- The Gelman plume of 1,4-dioxane is over 40 years old, but it’s unknown how it could have affected residents who drank contaminated well water before their houses were hooked up to city water.
- Dioxane moves easily with water and is difficult to break down. Experts say that makes it a “forever chemical,” similar to PFAS.
- The state and county say no one is being exposed to the plume today in their drinking water. But advocates want more proactive solutions from the government.
If you go to the third floor of the Ann Arbor District Library’s downtown building, you’ll find an entire bookshelf of thick three-ring binders full of technical reports, communications and information about the Gelman Plume. It’s a long-known environmental problem in Ann Arbor, so reams of information about it are readily available.
Gelman Sciences, LLC used an estimated 850,000 pounds of dioxane between 1966 and 1986. The company dumped wastewater contaminated with dioxane on its property in Scio Township west of Ann Arbor, where it spread underground to nearby drinking water wells.
But over 40 years after the contamination was first identified, crucial information is still missing: How has the plume impacted the health of the people who drank water contaminated with dioxane?
There is no record of any long-term monitoring of those who were exposed to the plume. That’s unacceptable, said Rita Loch-Caruso, a professor emeritus of toxicology at the University of Michigan.
“One of the biggest challenges is that we don't know enough about it [dioxane] and about its toxicity,” she said.
An epidemiological study of those affected by the Gelman plume could help toxicologists like her better understand the potential threats dioxane poses to human health, she said.
And, she said, it would provide a bit of justice for those who were drinking contaminated water for years.
“There isn't even a registry of exposed persons,” Loch-Caruso said. “And so there's been no attempt to document whether any people have really gotten sick. And there were some really outrageous historical exposures.”
“I wanted the world to pay attention.”
Loch-Caruso has a PhD in toxicology and spent her career studying how environmental contaminants affect pregnancy and fetal development. Now, she uses her expertise to advocate for a more aggressive response to the Gelman plume. She serves on the board of directors of the Coalition for Action on Remediation of Dioxane.
The coalition formed in 2006 and includes residents and representatives from local governments. Loch-Caruso joined because she wanted to use her professional background to help others understand — and evaluate — the information that the state government provides about the risk the plume poses.
No one is currently being exposed to the plume’s contaminated water and there are measures in place to protect residents if that changes, said Chris Svoboda, the site’s project manager at the Michigan Department of Environment, Great Lakes and Energy (EGLE).
“We are monitoring what we need to monitor. We're making sure that nobody's being exposed,” he said. “That is really our objective.”
Regular monitoring tracks the plume’s movement. Groundwater use in the affected part of west Ann Arbor is banned. But many coalition members are worried the state still isn’t being proactive enough to prevent future exposures.
In 2022, Loch-Caruso and other members of the coalition wrote a peer-reviewed paper summarizing the plume’s history and current state. It’s written in lay terms, making it more accessible to a general audience. That was on purpose, Loch-Caruso said.
“I wanted the world to pay attention to the Gelman site,” she said. She and her co-authors argued that crucial information is still missing: full delineation of the plume and a study of how it has potentially affected human health.
An emerging contaminant
There are very few studies researching human exposure to dioxane. Most previous research was done on animals. It’s why the EPA classifies dioxane as a “probable carcinogen,” said Vasilis Vasiliou, director of the Yale Superfund Research Center.
“Although there is substantial evidence that this is a carcinogen in animal models in rats and mice, that is not a logical study,” for understanding human health effects, he said. And he said the few small studies on human exposure do not provide enough data to make scientifically sound conclusions.
The National Institutes of Health funds 23 Superfund research centers, each exploring ways to reduce human exposure to environmental contaminants. Loch-Caruso is a member of the external advisory board for the Yale center, in part because of her involvement with the Gelman plume.
“Superfund” refers to a list of hundreds of severely contaminated sites the EPA manages. These sites take years and millions of dollars to clean up, often at the federal government’s expense.
Yale’s center focuses on 1,4-dioxane as an emerging contaminant. Those are chemicals that have been released into the environment, but whose effects are not fully understood.
