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Metro Denver’s wastewater treatment system is spreading sewage biosolids laced with toxic PFAS “forever chemicals” at its farm in eastern Arapahoe County and on private farms that buy the material as fertilizer, according to test records obtained by the Colorado Sun. 

The likely presence of the ubiquitous and dangerous chemicals on Colorado farmland, placed there through biosolids spread by Metro Water Recovery and more than 100 other municipal waste agencies, adds to a growing list of potential health threats and underscores the need for widespread testing, researchers and watchdog groups said. 

No agency requires Metro Water Recovery or other Colorado municipal waste handlers to test the soil or groundwater where biosolids are spread to determine if the chemicals used to make nonstick pans and waterproof hiking clothes are creating the type of human health threats routinely documented by local and national researchers. Study after study shows detectable levels of PFAS in nearly all humans, in all the fish captured in one Colorado test, and in other living creatures. 

Wastewater agencies say they are taking PFAS in as runoff from industry, food containers, plastics and waterproofed consumer goods, meaning metro areas are delivering PFAS contamination to rural areas in the form of biosolids.

Metro Water Recovery did testing in 2019 for its own research purposes and found occasional spikes in some types of PFAS chemicals before the biosolids were spread on farms. Metro Water Recovery officials say their 2019 testing showed that overall PFAS levels in biosolids are “low,” and “not far above the detection level in most samples.”

Outside researchers say some of those levels are disturbing evidence that soil, water and crops at farms need comprehensive testing. State water quality regulators have now formed a working group on PFAS in biosolids, saying they plan to begin requiring testing at some point.

After inquiries by The Sun, Metro Water Recovery (formerly Metro Wastewater Reclamation District) said it is considering water testing in the area of its 52,000-acre Metrogro farm about 65 miles east of Denver. Tainted biosolids have contaminated water with PFAS in other states. 

Combines working a Metro Water Recovery field at the Metrogro farm in eastern Arapahoe County. Metro Water Recovery has spread biosolids as fertilizer since 1982, and sold to other farmers. They say they work with farmers on how to apply the biosolids, but there is no current testing requirement for levels of PFAS “forever chemicals” in the fertilizer. (Metro Water Recovery biosolids fact sheet)

University researchers and environmental watchdog groups say tainted biosolids spread as fertilizer by most major cities across the nation — in part because there is no disposal alternative — pose the next major question for local health officials already confronting PFAS contamination in Colorado and nationwide. 

Municipal sewage handlers across the nation, including Metro Water Recovery, have known about the presence and potential risks of PFAS chemicals in their effluent and biosolids since at least 2010, when a group of studies came out, said Christopher Higgins, a professor of civil and environmental engineering at Colorado School of Mines who has co-authored multiple studies on PFAS and testifies for both plaintiffs and defense in contamination cases. 

A series of studies co-authored by Higgins published beginning in 2011 demonstrated versions of PFAS chemicals in soil, earthworms and crops where municipal biosolids had been spread from Chicago waste. The studies called for much more testing of soil, crops and water in areas where biosolids are spread. 

“The broader wastewater community, including people at the Environmental Protection Agency and in the biosolids community, knew about this by 2010, that this would be an issue,” Higgins said. He recalls warning national wastewater trade groups about accumulating study results, and offering to help, and hearing back, “no one’s going to care about this.”

The Forever Problem

“Forever chemicals,” or PFAS, are an increasing toxic burden on Colorado. We’re committed to covering the public health threats, from water and croplands to the costs to clean them up.

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Levels are low, concerns still high

Research regularly uncovers new dangers to humans from PFAS, said Elsie Sunderland, professor of environmental science and engineering in the Department of Environmental Health at Harvard’s School of Public Health. 

“What we’re finding is that very low levels are associated with some toxicological impacts,” Sunderland said.

The group of chemicals known as PFAS, encompasses thousands of compounds used in consumer and industrial products ranging from stain-resistant carpet and nonstick kitchenware to firefighting foam and waterproof clothing. Produced since the 1940s, some versions do not break down over time and have been shown to contribute to human health problems including low birth weight babies, high cholesterol, compromised immunity, increased cancer risk and infertility.

