MINNEAPOLIS (AP) — In an effort to draw attention to proposed federal rules to reduce mercury emissions, the Minnesota chapter of the Sierra Club has released test results suggesting that many residents of the state have at least trace levels of mercury in their bodies.

The Sierra Club collected hair samples last month in 25 American cities, including Minneapolis and Rochester. All of the 70 Minnesotans who agreed to share their test results had at least some mercury in their hair, the environmental group said Wednesday. And nine had levels higher than the federal guidelines for children and women of childbearing age, although those levels are not considered a health risk for men and older women.

The Sierra Club is trying to draw attention to a new federal proposal to limit mercury and other pollutants emitted by coal-burning electric generating plants. The proposal issued by the Environmental Protection Agency in March could force the closing of some older power plants in other states, and it’s being challenged by utilities and Republicans in Congress.

None of the problem plants is in Minnesota, where a 2006 state law required utilities to reduce mercury emissions. Three of the largest units already have installed scrubbing equipment that has reduced their emissions by 90 percent. Pollution control officials said three more are on track to do the same. But much of the mercury that lands in Minnesota comes from plants elsewhere.

Federal officials have estimated that compliance with the new rules would cost about $10 billion annually, though some in the industry say it could be higher and add another $3 or $4 per month to household utility bills.

The Sierra Club is one of many national environmental groups advocating for the new rule, said its hair testing campaign was not intended to be a scientific analysis. The U.S. Centers for Disease Control and Prevention estimates about 3 percent of women of childbearing age have blood mercury levels exceeding 5.8 micrograms per liter, the top limit considered safe. For hair, the standard is 1.2 parts per million, though officials from the Minnesota Department of Health said hair testing is not always a reliable measure.

Federal standards are aimed at protecting children and fetuses because they are very sensitive to the toxic effects of mercury, which can cause neurological and developmental problems. The limit was designed to err on the side of safety. The safe level for men and older women is three times as high.

Mark O’Byrne, of Rochester, told the Star Tribune that he, his wife, Elena and their 2-year-old daughter all had their hair tested, and found they all were below 1.2 parts per million. They decided to be tested because they were concerned about amalgam dental fillings that contain mercury. They had no idea that coal-burning plants are the primary source of mercury pollution, he said.

“It gave us pause to think about what kind of mercury we are exposed to in our community,” he said. “This is not something people are aware of.”

When mercury from coal-burning plants drifts over Minnesota and collects in surface water, it accumulates in fish, the chief source of mercury in humans.

Lois Norrgard, of Minneapolis, said she believes she became ill from mercury six or seven years ago because she ate too much fish. Her doctor could not figure out what was causing her fatigue and memory loss, she said. After she read an article about mercury toxicity, she quit eating fish and started feeling better. Now she eats only salmon, which does not accumulate mercury as much as larger, longer-lived species like tuna.

Norrgard decided to get her hair tested to be sure her levels still were low, and she learned they were.

“Now, I’m clean,” she said.