Testing fish for consumption
- LAKE magazine
- Mar 20
- 15 min read
By Michael Scott
State agencies test fish for contaminants regularly at Michigan’s inland lakes, streams and rivers. However, experts say the inability to test all waterbodies, and concerns over the impact of per- and polyfluoroalkyl substances (PFAS) should influence how much fresh fish anglers and residents consume.
Testing fish for contamination in Michigan is a coordinated process that each year produces published advisories warning residents about potential consumption issues. This process continues to be refined as more information is uncovered each year about pollutants that exist in the state’s inland waterbodies, particularly the presence of PFAS.
PFAS are synthetic chemicals widely used for more than 60 years to make plastics, firefighting foams and lubricants. The term is an acronym for a class of more than 17,000 “forever” chemicals, said Denise Key, CEO for Enspired Solutions, an East Lansing-based remediation company that focuses on eliminating forever chemicals. PFAS are created by humans and represent the strongest single bond in nature.
Since 1970, the Michigan Department of Health and Human Services (MDHHS) has issued fish consumption guidelines providing Michigan residents with the information they can use to make informed decisions about personal fish consumption. More than 50 years of testing have revealed health risks associated with consuming fish that contain chemicals such as mercury, polychlorinated biphenyls (PCBs), Dichlorodiphenyltrichloroethane (DDT), dioxins and PFAS.
The MDHHS’ Eat Safe Fish (ESF) program tests for chemicals in edible portions of fish caught in lakes and rivers around Michigan. The results from those tests are used to create the fish consumption guidelines found in the department’s Eat Safe Fish guides, produced annually by the MDHHS. Each year, ESF reviews data from approximately 1,800 fish collected from statewide waterbodies to determine if new or updated consumption guidelines are necessary, according to MDHHS Associate Public Information Officer Laina Stebbins.
“The ESF program provides consumption guidelines that reflect the best available science to ensure that our recommendations are protective of human health,” Stebbins said. Testing results are also available at Michigan.gov/EatSafeFish.
ESF guidelines are designed to help protect all Michigan adults and children, including those with existing health challenges, compromised immune systems, pregnant people and more. Michigan has routinely tested fish filets for PFAS since 2012.
The guidelines are provided as Michigan servings (referenced in the guide as MI Servings). One MI Serving for adults equates to six to eight ounces of fish, which is comparable to about the size of an adult’s hand. For children, one MI Serving is two to four ounces of fish, or about the size of an adult’s palm.
MDHHS communicates the fish contaminant findings in other ways as well. For example, signage may be posted around waterbodies where fish should not be consumed based on local testing results, generally referred to as “do not eat” advisories, which MDHHS manages. ESF program staff set up displays to educate anglers and attendees at fishing events and outdoor festivals. They will speak to schoolchildren and teachers, members of special interest groups and more.
Stebbins said most signage posted by MDHHS warning residents of important advisories includes a QR code linked to an informational website. “There, they can find more information about fish consumption guidelines specific to that waterbody,” Stebbins said.
MDHHS has collected fish from Oakland County lakes, rivers and streams for testing since 1983, Stebbins said. Over that more than 40-year period, she said a total of 30 Oakland County lakes and ponds, four rivers and one creek have been tested at least once for contaminants. As is the case around Michigan, mercury, PCBs, PFAS and/or DDT are present in some bodies of water, with results available online and in the ESF guide.
The Michigan Department of Environmental, Great Lakes and Energy (EGLE) manages its Fish Contaminant Monitoring Program, coordinated by Aquatic Biology Specialist Brandon Armstrong. The program’s three main goals include:
• Collecting data that is used by MDHHS to help establish fish advisories through membrane testing of a fish’s edible parts in bodies of water throughout the state.
• Monitoring containment trends at 22 fixed sites both inland and on the Great Lakes.
• Evaluating state waterways for chemical contamination and measuring remediation activities.
Containment efforts include utilizing empowerments, connected channels, and testing fish as part of a coordinated containment or evaluation process, Armstrong said. That waterway evaluation process includes EGLE professionals measuring the level of chemical containments in fish gills over a 28-day period while fish are housed in a cage in a body of water, he added.
