When Wisconsin Department of Natural Resources officials announced last month that they had found high levels of PFAS chemicals in Lake Superior smelt — high enough to warn people to limit how much smelt they eat — it left many people who follow fish consumption advisories scratching their heads.
First, smelt are small and have relatively short lifespans, and so shouldn’t be bioaccumulating toxins in high levels. The general rule with traditional fish contaminants — like mercury, PCBs and dioxins — are that bigger fish higher in the food chain are usually the highest threat for passing along contaminants to people, fish like sharks in the ocean and musky, trout and big walleye in Northland lakes and rivers.
Second, the bigger fish that often eat smelt, like lake trout and salmon, didn’t show PFAS levels high enough to trigger additional fish consumption advisories for people. Somehow, the PFAS in smelt was not working its way up the food chain.
“To be honest, we really don’t know why it’s not showing up as high in other fish, or why it’s just smelt at these higher levels,’’ said Sean Strom, environmental toxicologist for the Wisconsin DNR. “It’s an area of research we’re still trying to make sense of — the accumulation patterns for PFAS.”
As part of the DNR's statewide PFAS-monitoring efforts to monitor fish tissue and water chemistry at select sites around the state, smelt were collected from two sites in Lake Superior in 2019 — near the Apostle Islands and off Port Wing. PFAS was detected at both locations.
The DNR also tested samples from bloater chub, cisco/lake herring, lake whitefish and lake trout in Lake Superior and crappie, yellow perch, channel catfish, carp, northern pike, walleye and musky from the St. Louis River. All fish contained some PFAS, but none of them at levels that would trigger a fish consumption advisory change at this time. (Many fish in Lake Superior and the St. Louis River already carry advisories for other contaminants like mercury and PCBs.)
Smelt running soon
The advisory to limit meals of smelt to one per month is the first PFAS-specific warning for Lake Superior, and for the Great Lakes, and has now been adopted by the Minnesota Department of Health as well, said Patt McCann, an environmental health researcher and coordinator of Minnesota’s fish consumption advisory program.
The new smelt advisory will become an issue by April and into May when the tasty little fish begin to spawn, along Lake Superior’s sandy beaches and into rivers. Thousands of Northlanders are joined by people from across the Midwest each spring to net smelt along Minnesota and Wisconsin points in Duluth and Superior as well as North Shore streams like the Lester River and along the waterfront in Ashland.
But PFAS is far from just a Lake Superior smelt problem, and in fact it’s showing up in fish, deer and people across the region and the world. PFAS is “ubiquitous,’’ Strom noted. But only in a some cases are the levels high enough to trigger fish consumption advisories. And it’s not clear what makes those specific lakes or streams, or a specific species of fish, more likely to hold the toxins and pass them on to people. PFAS advisories have also been issued for trout in Miller Creek in Duluth and crappie, sunfish walleye and pike in Wild Rice Lake reservoir north of Duluth.
Generally, fish as small as smelt are considered the best options to eat to avoid soaking up toxic chemicals. In fact before the PFAS warning, smelt were considered among the safest fish in Lake Superior, with no restrictions on how much should be eaten.
To confuse matters even more, fish that have high levels of PFAS can suddenly shed the contaminant and test clean — not just the species but the same fish, McCann noted. That’s unlike mercury and other toxins that bioaccumulate or increase as long as the fish is alive.
“There’s some evidence that fish sometimes excrete PFAS,’’ she said. "PFAS doesn't seem to follow the normal patterns for bioaccumulation."
PFAS 'wherever we look'
There are more than 5,000 PFAS compounds — often called "forever chemicals" because they don’t ever break down entirely — that have been used for decades in hundreds of industrial processes and products, especially for nonstick cookware, waterproofing compounds, packaging and firefighting foam.
PFAS chemicals are now found in food, groundwater, drinking water, lakes, rivers, fish tissue and even in deer. Several other states have issued advisories to avoid or limit fish due to PFAS contamination, and some areas in Michigan and Wisconsin have PFAS advisories for limiting or not eating venison from deer shot near highly contaminated PFAS sites.
In some cases, geographic proximity hints to where the stuff is coming from. The chemicals have already been found at high levels in groundwater near the Duluth Air National Guard base and in surface water that originates near the base, including Miller Creek and Wild Rice Lake Reservoir, likely from firefighting foam used in training at the base for decades. At least one homeowner in the area has been provided bottled water because their well is contaminated with PFAS.
