More private wells at homes in Plainfield Township showed levels the toxic PFAS chemical after continued testing by Wolverine Worldwide, the Department of Environmental Quality said Saturday.

Wolverine Worldwide tested 640 private wells in Plainfield for the chemicals, which are linked to the Scotchgard product the company used to waterproof shoes at its old tannery.

The Environmental Protection Agency's lifetime safe drinking water advisory level for PFAS is 70 parts per trillion (ppt). Of the 413 obtained results, 28 homes tested above 70 ppt. and 145 detected the chemicals but tested below the advisory level, according to the DEQ.

Although many homes tested below the EPA advisory, people in the study areas with detectable levels of PFAS should not drink the well water, said Christina Bush, a toxicologist with the Michigan Department of Health and Human Services.

"If there are any detections, because we don't understand the source, or the site, we would recommend that people do not use their water for drinking or cooking," Bush said.

Health and Human Services makes that recommendation based on both the level PFAS in the water and how close a well is to a possible contamination site. Until the DEQ understands the full scope of the contamination's source, homeowners with PFAS should stay on bottled water, said Abigail Hendershott, a supervisor for the DEQ.

"If they've only got one sample, and they might be in a source area, then we need to do further evaluation, and they might need to do some point-of-use filters or under-the-kitchen-sink filters," Hendershott said.

Wolverine initially promised whole-house filters to all 338 homes in the first testing buffer zone, but only to homes that tested above 70 ppt. in the southeast expansion. The company aligned with the state recommendation on Nov. 15, offering filters to any home in the new zone with a PFAS detection.

"If we give someone the OK [to drink] something less than 70 ppt. -- that concentration may fluctuate," Hendershott said. "So we want to make sure that we understand what the context of their groundwater sample actually represents."

Wolverine Worldwide is also testing 175 private wells in Algoma Township near Wolven Avenue and 11 Mile Road, just north of the Plainfield Township testing border.

Beyond Wolverine's House Street dumpsite in Belmont, the DEQ is investigating more than 60 possible dumpsites in the area -- but only about 25 percent are connected to the company, Hendershott said.

Make it easy to keep up to date with more stories like this. Download the WZZM 13 app now.

Have a news tip? Email, visit our Facebook page or Twitter.