The Earth
PFAS are turning up in the Great Lakes, putting fish and water supplies at risk – here’s how they get there
PFAS “forever chemicals” are entering the Great Lakes through rivers, groundwater, and rain, threatening drinking water, fish, and one of the world’s largest freshwater systems.
Christy Remucal, University of Wisconsin-Madison
No matter where you live in the United States, you have likely seen headlines about PFAS being detected in everything from drinking water to fish to milk to human bodies.
PFAS, or per- and polyfluoroalkyl substances, are a group of over 10,000 synthetic chemicals. They have been used for decades to make products waterproof and stain- and heat-resistant – picture food wrappers, stain-resistant carpet, rain jackets and firefighting foam.
These chemicals are a growing concern because some PFAS are toxic even at very low levels and associated with health risks like thyroid issues and cancer. And some of the most common PFAS don’t naturally break down, which is why they are often referred to as “forever chemicals.”
Now, PFAS are posing a threat to the Great Lakes, one of America’s most vital water resources.
The five Great Lakes are massive, with over 10,000 miles of coastline (16,000 kilometers) across two countries and containing 21% of the world’s fresh surface water. They provide drinking water to over 30 million people and are home to a robust commercial and recreational fishing industry.
My colleagues at the University of Wisconsin-Madison and I study how chemicals like PFAS are affecting water systems. Here’s what we’re learning about how PFAS are getting into the Great Lakes, the risks they’re posing and how to reduce those risks in the future.
PFAS’ many pathways into the Great Lakes
Hundreds of rivers flow into the lakes, and each can be contaminated with PFAS from sources such as industrial sites, military operations and wastewater treatment plants in their watersheds. Some pesticides also contain PFAS, which can wash off farm fields and into creeks, rivers and lakes.
The concentration of PFAS in rivers can vary widely depending on these upstream impacts. For example, we found concentrations of over 1,700 parts-per-trillion in Great Lakes tributaries in Wisconsin near where firefighting foam has regularly been used. That’s more than 400 times higher than federal drinking water regulations for PFOS and PFOA, both 4 parts-per-trillion.
However, concentration alone does not tell the whole story. We also found that large rivers with relatively low amounts of PFAS can put more of these chemicals into the lakes each day compared with smaller rivers with high amounts of PFAS. This means that any effort to limit the amount of PFAS in the Great Lakes should consider both high-concentration hot spots and large rivers.
Groundwater is another key route carrying PFAS into the Great Lakes. Groundwater is a drinking water source for more than one-third of people in the U.S., and it can become contaminated when PFAS in firefighting foam and other PFAS sources seep into soil.
When these contaminated plumes enter the Great Lakes, they carry PFAS with them. We detected PFAS concentrations of over 260 parts-per-trillion in the bay of Green Bay in Lake Michigan. The chemicals we found were associated with firefighting foam, and we were able to trace them back to a contaminated groundwater plume.
PFAS can also enter the Great Lakes in unexpected ways, such as in rain and snowfall. PFAS can get into the atmosphere from industrial processes and waste incineration. The chemicals have been detected in rain across the world, including in states surrounding the Great Lakes.
Although PFAS concentrations in precipitation are typically lower than in rivers or groundwater, this is still an important contamination source. Scientists estimate that precipitation is a major source of PFAS to Lake Superior, which receives about half of its water through precipitation.
Where PFAS end up determines the risk
Much of the PFAS that enter Lake Superior will eventually make their way to the downstream lakes of Michigan, Huron, Erie and Ontario.
These chemicals’ ability to travel with water is one reason why PFAS are such a concern for drinking water systems. Many communities get their drinking water from the Great Lakes.
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PFAS can also contaminate other parts of the environment.
The chemicals have been detected in sediments at the bottom of all the Great Lakes. Contaminated sediment can release PFAS back into the overlying water, where fish and aquatic birds can ingest it. So, future remediation efforts to remove PFAS from the lakes are about more than just the water – they involve the sediment as well.
PFAS can also accumulate in foams that form on lake shorelines during turbulent conditions. Concentrations of PFAS can be up to 7,000 times higher in natural foams compared with the water because PFAS are surfactants and build up where air and water meet, like bubbles in foam. As a result, state agencies recommend washing skin that comes in contact with foam and preventing pets from playing in foam.
Some PFAS bioaccumulate, or build up, within fish and wildlife. Elevated levels of PFAS have been detected in Great Lakes fish, raising concerns for fisheries.
High PFAS concentrations in fish in coastal areas and inland waters have led to advisories recommending people limit how much they fish they eat.
Looking ahead
Water cycles through the Great Lakes, but the process can take many years, from 2.6 years in Lake Erie to nearly 200 years in Lake Superior.
This means that PFAS that enter the lakes will be there for a very long time.
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Since it is not possible to clean up the over 6 quadrillion gallons of water in the Great Lakes after they have been contaminated, preventing further contamination is key to protecting the lakes for the future.