The EPA also requests and receives reports from EGLE related to its monitoring program. These efforts occasionally identify fish contamination from high levels of common contaminants. One of the program’s most highly publicized outcomes was the high levels of contamination found in the Huron River in 2018, which instituted a “do not eat” advisory. The advisory was instituted based on the level of PFAS contamination in the river from the N. Wixom Road crossing in Milford to Lake Erie.
In the case of the Huron River contaminations, EGLE ramped up efforts to increase testing around the watershed and in other waterbodies bordering the Huron River watershed to determine if high levels of PFAS were elsewhere, Armstrong said.
“When we hit a certain threshold, we’ll collect surface water samples so we can identify the source of the information,” he said. “We’ll look at all waterbodies that are connected and possibly impacted and expand (testing) from there.”
The fish testing process through EGLE’s Fish Contaminant Monitoring Program starts with Armstrong and his team collecting data on fish fillets and sending the results of contaminant levels to MDHHS. Following data calculations, EGLE experts make one or more recommendations to MDHHS, which may lead to an advisory. If MDHHS does release an advisory, it will notify residents through its ESF guides and the MDHHS website. The identification of a “do not eat” advisory for example will also trigger a variety of additional communications and signage based on the collective discretion of the MDHHS team.
While advisories aren’t common, testing can uncover notable contamination issues. The monitoring program managed by EGLE uncovered elevated levels of PFOS at the WMP Thompson Pond near Port Huron and in a section of the lower Rouge River last year, Armstrong said. A third inland pond in West Michigan near Wyoming fell just below the level of a “do not eat” advisory, but community leaders there decided to proactively post signs warning fishing enthusiasts anyway.
Elevated levels of contamination in fish alone do not necessarily mean an advisory is recommended, Armstrong said. However, EGLE is testing fish in more inland bodies than ever. He estimates that EGLE tested 20 to 40 sites around 15 years ago. As public interest in fish testing and awareness of PFAS has increased, so have the agency’s fish testing efforts. EGLE tested fish in more than 90 bodies of water in Michigan in 2024, the majority of which included inland lakes, rivers and streams.
“I see us getting to that level again if not well over 100 (waterbodies) this year,” Armstrong said. ”There’s demand and public interest.”
The concern over PFAS has been elevated in recent years as researchers learn more about these substances. PFAS are unique because they do not naturally break down as easily as most other harmful substances, according to Enspired Solutions CEO Key. These contaminants exist in some household cleaners and other things humans use abundantly like waterproofing and stain resistant chemicals, makeup, clothing and certain types of packaging and clothes. PFAS chemicals have also been found to exist in firefighting foam.
High PFAS exposure can lead to liver damage, thyroid disease, decreased fertility, high cholesterol, obesity, hormone suppression and cancer in humans, according to the Centers for Disease Control and Prevention. Key said that the presence of PFAS in groundwater and wastewater is a threat to everyone’s health, and that the substances exist in many inland lakes and rivers across the U.S., including Michigan.
Combined with dioxins and PCPs, these chemicals access freshwater bodies through runoff, seepage, access to watersheds and in other ways.
Public awareness of perfluorooctane sulfonic acid (PFOS) has also increased in recent years. PFOS is a synthetic chemical used to make products resistant to stains, grease, soil, and water. It is part of a class of PFAS chemicals, Key said.
PFAS and PFOS can bioaccumulate and impact fish directly, often through their gills, or the sediment in the lake where fish feed, Key says. For that reason, researchers and governmental agencies have taken steps to interrupt the pathway for these chemicals to get into the water, which she believes is the only way to protect fish, and thereby humans that eat the fish, from contamination.
“In my experience with these chemicals, you can predict what the impact will be on fish with some testing and data,” said Key, who is not involved in fish testing personally. “Typically, more predatory fish accumulate higher amounts of chemicals than a fish that feeds primarily on algae.”
That’s why anglers should confirm the types of fish they are catching and eating, she adds. Having more knowledge about potential chemical impact could inform anglers how best to remove the skin and clean the fish, Key said. That’s important because plenty of unknowns remain. For example, the volume at which PFAS bioaccumulates in specific environments, such as sandy or muddy lake bottoms, can differ from one body of water to another, and is often difficult, if not impossible, to calculate through current testing methods.
