Pollution control officials still don't know how the chemical, called PFOS, got into Lake Calhoun. 3M manufactured it until 2002 for use in stain and water resistant products like Scotchgard.
Other companies used the chemical, too, in more than a dozen different products from firefighting foam to teflon, to pesticides and shampoos.
Many of the residents who attended the public meeting had theories about the possible source of the PFOS contamination. Some suggested that state officials check out an old creosote plant site in nearby St. Louis Park. Others wondered if the chemical was coming from products within their own homes.
Minnesota Pollution Control Agency officials listened intently to all of the ideas. But they couldn't tell residents much about the source, other than to say they're looking at several possibilities -- from contaminated soil to storm water runoff, and even air pollution.
Resident Gary Farland told the agency he was surprised to learn about the wide range of products containing PFOS. He asked if the levels found in the lake and elsewhere could increase.
"If it doesn't degrade, if it doesn't break down, isn't it inevitable that the level in the environment will just keep going up?" Farland asked.
“It's still widely distributed in some of those products that have a long shelf life, such as fire extinguishers, firefighting equipment, that sort of thing.”MPCA supervisor Paul Hoff
MPCA supervisor Paul Hoff told Farland that's a possibility, as long as products containing PFOS remain in circulation.
"It's still widely distributed in some of those products that have a long shelf life, such as fire extinguishers, firefighting equipment, that sort of thing -- where they haven't had a chance to use it or there are still large stockpiles being used up," Hoff said.
Residents also had more immediate worries. Bruce Sebotke wanted to know if PFOS in the lake poses any risk to his drinking water.
"Is there a danger over time, or a measurable timeframe, where these chemicals can penetrate the aquifer?" Sebotke asked.
The Department of Health monitors drinking water. The agency's John Linc Stine told residents that so far, the chemical has not been detected in the city's water supply or in water from the hand-operated pumps scattered around the lakes.
But Stine said the concern is valid, especially if the source is releasing a significant amount of the chemical.
"If there are high concentration sources, migration of that water through the aquifers is very likely. What we know about the compounds is they move as quickly as the water does in the ground," Stine said.
But so far, Health Department officials say the main threat from PFOS in Minneapolis is eating contaminated fish. The agency issued a new fish consumption advisory last month for the chain of lakes, that limits consumption of bluegills to one meal a month.
The mood of the Minneapolis meeting was more relaxed than community meetings held in the east metro earlier this year.
Those meetings attracted hundreds of anxious residents, who frequently berated public officials for not doing enough about perfluorinated chemicals found in the drinking water. That contamination has been traced to several former 3M landfills in the east metro.
Sen. Scott Dibble, DFL-Minneapolis, says residents in his city are equally concerned about the contaminants in their community. But he says the situation in Minneapolis isn't quite as alarming.
"If people discovered that these chemicals were coming into their homes through their taps, or if the chemicals were coming up through the hand pumps around the lakes, the tone and tenor, the temperature of tonight's meeting would have been vastly different," said Dibble. "It's in the fish. We can control the amount of fish that we catch and consume. So I think people weren't unnecessarily, unduly alarmed."
The Minnesota Pollution Control Agency has ramped up its investigation into perfluorochemicals. The agency just finished sampling 31 treatment sites around the state to see if the chemicals are present in wastewater.
The MPCA is also testing fish in other lakes throughout the Twin Cities metro area for perfluorochemical contamination. The agency expects to get those results back later this summer.