Swimming with forever chemicals

Colorado’s river fish are contaminated — but the news isn’t all bad


From stunning canyons to babbling brooks, Colorado’s rivers draw an estimated 1.1 million anglers annually — but an unseen danger is lurking in nearly every catch. 

An analysis published earlier this year in the journal Environmental Research found “forever chemicals,” a group of thousands of synthetic compounds known as PFAS, in nearly every fish sampled, including those from the South Platte, Yampa, Gunnison, Rio Grande and Colorado rivers here in the Centennial State. The study, conducted by the nonprofit Environmental Working Group (EWG), likened eating one serving of contaminated fish to drinking a month’s worth of contaminated water. Of 501 fish samples, only one had no PFAS detected. 

PFAS have been linked to a range of health impacts including a weakened immune system, damage to the reproductive system, changes in the liver and increased risk of cancer. The chemicals were developed in the 1940s and have been used in a variety of products including firefighting foam, cookware, food packaging and cosmetics.  

Another recent analysis by EWG found the chemicals in more than 330 species of wildlife across the globe. 

Brendan Besetzny, a 31-year-old angler who has been fishing for most of his life and lives in Boulder, says he found the study results “extremely concerning,” but not surprising. 

“Having that information now would definitely deter me from harvesting and consuming fish,” he says. “You can go out and catch fish that are looking totally normal and healthy. You’re not seeing this massive negative impact with the naked eye.”

The Environmental Protection Agency (EPA) has no current standard for PFAS levels in fish sold to consumers, but recently it sharply reduced its drinking water lifetime advisories for PFOA and PFOS, two of the most widespread and harmful PFAS, from 70 parts per trillion (ppt) to .004 ppt for PFOA and .02 ppt for PFOS. 

The new advisories mean the EPA links extremely low rates of PFAS with adverse health effects. For reference, one part per trillion is equal to one drop in 20 Olympic-sized swimming pools. The study compared one serving of fish to drinking water contaminated at 48 ppt for a month. 

The EWG study’s findings echo those of a pilot study released in 2022 by the Colorado Department of Public Health, the Colorado School of Mines and the Colorado Parks and Wildlife that sampled fish from several popular fishing areas in the state and found PFOS in 100% of the fish sampled. 

“Fishing is a part of life in Colorado and we definitely want people to still enjoy the beautiful environment and the great fishing that we have here,” says Kristy Richardson, Colorado’s state toxicologist. Richardson notes that PFAS have been used in consumer products for about 70 years, and exposure is decreasing due to efforts to phase them out in the past decade. “It’s important for people to have information and, if they’re concerned about the potential health impacts, to understand where they might want to decrease exposure.”

Shutterstock A high plains trout stream in Colorado.

After the pilot study, Richardson says signs were posted where high levels of PFAS were found, advising against eating the fish, but there are no statewide advisories because “the data that we have across the state is quite limited, and we don’t have enough information yet about the levels in different water bodies and in different types of fish.”

In 2020, the state tested water systems, fire fighting districts, groundwater sources and surface water sources across the state as part of a sampling project. Of the drinking water systems that participated, 25% had some level of PFOA or PFOS chemicals detected in their treated drinking water, including in Lafayette and Thorton.

Ron Falco, Colorado’s safe drinking water program manager, says the state currently considers PFAS contamination “a concern, but not a crisis.” He says the state notifies the public when PFAS levels in water are higher than federal advisories and that the next step is to work with public water systems to reduce PFAS levels. 

To reduce PFAS, Colorado has banned the use and sale of firefighting foam and requires some dischargers to monitor and limit their releases of the chemicals into water bodies. Potential sources of PFAS discharges include manufacturing facilities, municipal landfills and wastewater treatment plants, airports, and sites where PFAS-containing fire-fighting foams have been used, the EWG study says. 

As for anglers like Resetzny, Richardson says catch-and-release is the best way to reduce exposure to the chemicals in fish. 

Besetzny says the study still raises concerns for him about watershed quality and lineage of the fish going forward. As someone who regularly eats fish, “[it] makes you think a little bit harder about where it came from and how it was produced and raised,” he says. 

PFAS levels in locally caught freshwater fish were 278 times higher than fish sold in grocery stores, according to the EWG study, presenting an environmental justice issue — purchasing fish in a grocery store may be cost prohibitive for those who rely on the fish they catch for sustenance, says Tasha Stoiber, EWG senior scientist and co-author of the study. 

The EWG study, which analyzed EPA samples from 2013-2015, did have one silver lining. Earlier EPA samples had higher PFAS levels, and more recent data from the EPA shows slight decreases from the 2013-15 data — something Stoiber says is encouraging. 

“Actions can make a difference,” she says, adding that officials need to “turn off the tap” on these chemicals by phasing out nonessential uses and creating strict regulations for releases into the environment. 

“Now is the time for action,” she says, ”because these fresh waters are so vulnerable and fish is an important food source for so many people.” 


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