ROCKFORD, MI -- Extremely high levels of toxic fluorochemicals once used to waterproof shoe leather are in groundwater at Wolverine World Wide's former tannery property and lower levels have been found in the Rogue River north and south of Rockford.

One spot on the property adjacent to downtown tested at 490,000 parts-per-trillion (ppt) for perfluorooctanoic acid, or PFOA, and perfluorooctanesulfonic acid, or PFOS.

Both compounds are among per- and polyfluoroalkyl substances collectively called PFAS, (also PFCs) -- a class of chemicals tied to cancer, thyroid problems and other diseases.

The chemicals were in 3M Scotchgard, which Wolverine used to make Hush Puppies shoe leather at the tannery.

Wolverine announced the test results on Thursday, Nov. 9.

The groundwater samples were taken from existing monitoring wells at the tannery site, which was demolished in 2010.

Results ranged in concentration from 12,700 to 490,000-ppt.

"I think that's the highest level I've seen in groundwater," said Richard Rediske, an environmental chemist at Grand Valley State University's Annis Water Resources Institute.

"It's higher than at Wurtsmith Air Force Base."

"Those levels show (Wolverine) has historically spilled a lot of material at that site," Rediske said. "It also shows the kind of waste they were handling just because of the residual left behind. There hasn't been any (Scotchgard) use at that site for at least 10 years and there's still that much there."

The results released Thursday also included pore water sediment samples taken from the Rogue River and Rum Creek, which found PFAS at 12,400 ppt.

Wolverine did not disclose the exact locations of sediment sampling or the exact location of the high groundwater levels at the tannery site. The official report sent to state regulators was not released.

Testing also found PFAS in Rogue River water both up and downstream of the Rockford dam at lower concentrations.

The river near 12 Mile Road NE -- the location of an old city dump where tannery waste was disposed in the 1960s -- tested at 6.2-ppt.

At the mouth of the Rogue where it reaches the Grand River, testing found PFAS at 16.4-ppt. Upstream, where Childsdale Ave. NE crosses the river, testing found PFAS at 14.8-ppt.

A map showing locations and average concentrations of PFAS (PFOS & PFOA) found in samples of the Rogue River this fall.

Rediske said the concentrations downriver indicate the Rogue may be impacted by the PFAS coming from Wolverine's House Street landfill in Belmont, from which a pollution plume has contaminated private drinking water wells with unsafe PFAS levels.

"It shows there's potential for other groundwater plumes coming in."

The numbers suggest fish consumption advisories for PFAS in the Rogue River need to be revisited, Rediske said.

Michigan has surface water thresholds of 11 ppt for PFOS and 42 ppt for PFOA, established to guide fish consumption advisories. Those were developed to account for bioaccumulation, which magnifies chemicals in fish tissue.

Wolverine's announcement included a risk assessment by Integral Consulting toxicologist Janet Anderson, who claimed the numbers indicate there's "no health risk" to swimmers, kayakers or others using the river for recreation.

State public health experts have said the primary risk from PFAS is through ingestion, not body contact. However, officials at the Kent County Health Department on Thursday noted that Wolverine's risk assessment was not developed with input from state or local health departments.

Chris Hufnagel, Wolverine senior vice president of strategy, said in a statement the test results were issued "because we want residents to know what we know."

"We continue to work in collaboration with the MDEQ and other agencies on this issue and as we conduct further evaluation and receive additional information, we will notify our neighbors and the community," Hufnagel said.

"Our first priority has been and continues to be the health and well-being of the community," he said.

Wolverine began testing the river and tannery for PFAS in August under pressure from the Michigan Department of Environmental Quality and the Concerned Citizens for Responsible Redevelopment group in Rockford, which has been critical of Wolverine's environmental practices for years.

Wolverine was under a DEQ deadline to produce all data related to PFAS testing at the former tannery site by Wednesday, Nov. 8.

Last week, the company began removing leather scraps leftover from tannery operations that had littered the riverbank next to the White Pine Trail for years.

The DEQ has overseen the Rockford tannery site since 2012, when the Environmental Protection Agency decided not to designate the property as a Superfund site partly at the urging of Rockford city officials, who wanted to expand the downtown commercial district onto the property.

On Thursday, the DEQ said it was "extremely concerned" about the test results and is reviewing all the data.

The DEQ is "focused on ensuring that any potential health risk is mitigated and contamination is thoroughly investigated," said spokesperson Melanie Brown.

The DEQ has asked Wolverine to develop a work plan and schedule to "fully define the vertical and horizontal extent of impacts to groundwater, soils, surface water and sediments" by Nov. 27.

Additionally, "we have requested that they provide us with a site model that includes cross sections that locate former buildings and industrial piping runs, iso-concentration maps for both ammonia and PFAS separately, data tables, and all other relevant information."

"The DEQ is committed to ensuring that residents have a healthy and safe environment, which is why we are leaving no stone unturned in our investigations to determine the true extent of any potential contamination," Brown said.

Rediske said the results call into question the safety and disposal practices of debris from when Wolverine demolished the tannery. Soil trucked from the site was never checked for PFAS. He said past examination by the EPA likely didn't take PFAS into account and new data could change the Superfund score.

He's concerned contaminated groundwater from the tannery may have migrated underneath the riverbed, as PFAS plumes have done with the Au Sable River near Wurtsmith base in Oscoda.

"There's more work that needs to be done," Rediske said.

Thad Beard, Rockford city manager, said Wolverine shared the results with him Thursday morning and he was happy to see low concentrations in the river.

"That would confirm the water is safe for recreational purposes."

Rockford stopped using the river as a drinking water source about 20 years ago. Wolverine began using Scotchgard at the tannery in 1958.

Beard said it's not known what contamination levels may have been in the river in the past but PFAS levels released Thursday "would be within the threshold for safe consumption."

The EPA's health advisory level for PFOS and PFOA in drinking water is 70-ppt, a non-enforceable guidance level at which chronic exposure is considered unsafe. Several other states have set lower limits on PFAS in drinking water.

'I don't know what the numbers were (when the city was drinking from the river)," Beard said. "I don't see it as a concern at this point."