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.

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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.

Dive into “The Knowledge,” where curiosity meets clarity. This playlist, in collaboration with STMDailyNews.com, is designed for viewers who value historical accuracy and insightful learning. Our short videos, ranging from 30 seconds to a minute and a half, make complex subjects easy to grasp in no time. Covering everything from historical events to contemporary processes and entertainment, “The Knowledge” bridges the past with the present. In a world where information is abundant yet often misused, our series aims to guide you through the noise, preserving vital knowledge and truths that shape our lives today. Perfect for curious minds eager to discover the ‘why’ and ‘how’ of everything around us. Subscribe and join in as we explore the facts that matter.  https://stmdailynews.com/the-knowledge/

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Emily A. Margolis, Smithsonian Institution

While I was leading a tour of the National Air and Space Museum in January 2026, a visitor posed this insightful question: “Why has it taken so long to return to the Moon?”

After all, NASA had the know-how and technology to send humans to the lunar surface more than 50 years ago as part of the Apollo program. And, as another tour guest reminded us, computers today can do so much more than they could back then, as evidenced by the smartphones most of us carry in our pockets. Shouldn’t it be easier to get to the Moon than ever before?

The truth is that sending humans into space safely continues to be difficult, especially as missions increase in complexity.

New technologies require years of study, development and testing before they can be certified for flight. And even then, systems and materials can behave in ways that surprise and worry engineers and mission planners; look no further than Boeing’s Starliner CFT mission or the performance of the Orion heat shield on Artemis I.

Issues with Starliner’s thrusters led NASA to return the spacecraft from the International Space Station without its crew. Unanticipated chipping of the Orion heat shield resulted in years of research, culminating in NASA altering the atmospheric reentry plans for the Artemis II mission.

NASA’s programs also require sustained political will and financial support across multiple presidential administrations, Congresses and fiscal years. As a historian of human spaceflight, I have studied the space agency’s efforts to engage the broader public to convince American taxpayers that their programs hold value for the nation.

NASA is now on the eve of the first crewed flight to the Moon since the Apollo era: Artemis II. A crew of four will conduct a lunar flyby, laying the groundwork, the agency hopes, for a landing on the Artemis IV mission.

The story of NASA’s effort to return humans to the Moon is long and winding, demonstrating the complexities of turning grand ambitions into real missions.

Post-Apollo

In early 1970, with two successful Moon landings on the books, President Richard Nixon sought to reduce NASA’s budget to better align with his administration’s priorities. This decision put the space agency in a difficult position, which ultimately led to the cancellation of three planned Apollo missions to conserve funding for its plans for long-term human activity in low Earth orbit.

NASA repurposed the third stage of a Saturn V rocket to create the first U.S. space station, Skylab, which operated from 1973 to 1974. The space agency used leftover Saturn IB rockets and Apollo command and service modules to send crews to the station.

Over the next three decades, NASA developed and operated the space shuttle. The fleet of space shuttle orbiters supported satellite deployment and microgravity research on orbital missions of up to 17 days. This work was meant to enable future long-duration human missions and provide benefits to people on Earth. For example, data from protein crystal growth experiments have informed the development of medicines.

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The space shuttle program facilitated the construction, maintenance and staffing of a continuously inhabited research platform in orbit, the International Space Station. The first modules launched in late 1998.

Where to next?

As the new millennium approached, the Clinton administration tasked NASA to think beyond the space station. What could robots and humans do next in space? And where could they do it? Notably, the White House expressed an interest in locations beyond low Earth orbit.

NASA, it turned out, was well positioned to meet the administration’s request. NASA Administrator Daniel Goldin was already thinking about preparing proposals for the next presidential administration and had recently sponsored a human lunar return study. In 1999, he established a team to investigate new technologies, missions and destinations for the 21st century.

This work took on new significance following the tragic loss of the space shuttle Columbia crew in February 2003. Many people, including those in the new George W. Bush White House, wondered whether the human spaceflight program should continue – and, if so, how.

Administration discussions culminated in Bush’s Vision for Space Exploration in 2004, which directed NASA to retire the space shuttle after the completion of the space station. It called for returning humans to the Moon on a crew exploration vehicle designed for destinations beyond low Earth orbit.

It also called for continuing robotic exploration of Mars and engaging companies and international partners in space. Fifteen years earlier, President George H. W. Bush had also announced a Moon and Mars exploration program, but congressional concerns about cost kept space travelers close to home.

The Constellation program’s legacy

In December 2004, NASA began the process of finding a manufacturer for the crew exploration vehicle. By August 2006, the space agency awarded Lockheed Martin the contract to build the capsule, which it had named Orion – the same Orion planned to carry Artemis astronauts to the Moon.

