from the University of Arkansas for Medical Sciences. A rural region of at least 15,000 square miles, the Arkansas Delta is home to roughly 1.1 million people and 57 percent of what the Arkansas Department of Health and other agencies deem “red counties”: those with exceptionally high rates of mortality compared to the national average. The Delta has the lowest life expectancy and the highest cancer mortality rates in the state, according to the Department of Health. In 2021, 17,980 Arkansans were diagnosed with cancer, and the disease claimed 6,250 residents’ lives—one of the poorest outcome rates in the nation.

Lack of access to preventive care and treatment has compounded the public health crisis in a state where 41 percent of the population resides in rural areas, and 15 to 16 percent lives below the poverty line. With 119 hospitals total, Arkansas has fewer per county than the national average of 1.8 per county; 23 of the state’s 75 counties do not have a hospital, and 39 others are served by a single hospital, 18 of which are considered “critical access” and offer limited services. Race further multiplies those disparities. While Black residents make up 15.6 percent of Arkansas’ population, compared to 13.7 percent nationwide, they account for 41 percent of the population in the state’s rural areas of persistent poverty and see higher rates of cancer morbidity and mortality.

“We’ve been asking for years for people to find out why so many people from Rector have MS,” Hagler says.

Monitoring—and maybe interrupting

DDT is outlawed under the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), which regulates pesticide sales and distribution and is enforced by the EPA, alongside federal, state, territorial and Tribal partners. Concerned citizens can report suspected pesticide violations anonymously via the EPA website or to their state’s governing body.

Since 2021, the EPA has received 11 reports alleging DDT use across the country. Although each incident was investigated, the last federal criminal prosecution for DDT sale and distribution occurred in 2010, when the manager of an environmental services company in California was found guilty of selling banned pesticides. While no reports of DDT have been filed in Arkansas in recent years, the state has prosecuted farmers for spraying dicamba, an herbicide used on soybean and cotton crops, after the state first banned it in 2017.

In Arkansas, before pesticides can be sold they must be registered with the Department of Agriculture’s State Plant Board—amounting to about 11,000 pesticides listed each year. Failure to comply with FIFRA or state law can result in penalties ranging from a warning letter to a $1,000 fine and license revocation. The Department of Agriculture also holds regular events where farmers can dispose of old or unwanted pesticides safely, with some 6.3 million pounds collected statewide since 2005. And yet, traces of illegal DDT and legal but dangerous chemicals remain in the environment.

There are some steps the public can take to reduce the risk of exposure, according to the Washington State Department of Health, one of the only state agencies in the nation that provides DDT-specific guidance to the public. When eating foods likely exposed to pesticides—which, according to the U.S. Department of Agriculture, included 72.4 percent of produce tested for pesticide residues in 2022—Washington health officials suggest thoroughly washing fruits and vegetables. For fish, they recommend removing the skin and visible fat then cooking until any remaining fat drips off.

People also should avoid swimming in or drinking from DDT-contaminated waters. Nationwide, the U.S. Geological Survey monitors streams, lakes and groundwater from a network of wells across the country for pesticide pollution, including chemicals like DDT and chlordane that do not dissolve easily in water and can persist for years in sediment. In Arkansas, the Department of Agriculture and the Division of Environmental Quality monitor groundwater—as well as water sources, wells and springs—in areas considered vulnerable to agricultural pesticide contamination, with each part of the state sampled approximately every three years. While no Arkansas agency currently tracks DDT, representatives say the Division of Environmental Quality has analyzed DDT and its metabolites in groundwater as recently as 2016.

Another strategy for limiting risk, according to scientists: weight loss. Because DDT can accumulate in fatty tissue and can bind to estrogen hormone receptors, losing weight “will cause your body to remobilize, recirculate and metabolize DDT, then excrete it,” Gandy says. That isn’t without risk, however, as DDT can damage the nervous system and liver as it circulates in the bloodstream if levels are high enough.

Farmers likewise can take steps to reduce pesticides’ impacts on wildlife and humans, according to Jeffrey Landis of the EPA. He suggests keeping pesticides out of storm drains and gutters, knowing which pesticides leach into groundwater, properly cleaning any spills, leaving a border of untreated vegetation between agricultural fields and wildlife habitats, and always following pesticide product labels. “When risks of concern are identified, EPA incorporates mitigations to reduce or eliminate potential exposures, which has the effect of reducing or removing identified risks,” he says.

All of the above requires farmers to take a personal interest. Angela Schenk, who grows soybeans, corn and winter wheat in southeastern Arkansas, has permitted Hunt to catch bats and rodents on her 1,150-acre property for his research. She and her husband approach pesticide use with caution, only spraying when no rainfall is expected and using specialty nozzles to target precise locations, minimizing pesticide drift. She says she has seen pesticides’ negative impacts firsthand, both on her own land, where she has lived for 16 years, and on her parents’ farm, about three hours northeast.

“Growing up, we saw lightning bugs everywhere,” Schenk says. “We used to catch them, put them in jars, bring them in at night. Then it got to where there were none; they were nonexistent. You just didn’t see them anymore, and I’m sure that’s from some sort of pesticide being sprayed.” Schenk says she also sees fewer bullfrogs in areas where frog hunting once was common and fewer softshell turtles in ponds where she would fish. “Road ditches don’t have aquatic vegetation as much anymore, likely from the impact of runoff and residue that settles from the chemicals sprayed,” she says.

Like Hagler, Schenk says she knows many people who have experienced cancers or neurological disorders that she speculates are due to chemical exposure. “My father-in-law and his siblings have neuropathy in their hands and feet, but they’re not diabetic,” she says. “[My father-in-law] is 85, and back then, they did a lot of things we now have precautions for. I think there’s a great chance that it’s something environmental. Their parents did not have that problem, so it’s not genetic. Something is causing it.” Even so, some pesticide use is necessary to keep insects from destroying crops, according to Schenk. “We still have to feed everyone,” she says. “For the greater good of the world, we sacrifice people in the Delta.”

Further research—including broadening the range and number of species sampled to include local insects, bobcats, black bears, bald eagles, migrating barn swallows and farmers, among other human residents—could help determine current and future threats related to DDT, but that requires funding. “We are looking for small grants to evaluate the real risk and long-term physiological effects,” Grilliot says. “We want to know things like how toxins are affecting offspring, what skin concentrations are like, if bats can get rid of toxins through molting and, of course, what is the human risk.”

Despite challenges, the team remains resolute. “You can’t know what the effects are until you know how widespread it is,” Hunt says, tapping his yellow sneakers against the aging linoleum of his office floor. “These chemicals should not be anywhere.”

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Protection From Pesticides

Pesticides—whether insecticides, herbicides or other types, from DDT and dicamba to glyphosate and neonic-otinoids—pose a great risk to wildlife and people. The National Wildlife Federation and affiliates have worked for decades to educate the public about pesticide-free gardening techniques, to help the agriculture community optimize its pesticide use and with legislators to better regulate harmful chemicals, with the goal of minimizing impacts on people, wildlife and ecosystems. Learn more. 

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Read about writer Brontë Spencer.

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