GRAND RAPIDS, MI -- Grand Rapids municipal drinking water contains low levels of toxic per- and polyfluorinated compounds called PFAS, according to recent tests from the city's water department.

Michigan health officials say the low PFAS levels are not cause for alarm.

Test results show combined levels of PFOS and PFOA, two PFAS compounds, in finished tap water product at 3.19-parts per trillion -- nearly 22 times below the federal lifetime health advisory of 70-parts per trillion, or ppt.

Previous tests of the city's water system as late as November 2017 did not detect PFAS. But previous tests also had much higher reporting thresholds of 20-ppt for PFOA and 40-ppt for PFOS, meaning that anything below those levels was labelled "non-detect," according to Dave Harran, the city's water system manager.

"These tests are getting more refined," Harran said.

The system serves about 300,000 people in multiple municipalities across the greater Grand Rapids area. The detected levels, state health officials say, aren't cause for concern.

"If it's a level of 3-ppt, it's not something residents should be concerned about in their municipal water," said Angela Minicuci, spokeswoman for Michigan Department of Health and Human Services. "As far as municipal water goes, 3-ppt is not something we would be taking action on at this point."

The state of Michigan has cleanup standards for PFOS and PFOA in groundwater that people drink but does not have a maximum contaminant level for public water systems.

Exposure to PFAS has been linked in human studies to some cancers, thyroid disorders, elevated cholesterol and other diseases. PFAS compounds are called "forever chemicals" because they accumulate in the body and do not breakdown in the environment.

Levels found in the Grand Rapids municipal water system also are below stricter health guidelines proposed in a new federal study. According to environmental chemists, the study's suggested "minimum risk levels" translate roughly to 7-ppt for PFOS and 11-ppt for PFOA.

Because of that, Harran said he feels "comfortable" with the levels found and doesn't expect them to change. At this time, there are no plans to install PFAS filtration systems, he said.

"Our test results showed what was expected: PFAS-related compounds have been in use around Lake Michigan for decades and a very small amount -- below the detection limits -- is present," Harran said in an email. "We expect PFAS levels to remain relatively consistent since Lake Michigan is a stable source of water."

The Grand Rapids municipal system draws its water from Lake Michigan at a depth of 50 feet and about a mile from shore, according to Mike Grenier, superintendent of the Lake Michigan filtration plant.

Of 24 PFAS compounds tested for in the water system, only PFOS, PFOA and 6:2 FTS were detected at levels above the reporting limit. PFOA was detected at 1.38-ppt, PFOS at 1.81-ppt and 6:2 FTS at 1.55-ppt, according to the results.

The combined PFAS levels are 4.74-ppt. Unlike PFOS and PFOA, there is no federal health advisory for 6:2 FTS.

The chemicals have been used in fire suppressant foam at airports, fire departments and refineries, as well as by industrial chrome platers and apparel manufacturers. They repel water and oil and resist heat.

The recent testing was prompted by a pledge from the state of Michigan to test 1,380 public water systems and about 460 schools for PFAS.

Results already coming in have sparked a public health crisis in a community of about 3,000, when PFOA levels of 670-ppt and PFOS levels of 740-ppt were found in the Parchment city water system.

Harran said his team wanted to get ahead of the state's testing, so it took samples and sent them out for analysis about two weeks ahead of the state.

They did so mirroring the state's testing protocol and used the same lab, Vista Analytical in California, for analysis, he said.

The state's results are due any time now.

Unlike the city's results, Harran said, the state plans to cut its reporting limit off at 2-ppt for each compound, meaning the state's results for the Grand Rapids water system would be a "non-detect" for PFAS if found at similar levels.

Representatives for the Michigan Department of Environmental Quality could not be reached for comment.

The Grand Rapids water system serves Grand Rapids, East Grand Rapids, Walker and parts of Kentwood, as well as the townships of Ada, Cascade, Grand Rapids and Tallmadge.

In Ottawa County, the system serves Coopersville, Allendale Township and portions of Grand Haven and Robinson Townships.

"We are proud of the high-quality and safe drinking water that we provide our customers every day, and we take this responsibility very seriously," Harran said. "Our customers should be confident in the system's water quality and safety."