More Information About PFAS

PFAS contamination of Maine’s groundwater was first identified near military bases, where fire-fighting foam containing fluorinated surfactants was used for training and fire suppression. At those sites, PFAS and other toxic substances used at the bases have been detected in groundwater and freshwater fish. The potential for more widespread contamination of potable groundwater and other media was not recognized in Maine until late 2016, when an Arundel dairy farm was forced to end operation due to PFAS contamination of soil, groundwater, forage, and milk produced on the farm.

The contamination was attributed to repeated applications of wastewater residuals (sludge and compost) from municipal and paper mill sources as a soil amendment beginning in the early 1980s. A July 2021 news article in the Portland Press Herald reported that over 500,000 cubic yards of sludge (also called wastewater residuals or biosolids) from treated paper mill wastewater was spread on Maine farm fields between 1989 and 2016.

The origin of wastewater sludge traces back to passage of the Clean Water Act in 1972, one of several environmental laws championed by Maine’s late Senator Ed Muskie. Prior to passage, the wastewater generated by towns and industries received minimal screening before discharge into our country’s waterways. Maine’s rivers became foul sewers lined with solid waste material headed for the ocean. After passage of the Clean Water Act, towns and industries gradually implemented more effective biological wastewater treatment systems that removed oxygen-depleting organic matter, converting it to solid biomass that could be separated from the effluent stream discharged to the rivers. Water quality in our rivers greatly improved, yet management of the resulting semi-solid sludge material became a challenge. In the 1980s the state encouraged farmers to spread it on their agricultural fields as a fertilizer and soil amendment due to the high levels of nutrients essential to plant growth in sludge. While EPA imposed limits on the concentrations of metals that could be present in sludge applied to farm fields, there was no awareness, concern, or testing of PFAS contamination.

In March of 2019 Maine DEP required PFAS testing in sludge from all of Maine’s municipal wastewater treatment plants before land application. Concentrations of individual PFAS analytes exceeded the Maine screening level in 93% of raw residual sludge and 89% of composted sludge samples. The state also began testing farm soils in fields where sludge had been applied as a soil amendment, as well as the milk from Maine dairy farms. DEP continues to allow farm application of PFAS contaminated sludge if the resulting soil concentration, after mixing, does not exceed the screening levels for PFAS. However, while soil testing of fields licensed to receive residual sludge is still in process, in 2019 almost 60% of the fields tested had PFAS concentrations above screening levels and can no longer receive residuals. As a result, thousands of cubic yards of residuals were sent to landfills in 2019.

PFAS contamination of farm fields from wastewater sludge is a national problem, first identified here in Maine in 2016 when water from a public well on Fred Stone’s dairy farm in Arundel was reported to have 50 ppt PFOS. Maine DEP’s subsequent investigation on the Stone’s farm found more extensive contamination. In January 2017, the combined PFOA (perfluorooctanoic acid) and PFOS concentrations reached  . In surface soil, combined PFOS and PFOA reached roughly 900 ppb, over 25 times greater than Maine’s screening level for contaminated soils to prevent groundwater contamination. Blood PFOS concentrations in Fred Stone and his wife, two years after they stopped drinking contaminated milk and well water, were 111 and 94 ppb, respectively, three times greater than the geometric mean for adults in the U.S. Two additional farms are now known to have PAS-contamination from wastewater sludge applications. In 2019 the Larrabee Road farm in Knox was found to have PFAS concentrations in soil over 90 ppb, three times greater than Maine’s screening levels. And in the summer of 2020 PFOS concentrations in milk from the Tozier Farm in Fairfield Center reached 32,200 ppt, 153 times greater than the PFOS action threshold for unadulterated milk, 210 ppt. Since then, the contamination of selected Maine dairy farms has expanded to include hay fields that grow forage for farm animals and vegetable farms, some of which have suspended operation because of contamination of their crops.