ROCKFORD, Mich. (AP) — Biologists with the Michigan Department of Environmental Quality are planning to take a second look at fish in the Rogue River because of growing water contamination concerns from nearby tannery dump sites.

Testing from four years ago found elevated levels of toxic industrial chemicals in fish north of the Rockford dam, prompting the state to issue limits to eating those fish in a health advisory, the Grand Rapids Press reported .

New test results released Thursday show that the same chemicals known to have been used by Wolverine World Wide in waterproofing shoes are present in the river both north and south of the dam. Wolverine had a landfill in Belmont, from which a pollution plume has contaminated private drinking water wells with unsafe chemical levels, according to environmental tests.

Scientists said the toxins are perfluoroalkyl and polyfluoroalkyl substances, a class of chemicals tied to cancer, thyroid problems and other diseases.

Some environmentalists said the new findings mean the state should revisit the health advisory over a wider fishing area that extends south of the dam.

"I think the state should consider expanding the advisory and to other fish species as well," said Bill Wood, director of the West Michigan Environmental Action Council. "It seems like every time there's testing that's expanded, that we keep finding it more and more. It seems the science continues to evolve with what level is safe."

The department is planning for a wider Rogue River fish study in 2018 in response to the growing number of Wolverine dump sites in the Belmont area and contaminated groundwater, said Joseph Bohr, aquatic biologist for the department's Water Resources Division.

"We are planning to collect some fish upstream and downstream of Rockford next year just to see the extent," he said.

The state Health Department is waiting on that fish collection before making any changes to the health advisory for fish consumption.

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Information from: The Grand Rapids Press, http://www.mlive.com/grand-rapids

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