That starts with identifying contaminated groundwater and rivers that are adding PFAS to the lakes. The Sea Grant College Program and the National Institutes of Water Resources, including the Wisconsin programs that I direct, have been supporting research to map these sources, as well as helping translate that knowledge into actions that policymakers and resource managers can take.
PFAS contamination is an issue beyond the Great Lakes and is something everyone can work to address.
- Drinking water. If you are one of the millions of people who drink water from the Great Lakes, find out the PFAS concentrations in your drinking water. This data is increasingly available from local drinking water utilities.
- Fish. Eating fish can provide great health benefits, but be aware of health advisories about fish caught in the Great Lakes and in inland waters so you can balance the risks. Other chemicals, such as mercury and PCBs, can also lead to fish advisories.
- Personal choice. Scientists have proposed that PFAS only be used when they have vital functions and there are no alternatives. Consumer demand for PFAS-free products is helping reduce PFAS use in some products. Several states have also introduced legislation to ban PFAS use in some applications.
Decreasing use of PFAS will ultimately prevent downstream contamination in the Great Lakes and around the U.S.
Christy Remucal, Professor of Civil and Environmental Engineering, University of Wisconsin-Madison
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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Last Updated on April 17, 2026 by Daily News Staff
Earth Day is celebrated annually on April 22nd, and it serves as a reminder of the importance of taking care of our planet. It’s a day to reflect on our impact on the environment and to take action to create a better future for our planet.
The first Earth Day was celebrated in 1970, and it marked the beginning of the environmental movement. Since then, Earth Day has grown into an international event, with millions of people around the world participating in activities and events to raise awareness about environmental issues.
One of the main goals of Earth Day is to encourage people to take action to reduce their impact on the environment. This can include simple actions like recycling, conserving energy, and reducing waste. It can also involve more significant actions like advocating for environmental policies and supporting sustainable businesses.
Another important aspect of Earth Day is education. It’s a time to learn about environmental issues and to understand how our actions can impact the planet. Many schools and organizations use Earth Day as an opportunity to teach children about the importance of taking care of the environment.
This year’s Earth Day theme is “Restore Our Earth”, and it focuses on the idea that we can all play a role in restoring the planet’s ecosystems. This can include actions like planting trees, reducing plastic waste, and supporting sustainable agriculture.
Earth Day is an important reminder of the impact that we have on the environment and the importance of taking action to create a better future for our planet. By working together and taking small steps, we can make a big difference in protecting the planet and ensuring that it remains healthy and beautiful for generations to come.
Earth Day – April 22
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The Knowledge
Mosquitoes carrying malaria are evolving more quickly than insecticides can kill them – researchers pinpoint how
Jacob A Tennessen, Harvard University
The fight against infectious disease is a race against evolution. Bacteria become resistant to antibiotics. Viruses adapt to spread more quickly. Diseases transmitted by insects present another evolutionary front: Insects themselves can evolve resistance to the poisons that people use to kill them.
In particular, the mosquito-borne disease malaria kills over 600,000 people annually. Since World War II, people have battled malaria with insecticides – chemical weapons intended to kill Anopheles mosquitoes infected with the Plasmodium parasites that cause the disease.
However, mosquitoes are quickly evolving counterstrategies that make these insecticides ineffective, putting millions of people at greater risk of deadly infection. My colleagues and I have newly published research showing how.
Insecticide resistance threatens public health
As an evolutionary geneticist, I study natural selection – the basis for adaptive evolution. Genetic variants that best promote survival can replace less advantageous versions, causing species to change. Anopheles mosquitoes are frustratingly adept at evolving.
In the mid-1990s, most African Anopheles were susceptible to pyrethroids, a popular type of insecticide originally derived from chrysanthemums. Anopheles control relies on two pyrethroid-based methods: insecticide-treated bed nets to protect sleepers, and indoor residual spraying of insecticide against the walls of homes. These two methods alone likely prevented over a half-billion cases of malaria between 2000 and 2015.
However, mosquitoes today from Ghana to Malawi are often able to survive insecticide concentrations 10 times the previously lethal dose. Along with Anopheles control efforts, agriculture also inadvertently exposes mosquitoes to pyrethroids and contributes to insecticide resistance.
In some African locales, Anopheles is already showing resistance to all four main classes of insecticide used for malaria control.
Adaptation in Latin American mosquitoes
Anopheles mosquitoes and the malaria-causing Plasmodium also occur outside Africa, where insecticide resistance is less well-researched.
In much of South America, the main malaria vector is Anopheles darlingi. This mosquito species has diverged evolutionarily from the African vectors so extensively that it might be a different genus, Nyssorhynchus. Along with colleagues from eight countries, I analyzed over 1,000 Anopheles darlingi genomes to understand its genetic diversity, including any recent changes due to human activity. My collaborators collected these mosquitoes at 16 locations ranging from the Atlantic coast of Brazil to the Pacific side of the Andes in Colombia.
