1 in 5 Americans may have a dangerous toxin in their tap water

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(CNN) — Over 62 million Americans — roughly 1 in 5 people — may be exposed to potentially dangerous levels of nitrates in their tap water, a new report has shown.

A compound of nitrogen and oxygen found naturally in air, water, soil and plants, nitrates become a health risk when rainfall causes nitrogen-rich fertilizers used in agriculture to leach into groundwater, streams and rivers and end up in public water systems miles downstream.

Invisible, tasteless and odorless, nitrates at low concentrations in drinking water have been linked to thyroid disease, gastric, kidney, bladder and colon cancers, preterm births and birth defects, and other health harms, according to the report released Thursday by the Environmental Working Group, or EWG, a nonprofit health advocacy organization.

Thirteen-year-old Ben is so concerned about nitrates in the tap water of his hometown of Des Moines, Iowa, that he recently sent his local congressman a letter and poem.

“I remember when I could drink water from the faucet, but now it is a health concern,” Ben wrote Iowa State Rep. Dr. Austin Baeth. “Please don’t ignore this problem!”

Des Moines is a hot spot for nitrate pollution in source water, with levels so high in local rivers the city had to build one of the largest nitrate removal plants in the world. The cost to operate is more than $10,000 a day.

“I’ve read Ben’s letter and poem numerous times, and I still get choked up,” said Baeth, an internist who is calling attention to Iowa’s nitrate levels with hard-hitting, sometimes satirical videos on social media. “Isn’t it sad children have to worry about water that might be harming their health?”

Dangers at lower levels of exposure

Federal guidelines established in 1962 — which have never been updated —set nitrate safety levels at 10 milligrams per liter. A growing number of peer-reviewed studies, however, show an association with health impacts at 5 milligrams, 3 milligrams, and even as low as 2 milligrams per liter.

To see how many Americans are exposed to nitrates at those lower concentrations, researchers used the EWG tap water database, which aggregates data from nearly 50,000 public water systems in the United States.

“We used measurements of nitrates in public drinking water between 2021 and 2023 in cities and towns in all 50 states, mapping exposure down to 3 milligrams per liter,” said report author Anne Schechinger, EWG’s senior director of agriculture and climate research.

“This is a first-of-its-kind map — no one has done this before,” Schechinger said. “And it’s searchable by zip code so people can go and check their own levels of nitrates and other contaminants.”

The report does not cover private well water, which is not regulated by the US Environmental Protection Agency.

More than 6,000 community water systems, serving more than 62.1 million people, tested at or above the 3 milligrams per liter of nitrates, according to the report. Studies have linked these levels to pediatric cancers and other health harms.

More than 3,200 of the 6,000 systems tested at or above 5 milligrams per liter, a level connected to colorectal and ovarian cancer.

The Los Angeles Department of Water and Power, which serves nearly 4 million people, tested at or above 3 milligrams per liter on 255 different occasions, the report found. Other major cities with more than 1 million residents that also tested at 3 milligrams per liter or above included Phoenix; Philadelphia; Las Vegas; San Jose, California; and Columbus, Ohio.

A spokesperson for The Fertilizer Institute, which represents industry, told CNN in an email that US farmers have doubled corn production over the past three decades with just a slight increase in fertilizer use.

“Nitrate is a naturally occurring compound found throughout the environment,” said TFI Vice President of Public Affairs Christopher Glen. “While fertilizer is one source, others include organic matter mineralization, septic systems, urban stormwater, and atmospheric nitrogen deposition from industrial and vehicle emissions. Attributing elevated nitrate levels in drinking water primarily to fertilizer use, as the EWG report implies, oversimplifies a complex issue.”

Extremely high contamination from well systems

More than 3 million people, served by 606 water systems in the US, were exposed to nitrates at or above the legal limit of 10 milligrams per liter.

Seventy of those systems had nitrate levels at or above 20 milligrams per liter, twice the federal limit. Another 21 systems contained levels at 30 milligrams per liter or even higher: A water system serving 31 people near Dinuba, California, tested at 50 milligrams per liter — the highest in the nation.

Most of the communities with the highest levels were quite small, serving under 1,000 people, but not all. More than half a million people in Fresno, California, used tap water with up to 14 milligrams of nitrate per liter.

More than 35,000 people in Garden City, Kansas, were exposed to up to 37 milligrams of nitrate per liter, while some 32,000 people in Laverne, California, used tap water with 26 milligrams per liter.

“Nearly all of the water systems with extremely high levels are groundwater systems that obtain their water from local wells,” said biologist and chemist Christopher Jones, a former research engineer at the University of Iowa who monitored the state’s water quality. Today, Jones is running to be Iowa’s next secretary of agriculture.

“Having 40 milligrams per liter in groundwater is not unheard of, not at all,” said Jones, who was not involved in the EWG report.

The primary sources of nitrates in groundwater are from livestock manure and other nitrogen-rich fertilizers placed on crops by farmers and ranchers, experts said.

Without proper safeguards, rainfall and water irrigation flow easily into groundwater and into wells, while also spilling into rivers and streams that feed into public water systems. And you don’t have to be close to agriculture to be affected, Schechinger said.

“The nitrate contamination can affect people far, far downstream from farms,” she said. “Your water may come from a reservoir outside your major city, but the stream or the river that feeds that reservoir comes from miles and miles upstream where farms may be.

“Although it’s an agricultural issue, it affects people across the country in really tiny, rural towns and really large cities,” Schechinger said.

What can be done

Public water systems that regularly test at levels above the legal limit of 10 milligrams per liter are required to notify residents and take action to clean the water.

That requires expensive mitigation systems — costs that water utilities often pass on to the consumer. Des Moines spent more than $4 million in 1990 to construct its ion-exchange treatment plant.

For consumers, the best choice is a reverse osmosis system, which forces water through a semipermeable membrane that captures up to 99% of contaminants, Jones said.

“You want to put the reverse osmosis system on your cold-water kitchen tap and then use that for drinking and for making coffee and cooking,” he said. “There’s no need to put it on the whole house — there’s no risk associated with bathing in high-nitrate water or washing dishes and the like.”

If you use water from a filter on a refrigerator, that also needs to be connected to the reverse osmosis system, he said.

“Don’t turn to bottled water as a solution — it’s less regulated in general than tap water,” Schechinger said. “Just look up your zip code in our tap water database to see if you need to filter or not. We also provide information about at-home water filters as well.”

Until tighter regulations are passed, it’s up to the consumer to decide on a course of action, experts said.

“It’s a peace-of-mind issue,” Jones said. “If you know the water coming out of your tap is above 3 milligrams per liter of nitrates and you want peace of mind, then I think a reverse osmosis system on the kitchen cold tap is advisable.”

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