“We have to do something to destroy the PFAS, or they will continue to accumulate in the environment. (These chemicals) never go away,” Key said. “They just move from a person to some other (physical) property. We aren’t anywhere near having an understanding of how PFAS behave once they are released into water.”
The “newness” of PFAS in fish presents a challenge. There have been a set of generally accepted guidelines for many years for how people can avoid consuming fish with higher levels of mercury, said Tasha Stoiver, PhD., a senior scientists with the Environmental Working Group, an activist group that engages in environmental research in Washington DC. Stoiver agrees that consuming fish that aren’t predators, and are lower on the food chain, mitigate consumer health risks, especially when it comes to mercury.
“We have some straightforward recommendations for dealing with mercury, but it’s completely different with PFAS because they have been found everywhere, including in smaller fish,” Stoiver said. “The mercury guidelines don’t seem to apply (to PFAS).”
While there is data for PFAS levels in some inland bodies of water in Michigan and elsewhere, many consumers have little data they can reference to determine the threat of PFAS in their community. Stoiver said that while inland waterbodies in rural areas generally have been shown to have lower levels of PFAS contaminants, which is far from a certainty, as testing has confirmed that PFAS can exist in rainwater in areas around the U.S.
“We see these chemicals in just about every type of testing,” Stoiver said. “If you consume freshwater fish, chances are you will have some PFAS in your system. You could recommend that people just may not want to eat freshwater fish. But that’s a difficult thing to say.”
Key confirms the best source for inland lake fish testing is MDHHS and its ESF guides. She acknowledges that it’s important for the state to test the muscles and tissue of fish.
“Obviously if there’s more (chemicals) in the muscle of the fish, which will have a greater impact on humans, because that’s the part of the fish you want to eat,” Key said. “If there’s more concern over the tissue, I would think it could lead to a greater chance for (an advisory) or other guidelines for residents.”
Testing can be initiated directly by residents, environmental groups and any interested party on EGLE’s website at https://tinyurl.com/bdz9sau3. EGLE will consider all completed forms and can work collaboratively with MDHHS in the testing process. Both Stebbins and Armstrong agree that EGLE’s Targeted Monitoring Request form is a critical source of information from the public.
“It’s been an important part of what we do because if there are waters we haven’t tested, people can submit a request,” Armstrong said. “Depending on available funding, we may be able to add it into our schedule for the year.”
In terms of Oakland County lakes, EGLE’s Fish Contaminant Monitoring Program professionals tested Lower Straits Lake in Commerce Township, Kent Lake in Lyon Township and Milford, and Stony Lake in Oxford in January and February of this year. Program professionals will return to the county to test Middle Straits Lake in Commerce Township and White Lake in White Lake Township this spring. Other Oakland County waterbodies will likely be tested later this year, Armstrong said.
Collected fish will be filleted and sent to EGLE’s testing lab. It usually takes about six to eight months to receive results. The lab is currently finishing up the fiscal year 2024 samples, Armstrong said.
If contamination is detected, MDHHS and EGLE coordinate to determine the fish testing needs, Stebbins said. After fish have been collected for edible portion testing, the MDHHS Bureau of Laboratories Environmental Chemistry Section analyzes the fish for contaminants. Results from those Oakland County lakes will be summarized and published in future ESF guides.
“Guidelines are typically issued in the next version of the regional ESF guides, but may be issued as soon as possible in certain situations, for example, when new do not eat guidelines are being issued for fish species in a waterbody,” Stebbins said.
At the request of MDHHS and/or EGLE, expanded collections will be conducted on waterbodies with documented chemical contamination or previous data showing elevated chemical concentrations in fish, extensive fishing activity, or outstanding public health questions, Stebbins said.
This includes testing in and around a watershed where contamination was found, among them rivers, streams and tributaries, she added. Based on the results of EGLE investigations, the two state agencies will work together to determine if additional fish collections are needed for that waterbody.