“Metro’s preliminary sampling results indicate there are low levels of PFAS in biosolids,” a fact sheet on the chemicals posted on Metro Water Recovery’s site says. The utility manages the sewage of 2.2 million people in Denver and parts of Adams, Arapahoe, Douglas, Jefferson and Weld counties, and has spread biosolids on agricultural land since 1982. Like other wastewater and clean water agencies, Metro Water Recovery says local and state officials should be working to eliminate PFAS from products in order to stop them at their source.

A lawsuit by the Colorado Attorney General’s Office filed in February against DuPont and other PFAS manufacturers says exposure to high levels may cause liver damage; lower effectiveness of vaccines;  increase the risk of high blood pressure in pregnant women; lower infant birth weights; and be associated with a higher risk of kidney or testicular cancer. 

Without a rigorous new testing regime for biosolids, crops and farm-area water, regulators won’t know if the PFAS they have already measured coming out of Metro Water Recovery in north Denver are tainting eastern Colorado, experts said. Wheat, corn and sorghum are raised at the Metrogro location.

Municipal waste handlers around the nation already test treated effluent and biosolids for presence of heavy metals, said Harvard’s Sunderland. “If they’re selling and spreading this on farmland, there has to be a quality-assurance process.” 

Health studies have already detected PFAS accumulations in most humans, while the number of products using more than 5,000 variants is difficult to track, environmental researchers said. 

The Colorado AG’s lawsuit says the chemicals have been detected in soil and water in 50 of Colorado’s 64 counties, and cites studies showing that firefighters exposed to PFAS chemicals have higher levels of the agents in their blood than other residents. Researchers looking into biosolids have detected similarly high levels in the blood of those living on tainted farms

Perfect fertilizer, forever chemicals

Metro sewage agencies have long touted biosolids as a perfect fertilizer, the researchers note, but it’s also true that they spread it on U.S. farms because there’s nowhere else to dispose of millions of tons of sludge except landfills — which also leak. 

“Saying there is nothing else to do with it sounds like giving up. And that is not a solution,” said David Andrews, a chemist with the nonprofit pollution watchdog Environmental Working Group. 

Maine was the first state to ban spreading municipal biosolids on agricultural land after farms there showed high levels of contamination. Some Maine farmers were shocked to learn of toxic levels of PFAS variants in their soil, drinking and irrigation water, crops, chickens and their own blood samples.

Maine and Michigan are among the first states to require testing of biosolids and farms for PFAS.

A sign at Metrogro Farm near Deer Trail, photographed on Sept. 19, 2018. The 52,000-acre farm, which grows wheat, corn and sorghum, is owned by the Metro Wastewater Reclamation District and uses biosolids — sewage sludge treated at a Metro Wastewater plant — as fertilizer. (John Ingold, The Colorado Sun)

Denver’s Metro Water Recovery officials acknowledge there is a growing number of questions about PFAS in treated liquid effluent, which is returned to the South Platte River just north of Denver’s city limits, and in biosolids it uses in eastern Colorado. They say they are joining a working group on the questions, set up by the Colorado Department of Public Health’s Water Quality Control Division. 

They add, however, that municipal water and wastewater agencies can only work with what they take in, and that PFAS variants that are turning up everywhere need to be shut off at the manufacturing level and distribution level. The Colorado legislature began that effort this year, they note. 

Their analysis shows that most of the PFAS variants come into metro Denver wastewater not from large industrial users, but residue from the thousands of household and business items using PFAS. Industries have produced and used thousands of variants of the chemicals, and states are only now starting to regulate their sales while researchers look for health effects from versions not previously known to be in consumer products.

“We abide by regulations that come our way,” said Liam Cavanaugh, chief operating officer of Metro Water Recovery. “At this point in time, there is no regulation associated with PFAS for biosolids. Whether or not that happens in the future in Colorado … I think it’s something that (state health) would have to respond to as well.”

State water and wastewater regulators say they have the authority to require biosolids PFAS testing by local sewage handling agencies, and plan to do so after their working group gathers opinions and recommendations. They said they plan to let the working group play out for much of the rest of this year. 

“We don’t have any information to show that PFAS in biosolids poses a risk to human health or drinking water quality in Colorado, but we’re committed to staying on top of these contaminants of emerging concern,” said Nathan Moore, clean water compliance and enforcement section manager at the state health department’s Water Quality Control Division.

Moore acknowledged, though, that Colorado PFAS testing has focused on drinking water sources so far, and that for biosolids and the surrounding land and water, the state doesn’t have data. 

