Good news for the city of Ann Arbor's drinking water - and the residents who drink it.
The city's Drinking Water Quality Manager, Sarah Page, says tests have detected no PFOS and PFOA compounds in the past five months. PFOS and PFOA are two of the most worrisome PFAS compounds.
That's after the city installed new activated carbon filters earlier this year.
Page says PFOS and PFOA are "long-chain" PFAS compounds.
"The long chain PFAS compounds have greater health impacts," says Page, "because they accumulate more and have longer lifetimes in your body."
Page says another thing that has likely helped the city's drinking water quality is the state's work to determine who is dumping the chemicals into the Huron River, which is the source for most of Ann Arbor's drinking water.
State environmental investigators have been laboriously working their way upstream since May, 2018, to find the sources of the contamination.
Most of the PFOS has been coming from the City of Wixom wastewater treatment plant, and most of that plant's PFOS was traced to Tribar Manufacturing, which provides chrome plating, among other services, to industry.
At its highest point, Tribar was discharging 28,000 parts per trillion of PFOS (August 29, 2018) into the wastewater it sent to Wixom to be treated. At its highest point, also in August, 2018, Wixom's wastewater treatment plant discharged 4,800 ppt of PFOS into the Huron River.
That's 436 times higher than the state's newly adopted standard for PFOS and PFOA in surface water of 11 ppt.
Other, smaller sources of PFOS have also been discovered, including the Daimler Chrysler Scio Facility. The state is continuing to look for other sources.
State environmental regulators say the Wixom treatment plant's discharges have dramatically fallen since Tribar Manufacturing installed filtering equipment.
The PFOS discharge level from the plant in November, 2019 was 28 parts per trillion. That's still above the 11 ppt standard, but a dramatic improvement from 2018.
Starting in 2021, wastewater treatment plants will have to get discharge permits for PFOS and PFOA. But the state will not require permits for the businesses that use the chemicals, saying the current voluntary system is working well.
Page says most companies have now switched to using "short-chain" PFAS chemicals, which are considered less harmful. She says Ann Arbor's drinking water does contain a number of these short-chain PFAS compounds, because the new carbon filters do not work very well at keeping them out.
The state does not require businesses or wastewater treatment plants to test for or limit short-chain PFAS compound discharges.
Meanwhile, the state's advisory warning people not to consume any fish from the Huron River remains in place, due to high levels of PFOS and PFOA chemicals in them.