Years of research, development and testing followed for Orion as well as the Ares I crew and Ares V cargo launch vehicles. Together, these technologies made up the Constellation program.

Constellation had two primary objectives: in the near term, to help transport crew to and from the space station after the space shuttle program ended; in the long term, to enable human lunar exploration.

Building systems that could work in both Earth orbit and around the Moon was supposed to save the time and cost of developing two vehicles. Similarly, adapting space shuttle program hardware could supposedly cut costs.

During the first months of Barack Obama’s presidency in 2009, the administration initiated an independent review of NASA’s human spaceflight plans. The Augustine Committee, chaired by retired aerospace executive Norman Augustine, found that the agency’s ambitions outstripped its limited budget, leading to significant delays. The first Orion spacecraft was likely to arrive after the space station ceased operations.

The committee proposed several paths forward at the current funding level, which prioritized space shuttle and space station programs. An additional annual investment of US$3 billion would allow for human exploration beyond low Earth orbit.

Ultimately, the Obama administration canceled Constellation, but two of its technologies lived on, thanks to U.S. senators from states that would have been affected by cuts.

The NASA Authorization Act of 2010 funded Orion’s continued development, shifting responsibility for space station crew transportation to commercial vehicles. It also directed NASA to develop the space launch system, a redesigned Ares V heavy booster, to send Orion to the Moon. The technical strategy had political benefits, too, preserving jobs in numerous congressional districts by providing continuity for aerospace contractors.

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In December 2014, a Delta IV heavy rocket launched the first Orion capsule on a test flight, providing engineers with data on spacecraft systems and the heat shield. By October 2015, the space launch system had completed a critical design review, the last step before manufacturing could begin.

Introducing Artemis

In December 2017, the new Trump administration issued a policy directive shifting the focus of NASA’s human spaceflight program back to the Moon. The space agency would use Orion and the space launch system in a race to meet an ambitious 2024 landing date. NASA officially named the program Artemis in May 2019.

The 25-day Artemis I mission, launched in November 2022, was a major milestone for the program. This uncrewed flight was the first flight of the space launch system and the first to integrate SLS and Orion. It laid the groundwork for Artemis II, which will be the first crewed flight of the SLS.

Over more than 50 years, each new presidential administration has reassessed the place of spaceflight among its priorities, either encouraging or curtailing NASA’s efforts to return humans to the lunar surface.

Each crewed flight requires the alignment of technical expertise, political will and financial support over years if not decades. For the space fans who plan to watch the Artemis II launch, the wait for countdown may feel long. But it’s just a blink in NASA’s long journey back to the Moon.

Emily A. Margolis, Curator of Contemporary Spaceflight, National Air and Space Museum, Smithsonian Institution

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Dive into “The Knowledge,” where curiosity meets clarity. This playlist, in collaboration with STMDailyNews.com, is designed for viewers who value historical accuracy and insightful learning. Our short videos, ranging from 30 seconds to a minute and a half, make complex subjects easy to grasp in no time. Covering everything from historical events to contemporary processes and entertainment, “The Knowledge” bridges the past with the present. In a world where information is abundant yet often misused, our series aims to guide you through the noise, preserving vital knowledge and truths that shape our lives today. Perfect for curious minds eager to discover the ‘why’ and ‘how’ of everything around us. Subscribe and join in as we explore the facts that matter.  https://stmdailynews.com/the-knowledge/

Craig Fehrman, Indiana University

Astronaut Victor Glover

In April 2026, four astronauts are scheduled to fly around the Moon. As part of NASA’s Artemis II mission, they will become the first humans to do so in half a century. One crew member, pilot Victor Glover, will become the first Black astronaut to ever orbit the Moon.

Glover’s achievement is worth celebrating. But it’s also worth remembering that he belongs to a long and underappreciated history. America’s first Black explorer didn’t fly an Apollo rocket or sail with the U.S. Exploring Expedition. He traveled with Lewis and Clark, and he was known by a single name: York.

I’m a historian who spent five years writing a book about Lewis and Clark, and I found new documents that show York was one of the most important people on their expedition. Even in a party that could number as many as 45 men, York stood out – for his courage, his skill and his sacrifices that helped the famous captains reach the Pacific Ocean.

York’s life as a slave

York was born in Virginia around 1770. Growing up, he was a creative and sociable child, unusually tall with dark hair and a dark complexion – “black as a bear,” a contemporary noted.

He was also enslaved by the Clarks. William Clark, who was around the same age, was also unusually tall, though his hair was a rusty red, and sometimes the boys played together. But the playing stopped once York turned 9 or 10. That’s when he joined the adult slaves in working full time. That’s also when he began to note the differences between his life and William’s – differences that became only clearer once William started ordering him around.

