Another 120 households in the east metro area are being advised to drink bottled water after Minnesota health officials drastically cut the exposure limits for a class of toxic chemicals that has long contaminated drinking water there.

Minnesota regulators concluded after months of review that the current federal standards are insufficient to protect infants and small children from the chemicals' health risks.

The state's updated limits — half the level recommended by the U.S. Environmental Protection Agency — reflect the latest scientific findings on the exposure and health effects of the two chemicals, known as PFOA and PFOS. They are among a class of chemicals called PFCs that were made for decades at a 3M Co. manufacturing site in Cottage Grove and were among the most widely used in the world.

Decades of research has shown that exposure to PFCs in drinking water has been linked to certain cancers, liver and thyroid ailments, and developmental problems in infants. Since the 2002 discovery that they had contaminated groundwater from the 3M plant and dump sites in Washington County, east metro cities and hundreds of homeowners have had to add filtration and treatment systems to protect their drinking water.

Water with PFOA or PFOS, even at levels above the new recommended limits, does not represent an immediate health threat, state officials noted. Concentrations in the groundwater also have not changed, they said. But scientists' understanding of their potential health impacts has grown.

The much lower limits are designed to reduce long-term risks for fetuses, breast-fed infants and young children. That makes them overprotective for most people, health officials said Tuesday, and women who are breast feeding infants should continue to do so because the health benefits outweigh the risks, they said.

"We err on the side of caution to protect the most vulnerable as best we can," said Dr. Ed Ehlinger, Minnesota health commissioner.

Dr. Carol Ley, 3M's vice president and corporate medical director, said in a statement, "We believe the advisory levels announced by MDH are overly conservative. We believe that PFOS and PFOA do not present health risks at levels they are typically found in the environment or in human blood."

Contaminated wells

Last year, after new research heightened concerns about the chemicals' health affects, the EPA advised states and municipalities across the country to set a lower concentration — 70 parts per trillion — a significant cut from the previous health standard of 300 or 400 parts per trillion. As a result, about 200 more homes in Woodbury, Lake Elmo and Cottage Grove, which lie along the flow of contaminated groundwater, were provided with bottled drinking water.

Now, Minnesota health officials say they are advising cities and homeowners to adopt a standard of 35 parts per trillion for PFOA and 27 parts per trillion for PFOS.

As a result, 120 additional homeowners with private wells — mainly in parts of Lake Elmo and Cottage Grove not served by city water — have drinking water that exceeds the new limits and could be provided with bottled water by the state.

In addition, the cities of Cottage Grove, Oakdale, Woodbury, St. Paul Park and Bemidji have a number of municipal wells affected by the updated values. They can take interim steps that will provide drinking water at or below the new standards, state officials said. But residents of Cottage Grove will be under lawn watering and other use restrictions while the city adds new toxin removal systems to one of its wells.

"Our water is safe to drink and will be going forward," Cottage Grove Mayor Myron Bailey said in a statement to residents Tuesday. He said the city had stopped pumping water from one of its wells until it can set up a carbon filtration system. In the meantime, he asked them to stop watering their lawns and other nonessential water use.

Jim Kelly, the Health Department's environmental health manager, said Minnesota is one of several states that's conducted its own analyses of safety and exposure data to come up with recommendations considerably lower than the EPA's. The main difference, he said, is that the department's calculations included the greater consumption of water, compared to adults, that is typical of infants and children. That increases their exposure to the chemicals, he said, a finding that the Health Department has shared with the EPA.

Cleanup agreement

For decades, the chemicals formed the foundation of consumer and industrial products from Scotchgard to Teflon to solvents and firefighting foam. 3M stopped making them at its plants in Cottage Grove and Alabama in the early 2000s, and under pressure from the EPA, other companies stopped making and using them by 2015.

But they are water-soluble and persist for decades in the environment. As a result, they have contaminated drinking water systems across the country, are a major contaminant in fish, and have even been found in polar bears in the arctic.

Bemidji's drinking water system is contaminated by PFCs from firefighting foam used at a nearby training site.

In 2007 the state and 3M agreed to a cleanup plan and to install drinking water protections for residents in the east metro area. 3M has paid the state at least $13 million so far. In addition, Minnesota Attorney General Lori Swanson filed suit against 3M in 2010, accusing it of damaging the state's natural resources. The case is expected to go to trial in 2018.

Residents of south Washington County who live in affected areas will have an opportunity to meet with Health Department experts and officials from the Minnesota Pollution Control Agency next month. Meetings will be held June 6, from 6 p.m. to 8:30 p.m. at the Oak-Land Junior High School cafeteria in Lake Elmo and June 7, 6 p.m. to 8:30 p.m. at the Cottage Grove City Hall.