Water samples taken from the storm sewers at West Park in Ann Arbor reveal an increase in the levels of 1,4 dioxane — a likely carcinogen — in the groundwater. Within a year, the samples jumped from 4.4 parts per billion to 19 parts per billion.
In response to the increase in dioxane contamination, the Michigan Department of Environmental Quality has confirmed plans for further dioxane testing in Ann Arbor.
Evan Pratt, water resources commissioner of Washtenaw County, said while he does not think the dioxane in the West Park groundwater is dangerous to residents, he supports continued testing in the area.
“What I’ve asked of the DEQ is for them to) take samples every month for six months. Then we can have a better understanding of whether it is something that is a trend at that location or just something that fluctuates,” Pratt said. “In addition, I’ve asked for sampling at four or five other locations.”
In an MLive article, Gerald Tiernan, district supervisor of the DEQ’s Remediation and Redevelopment Division, confirmed Pratt’s sentiments, explaining the DEQ plans to take monthly samples from multiple locations within the area.
Mayor Christopher Taylor said the city will continue to support further testing.
“We are always looking for more testing — it is of critical importance to the city of Ann Arbor,” Taylor said. “We need to make sure that our homes are safe, that our drinking water is safe. We are going to continue to learn more about the location and direction of the plume and we are going to continue to work with our partners.”
The dioxane plume was introduced to the groundwater after Ann Arbor manufacturer Gelman Sciences, now Danaher Corp., released the chemical as an industrial byproduct into an unlined lagoon from 1966 to 1986. The chemical was able to leech into the underlying groundwater and the contaminated plume continues to spread underground. The plume was first reported in 1969 and has since spread, covering an area more than three miles long and a mile wide.
As the pollutant progresses underground through the Allen River and West Park, it moves toward the Huron River. and possibly Barton Pond, Ann Arbor’s main source for drinking water.
“Once it’s in West Park, it’s pretty easy for it to get to the river,” Pratt said. “It’s really primarily testing to find out if the tip of the plume, which is the weakest part, is headed towards the park.”
The tip of the plume, as estimated by test results, is believed to be moving east through West Park. Pratt said one of the primary aspects the tests is looking at is which way the plume is heading.
“We are definitely going to keep monitoring it and making sure it is moving east and not north because if it’s headed north, there’s potential it could get upstream and head towards the water treatment plant,” Pratt said. “One of our primary goals is to make sure it’s not moving toward the water treatment plant.”
Outside of polluting water, the DEQ acknowledges dioxane could potentially pose vapor intrusion health risks.
The Agency for Toxic Substances and Disease Registry explains humans can be exposed to the contaminant through both air and direct skin contact.
“1,4-Dioxane can be released into the air, water, and soil at places where it is produced or used as a solvent,” the website reads.
While dioxane can enter the air, skin contact is unlikely and usually through substances like lotions.
“Your skin may come into contact with 1,4-dioxane when you use cosmetics, detergents, and shampoos containing 1,4-dioxane,” the website reads.
Despite potential vapor intrusion health risks, Pratt argues dioxane is not a chemical like gasoline, which is can be easily separated from water and released into the air.
“Dioxane is not a good thing at any levels, but it is not absorbed through the skin and the likelihood of the chemical entering the air is not high,” Pratt said. “From my understanding, it is not a chemical that wants to break free from water. It wants to stay in water once it’s in water. It does not want to vaporize and go into the air.”
However, Pratt said the DEQ will continue to look into vapor intrusion risks.
Residents have also expressed concern regarding whether the polluted groundwater may find its way into their basement. But Pratt said the residents near West Park need not worry, explaining any flooding the residents might experience is caused by rainwater, not the plume.
“A lot of people are quick to tie rain water in the basement to the dioxane plume, but the two are not correlated,” Pratt said. “The houses are substantially higher than the ground and the ground is a little bit higher than the groundwater. The groundwater is separated from the basements beyond where the EPA would even think about keeping an eye on it, as far as would it possibly get into somebody’s basement. Right now, it doesn’t seem possible.”
The U.S. Environmental Protection Agency classifies dioxane as likely to be carcinogenic to humans via water, air and, in some cases, direct skin contact. The chemical is also linked to potential kidney and liver damage as well as respiratory issues through long-term exposure.
According to the EPA, only a few parts per billion of dioxane in drinking water over a long period of exposure can pose a 1 in 100,000 cancer risk.
The dioxane levels are well below state standards even though Michigan standards for dioxane in groundwater venting to surface water were tightened earlier in the year.
The national advisory for dioxane in surface waters that are protected as drinking water is 3.5 parts per billion, while the limit for dioxane in surface waters that are not protected as drinking water sources is 280 parts per billion. For the dioxane in residential drinking water, the state’s separate limit is 7.2 parts per billion.
Taylor emphasized dioxane has never been found in Ann Arbor drinking water.
“It is incredibly important that we understand the nature of the plume and the risks that are associated with dioxane,” Taylor said. “It’s also important to understand that it’s never been found in Ann Arbor drinking water and that we are doing everything we can that folks in Ann Arbor remain safe.”
While Pratt supports further testing, he said much of the testing for dioxane has come up negative and he does not currently see the pollution as a threat to the city.
“There isn’t any threat specifically to anybody — everybody in the city is on wells, but we’d like it cleaned up even though that’s not what the current legal system says (and) the county is in court fighting for something better.”
The plume is a source of an ongoing legal battle against Gelman Sciences by Ann Arbor, Washtenaw County, Scio Township, The Huron River Watershed Council and the state.