ST. PAUL, Minn. -- In some Minnesota lakes, invasive species are limiting the growth of a popular fish, according to a new study of the effects on walleye.

University of Minnesota researchers say the culprits are zebra mussels and spiny waterflea. They found in lakes where these are present, they can reduce the growth size of walleye from 12% to 14%. The species take away zooplankton, a food source for the fish.

Jeff Forester, executive director of the group Minnesota Lakes and Rivers Advocates, said the findings should spur stronger action by the state to prevent the spread of these species.

"What we've been doing -- this kind of emphasis on education and personal responsibility -- that's not getting it done," he said. "I think it's slowed the spread, but it certainly hasn't stopped it."

Forester said he'd like to see the state adopt more stringent boat-inspection policies, such as making it a requirement for people getting an operator's license. The Department of Natural Resources said that, in coordination with local governments, it conducted more than 500,000 watercraft inspections last year, a record number.

Walleye is a favorite fish for anglers and many resorts rely on its popularity for business. Forester acknowledged that it's a difficult balance for the state because boats are helping to spread these species, but many lake communities are dependent on water recreation.

"How do we use the lakes in such a way that they're protected for the future," he said, "and we're protecting the resource, which is not the lake itself, but the quality of life and the economics."

One of the lakes in the study, Mille Lacs Lake, has seen many controversies surrounding walleye fishing in recent years. The DNR has enforced strong limits for anglers so the walleye population can rebound. Some of those restrictions have been slowly lifted as walleye makes a comeback in the popular lake.

The study is online at springer.com.

By Gabriella Sotelo for Sentient.
Broadcast version by Mark Moran for Iowa News Service reporting for the Sentient-Public News Service Collaboration

The EPA has set its sights on fluoride. The Environmental Protection Agency announced on April 7 that it will “expeditiously” review the health risks of fluoride in our drinking water to inform the agency’s standards under the Safe Drinking Water Act. EPA Administrator Lee Zeldin praised Health and Human Services Secretary Robert F. Kennedy Jr. in the announcement, calling his advocacy on this issue “instrumental.” But while the EPA turns its attention to a compound that’s been widely considered safe and beneficial for decades, its review of a known public health threat — nitrate contamination fueled in part by factory farming — has been stalled for more than a decade and a half.

The interest in fluoride is especially popular among some Republican representatives and constituents in the Make America Healthy Again, or MAHA, contingent. Many in the MAHA movement believe a number of myths about fluoride in the water, seeing it as a symbol of government overreach and a threat to personal autonomy. By contrast, addressing contaminants like nitrates would mean the agency would have to hold polluters in the agriculture industry accountable. That’s a far more politically tricky move, since many Republican lawmakers have close ties to the beef and agribusiness industries, often counting on them for campaign support.

One source of nitrate contamination is manure from livestock operations. Factory farms are responsible for producing 941 billion gallons of animal manure each year, according to Food and Water Watch. This pollution, often overlooked by state and federal environmental agencies, is responsible for toxic runoff that seeps into public waterways, including sources for drinking water.

The apparent disconnect between actual risk and the EPA’s new focus doesn’t sit well with David Cwiertny, the director of the University of Iowa’s Center for Health Effects of Environmental Contamination. “They should at least apply a uniform standard to how they want to reevaluate new science,” Cwiertny tells Sentient. “It would seem that there’s a pretty compelling case that we need to reevaluate science on nitrate, just as much, if not more, than what we need to be doing on fluoride.”

Fluoridation of drinking water was named one of the “ten great public health achievements” of the 20th century by the Center for Disease Control and Prevention (CDC) in 1999. According to a web page from the CDC last updated May 2024, fluoride in the water helps reduce cavities by around 25 percent.

Meanwhile, a 2018 review on nitrate and human health found that nitrate in drinking water was linked to a rare blood disorder, increased risks of colorectal cancer, thyroid disease and certain birth defects.

Despite this, the EPA remains intent on shifting its regulatory attention to fluoride, though it has yet to move forward an investigation of agricultural runoff in drinking water. The agency first initiated a health assessment of risks from nitrates back in 2017, and it remains uncompleted today. The assessment was still in progress in 2018, when it was paused during President Trump’s first term. It was restarted under President Biden, but not completed by the time Trump returned to the White House.

What We Know About Nitrates in Water

Nitrate contamination comes from a number of sources, including human wastewater and synthetic fertilizer, as well as the massive amounts of manure produced by factory farms.

Industrial animal agriculture operations — colloquially referred to as “factory farms” and regulated either as animal or concentrated animal feeding operations (CAFOs) — are significant contributors to nitrate pollution in drinking water sources.

These operations produce vast amounts of manure, and with that comes a lot of nitrogen. As manure decomposes and comes into contact with oxygen in soil, microbial processes in the soil convert both ammonium and organic nitrogen from manure into nitrate. When the manure is spread on fields as fertilizer, the nitrogen that isn’t absorbed by the soil or crop leaches into the groundwater or runs off into nearby rivers and streams, and in doing so can contaminate local water supplies.

“If there’s no regulatory mechanism trying to limit those discharges, it’s really hard to see how we’ll oversee meaningful improvement,” says Cwiertny. “All we can do is think about how we want to limit what’s being applied to land. But that seems to be a conversation folks aren’t going to have.”

Iowa has become a major hub for industrial hog farming, among other types of factory farming operations in the state. Though Iowa has been a major hog producer since the 1880s, the hog population increased in the early 1990s. Iowa’s hog inventory increased from around 15 million in 2004 to around 25 million in 2023.

