There is growing concern that a state policy enacted three decades ago to encourage the use of treated municipal sewage sludge as fertilizer might have contaminated farmland across Maine.

It’s a potentially major problem for the more than 175 sites in the Pine Tree State that accepted sludge over time, including at least 17 in Androscoggin County, 10 in Oxford County and seven in Franklin County.

The Lewiston-Auburn Water Pollution Control Authority alone provided sludge in 2000 for sites in a dozen municipalities, according to records compiled at the time by the Toxics Action Center in Portland.

Among the towns with the most sludge sites at that time were Auburn, which had six, and Farmington, home to seven sites where the material was spread.

It isn’t clear, though, that any of the sites pose a danger. The state is only beginning to ramp up efforts to test for the presence of PFAS, a group of water-repelling chemicals widely used since the 1940s to create nonstick coatings on cookware, food packaging and fabrics, as well as in firefighting foam.

The issue has become a hot topic in Maine following revelations that a dairy farm in Arundel had elevated levels of the contaminant in its soil, water and milk.

Michael Belliveau, the executive director of the Environmental Health Strategy Center, said the Arundel case “is likely the tip of the toxic iceberg.”

Gov. Janet Mills has established a task force to look into the issue and environmental regulators are adding new testing requirements to look for the chemical.

She issued a statement that called on regulators “to identify any locations in Maine where PFAS are prevalent; examine its effects on drinking water, freshwater fish and marine organisms; and take steps to create and implement treatment and disposal options.”

The state declared last week that “producers of sludge materials” proposed for application on the ground need to establish new testing and “prove that all the sludge is below regulatory levels before it can be applied.”

Clayton Richardson, superintendent of the water pollution control authority in the Twin Cities, said that since the Maine Department of Environmental Protection’s notice came down recently, he has been readying a plan for testing the plant’s material.

Until last week, he said the plant was bringing material — known as biosolids — to roughly 25 regional farms of various sizes.

He said none of the farms receiving material from LAWPCA have experienced similar issues to Stone Ridge Farm in Arundel — and questioned whether the sludge spread there actually caused its problems.

A recent state investigation, though, found that “although not conclusive,” results of testing at the farm “indicate that the land application of wastewater treatment plant sludge/biosolids may have contributed to the contamination of this farm with PFAS compounds.”

It is not clear exactly where the sludge from Richardson’s plant is going, but in 2000 it sent sludge to farms and open space in Auburn, Bowdoinham, Durham, Fayette, Hartford, Hebron, Leeds, Lewiston, Minot, New Gloucester, Poland and Sumner.

A fact sheet distributed by the authority said the level of PFAS and related toxins in human blood in the United States has declined sharply in the past two decades, from an average of 35 parts per billion in 1999 to 8 parts per billion by 2012, a consequence of companies phasing out their use.

Because treatment plants don’t use PFAS, it said, any PFAS in their sludge “essentially reflect the chemical profiles of the communities they serve.”

It also pointed out that testing protocols for finding PFAS in biosolids don’t yet exist. Only drinking water standards have been developed so far.

The science involved, according to the authority, is “unsettled and rapidly expanding.”

Richardson said “sludge” is a general term used to refer to biosolids, which are solids generated in wastewater treatment that have undergone appropriate treatment, such that they can be safely and appropriately put back to the land.

What’s left, he said, contains a lot of compounds and properties beneficial to growing plants.

When the treatment plant in Lewiston first opened, the solids were put in a landfill next to the city landfill on River Road, which was capped in 1992. At that time, LAWPCA began a compost facility, and until recently more than half of the biosolids went there.

Richardson said the solids that went to the compost facility are treated to a Class A standard, which can be sold without additional regulations.

The remaining solids were treated to what’s known as a Class B standard, which Richardson described as solids that are treated to the point that the pathogen level is less than is found in common manure. He said Class B material, pending a DEP permit, can be spread at farms.

Late last year, LAWPCA suspended operations at the compost facility.

The amount of solids the plant generates has been cut in half since the facility employed anaerobic digestion, a process in which microorganisms break down material, resulting in biogas, which can be combusted to generate electricity and heat.

The per- and polyfluoroalkyl chemicals collectively known as PFAS degrade slowly and linger in the environment for long periods, leading critics to dub them “forever chemicals.” The subject of increasing scrutiny, some PFAS have been linked to cancer, liver damage, low birth weight and other health concerns.

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