“We need data from Colorado to understand if PFAS is occurring in biosolids in Colorado,” Moore said, in an interview. “Coupled with the existing effort we have to start gathering effluent data from wastewater treatment plants. That will give us an idea of where we are in Colorado right now.” 

State regulators note there are rules on where biosolids can be spread, and how thickly, and that most crops grown with biosolids help are used for animal feed. Studies have shown accumulation of PFAS in farm animals in the same way humans have accumulated the chemicals, the state acknowledged. 

“So there is a missing piece in our knowledge there,” Moore said.

‘Afraid of my ski jacket’

On June 7, in the first state-organized working group meeting to develop policies on PFAS in biosolids, regulators pointed to how states like Michigan are requiring extensive testing of all biosolids, and then searching up the chain for sources of PFAS contamination. But Colorado regulators also acknowledged the science on detecting PFAS, and how the chemicals affect human health, is “moving quickly.”

“I always kind of just point out the fact that I didn’t know I was supposed to be afraid of my ski jacket until a few years ago,” one state water regulator said in the meeting. “I hate nonstick pans, but I do like my Gore-Tex jackets and clothes.”

Metro Water Recovery’s Metrogro farm is on 52,000 acres near Deer Trail in eastern Arapahoe County, nearly twice the size of Denver International Airport’s footprint. 

The South Platte River is seen from Metro Water Recovery on April 6, 2022, in Denver. Metro Water Recovery is the largest wastewater treatment facility in the western U.S. and treats up to 130 million gallons of water daily. (Olivia Sun, The Colorado Sun via Report for America)

About 120 entities, mostly municipal sewage treatment operations, also produce biosolids and spread them on farms in the state, health officials said during the first working group meeting on PFAS. About 53,000 dry metric tons of biosolids are spread on Colorado farm fields each year, according to previous statistics from the Colorado Department of Public Health and Environment.

In Colorado, PFAS runoff from firefighting foam used at military bases and at other fire stations has contaminated drinking water, resulting in a full-on emergency drinking water replacement for the Fountain community and a statewide drinking water testing program looking for further contamination. In April, The Colorado Sun reported on a state health study of three popular fishing ponds showing PFAS contamination in 100% of the fish sampled, sometimes at elevated levels. 

Last fall, The Sun reported on a PEER database acquired from federal records showing Colorado may have more locations that have handled PFAS than any other state, with about 21,000 state locations documented, heavily concentrated in oil and gas production regions. 

While the EPA says it is in the middle of a deep scientific review of PFAS toxicology and policy, its national guidance for a drinking water standard sets PFAS limits at 70 parts per trillion for two of the variants. It is only a guideline for municipal water, though, not an enforceable regulation. Colorado officials said in October they were considering moving forward on their own drinking water standard, as other states have done, if the EPA does not toughen its limits, but the state has not announced any such change. 

Other states are pushing for much tighter restrictions on PFAS. California health officials are considering a sharply lower drinking water standard of .007 parts per trillion for the variant PFOA, and 1 part per trillion for PFOS. Massachusetts set its standard at 20 parts per trillion for six PFAS variants. 

EPA, state and local officials say there is not a direct comparison between drinking water standards for PFAS and levels of PFAS in biosolids. Without more testing, they say, it is unclear whether versions of PFAS in biosolids spread on the ground will contaminate the surrounding area, or at what levels of harm. 

Metro Water Recovery’s sampling of biosolids in 2018 and 2019, which was not required by the state but done as part of the agency’s research into PFAS handling, showed occasional high levels of chemicals in the PFAS family, according to outside researchers who looked at the reports. 

The Metro Water Recovery test results include one reading, on Jan. 28, 2019, for a PFAS variant in biosolids at its Northern Treatment Plant in Brighton, which translates to 9,300 parts per trillion, said Kyla Bennett, science policy director and Massachusetts state director for PEER. The particular variant measured is not yet singled out by EPA guidelines, but Bennett and other researchers say many of the substances found by Metro Water Recovery can later break down into more dangerous forms of PFAS.

Though there may not be a direct correlation established yet between parts per trillion in biosolids being spread on the ground, and contaminants that may end up in area crops, animals or water, any level of PFAS or its precursor chemicals should be worrisome, Bennett said. 

