Levels of perfluorochemicals (PFCs) in the blood of longtime east-metro residents continue to decline, 10 years after steps were taken to reduce those chemicals in drinking water to levels that posed no health risk, the Minnesota Department of Health said this week.

Findings from the East Metro PFC3 Biomonitoring Project confirm that efforts to reduce PFCs in drinking water are working, state health officials concluded in their report. Another key finding was that PFC levels in people who since 2006 had moved to Oakdale, one of the cities of concern, are similar to levels seen elsewhere in the U.S.

“Levels in longtime residents went down by 35 percent to 60 percent from what they were in 2008,” said Jessica Nelson, the project’s lead investigator.

“While still above average U.S. levels, they are getting closer. It’s certainly good news that levels in long-term residents continue to drop as we’d expect them to and that newer residents don’t appear to have unusual exposures to PFCs.”

While there is not scientific agreement on whether PFCs cause illness, researchers continue to study the issue, the Health Department said.

The contamination sources were four legal dumping sites in Lake Elmo, Woodbury, Cottage Grove and Oakdale that the 3M Co. used for several decades to dispose of PFCs.

Beginning in 2004, some east-metro drinking water sources were found to have potentially unsafe levels of PFCs. The chemicals — used to make 3M products — leached into groundwater from old dumps.

In 2006, filtration systems were installed in city and private wells at 3M’s expense, under the supervision of the Minnesota Pollution Control Agency. Some private well owners were connected to city water.

Officials with 3M said that the company spent tens of millions of dollars to treat municipal and private drinking-water wells and that many homes were provided with filtration systems.

To determine if those measures were making a difference, the Health Department in 2008 began tracking blood levels of PFCs in residents of Oakdale, Lake Elmo and Cottage Grove. A 2010 study found decreases in blood levels.

In the third and latest round in 2014, researchers measured blood levels of eight different PFCs in two groups of east-metro residents: 149 long-term residents of Oakdale, Lake Elmo and Cottage Grove exposed to PFCs in drinking water before the intervention and who had participated in past studies, and 156 Oakdale residents who had moved to the area after the intervention.

“These findings tell an important story … [that] the presence of certain PFCs in the environment is being reduced in significant measure,” said Jean B. Sweeney, 3M vice president of environment, health, safety and sustainability.