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QUINCY — The sludge arrives by the ton, pumped through miles of underwater pipes from Deer Island to a waste-water treatment plant on the banks of the Weymouth Fore River, where it’s spun through centrifuges into a kind of wet cake, dried by large furnaces, and made into fertilizer pellets.

Converting much of the region’s sewage into a valuable byproduct was a major achievement of the Boston Harbor cleanup. Over the past three decades, the fertilizer has been sold or given away in massive amounts: tens of thousands of tons a year sent to farms and golf courses, parks and gardens across the region.

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“We call it black gold,” said Carl Pawlowski, manager of residuals operations at the Massachusetts Water Resources Authority, which sells the pellets in colorful 40-pound bags as Bay State Fertilizer, billed on its packaging as “The Responsible Choice for Healthier Lawns and Gardens.”

But recent tests of the fertilizer, which has been sold for nearly 30 years, have caused concern.They show levels of toxic chemicals known as PFAS, which have been linked to low infant birth weights, kidney cancer, and a range of other diseases.

The MWRA tested the material in March, after similar contamination was discovered at other treatment plants around the country. The results were alarming — the fertilizer contained more than 18,000 parts per trillion of just three PFAS chemicals. The overall amount of PFAS is probably higher, given the lack of testing for other chemicals.

Neither federal nor state regulators have set standards for the amount of PFAS — known as “forever chemicals” because they don’t fully degrade — allowed in waste-water sludge.

But in drinking water, the US Environmental Protection Agency recommends that municipalities alert the public if two of the most common chemicals add up to 70 parts per trillion. Massachusetts uses the same level for five PFAS chemicals.

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As a growing body of research has found that the chemicals can be toxic in much smaller amounts, federal and state regulators are reviewing their standards. Massachusetts officials are poised to lower the limits in ground water and drinking water to 20 parts per trillion for six of the chemicals combined.

Recent tests of the fertilizer, which has been sold for nearly 30 years, have caused concern.
Recent tests of the fertilizer, which has been sold for nearly 30 years, have caused concern. David Abel/Globe Staff

Scientists and environmental advocates have urged regulators to set standards for the sludge, also known as “biosolids,” because it can leach into ground water, get absorbed by plants, and be ingested by livestock.

“Applying biosolids with such high levels of PFAS to land risks contaminating drinking-water supplies and food crops,” said Laurel Schaider, a research scientist at the Newton-based Silent Spring Institute.

MWRA officials declined to answer questions about whether they should continue selling the fertilizer, but a spokeswoman said their products comply with current regulations.

“In the absence of existing state or federal standards for PFAS in biosolids, the Commonwealth, through the Department of Environmental Protection, will begin developing testing protocols and screening levels for biosolids and continuing to require entities that sell, distribute, and apply biosolid products to test for PFAS,” Ria Convery said in a statement. “Recognizing the emerging issue of PFAS contamination and the importance of ensuring public health, the MWRA will continue to test biosolid pellets for PFAS chemicals, while meeting all state and federal requirements for waste-water contaminants.”

But Schaider and others noted that MWRA’s fertilizer exceeds limits imposed this year in Maine after elevated levels of PFAS were found on a dairy farm in Arundel, which for decades used a similar type of fertilizer.

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Tests of the farm’s milk showed that it contained 1,420 parts per trillion of PFAS. The owners of the farm, Fred and Laura Stone, were later found to have more than 20 times the normal amount of PFAS in their blood.

In response, Maine banned farms from using waste-water sludge that contained elevated amounts of three common PFAS chemicals. The MWRA sludge, which is trucked across the region, had more than triple the amount for one of the chemicals.

Because of exemptions in Maine’s new rules, the MWRA has been allowed to sell its sludge to farms in Maine, though in smaller amounts per acre. That has angered some environmental advocates who learned of the high concentrations from the Globe. The MWRA has done little to publicize its test results.

“It shouldn’t be sold here or anywhere,” said Patrick MacRoy, deputy director of the Portland-based Environmental Health Strategy Center, a public health advocacy group. “It should be treated as contaminated waste and disposed of in a safe way — not given to farmers and gardeners.”

The MWRA has long tested the fertilizer, which comes from the waste water of 43 communities, for pathogens and heavy metals, as federal regulators require. But it only began testing for PFAS in March — after Maine set its standards — and is screening for just three out of thousands of PFAS chemicals, many of which are ubiquitous in the environment after being used for decades in everything from food packaging to furniture.