But PFAS also is showing up in lakes and streams hundreds of miles from any point source like a factory or air base.
“It’s not just at specific locations where we knew there was a (PFAS) source. It’s showing up in fish across the state now, wherever we look, and we really don’t know why or how it’s getting there,’’ said McCann, adding that there’s some theories that some PFAS chemicals can become airborne pollution like mercury.
McCann noted that the state Pollution Control Agency has applied for a federal grant to test fish in the Lake Superior watershed this summer specifically for PFAS, an often expensive process. It’s part of a larger, multi-agency push in Minnesota to not only test for PFAS but find out where it’s coming from and clean up the sources. The first order of business is for the Legislature to declare PFAS an official dangerous chemical by law, something already decided in court cases on PFAS contamination responsibility.
Since PFAS testing began in Minnesota’s lakes and streams in 2004, fish have been collected for PFAS from over 200 lakes and rivers, many of which have led to fish consumption advisories.
PFAS in deer
In October 2018, the Michigan Department of Health and Human Services issued a “Do Not Eat” advisory for deer taken within 5 miles of Wurtsmith Air Force Base, a site in eastern Lower Michigan with soil and groundwater contaminated with PFAS.
Last year the Wisconsin DNR and Department of Health Services issued a Do Not Eat advisory for deer livers for any deer harvested within five miles of the JCI/Tyco Fire Technology Center in Marinette. Deer sampled in that area had high PFAS levels in their livers.
“We want to be clear that people should feel comfortable eating venison from deer they’ve harvested near this area," said Tami Ryan, Wisconsin DNR wildlife health section chief, in a statement. "We just advise they do not consume the liver.”
In Minnesota, the Minnesota DNR last fall asked hunters who harvest deer near Duluth International Airport, home of the PFAS-contaminated Duluth Air National Guard base, to submit deer for sampling to determine the PFAS levels there.
So far the agency has found PFAS in all the deer sampled, but not yet at levels high enough to issue an advisory, said Barb Keller, big game program leader for the DNR.
“Some of the chemicals were not detected in any of the samples but all samples had at least one detectable chemical,’’ Keller said, adding that the PFAS levels in Duluth deer “were not concerning to our colleagues’’ at the Department of Health but that the DNR will seek more hunters to submit more deer in 2021 to get a larger sampling size.
The DNR also is testing deer near 3M manufacturing and disposal facilities in the eastern Twin Cities where PFAS has been found at high levels in groundwater, surface waters and fish. The state has issued Do Not Eat advisories for fish from Lake Elmo and other waters in the eastern Twin Cities.
Northland waters with PFAS fish consumption advisories
Lake Superior: Rainbow smelt — One meal per month for all people.
Wild Rice Lake Reservoir: Walleye, northern pike, crappie and sunfish — One meal per month for all people.*
Miller Creek: Brook trout — One meal per month for all people.
(*Northern pike and walleye from Wild Rice Lake also are high in mercury.)
Cancers, cholesterol, tumors and thyroid issues
Most people have been exposed to PFAS chemicals. Certain PFAS can accumulate and stay in the human body for long periods of time. There is evidence that exposure to PFAS can lead to adverse health outcomes in humans. Studies indicate that they can cause reproductive and developmental, liver and kidney, and immunological effects in laboratory animals. The chemicals also have caused tumors in animals. The most consistent findings are increased cholesterol levels among exposed human populations, with more limited findings related to low infant birth weights, immune system problems, cancer and disruption of thyroid hormones.
Source: Minnesota Department of Health
Statewide fish consumption advisory
All fish carry some contaminants, but some fish in some lakes and rivers carry much more. Check the statewide advisory first, then check specific lakes or rivers you may fish on at health.state.mn.us/communities/environment/fish/ to see if more restricive advisories are in place. In Wisconsin check the statewide and lake-specific advisories at dnr.wisconsin.gov/topic/Fishing/consumption. Advisories are more restrictive for children and women who may become pregnant because contaminants can affect fetuses and developing children more severely.
For women who may become pregnant and all children under age 15:
Eat up to two servings weekly of: Purchased catfish, cod, pollock, ocean salmon, sardines, shellfish, tilapia
Limit meals to once weekly of: Minnesota caught stream trout trout, bullhead, crappie, sunfish, perch, lake herring, lake whitefish or purchased tuna or halibut.
Limit meals to one per month of: Minnesota-caught bass, catfish, walleye, lake trout and northern pike.
