A termite pesticide banned in 1988 is still turning up in wildlife; researchers found toxic brain levels in nearly half the sick skunks they examined near Detroit

It was banned 37 years ago. You probably never even thought about it. But chlordane, a pesticide that was once injected into the soil around millions of American homes to kill termites, is still very much present in older neighbourhoods. And new research is showing just how much damage it still does.

In a 2025 study, ‘Chlordane-Induced Neurotoxicosis in Urban and Suburban Detroit, Michigan Striped Skunks (Mephitis mephitis)’ published in Toxics, researchers from Michigan State University and the Michigan Department of Natural Resources found striped skunks in and around Detroit with alarmingly high concentrations of chlordane-related compounds in their brain tissue, high enough to cause severe neurological damage and, in several cases, death. The researchers say this is the first documented case of skunks dying from chlordane-induced neurotoxicosis, but they caution it’s likely far from an isolated incident.

What is chlordane, and why does it still matter?
If you grew up in a house built before 1988, there’s a good chance chlordane was sprayed into the soil around your foundation. According to the US EPA's chlordane fact sheet, chlordane was used as a pesticide in the US from 1948 to 1988, when all approved uses were cancelled (its last permitted application was termite control in homes). This EPA document lists chlordane as a probable human carcinogen. Neurological effects, including headaches, dizziness, and convulsions, have been reported in humans following acute exposure.


Chlordane doesn’t just go away. ATSDR's 2018 Toxicological Profile for Chlordane states that neurotoxicity is a consistent finding in humans and animals exposed to chlordane and includes symptoms such as headaches, convulsions, and seizures with multiple routes of exposure.

What happened to the skunks in Detroit?
A total of 17 striped skunks were brought to the Michigan Department of Natural Resources Wildlife Disease Laboratory between July and November 2022. Most of the skunks exhibited neurological signs, including loss of balance, tremors, convulsions, and altered mental states. According to the Toxics study, researchers ruled out rabies, canine distemper virus, highly pathogenic avian influenza, bromethalin poisoning, and other common toxic and infectious causes before concluding that chlordane was the cause.

This research found that 8 of 17 skunks had combined oxychlordane, heptachlor epoxide, and trans-nonachlor concentrations in brain tissue above the diagnostic threshold of 1,000 ng/g (wet weight) for toxicosis. Three animals had brain oxychlordane levels above the lethal threshold of 10,000 ng/g wet weight previously reported in birds. The same study also found that liver concentrations were about 10 times higher than brain concentrations on a lipid-weight basis, which may help predict fatal brain residues when brain tissue is harder to collect.

Why skunks? The study shows that striped skunks build dens under porches, garages, and home foundations, exactly where chlordane was used decades ago to control termites. They also eat beetles, earthworms, and other insects that are known to carry large residues of chlordane metabolites. They are in effect absorbing this poison through their point of slumber and their food.

This is not just a wildlife story
Of the 17 skunks, 10 (59%) were from Wayne County, Michigan, which includes Detroit suburbs such as Livonia, Dearborn Heights, and Redford. The Toxics study says this area overlaps with the River Rouge Watershed, an EPA Area of Concern since 1987, from decades of industrial contamination.

This is not contamination sitting quietly below ground. In 2022, a study published in Environmental Research by Wattigney et al. , titled, ‘Biomonitoring of toxic metals, organochlorine pesticides, and polybrominated biphenyl 153 in Michigan urban anglers’ reported that a biomonitoring program conducted by the ATSDR and the Michigan Department of Health and Human Services found chlordane-related compounds in the blood of Detroit-area anglers who ate locally caught fish, demonstrating that the chemical is actively moving through the food chain into people.

Decades of research on Great Lakes wildlife, including bald eagles, snapping turtles, and mink, show a broad spectrum of health effects from persistent organic pollutants that are strikingly similar to those seen in nearby human populations, says Fox GA in a 2001 study published in Environmental Health Perspectives. This study demonstrated that these effects were the most intense at the most contaminated sites. Sick wildlife in these areas has long been an early warning for human health risk.

What you can actually do
If your home is pre-1988, here are some practical steps you might consider: have the soil around your foundation tested for chlordane if the home has had termite treatments; avoid planting vegetable gardens right next to an untested older foundation; and when buying or renting a pre-1988 property, ask about its pesticide treatment history.

The Michigan researchers are calling for systematic monitoring of chlordane in urban wildlife, soil, and human populations across US cities where these chemicals were heavily applied in the past. It’s an uncomfortable favor skunks may be doing us. Living close to our homes, eating what lives in our soil, and showing us, sometimes fatally, what is still down there.