“Resulting fish consumption guidelines not only apply to the waterbody where the fish were collected from, but any other connected waterbodies where fish movement is not impeded,” Stebbins said.
As a fisheries management biologist with the Michigan Department of Natural Resources, John Buszkiewicz visits rivers, streams and other bodies of water that flow into St. Clair River and the Detroit River, Lake St. Clair and parts of Lake Erie. He’s responsible for a range of tasks from fish population surveys and stocking fish to checking anything that impacts these bodies of water like dams or bridges.
Knowing how fish testing is handled, Buszkiewicz has full confidence in the data published by EGLE, MDHHS and other agencies. “You have genuinely passionate people in those jobs that want to raise awareness of contaminants in fish, so the public is aware of the risks, if any,” Buszkiewicz said.
He admits that researchers can be conservative in their assessments of fish contamination. This conservative approach can be reflected in the creation of “do not eat” advisories where the risk to human health is limited provided there is only occasional consumption. Regardless, Buszkiewicz said he believes “most” fish caught in Michigan’s waterbodies carry some type of contamination. Even though the individual risk is low, Buszkiewicz said residents should be aware that it does exist.
“It’s not a bad idea to limit consumption because it is your health after all,” Buszkiewicz said. “Plus, it’s hard to know which fish might be impacted by past actions of companies dumping chemicals into the state’s freshwater bodies. That contamination can affect different people in different ways. We’re becoming more aware of the impact of these chemicals, and where they came from every day.”
The main function of the Huron River Watershed Council (HRWC) is to track water quality and contaminants of the inhabitants of the watershed that covers six counties, including Oakland County, said program manager Andrea Paine. Council leadership and members conduct community outreach and education so residents can understand fish consumption guidelines. Paine said a “do not eat” fish advisory is still in effect for much of the Huron River.
“We track a lot of nutrients, bacteria and sedimentation,” Paine said. That also includes long-term biological and chemistry monitoring of small water bugs and other watershed inhabitants. “Most of our monitoring is in Wayne and Washtenaw counties. PFOS is our main concern right now.”
Council members also work with local governments on stormwater management and infrastructure issues. They work with residents on residential rain gardens in the ground and more as well, Paine said. The HRWC does not monitor fish populations.
“We (provide) a lot of community education,” Paine said. “That’s a big focus.”
The reason that chemical contamination, even at low levels, is prevalent is that it enters lakes and rivers through multiple methods, including wind, rain run-off, and flow from other waterbodies, Stebbins of the MDHHS said. Some of those chemicals can settle into the sediment at the bottom of the lake or river. Small aquatic creatures absorb some of the chemicals in the water or in the sediment. These aquatic creatures are eaten by larger fish and those fish are eaten by even larger fish.
“Each fish collects and stores some of the chemicals in their bodies,” Stebbins said. “Through this food chain, larger fish and older fish are more likely to have higher levels of some chemicals, such as mercury and PCBs, than smaller and younger fish. This trend does not apply to PFOS, however, which is sometimes found at higher levels in smaller fish.”
A frequent angler, Buszkiewicz also prefers to consume small, younger fish like bluegill or walleye, who have had less time and fewer opportunities to build up contaminants internally. “Typically, older, larger fish will have more contaminants because they can digest more and they’ve been around longer,” he said.
He prefers to broil or grill the fish before eating. Frying fish can make it harder to remove any of the dioxins, because they remain in a pan during the frying process and get mixed in with any spices or other ingredients.
“You want to remove as much of the fat as you can, because (contaminants) are more likely to be stored there,” Buszkiewicz said.
ESF guides provide an overview of the benefits and dangers of consuming fish. Benefits include fish serving as a low-fat source of protein with access to heart-healthy omega-3s. However, mercury has been shown to cause damage to the nervous system, which is particularly detrimental to pregnant people.
Some residents rely on freshwater fish as a regular part of their diet because of convenience, personal finance and other reasons, Stoiver added.
Even medium and lower-level PFAS over a consistent period of time could cause health concerns, she said. Multiple data points show that mitigation and cleanup efforts for PFAS and other contaminants can work. But it doesn’t result in an overnight solution given PFAS disposal methods still can lead to such chemicals reentering the environment and water sources through leaching, deposits and more.