Dozens of drinking water sources across the United States are already contaminated with dioxane. The synthetic chemical presents several challenges, Vasiliou said.
Dioxane 101
Dioxane is a human-made chemical used in the production of pharmaceuticals and plastics. It’s also sometimes an impurity found in some consumer products such as detergent and shampoo. It should be considered a “forever chemical” similar to PFAS, Vasiliou and Loch-Caruso said.
“Dioxane is a forever chemical because once it goes into water, it stays with water sources,” Loch-Caruso said. Dioxane is miscible, meaning it mixes with water rather than separating from it. And it travels wherever that water goes, Vasiliou said.
“Nothing could stop 1,4-dioxane from traveling,” he said.
Gelman began using (and dumping) dioxane in 1966, so the chemical had almost 20 years to spread in the groundwater under the city and township before it was discovered. That makes it difficult to track.
Ann Arbor’s groundwater follows glacial till formed thousands of years ago. It’s not stagnant — it moves.
“Groundwater flows, just like streams and creeks and rivers,” Loch-Caruso said. And the contaminant doesn’t break down easily, Vasiliou said.
“The degradation rate of [dioxane] is very, very low or almost impossible,” he said. Natural degradation is possible, but isn’t happening at a rate fast enough to remediate the aquifer, according to a study of the plume.
Water contaminated with dioxane has to be treated with ozone or ultraviolet light. Experimental bioremediation using bacteria has promise, but needs further testing, according to a paper Vasiliou co-authored.
Dioxane is still used to make everyday products like cleaners and PET plastics (the kind used for pop and water bottles). That means more releases into the environment from manufacturers, like the plume in Cape Fear, North Carolina, Loch-Caruso said.
“Despite these increased threats of potential exposure, because we're still using all this [dioxane], we still don't know that much about how dioxane affects human health,” she said.
A logical study
The Gelman plume is an opportunity to learn more about dioxane contamination and expose harm done to residents whose wells were contaminated, Loch-Caruso said. She wants to work with the Yale research center to do a population study of residents exposed to the plume.
“There is a big need for epidemiological studies,” Vasiliou said. “And that's what we're going to do.” The first step is to assemble a federal grant application. The study would require a lot of money, he said.
Recent funding freezes by the Trump administration have scientists at the National Institutes of Health concerned about the future of their research. The Superfund center is going to roll with the punches, Vasiliou said.
“Our scientific work [is] not going to stop,” he said.
The center wants to study three sites: the Gelman plume in Michigan, one in Florida and one in North Carolina.
To conduct such a study, researchers would need to track down everyone who drank well water contaminated by the plume. That includes residents, workers at businesses that used well water and Gelman’s own former employees. The center is already doing a study on Long Island.
But many of the people exposed in Ann Arbor have scattered across the country or died. Even if they could be tracked down, researchers would need to get their medical histories.
It’s a tall order, but it can be done, Loch-Caruso said. An epidemiological study would provide more precise information about how dioxane affects the human body, Vasiliou said.
Right now, the best option is to estimate that risk through calculations — which are also a source of disagreement.
Calculating risk
The biggest concern among regulators and advocates is that dioxane exposure through drinking water could increase residents’ risk of cancer.
“We are managing that risk,” Svoboda said, by regularly monitoring dioxane levels across the plume and banning groundwater use.
Every drinking water well with dioxane levels above the state’s limit has been plugged, according to the state and Gelman in technical documents and public meetings. Residents are not being exposed to the plume at levels the state considers harmful to human health, according to the state and county.
But that’s the rub for Loch-Caruso — the state isn’t strict enough about what is “harmful to human health,” she said.
Toxicologists calculate a maximum limit for how much dioxane someone can be exposed to in their drinking water over a lifetime. That limit is based on assumptions about how long a person is exposed to a contaminant and how much of it they are exposed to.
For dioxane, limits are measured in parts per billion (ppb). It sounds infinitesimally small, but daily exposure over decades could add up.
Michigan and the EPA use different assumptions about what “lifetime” means — and have come to different conclusions about how much dioxane constitutes a risk to public health.