The state’s many large-scale farms produce 109 billion pounds of manure each year. At the same time, along with slaughterhouses, these operations regularly pollute Iowa’s waterways, contributing to a growing water quality crisis in the state.

In many cases, this contamination has become so pervasive that residents of these areas must rely on filtration systems to remove the nitrates. In Des Moines, the city government’s Water Works operates one of the world’s largest nitrate removal facilities to treat the drinking water to address the nitrate problem.

The EPA’s Slow Response on Nitrates

Nitrate contamination in water has been linked to conditions like “blue baby syndrome,” which reduces oxygen in the blood and can be fatal, and higher rates of certain cancers and thyroid disorders in adults.

The legal limit for nitrate in drinking water is set at 10 milligrams per liter (mg/L), a standard established in 1992. Under the Safe Drinking Water Act, the EPA is required to review and potentially revise these standards, which should include the nitrate limit, every six years. Four reviews have been conducted so far. In the second review, released in 2010, the EPA announced it would assess the health effects of consuming elevated levels of nitrates. The agency also acknowledged concerns regarding developmental effects to babies in the womb from nitrates, as well as potential cancer risks.

Around this time, the EPA also conducted a study on nitrate contamination in Washington State, focusing on the Lower Yakima Valley, where multiple investigations over the past 30 years showed nitrate levels consistently exceeding the EPA’s maximum contaminant level of 10 mg/L. Livestock, primarily dairy farms, were one of three sources of contamination, according to EPA researchers, as the study identified dairy waste lagoons and manure piles, as well as synthetic fertilizers used on irrigated cropland.

In 2017, the EPA announced a 30-day public comment period for their draft IRIS Assessment Plans for nitrate and other contaminants. But this ongoing assessment was paused in 2018, under the first Trump administration.

In 2023, the Biden administration restarted the health risk assessment, but it remains uncompleted. The last status for the 2024 review reads “New information, but no revision recommended because [of] emerging information and/or data gaps.”

“I think it’s safe to say that it’s likely the current administration, if they paused it once before, it’s hard for me to think that they won’t pause it again” Cwiertny says. “And so here we are. 15 years after we realized we need a health assessment and we still don’t have it.”

The Bottom Line

At safe levels, fluoride continues to be endorsed by leading health organizations like World Health Organization and, at least for now, the CDC. In contrast, nitrate contamination from factory farming is a documented threat to public health that has essentially been stalled at the investigation stage for nearly two decades.

“There’s clearly already evidence from the EPA for 15 years that we need to be reevaluating the health assessment for nitrate,” Cwiernty says.

Targeting fluoride seems like a “win” for lawmakers, while addressing nitrate contamination would require regulating the impacts of the meat industry. Sentient reached out to the EPA with questions regarding the recent fluoride announcement and nitrate regulations but received no response.


Gabriella Sotelo wrote this article for Sentient.


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Arkansas lawmakers passed several bills during this year's legislative session to upgrade and improve the state's water and wastewater systems.

One of the measures is Act 578, which would provide $500 million for projects through 2043.

Arkansas Secretary of Agriculture Wes Ward said the state's current infrastructure has been in place for decades, and repairs are constantly needed.

"There's still a very big need," said Ward. "Just about every week, we hear stories of some sort of water-wastewater system failing, or not adequate or needs to expand or needs to contract. All of those infrastructure issues continue."

Act 578 must be approved by voters in the 2026 general election. Lawmakers also passed a $25 million grant program to help municipalities in emergency situations.

More than a half a million dollars in bills were passed during the session to address current and future water needs of all 75 Arkansas counties.

Ward said the state's water plan was updated last year for the first time since 2014.

"We expect when we turn on our faucet that it's going to work and that it's going to be clean and you can use it," said Ward. "We're seeing growing instances where that's not always the case, and so it's incredibly important - we do want people to take it for granted, but they also need to understand there's a lot of infrastructure and things behind the scenes to make that work."

Officials are currently taking an inventory of all levees across the state to ensure they are structurally sound and can function properly during heavy flooding.





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North Dakota is facing growing opposition to two massive dairy operations planned near the Red River. Environmental advocates say the projects could harm water quality locally and in downstream communities - including Lake Winnipeg in Canada.

Madeline Luke, a volunteer with the Dakota Resource Council, said farms proposed in Trail County and Abercrombie would accommodate more than 37,000 animals. She said she believes the massive operations would generate waste on a scale the state has never seen.

"These dairies are situated within a mile and a half of the Red River," she said. "Any water pollution that occurs will go straight into the river and end up in Lake Winnipeg. Lake Winnipeg has been labeled the most endangered lake in the world."

North Dakota's anti-corporate farming law, which once limited large-scale livestock operations, was weakened in 2021, opening the door to more industrial agriculture across the state.

James Beddome, executive director of the Manitoba Eco-Network, said cross-border collaboration is essential, since manure runoff from North Dakota could feed algae blooms in one of Canada's largest lakes.

"Sixty football fields worth of manure slurry, and both of these operations are within one and a half miles of the Red River," he said. "The Red River then connects to Lake Winnipeg. What they're doing there is going to have impacts to us downstream here in Manitoba."

Opponents have argued that the mega-dairies threaten local water, public health and small farms, warning that decisions made in North Dakota could have international consequences. Groups on both sides of the border are urging stricter oversight before permits are finalized.