The 2018 and 2019 benchmark testing by Metro Water Recovery included searching for PFAS chemicals in influent, the raw sewage and runoff taken in by its two treatment plants; effluent, the treated water from which solids and contaminants have been filtered and that is returned to the South Platte River; and biosolids, shipped to Metrogro or other locations.

Explanation of the ways chemicals from biosolid fertilizer can affect the land, animals and humans in areas where they are spread, from an EPA presentation at a June 2022 Colorado working group on PFAS. (EPA “Risk Assessment of Chemicals in Biosolids”)

Metro Water Recovery’s influent testing records reflect the agency’s contention that they have no control over what substances enter their treatment areas, and that PFAS runoff from consumer goods is everywhere. Some days show influent tests not rising above the detectability threshold set by the lab. Other days show influent with PFAS contamination of 8.7 or 10 or 27 parts per trillion.

Effluent measurements range from undetectable, meaning they fall below a calibration threshold set by the lab, to 3.7 parts per trillion, to 13 or 15 parts per trillion on some days, the records show. There are occasional spikes far higher, as in 100 parts per trillion at the Northern Treatment Plant on Aug. 8, 2018. That particular reading, Metro Water Recovery said, was for a PFAS version or “analyte” that does not have a federal advisory limit. 

As a general response to high reading days, Metro Water Recovery officials said, “it is important to stop PFAS chemicals from being introduced into the water cycle by removing PFAS from consumer products.” Furniture companies, clothing manufacturers and fast food retailers have pledged to remove PFAS chemicals from their products and packaging, though there are thousands of variants of fluorinated chemicals that are hard to track.

As part of the Metro Water discharge permit renewal from state health, Colorado began regular testing of PFAS in the effluent only, as of January. All those results so far have been well below state guidelines for environmental accumulation of PFAS, Metro Water Recovery officials said. 

Biosolid readings in 2018 and 2019 range from undetectable, to 870 parts per trillion, to 4,100 parts per trillion, to 12,000 parts per trillion. 

In states such as Massachusetts and Maine, where biosolids have caused contamination, some municipal water providers can add PFAS cleanup technology to filter it out of drinking water, but outlying farms and other users with private wells don’t have that option, Bennett noted. 

“So the bottom line is they need to stop spreading this,” she said. “But in the meantime, they should make absolutely sure that this stuff is not applied anywhere near a drinking water source, near a private well, on a farm where there’s going to be vegetables, or meat or eggs or milk consumed. It shouldn’t be spread anywhere, but at the very least in those places.”

Metro Water Recovery said readings in the thousands of parts per trillion for biosolids are not comparable to the EPA’s 70 parts per trillion guideline for drinking water. They added that the sample highlighted by Bennett was for a version of perfluorinated chemicals, NMeFOSAA, that is not included in EPA’s advisories for drinking water. Researchers have identified thousands of variants of perfluorinated chemicals in the PFAS family, and continue to seek information from the manufacturers on all variants. 

Researchers responded that many of the PFAS versions now being detected are “precursors” to the most toxic forms already identified, and can mix or break down into the more toxic versions while in water treatment plants or in the environment. They also note that many farms, including in Colorado, have been spreading municipal biosolids for decades, and that PFAS levels in previous years might have been higher. 

Calling levels in biosolids irrelevant to the levels in drinking water “is a lame argument,” said Harvard’s Sunderland. “You know you are going to get a run off of some of these PFAS into drinking water sources, from the biosolids. That’s how they first detected the problem in Maine,” she said.  

While the EPA advisory doesn’t yet include versions like NMeFOSAA that are part of the thousands of chemical compounds in the PFAS classification, “it absolutely does not make exposure safe or less worrisome,” Andrews, of the Environmental Working Group, said. The compound is considered a precursor of one of the regulated PFAS chemicals included in EPA guidelines because it will eventually break down into the more toxic version, he said.

A floating hydraulic dredge pumps biosolids from a city of Kennewick, Wa., lagoon for processing into a cake-like material for spreading as fertilizer on a wheat field in September 2012. Cities across the country use fertilizer from biosolids as a way to dispose of tons of treated sewage, though more and more are testing for PFAS problems. (AP Photo/The Tri-City Herald, Bob Brawdy)

Higgins of the Colorado School of Mines agreed, saying studies have shown precursor versions of perfluorinated chemicals breaking down into the more toxic substances while at a sewage treatment facility, or while applied on farmland as biosolids. 