We found that, like its African counterparts, Anopheles darlingi shows extremely high genetic diversity – more than 20 times that of humans – indicating that very large populations of this insect exist. A species with such a vast gene pool is well poised to adapt to new challenges. The right mutation giving it the advantage it needs is more likely to pop up when there are so many individuals. And once that mutation starts to spread, it’s protected by numbers since it won’t be wiped out if a few mosquitoes die by chance.
In contrast, bald eagles in the contiguous U.S. were never able to evolve resistance against the insecticide DDT and approached extinction. Evolution is more efficient among millions of insects than mere thousands of birds. And indeed, we saw signals of adaptive evolution in the resistance-related genes of Anopheles darlingi occurring over the past few decades.
Mosquitoes evolve to detoxify poisons
Insecticides like pyrethroids and DDT share the same molecular target: channels in nerve cells that can open and close. When open, the nerve cell stimulates other cells. These insecticides force the channels to remain open and continuously fire, causing paralysis and death. However, insects can evolve resistance by changing the shape of the channel itself.
Earlier genetic scans performed by other researchers had not detected this type of resistance in Anopheles darlingi, and neither did ours. Instead, we found that resistance is evolving in another way: a group of genes encoding enzymes that break down toxic compounds. High activity of these enzymes, called P450, frequently underlies resistance to insecticides in other mosquitoes. The same cluster of P450 genes has changed independently at least seven times across South America since insecticide use began in the mid-20th century.
In French Guiana, a different set of P450 genes exhibits a similar evolutionary pattern, cementing the clear connection between these enzymes and adaptation. Moreover, when we exposed mosquitoes to pyrethroids in sealed bottles, differences among the P450 genes of individual mosquitoes were linked to the length of time they stayed alive.
Insecticide-heavy campaigns against malaria have been only sporadic in South America and may not be the main driver behind this evolution. Instead, it’s possible that mosquitoes are being exposed indirectly to agricultural insecticides. Intriguingly, we saw the strongest signs of evolution in places where farming is prevalent.
Toward more sophisticated vector control
Despite new vaccines and other recent advances against malaria, mosquito control remains essential for reducing disease.
Some countries are launching trials of gene drives to control malaria, which involve forcing a genetic modification into a mosquito population to reduce their numbers or their tolerance for Plasmodium. Such prospects are exciting, though the relentless adaptability of mosquitoes could be an obstacle.
I and others are revising methods to efficiently test for emerging insecticide resistance. Genome-scale sequencing remains important to detect new or unexpected evolutionary responses. The risk of adaptation is highest under a continuous, strong selection pressure, so minimizing, switching and staggering pesticides can help thwart resistance.
Success in the fight against evolving resistance will require a coordinated effort of monitoring, and reacting accordingly. Unlike evolution, humans can think ahead.
Jacob A Tennessen, Research Scientist in Immunology and Infectious Diseases, Harvard University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
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home improvement
Simple Ways to Make At-Home Recycling More Effective
To create a more eco-friendly household, consider these practical tips to help you reduce waste, stay organized and make at-home recycling part of your everyday routine.
Simple Ways to Make At-Home Recycling More Effective
(Feature Impact) Recycling is a simple way households can reduce waste and help protect natural resources. While many communities offer curbside recycling programs, some people still wonder if they’re doing it correctly or if they’re missing opportunities to recycle more.
To create a more eco-friendly household, consider these practical tips to help you reduce waste, stay organized and make recycling part of your everyday routine.
Know What Your Local Program Accepts
Recycling rules vary depending on your city or waste management provider. Most curbside programs include items like cardboard, paper, aluminum cans and plastics, but others – such as glass – may require drop-off recycling. Review your community guidelines so recyclables don’t accidentally end up in the regular trash.
Create a Simple Sorting System
Set up clearly labeled bins – separated for paper, plastics and metals – in a high-traffic area like the kitchen, garage or laundry room.
Rinse Before You Recycle
Food residue can contaminate other recyclables and may cause entire batches of materials to be rejected during the recycling process. Quickly rinsing yogurt cups, jars or soup cans of leftover residue helps keep recycling streams clean and more likely to be processed properly.
Break Down Boxes
Cardboard boxes are among the most commonly recycled household materials. Flattening boxes before placing them in the recycling bin saves space and allows collection trucks to hold more.
Compost Food Scraps
Not everything belongs in the recycling bin, particularly food waste. Composting fruit peels, vegetable scraps, coffee grounds and eggshells is an easy way to reduce the amount of trash your household produces. Finished compost can be used in gardens, flower beds or houseplants, turning kitchen waste into a valuable resource.
Find more ideas for making recycling a natural part of your household routine at eLivingtoday.com.
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