DULUTH -- When Wisconsin Department of Natural Resources officials announced in January 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 lakes and rivers in the Northland region.
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.)
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.
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.
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.
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 www.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