“If one were to do a risk assessment, you could basically look at that chemical and say, I’m gonna assume all of that gets converted to PFAS,” Higgins said.  

Some more recent sampling of biosolids has shown a decrease in levels of two of the earliest hazardous PFAS variants abbreviated as PFOA and PFOS, Higgins said, after manufacturers slowed their use of those versions. But that doesn’t account for either the long-term or “forever” presence of those chemicals applied in biosolids going back decades, or for other versions of the chemicals that can break down into more toxic substances.

Colorado should be testing animals and milk at farms that have used any municipal biosolids, Sunderland said. 

PFAS concerns keep piling up

Concerns about PFAS in biosolids follow other news about the “forever chemicals” in Colorado, and across the nation: 

  • The state health department study of fish focused on three popular fishing holes where anglers often eat their catch, in order to zero in on pathways where the dangerous chemicals may reach humans. The highest concentrations of the forever chemicals were in fish from Willow Springs Pond, fed by Fountain Creek, the location of drinking water contamination from military base runoff in 2016 that forced the town of Fountain to find alternate sources

In wildlife, the state measures nanograms per gram, and found up to 241 nanograms per gram of PFAS in the fish pulled from Willow Springs Pond at Fountain Creek Regional Park. The state study says that “In states that have fish consumption guidelines …  the ‘Do not consume’ level ranges from 50 ng/g to 300 ng/g, with most advisories set at around 200 ng/g.”

Willow Springs Pond also had by far the highest concentration of forever chemicals in samples of the water itself, well above the EPA’s current drinking water guideline of 70 parts per trillion. “The project has a number of limitations and was too small to determine whether PFAS in the fish sampled are high enough to harm human health,” the study said. “People who are concerned about PFAS in fish caught in Colorado waterbodies may want to limit the amount of recreationally-caught fish they eat. However, fish is part of a healthy diet,” said State Toxicologist Kristy Richardson, in summarizing the study.

  • The Colorado Attorney General’s Office in February sued 15 makers of firefighting foam that contains PFAS, alleging the companies caused contamination found in water samples taken across the state and endangered public health.

The lawsuit filed in Denver District Court says the companies, including five related to DuPont, knew or should have known their products harm the environment and public health, and asks the court to require these manufacturers to pay for all costs to investigate, cleanup, restore and monitor contamination at all sites, the AG’s office said. The investigation into PFAS contamination is continuing, Weiser’s office said, along with settlement negotiations with other producers.

Through 2030, the Colorado Department of Public Health and Environment would be charged with identifying more categories of goods, and those would be added to the banned list.

The Colorado Attorney General’s lawsuit and many more like it around the nation point to one of the big lingering questions about the future of PFAS contamination, and the liability fears that a word like “forever” raises for public and private officials. Remediation of drinking water sources contaminated with PFAS even in modest-size communities runs into the millions of dollars for each location. 

For sewage effluent and biosolids, there is no clear remediation technique for municipal agencies. 

Metro Water Recovery officials said they already have more than $600 million in capital spending scheduled over the next 15 years to improve quality in effluent, the cleaned water discharged back into the South Platte River. That amount does not include spending for PFAS removal, “which would undoubtedly involve significant additional cost,” Metro Water Recovery said. 

In an interview, Cavanaugh said, “It’s important the public understands the cost associated with what we’re talking about, in terms of the potential limits that may come down.” 

And, consistent with the PFAS reputation as the “forever chemical,” Metro Water Recovery’s director of environmental services Jennifer Robinett said even removing PFAS from sewage is not a final step. 

“There’s not a technology that destroys the PFAS,” she said. “So if we remove it, if drinking water facilities, remove it, it still exists. And it has to undergo some sort of disposal.”

Michael Booth is the Sun’s environment writer, and co-author of the Sun’s weekly climate and health newsletter The Temperature. He is co-author with Jennifer Brown of the Colorado Book Award-winning food safety investigation “Eating Dangerously.” Booth was part of teams that won two Pulitzer Prizes for breaking news. He also writes frequently about inexplicable obsessions that include tamarisk, black-footed ferrets and tire fires. Booth also serves as the underpaid driver for four children, and plans to eventually hike every inch of Colorado.