In the 1780s, the Clark household headed to Kentucky. York met a Black woman there and married her. He also became William’s “body servant.”

A body servant was a slave who stayed close to his owner and prioritized his comfort, laying out his clothes and serving his meals. When Meriwether Lewis asked Clark to join his expedition, in 1803, Clark ordered York to accompany him.

Perhaps York was excited for this adventure. Perhaps he was not – it would be punishing, and he would be separated from his wife.

Either way, York didn’t have a choice.

The Corps of Discovery

York proved his worth from the start. Once they reached St. Louis, the soldiers, later known as the Corps of Discovery, rushed to raise winter quarters. Working in hail and snow, York and the others built log huts. They needed rough planks for their tables and bunks, but the carpenters had only a single whipsaw to make them. They chose two men to operate this crucial tool. One of them was York.

On May 14, 1804, the corps began ascending the Missouri River. York helped row and tow the party’s barge, which was the size of a semi-truck trailer. He carried a rifle and hunted – according to the expedition’s journals, he was only the fifth named member to bring down a buffalo. York cooked for the captains. He collected scientific specimens. He nursed the sick, including several soldiers and, later on, Sacagawea, a Shoshone woman who would also prove essential to the expedition’s success.

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The soldiers were not always kind in return. During this period, officers rarely brought along enslaved body servants. York’s race probably made some of the men angry or uncomfortable. One day, someone threw so much sand in his face that it nearly blinded him. Clark claimed it was “in fun,” but he also wrote that York was “very near losing his eyes,” and no one else got cruelly sprayed with sand.

That fall, during councils with Native leaders, York played a surprising and vital role. The Arikara, Mandan and Hidatsa all crowded in to see him and to touch his skin. They had never met a Black person before, and York showed off his strength and played with the Native children. Later, the Arikara said York was “the most marvelous” thing about the corps.

The next year, the expedition crossed the Rockies and the Continental Divide. York’s most important – and most overlooked – contributions came soon after. On the Columbia River and its tributaries, the party had to dig out five new canoes and then paddle them through treacherous rapids.

Lewis and Clark allowed only their best rivermen on these foaming, rock-riven waters. One of them was almost certainly York. During my research, I found an unpublished letter in which Clark praised York’s ability to “manage the boats.”

Just as important, York was a strong swimmer, a rare thing in an era when many people never learned to swim.

York’s life as an explorer

On the Columbia River, the corps survived a series of terrifying choke points – soggy hazards they referred to as the “Long Narrows” and the “Great Chute.” After that came the ocean. They had traveled together for more than 4,000 miles (6,400 kilometers), and when the captains asked the men to vote on where to put their final winter quarters, they made sure to ask York, too.

It was the latest sign that his role had changed during this epic journey. But those changes began with York. In the West, he found ways to make choices and assert himself. He sent a buffalo robe to his wife in Kentucky. When Clark told him to scale back his performances for Native people, York ignored him – because he wanted to, and because he could.

York’s vote was also evidence that, like Victor Glover today, he was an official American explorer, a key member of a sprawling, federally funded mission. From 1804 to 1806, the government devoted a larger percentage of its budget to the corps than it devotes to NASA today.

Part of that money was earmarked for York. The Army gave officers who brought along their slaves a monthly ration or its cash equivalent. When the corps made it home, the government paid US$274.57 for York’s labor, a sum similar to what the privates received. But that money didn’t go to York. It went to Clark.

The hidden history of Black explorers

There have been many Black explorers in American history. Thomas Jefferson launched other expeditions besides Lewis and Clark’s, and those expeditions also included enslaved people, though their names have not survived. Isaiah Brown served on the Wheeler Survey, which mapped the West in greater detail after the Civil War. Matthew Henson accompanied Robert Peary on his Arctic expeditions, which received some federal support. More recently, NASA has depended on Black astronauts such as Guy Bluford, Mae Jemison and Jeanette Epps, among others.

York and Victor Glover are, for now, the first and most recent examples of this inspiring tradition. But their contributions go beyond that. When the captains asked York to vote on the winter quarters, they were acknowledging in some small way that he’d proven he was more than a body servant.

Of course, York had always been more than that. It just took 4,000 miles for Lewis and Clark to see it.

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Craig Fehrman, Adjunct instructor at the Media School, Indiana University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Forgotten Genius Fridays is a weekly collection of short videos and articles dedicated to inventors, innovators, scientists, and creators whose impact changed the world—but whose names were often left out of the textbooks.

From life-saving inventions and cultural breakthroughs to game-changing ideas buried by bias, our series digs up the truth behind the minds that mattered.

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