Do not eat any: Minnesota caught musky or purchased swordfish, shark or mackerel.
For males over 15 and women over 50:
Unlimited meals of: Minnesota caught bullhead, crappie, stream trout, lake herring, lake whitefish, sunfish, perch.
One serving per week of: Minnesota-caught bass, catfish, walleye, lake trout.
Lower St. Louis River/Duluth-Superior harbor
Walleyes 22" and larger: Women who are or may become pregnant and all children under 15: Do not eat due to high mercury concentrations. Men 15 and older and women over 50 should limit meals of large walleyes from the river to one per month.
Lake Superior fish consumption advisories
Children under age 15 and women who are or may become pregnant: One meal per week of brown trout, chinook salmon, coho salmon, lake herring, whitefish and rainbow trout (steelhead). One meal per month of all lake trout, walleye and smelt.
Men over age 15 and women over 50: Unrestricted number of meals of coho salmon, lake herring and rainbow trout. One meal per week of brown trout, chinook salmon, whitefish and walleye. One meal per month of all lake trout and smelt.
Per- and polyfluoroalkyl substances — PFAS — are a group of 5,000 man-made chemicals that includes PFOA, PFOS, GenX and many other chemicals often found in waterproofing products, firefighting foams, packaging and nonstick cookware, among other items. PFAS have been manufactured in the U.S. since the 1940s and also around the world.
PFOA and PFOS have been the most extensively produced and studied of these chemicals. Both chemicals are very persistent in the environment and in the human body — meaning they don’t break down and they can accumulate over time. There is evidence that exposure to PFAS can lead to adverse human health effects.
PFAS can be found in:
Food that’s packaged in PFAS-containing materials, like pizza boxes, or that’s processed with equipment that used PFAS, or grown in PFAS-contaminated soil or water.
Commercial household products, including stain- and water-repellent fabrics, nonstick products like Teflon, polishes, waxes, paints, cleaning products, and firefighting foams, which are a major source of groundwater contamination at airports and military bases where firefighting training occurs.
Workplaces, including production facilities or industries such as chrome plating, electronics manufacturing or oil recovery.
Drinking water, typically localized and associated with a specific facility such as a manufacturing plant, landfill, wastewater treatment plant or firefighter training facility.
Living organisms, including fish, animals and humans, where PFAS have the ability to build up and persist over time.
Although some PFAS chemicals like PFOA and PFOS are no longer manufactured in the U.S. they are still produced internationally and can be imported into the United States in consumer goods such as carpet, leather and apparel, textiles, paper and packaging, coatings, rubber and plastics.
Source: U.S. EPA
Eat fish lower in contaminants
Eating fish is good for you. Fish are generally low in saturated fats and high in protein. Fish contain vitamins and minerals and are the primary food source for healthy omega-3 fats. Studies suggest that omega-3 fats may be beneficial during fetal brain and eye development, and eating modest amounts of fish containing these healthy fats may lower the risk of heart disease in adults.
Omega-3 fatty acids also may decrease the risk of depression, ADHD, Alzheimer’s disease, dementia, and diabetes. And they may prevent inflammation and reduce the risk of arthritis.
Fish also provide a good source of protein and vitamins such as D and B2 (riboflavin). Fish are rich in calcium and phosphorus and are a great source of minerals, such as iron, zinc, iodine, magnesium, and potassium.
But fish may also have high levels of mercury, PCBs and PFAS — even fish from remote lakes and rivers — prompting recommendations that people limit or avoid eating certain species of fish from many waters throughout the nation. You can get the health benefits of eating Northland fish while also reducing potential health risks from unwanted pollutants by following the Minnesota and Wisconsin fish consumption guidelines. Compare the type of fish and where you caught your fish with the consumption advice. After consulting the recommendations, you may find that you do not have to change your eating habits, you may choose to eat different types of fish or eat some species less frequently.
In general, smaller fish lower on the food chain have less contaminants — such as panfish and smaller walleyes or pike. Larger, older fish have more time to bioaccumulate contaminants.
Sources: Wisconsin Department of Natural Resources, Minnesota Department of Health
- MPCA rings alarm: Old landfills leaking contaminants in Northland, across state
- Duluth officials praise statewide blueprint addressing 'forever chemicals'
- State, feds agree on $16 million cleanup plan for Erie Pier ponds along Duluth harbor
- First ever PFAS fish consumption advisory issued for Lake Superior smelt
- Lake Superior contaminants face year of scrutiny