Michigan’s limit for 1,4-dioxane in drinking water is 7.2 ppb. The EPA’s is a health advisory: 0.35 ppb to 3.5 ppb.
In other words, Michigan residents have to be exposed to more dioxane before the state considers them endangered.
But Michigan’s limit is enforceable, while the EPA’s is a health advisory. There’s no federal regulation in place to keep 1,4-dioxane levels in drinking water below a certain threshold — it’s left up to the states. And out of the few states that limit dioxane in drinking water, Michigan’s is the highest limit.
Loch-Caruso favors the EPA’s risk calculation. The lower number (0.35 ppb) reflects a 1 in 1,000,000 risk of cancer. That’s standard for exposure risk calculations, Vasiliou said.
Michigan’s current criterion does not sufficiently protect human health, Loch-Caruso said. She’s also concerned there are other ways residents could be exposed to the plume.
“It’s coming.”
Most of the plume is confined to water that is dozens to hundreds of feet below the surface, and therefore won’t touch any dwellings. But in some areas of Ann Arbor, the water table is closer to the surface. If contaminated groundwater seeps into a house’s basement, then evaporates, the dioxane could still be present in the air under certain conditions.
The state’s current threshold for basement intrusion is 1,900 ppb. That’s too high, according to a peer-reviewed paper Loch-Caruso co-authored.
Groundwater with more than 150 ppb presents a 1 in 1,000,000 cancer risk if it enters a building and evaporates, she said. A dehumidifier would not be effective in removing the contaminant, according to the paper. Contaminated water would be a potential threat if it is within three meters of the surface.
It sounds like a hypothetical, but the groundwater in some areas of Ann Arbor is already very close to the surface. And there have already been dioxane hits in surface water in the city.
In 2018, testing found elevated levels of dioxane in stormwater under West Park, which is just northeast of the plume. Samples from the park’s pond have had hits every year since 2021, according to state data.
That dioxane could be coming from the plume, Loch-Caruso said. As the ground elevation changes, the water table is closer to the surface in some areas, and so, contaminated groundwater isn’t as far below the surface in some areas of the city as it is in others.
The city of Ann Arbor tested a few residents’ basements for dioxane from 2020 to 2022. Only three homes in the target area submitted samples, and all were non-detect.
Although there’s no evidence of groundwater contamination near the state’s threshold for action, the state is still looking into contamination entering surface water, EGLE’s Svoboda said.
“[EGLE] is advocating for further delineation of groundwater in the area,” he said in an email. The state has asked Gelman to conduct more testing in the eastern part of the plume to determine if contaminated groundwater is mixing with surface water, according to a December 2024 letter from EGLE to Gelman.
That threat isn’t just a possibility — it’s inevitable, Loch-Caruso said.
“It’s coming,” she said. “It's hundreds of parts per billion…and it's coming to basements in Ann Arbor.”
The state needs to be more proactive, she said.
“They should be working to prevent a situation where residents will be unnecessarily exposed to a health hazard.”
On the sidelines
The timeline to clean up the plume is now measured in decades and centuries because it has been spreading for so long.
Gelman was acquired by Pall Life Sciences, which became a subsidiary of Danaher Corporation in 2015. None of the three companies responded to repeated requests for comment over email, phone and mail.
Gelman has significantly reduced the highest concentrations of dioxane in the plume by pumping and treating contaminated water, according to sampling results. But the plume is still there — and it’s still moving, as dioxane likes to do.
After almost 20 years of advocacy, Loch-Caruso feels she still does not have a say in how the state manages the plume.
“When the state is the only representative at the table negotiating with the company, [then] the local interests are not always represented,” she said.
A litany of residents, scientists and local government officials have spent decades pushing for a more aggressive cleanup. But even with energetic involvement, locals say they feel left out of the decision-making process.
“I think there are good people working for the state. They know what needs to be done,” Loch-Caruso said. “And it's more than what's being done.”
In the final part of our series tomorrow, we’ll examine how local residents have pushed for a more aggressive cleanup of the plume and what EPA intervention could look like during Trump’s second term.
