Minnesota regulators are broadening their search for sites contaminated by a class of industrial chemicals known as PFAS, which have turned into a major environmental threat across the country.

It’s a major step in the state’s effort to contain pollution by the so-called “forever chemicals,” a project that until now has focused mainly on the east metro communities where 3M Co. made and disposed of such compounds for several decades.

The Minnesota Pollution Control Agency (MPCA) will expand the hunt to four counties, using a list of industries that have historically used the chemicals in their operations. The agency plans to sample local water first, then contact companies. The companies involved may have used products containing PFAS without knowing it.

“The goal is to make sure we know in Minnesota theoretically where it could be used, and check on it,” said MPCA Assistant Commissioner Kirk Koudelka, “just to make sure we’re not having any gaps.”

While it’s a significant expansion of the state’s PFAS monitoring efforts, some conservation groups remain critical. The Environmental Working Group, a nonprofit advocacy group that has pushed for greater research and regulation of the chemicals, said Minnesota should have started tracking down industrial sources earlier, because state and federal regulators knew a decade ago that metal plating facilities were discharging the compounds.

PFAS are a family of fluorinated compounds dubbed “forever chemicals” because they don’t break down in the environment. Prized by industry for their ability to repel oil and water, the compounds have been used since the 1950s in untold numbers of consumer products such as cellphones, waterproof mascara, brake fluid and hospital gowns. They have also turned up across the globe in fish, polar bears and bald eagles, as well as in food wrappers and lettuce.

Pinpointing the industrial sources of the contaminants — beyond the manufacturers who make them — can be very difficult. U.S. chemical manufacturers stopped making the original compounds, called PFOA and PFOS. But the compounds are made elsewhere, and there are hundreds of other PFAS compounds in active use — and companies aren’t required to disclose their use of them.

The compounds can be toxic to animals, and some are associated with serious human health effects such as cancers, thyroid problems and pregnancy-induced hypertension. There is a global movement to restrict use of all PFAS.

Discovered in Lake Calhoun

Early next year, MPCA staffers will start sampling groundwater and surface water at 10 sites near facilities in the targeted industries across four counties: Dakota, Olmsted, Stearns and St. Louis. The MPCA will reach out to individual companies if readings are high.

The four counties weren’t chosen because of any known contamination but because they are population centers with lots of industry, Koudelka said. The effort is a test to determine whether the agency should push it statewide.

Well-known sources of PFAS contamination in Minnesota include a 3M manufacturing facility in Cottage Grove and four east metro landfills where the manufacturer dumped PFAS-laden waste — the subject of an $850 million state settlement with 3M. Other sites around the state were contaminated by special firefighting foams containing PFAS.

Less is known about industrial sources, although the MPCA has some ideas.

Over a decade ago, the agency found high levels of one of the oldest PFAS compounds, PFOS, in Brainerd’s wastewater treatment plant, and traced contamination to Keystone Automotive, a chrome plating facility that specializes in bumpers. Keystone was using a mist suppressant, Fumetrol 140, which contained PFOS, to control dangerous emissions from a tank of plating solution. PFOS was also found at low levels in fish in the Mississippi River near the wastewater treatment plant. Keystone switched to a different product.

In a second case, after PFOS was discovered in Lake Calhoun in 2004, the MPCA traced the compounds to Douglas Corp.’s metal plating operation in St. Louis Park. Fumes with PFOS were being vented from the plant and collecting on the building’s roof and washing off with rain and snow into the stormwater and the lake. The company identified a product with PFOS and stopped using it in 2010, but PFOS issues continued. In 2016, the MPCA instructed it to monitor its discharge and capture or treat it to control the contaminant.

A Douglas Corp. executive told the local Sun Sailor newspaper at the time that he didn’t know the product contained PFOS because a material safety data sheet didn’t mention it. PFOS is now banned in chromium plating operations.

An MPCA spokeswoman said those are the only two industrial sources of PFAS, other than 3M, that the agency has investigated.

‘Somewhat frightening’

Asked why the state didn’t start tracking down industrial PFAS sources sooner, Jamie Wallerstedt, MPCA site remediation and redevelopment manager, said the agency knows more about PFAS now: “Our knowledge of where PFAS is has evolved.”

The MPCA declined to provide a list of specific companies that might have used PFAS, but provided a list of select industry classifications such as fabric mills, waterproof outerwear, metal foil and leaf, carpet and upholstery cleaning, and surgical and medical instruments.

A Star Tribune analysis found about 200 companies in the four counties fall into the classifications, half of them in Dakota County. The category on the list with the most companies — commercial printing and lithography — covers more than 60 businesses in those counties.

Other states have tried to measure the scale of PFAS use. New York, for example, surveyed companies and 28 reported having used PFAS or PFOA in the past.

According to the Environmental Working Group, government data show that at least 475 U.S. industrial facilities could be discharging PFAS into the air or water. The group’s senior scientist, David Andrews, lauded Minnesota’s new effort but called it overdue.

“It’s somewhat frightening that it really takes this long,” Andrews said. “This is an issue … that officials have been aware of for decades.”

Still, Andrews called identifying industrial uses of PFAS “an important next chapter” in the ongoing PFAS crisis.

“Even the regulators and EPA do not have a clear understanding where these chemicals are being used and released into the environment,” he said.