“You could even say that it would be advisable to limit your drinking water from (freshwater) sources,” Stoiver of the EWG said. “You certainly should find out the source of your drinking water at the very least.”
The level and types of chemicals found in fish has evolved over the years, Armstrong said. Prior to the increase in PFAS levels in fish tissue, mercury was the primary concern of state environmental departments, Armstrong said. Now, PFAS and PFOS play a much larger role, both because of the number of incidents and increased public awareness.
“We’re actively seeing more of these chemicals in our waters and our fish,” Armstrong said. “We’ve always chosen to be proactive.” Armstrong estimates that Michigan has been testing for PFAS and PFOS for around 15 years, before many other states started.
The impact of these chemicals within waterways and in fish vary based on the levels and types of containment. Mercury has long been a substance that is everywhere, getting into the atmosphere through human activities like fossil fuel combustion and mining. Fish absorb methylmercury from their food and from water as it passes over their gills. Mercury is tightly bound to proteins in all fish tissue, including muscle.
Many fish have some low levels of mercury in them that are of little concern to human health, Armstrong said.
PCP is an industrial contamination and a legacy containment that once its hits the water supply will appear in fish.
Researchers continue to learn more about PFAS and PFOS but it’s clear that these chemicals take an inordinate amount of time to degrade, Armstrong said. He said he is encouraged by findings from a granular activated carbon system installed by Wixom automotive manufacturer Tribar Technologies. Tribar installed the system after EGLE found extremely high levels of PFAS in adjacent Kent Lake, presumably caused by the manufacturer’s past disposal activities. Within two years of the carbon system’s installation, the concentration of PFOS fell by 500 percent.
“That’s a good sign when we can identify an issue,” Armstrong said. “We want to see how we can get those chemicals out of the waterways and fish.”
Applied technologies do not currently remove the contamination but rather capture the PFAS contaminants and transfer it elsewhere, Key said. One effective strategy to remove PFAS is using a carbon filter to remove nearly all harmful chemicals from water or other materials. However, it is difficult to dispose of carbon in an environmentally sustainable way. If not conducted properly, the carbon releases PFAS into the air or water.
High levels of contaminants in fish could also have an adverse impact on the fishing industry in the state. The Michigan United Conservation Clubs estimated that fishing-related purchases in the state generated more than $11.2 million annually in 2019. The same report estimated recreational fishing in Michigan generated $2.3 billion in economic activity.
Buszkiewicz admits that as an angler he may take more precautions than most residents before consuming freshwater fish he has caught. As someone who spent time earlier in his career working on commercial fishing boats, Buszkiewicz said he believes that keeping fish in a live well is detrimental not only to the fish, but to anglers because of the impact that stress has on a caught fish.
“A lot of people don’t understand this, but it’s actually more humane to kill a fish immediately after you catch it,” Buszkiewicz says. He believes that the most humane method is to cut underneath the fish’s gills, which releases the fish’s blood. That’s important because the gills are where a good portion of the contaminants are stored. Buszkiewicz will take off the skin which also attract contaminants and will remove discolored parts of the fish, such as other non-bloody, red areas.
Cooking can also make a small difference as frying may not remove as many contaminants as baking fish will, he added.
“You don’t want the fish to be stressed, no matter how contaminated it may be,” Buszkiewicz said. “Keeping it stressed means you’ll get a lower quality of (fish meat) to eat.”
While moderate freshwater fish consumption is not considered to be dangerous, Buszkiewicz recommends that anglers and consumers in general know the source of where caught fish originated from, and where it lived. “You can look up (contamination levels) in different bodies of water and find out yourself,” he said.
Stoiver says high levels of contaminants in fish affect everyone, and that is why improvements in testing and reporting are so critical. PFAS in particular is a recalcitrant substance and takes years, and even decades to fully break down, if at all. Despite the current testing that is being done, she said she believes that more data is needed to paint a complete picture of the potential health hazards.
“You want to know everything you can about (a waterbody) where you fish, but you might not have any data,” she said. “It’s too bad. We like to be outside enjoying water and fishing is a way of life for many people.”
