Eighteen months after the state's top pollution officials abruptly pulled out of a four-year-old federally funded research project to rid toxic mercury from fish in the St. Louis River, environmentalists and the Fond du Lac band of Lake Superior Chippewa are openly accusing the agency of protecting polluters at the expense of kids' health.

At a public forum Thursday night in Duluth, two top scientists from the state will refute the criticism and explain how the state is attacking the problem of poisoned walleye, bass and northern pike with greater scientific rigor than before.

"We haven't run away from anything,'' said Shannon Lotthammer, who heads the state Pollution Control Agency's environmental analysis division. "We are continuing to pursue the scientific questions around this. … It needs to be solved.''

At issue is a potent neurotoxin, mercury, that has been found at unsafe levels in the blood of 1 in 10 infants on the North Shore of Lake Superior despite long-running public health advisories against eating too much of the river's tainted game fish. State health officials say about 1 in 100 infants have high enough levels of mercury in their blood to cause neurological harm. The river's estuary is also a critical breeding ground for fish in western Lake Superior.

"The kids in this area are getting a dangerous load of mercury,'' said Len Anderson, a retired biology teacher and activist who lives along the St. Louis River.

Anderson said he believes the state's decision to go it alone in its mercury studies is a stall against a needed crackdown on mining companies and other industries that pollute the watershed with sulfate. Sulfate plays a role in turning mercury into methylmercury, the form that accumulates in fish.

Anderson said one possible answer would be to require polluters on the Iron Range to install water treatment systems, something that he said is too expensive for the likes of state policymakers.

"The profits of these industries are more important than protecting the brains of these babies,'' said Anderson, who is slated to speak at the forum.

Lotthammer said accusations that the state is dragging its feet to appease mining supporters are baseless and frustrating. She said that in April 2013 the MPCA found itself at odds with the Environmental Protection Agency, the Fond du Lac Band and Wisconsin Department of Natural Resources over a federally sanctioned computer model. It was designed to analyze how mercury gets into the food chain, and would have created a plan to eventually make fish edible based on inputs of data, including sulfate data. Though the EPA had spent nearly $1 million on the four-year effort, the state pulled out because its scientists viewed the model as "simplistic."

"They all say it's sulfates,'' Lotthammer said. "We know that sulfate is a factor, but it's not the only factor.''

She said MPCA researchers are now studying a range of possible factors that could convert mercury into a form that gets into the food chain and builds up in game fish.

Scheduled to continue at least through 2017, those studies relate to factors such as water temperature, water flow, sunlight, carbon and natural organic matter, she said. The research will dissect the complexity of the food chain, down to tiny bugs in the sediment.

Lotthammer said the state isn't just studying the St. Louis River. That river is one of at least five where mercury is exceptionally high in fish. State scientists think they can solve the riddle by looking at all five of them at once.

Still, Lotthammer said the MPCA can't yet predict when it will have a plan in place to fix the problem in the St. Louis. The MPCA received nearly $750,000 in state funds to tackle the work it has planned. But it still needs another $1.5 million.

"We have taken aggressive and continued action,'' she said.

Nancy Schuldt, water resource policy director for the Fond du Lac Band, said the agency is stalling and Thursday night's forum is an effort to "re-engage" the agency as a partner in the fight to make the reservation's fish edible again.

"They will tell you they are not dragging their feet,'' she said.

Schuldt and Anderson said the taconite industry isn't the only sulfate polluter in the watershed.

Minnesota Power, the paper mill in Cloquet and treatment facilities for wastewater and drinking water also contribute to the problem.

As long as the discharges remain unchecked, Schuldt said, the headwaters of the St. Louis River will continue to be contaminated even as $1.5 billion in federal cleanup projects are completed at the mouth of the river — the largest freshwater estuary in the world.

"We are allowing an industry to continue to pollute the headwaters,'' Schuldt said. ""I think there is an element of frustration and impatience that actions aren't occurring more quickly.''

Craig Pagel, president of the Iron Mining Association of Minnesota, said people should wait for the studies to come out before jumping to conclusions. The Minnesota Department of Natural Resources also is studying the issue, he said, including whether certain concentrations of sulfate actually lower levels of methylmercury. "We look forward to the scientific research,'' he said.

Lotthammer said the MPCA is an undisputed leader in curbing mercury in water bodies. Minnesota was the first state, in 2007, to adopt a statewide plan to reduce human-caused, air-deposited mercury in all water bodies.

That plan has lowered mercury levels in water and the rate is continuing to go down. But the St. Louis River is one of a number of Minnesota rivers that have exceptionally high levels of mercury that can't be accounted for by air deposits alone.

Despite the effort to put public pressure on the agency to rejoin the Fond du Lac Band and the state of Wisconsin in the computer modeling plan, the state agency is sticking to its plan to go its own way, according to e-mails that have crossed the desk of Commissioner John Linc Stine this year.

Andrew Slade of the Minnesota Environmental Partnership wrote to Stine and other agency officials in late May and June, inviting state officials to this week's public forum. "The planning group is very excited about the potential of this forum to generate a commitment to a prompt renewal of the St. Louis River mercury'' plan, Slade wrote in one e-mail.

Lotthammer responded with an e-mail that said the state has not wavered.

"We are pursuing a different recipe than the one they want,'' said Dave Verhasselt, an MPCA spokesman.

EPA officials in Chicago said Wednesday that they are still looking for the MPCA, Fond du Lac Band and Wisconsin DNR to devise a plan for the St. Louis River "when the science is sufficiently understood.'' It is seeking another $320,000 to fund work aimed at a solution.

Tony Kennedy • 612-673-4213