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The sludge moves along this conveyor belt and is then turned into a kind of wet cake. It’s then dried and converted into fertilizer pellets.
The sludge moves along this conveyor belt and is then turned into a kind of wet cake. It’s then dried and converted into fertilizer pellets. David Abel/Globe Staff/Globe Staff

Since 2016, the MWRA has sold more than 100,000 tons of New England Fertilizer, the brand name it uses for bulk sales, earning the agency over $1 million. In the same time, it has sold or given away more than 1,300 tons of Bay State Fertilizer, which goes mainly to individuals, earning about $61,000.

“The MWRA does not profit from the sale of Bay State Fertilizer or New England Fertilizer,” Convery said. “The MWRA’s goal is beneficial reuse of the disposed waste.”

She added: “The successful cleanup of Boston Harbor is tied directly to the cessation of dumping sludge into the harbor.”

EPA officials declined to comment on whether the MWRA should continue selling the fertilizer but said the agency is studying the issue.

“Addressing the uncertainty around potential risk for pollutants identified in biosolids is a top priority,” said Dave Deegan a spokesman for the EPA’s New England office. “The agency will also be taking steps very soon to bolster research efforts related to PFAS in biosolids.”

Researchers are working to determine whether ingesting crops grown from contaminated fertilizer is dangerous. It probably depends on the amount of fertilizer applied and the type of soil. The chemicals can also leach into water supplies, but the amount depends on the depth of ground water and the distance to wells.

Asked about the risks of consuming crops grown with contaminated sludge, Linda Birnbaum, a toxicologist who recently retired as director of the National Institute for Environmental Health Sciences, said she had concerns.

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“I wouldn’t want to use the more highly contaminated samples,” she said.

Linda Lee, an environmental chemist at Purdue University, has tested sludge from treatment plants around the country, including from the MWRA, where she found that Bay State Fertilizer contained 34,000 parts per trillion of more than a dozen of the chemicals.

At this point, however, she doesn’t think such fertilizers should be banned.

Reusing the sludge is preferable to dumping it in landfills or burning it in incinerators, which increase carbon emissions and could disperse it over large areas if released through smokestacks.

The best solution is to remove PFAS from consumer products, she said.

“These compounds are persistent, and they can cause adverse effects,” she said. “But we should also be concerned about the unintended consequences of overreacting.”

Officials at the North East Biosolids & Residuals Association, a trade group that represents the sludge industry, said the MWRA should continue selling its fertilizer, citing a National Academy of Sciences study in 1996 — conducted when few understood the dangers of PFAS — that found sludge use on soils presents “negligible risk.”

“Biosolids recycling is a significant part of making communities sustainable,” said Janine Burke-Wells, the association’s executive director.

But environmental and public health advocates said the risks of exposure to PFAS chemicals outweigh the benefits of recycling the waste. They also note that in 2018, after scientists established that even minute amounts of PFAS can be harmful to human health, the EPA’s inspector general told the agency that it shouldn’t rely on the outdated National Academy of Sciences report and that it should recognize more studies were needed.

Kyla Bennett, science policy director of the Public Employees for Environmental Responsibility, a Washington-based advocacy group, said it “defies logic” that the state recognizes the threats of PFAS while “simultaneously selling the exact same chemicals to be spread across farms, backyards, and golf courses throughout the state.”

“We need to pause and figure out a better answer,” Bennett said.

On a recent tour of the MWRA’s sprawling treatment plant in Quincy, where the sharp smell of ammonia fills the air, Carl Pawlowski acknowledged the concerns.

He compared PFAS to DDT, another toxic chemical that doesn’t break down easily and has had major environmental and health consequences. Standing beside four tanks that each hold a million gallons of the so-called black gold, he said he hoped federal regulators would place stricter limits on PFAS chemicals, reducing the amount produced.

Asked if he thought the state should be selling the fertilizer, Pawlowski appeared conflicted and weighed his answer carefully.

“At the end of the day, I just don’t know,” he said.

Should the state be selling the fertilizer? When asked Carl Pawlowski, manager of residuals operations at the Massachusetts Water Resources Authority, appeared conflicted.
Should the state be selling the fertilizer? When asked Carl Pawlowski, manager of residuals operations at the Massachusetts Water Resources Authority, appeared conflicted. David Abel/Globe Staff/Globe Staff

David Abel can be reached at dabel@globe.com.