ANN ARBOR, MI -- In response to heightened concerns about the Gelman dioxane plume spreading through the area's groundwater, Washtenaw County Public Health is working to supply residents with more information.

What can dioxane do to your health? How can you find out if dioxane is in your drinking water?

And where can you get your water tested?

Those questions and more are answered in a new five-page fact sheet the county has sent to Scio Township residents on private well water.

"If your water is not already being tested but you would like to test it, you are responsible for any cost," the fact sheet states, including contact information for three labs that can test for dioxane: Ann Arbor Technical Services, Brighton Analytical, and the DEQ's drinking water lab in Lansing.

Copies of the fact sheet were sent out a couple of weeks ago to any properties with detectable levels of dioxane in their wells over their testing history, said Kristen Schweighoefer, the county's environmental health director.

The county also plans to send copies to other properties where the well water is regularly tested for dioxane.

There currently are no detectable levels of dioxane in the city's municipal drinking water, but the expanding plume has poisoned wells in Scio Township and years ago forced the city to shut down one of its municipal supply wells.

The plume has been spreading for decades from the former Gelman Sciences site on Wagner Road on the border of Ann Arbor and Scio Township.

The Ann Arbor News reported earlier this month that a family with three young children at 5005 Jackson Road, as well as two adjacent businesses, have had concerning levels of dioxane in their well water for years.

Immediately following the news reports, the state took action to supply bottled water and then had the properties connected to municipal water.

Readings going back to 2005 show dioxane concentrations in the Jackson Road home's well water near 50 parts per billion.

Washtenaw County Public Health sent this map of the Gelman dioxane plume to local residents in March 2016. The many dots shown in Scio Township represent private wells for homes and businesses at risk of being poisoned as the toxic groundwater plume spreads.

The readings have gradually gone down over the years, dropping to 33 ppb by 2010, and then to 17 ppb in recent months.

That's below the state's allowable standard of 85 ppb, which is why nothing was done about it previously, but it's above what's believed to be safe.

Following years of pressure from Ann Arbor and Washtenaw County leaders and activists, the Michigan Department of Environmental Quality is finally proposing to strengthen the state's groundwater standard for 1,4-dioxane, shifting to a single-digit standard of 7.2 ppb that's closer in line with federal guidelines.

Dioxane from the Gelman plume has been detected in wells still actively being used along Jackson, Wagner and Elizabeth roads. But because it's not above the proposed 7.2 ppb standard, there's still no remedy for those people.

In the new fact sheet, the county is telling residents their well water is safe to drink if the dioxane readings are below 7.2 ppb.

"If your well water has been tested and is at or below the draft MDEQ drinking water criterion of 7.2 ppb, it is considered okay to use the water for drinking (including making things like tea and coffee)," the fact sheet states.

"Limited information is available on potential risks to infants from 1,4-dioxane exposure. If 1,4-dioxane is detected in your well water, but is at or below the draft MDEQ drinking water criterion of 7.2 ppb, it is recommended you talk with your pediatrician and use bottled water for preparation of infant formula."

The county's fact sheet adds, "If your well water tests above the draft MDEQ drinking water criterion of 7.2 ppb, you will be provided with bottled water by the MDEQ until you can be connected to city water."

The U.S. Environmental Protection Agency published findings in 2010 suggesting dioxane at 3.5 ppb in drinking water poses a 1 in 100,000 cancer risk. The state's 85 ppb standard was intended to result in the same cancer risk.

DEQ officials say the federal screening level of 3.5 ppb is not enforceable and assumes an exposure period of 70 years. The new 7.2 ppb state standard proposed by the DEQ assumes an exposure period of 32 years.

People with additional questions or concerns about dioxane as it relates to the Gelman plume and drinking water are encouraged to contact Jennifer Conn of Washtenaw County Public Health at 734-222-3855 or connj@ewashtenaw.org, or Dan Hamel of the DEQ at 517-780-7832 or hameld@michigan.gov.

The DEQ is planning to test another 38 wells north of the plume this year to be sure the pollution has not spread to those areas. The results will be available on the DEQ's website for the project, which can be found here.

"You can be exposed to 1,4-dioxane by drinking it, breathing it in, or getting it on your skin," the county's fact sheet states, noting the federal government has linked drinking and breathing dioxane to cancer based on studies on animals.

"Being exposed to levels of 1,4-dioxane over a long time is also linked to kidney and liver damage in laboratory tests in rodents."

The fact sheet also addresses whether there is a faucet filter that can remove dioxane from tap water.

"Unfortunately, filters such as carbon filters and reverse osmosis filters cannot effectively remove 1,4-dioxane," the fact sheet states.

Ryan Stanton covers the city beat for The Ann Arbor News. Reach him at ryanstanton@mlive.com.