Cambridge is reviewing a report from the U.S. Environmental Protection Agency finding that spreading sewage sludge contaminated with two of the long-lived chemicals known as PFAS on farmland could pose an unacceptable health and environmental risk.
Cambridge’s food waste collected in the city’s curbside composting program ends up at a sewage treatment plant in North Andover, and dried sludge from the plant is distributed as fertilizer to anyone from backyard gardeners to commercial farmers; a change in regulation could affect the city’s food scrap program, though the report points to stopping the problem at its source – manufactured products.
PFAS – the acronym stands for per- and polyfluoroalkyl substances – are causing increasing concern. The chemicals have been linked to cancer and a broad range of health problems including harmful effects on the liver, heart, growth and immune system. The chemicals have been used since the 1940s in applications such as nonstick cookware, firefighting foam, textile protectants and food wraps. Though the two chemicals examined in the federal agency’s assessment – PFOS and PFOA – have not been made in the United States for as long as 23 years, PFAS are known as “forever chemicals” because they don’t break down in the environment and are found virtually everywhere, including in water, soil, food and people.
Environmental regulators have turned their attention recently to PFAS in sewage sludge because the material is being spread on farmland and other soil as fertilizer or compost, as well as landfilled and incinerated. Some farmers have said their farms and harvests have become contaminated and their families have elevated levels of the chemicals in their blood from eating the food and drinking milk from cows grazing on the land. Maine has banned sludge from being applied to farmland and Massachusetts has been studying the issue and collecting information on levels of the chemicals in sewage sludge in the state.
The federal agency’s draft risk assessment found that the general public was not at risk from PFAS contamination of sewage sludge. Instead, people living close to the locations where contaminated sludge was applied or who depend on food from crops grown on affected farmland, milk from cows that grazed there or water from nearby sources face the greatest risks. People living near unlined sewage sludge disposal sites face danger from contaminated water, the report said.
Sewage sludge from Massachusetts is applied to land not only within the state but in Canada, New York, Connecticut, Vermont and as far away as Virginia and Ohio, according to a consultant’s report commissioned by the state Department of Environmental Protection.
The report predicted trouble if land application of sludge is curtailed. Restrictions proposed in Massachusetts, along with a future Connecticut ban on land application, “represent a looming massive disruption to the management of Massachusetts sludge,” as the state is already short on capacity to handle sludge, the report said. Shipping more of it out of state would increase greenhouse gas emissions and raise costs to sewage treatment plants and “ultimately ratepayers,” the report said.
Federal agency taking comments
The draft report could be the first step toward federal regulation of PFAS in sewage sludge. The agency will issue a final risk assessment after considering comments on the draft. “If the final risk assessment indicates that there are risks above acceptable thresholds when using or disposing of sewage sludge, the EPA expects to propose a regulation” limiting the two chemicals it studied, the agency said in a fact sheet for sewage treatment plant operators.
“With the report just being released, the city is still reading and processing the new draft risk assessment,” city spokesperson Jeremy Warnick said Thursday. He emphasized the importance of controlling PFAS contamination by focusing on the source, noting that the federal report echoed that sentiment.
“This is such a vital piece of the discussion, as the PFAS and PFOA found in sewage are not from the treatment processes, but rather from the waste from manufacturers, households and businesses that produce or use products that contact PFAS, including everyday items like clothing and cosmetics. Reducing these chemicals at their source is critical to reducing their presence in sewage,” Warnick said. The food waste processed at the North Andover plant contributes very little to PFAS contamination in sludge, he said.
Stopping PFAS at the source
A report presented to Cambridge city councillors last summer also emphasized the importance of reducing PFAS at the source – and that while levels of the chemicals in the environment had declined since manufacturing and uses had been eliminated, new PFAS chemicals could take their place.
“Even with new EPA and DEP rules for PFAS testing and reduction from drinking water and waste, the complete removal of all PFAS compounds in our waste is not expected,” the city report said.
The city’s food waste is sent to a Boston plant operated by the giant waste and environmental services company Waste Management, which processes it with similar food material as well as commercial food waste from other communities into a slurry. The slurry goes to the Greater Lawrence Sanitary District sewage treatment plant; adding it to wastewater creates methane gas that is used to heat the sludge and dry it.
The state has required sewage treatment plants to test dried sludge for many forever chemicals since 2020. The most recent test for PFOS reported by the North Andover plant, in September, showed a level of 3.12 parts per billion using one type of test; the level for PFOA was less than 1 part per billion. The federal draft risk assessment said a level as low as 1 part per billion could pose dangers to health and the environment.
Drinking water tested
On another front, the city has greatly reduced the level of PFAS in its drinking water by replacing carbon filters in its water treatment plant at regular intervals. The most recent results of tests, for the fourth quarter of 2024, showed 4.16 parts per trillion for one of the chemicals and none detected or a trace for five others. The state has set a limit of 20 parts per trillion for the sum of levels in six of the chemicals, which Cambridge has met regularly since it began replacing the filters in 2022.
New federal limits are another matter. The federal agency set new maximums for six PFAS chemicals last April but gave water systems until 2029 to comply. Cambridge has hovered around the limit of 4 parts per trillion for one of the chemicals selected by the agency: PFOA. The city reported 4.95 parts per trillion in the first quarter of 2024; a “trace” in the second quarter; 1.80 ppt in the third quarter; and 4.16 ppt in the fourth quarter. Other PFAS chemicals mostly registered nondetectable or trace.
The city plans to replace two filters this month, two in February and two in March, according to minutes of the December meeting of the water board.
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We are danged if we do, and darned if we doo doo.
Stopping the contamination at the source (i.e., not manufacturing and using these chemicals) seems critical to solving this problem.
But in the meantime, the public deserves to understand where contaminated sludge has been applied and what impacts the sludge is having on our food and water. Has it been applied to farms that are now selling PFAS contaminated food to the public? Has it been absorbed into groundwater in communities where people are now drinking PFAS contaminated well water?
In Maine, the state seems to be taking a very aggressive stance towards testing sludge application sites and understanding this. This seems like the right course of action for MA as well, especially considering we are continuing to apply sludge. Maine banned sludge application. //www.pressherald.com/2025/01/15/pfas-contamination-found-on-more-than-100-maine-farms/
This is a complex situation and I’m glad the author hinted at some of the potential sewage treatment challenges. But if PFAS are indeed a carcinogenic class of chemicals, we need to be much more aggressive about protecting our communities.
Excellent summary Paul. Like this one, most of our environmental problems are a result of ignoring the precautionary principle.