Updated December 27, 2024 at 17:20 PM ET
Increasing use of nitrogen-based fertilizer over the last half-century is putting Americans' health at risk. Excess nitrate in drinking water increases the risk of cancer, birth defects and thyroid disease.
The Environmental Protection Agency limits how much nitrate can be present in drinking water: a maximum of 10 milligrams per liter. But growing research ties serious health risks to nitrate levels far below that federal limit.
The EPA has spent more than two decades urging states to contain the runoff from Midwest farms that flows into rivers, sources for drinking water, and eventually the Gulf of Mexico. There, the pollution contributes to a dead zone where fish and other wildlife can't survive.
It's a critical concern in Iowa, which has one of the highest rates of nitrate pollution in the United States. Iowa also has the second-highest cancer rate in the country. Studies have linked high nitrate levels in Iowa water to kidney, bladder, thyroid, and other cancers.
In Des Moines, Iowa's capital, the water utility spends up to $10,000 per day when it's required to run its nitrate removal plant to stay in compliance with the EPA. In 2015, the utility ran that plant a record 177 days. Still, drinking water in Des Moines regularly registers just below the federal limit.
Although environmental groups have lobbied for restrictions, Iowa has very few regulations that limit how and when commercial fertilizer can be used. Powerful agriculture groups like the Iowa Farm Bureau and the Iowa Corn Growers have policy statements detailing how they oppose regulating farm runoff. In a statement to APM Reports, the Corn Growers Association wrote, "Regulations and a one-size-fits-all approach do not provide the flexibility needed to address variables such as soil type, weather, geography, management practices, and other factors."
The state's strategy is to try to persuade farmers to use voluntary conservation tools.
But many voluntary options are unpopular because they threaten crop production, reduce field acreage or require changes in farming practices.
One taxpayer-funded tool the state promotes doesn't cause farmers any of those headaches. It's called a saturated buffer. It's being installed on Iowa farms, along with a similar tool called a bioreactor, through a push called "Batch and Build."
Iowa Secretary of Agriculture Mike Naig did not agree to an interview with APM Reports, the investigative reporting unit at American Public Media, but in a press release this year, he said, "Saturated buffers and bioreactors are proven to keep nutrients out of our rivers, lakes and streams and our batch and build model gets them installed efficiently."
Iowa pushes for saturated buffers
Iowa State University researchers invented saturated buffers in 2010. They're made up of subsurface pipes and an above-ground control box. They're designed to capture nitrate from fertilizer, which would otherwise flow through farmers' underground drainage pipes into streams and rivers.
The devices work by rerouting polluted water to a perforated pipe, which is buried along a stream or ditch where it doesn't interfere with the farm. The water seeps into the soil, where microorganisms break down the nitrates.
In 2021, the Iowa Department of Agriculture and Land Stewardship, or IDALS, started the Batch and Build program, which pays farmers to allow saturated buffers on their property. The model of installing the tools in "batches" is meant to keep costs down and make the process more efficient.
The initiative also funds bioreactors, devices similar to saturated buffers, but almost twice as expensive. They only make up about a quarter of installations.
The state's top agricultural interests back Batch and Build. The Iowa Farm Bureau has published articles promoting it, and the Iowa Pork Producers Association invested in the program.
Agriculture Secretary Mike Naig has used Batch and Build as a talking point before federal regulators concerned about Iowa's contributions to the Gulf of Mexico's dead zone. Naig has also boasted about the model spreading to other states. Those include Minnesota and Illinois.
Saturated buffers are not as effective as promised
IDALS has said in press releases that saturated buffers remove at least 40% of nitrogen runoff. That's far different from a 2023 Iowa State University analysis. Scientists studied data collected from saturated buffers over more than a decade and found the minimum nitrate removal was in the single digits – at 7%, much lower than the state claims.
And they're not measuring up to the federal government's expectations, either. In 2024, APM Reports reviewed more than half of the designs for Batch and Build's saturated buffers in Iowa. It found most installed under the statewide initiative fall short of the original federal standard meant to ensure a "minimum level of acceptable quality."
IDALS declined repeated interview requests, but in a written statement, the department's communications director Don McDowell said that in recent years, Iowa has increased the money it spends on conservation tools, put in more nitrate-capturing wetlands, and seen "unprecedented demand" for cover crops that mitigate pollution.
"Saturated buffers are just one of many proven practices in our toolbox, and our team always works with landowners and partners to find the most effective combination of in-field and edge-of-field practices that will be successful on a particular landscape," he said.
The Natural Resources Conservation Service, part of the U.S. Department of Agriculture, created the federal standard to ensure saturated buffer quality. It includes a minimum on how much water the saturated buffer can treat – measured as a percentage of the entire field's drainage capacity.
The NRCS lowered its original standard twice. This allowed buffers to be built in landscapes where they capture less polluted water. Engineers said they have struggled to find farms that accommodate a long enough perforated pipe to meet the original standard.
NRCS engineer Jeff Lutz, who designs saturated buffers for the Batch and Build initiative, said the message from his supervisors and "those who are in influence" in state government is to "'get them done, do them out here, even though some of the treatment levels will vary.'"
The NRCS press office provided a statement saying that Lutz's account does not reflect "NRCS policy and procedures," and that the agency lowered the standard to give "additional flexibility for site-specific needs."
The statement also said the NRCS does not administer Iowa's Batch and Build project, and noted the $8 million the agency has committed for saturated buffers and other conservation projects in Iowa has not yet been spent. It added, "While a number of these state projects have received minor technical assistance from NRCS, funding and oversight falls under the Iowa Department of Agriculture and Land Stewardship and local counties."
Even if saturated buffers worked as intended in Iowa, APM Reports estimated it would take approximately 11,000 of them to remove 1% of the state's annual nitrate pollution load. The state has only installed 178 so far.
Critics and even supporters question the lack of data
"This is such a huge rip off of public money," said retired University of Iowa researcher Chris Jones. Jones, a critic of the Batch and Build program, called the findings "scandalous."
Jones formerly worked for the Iowa Institute of Hydraulic Research, the university's hydroscience and engineering center. He is one of few who speaks out publicly against the state's efforts, through a blog and frequent media appearances.
Many researchers and local officials who spoke with APM Reports refused to openly criticize Batch and Build, or to discuss fertilizer regulation. One scientist whose research is publicly funded said the Iowa Farm Bureau and IDALS "discourage monitoring" of water quality. He then asked that APM Reports not use his name, saying he feared that the Farm Bureau and state officials would try to defund his research.
In an emailed response, IDALS did not address the scientist's allegations.
Polk County, Iowa administrator John Norris said he's not surprised people didn't speak candidly about these topics.
"It's because of primarily the incredible political force of agricultural interests in the state," he said. "Everyone's thought that you can't talk about regulation of these issues. Or you face the backlash of the Farm Bureau, Corn Growers, Pork Producers, you name it."
The Iowa Farm Bureau and Iowa Pork Producers Association did not respond to requests for comment on the statements made by Norris and the unnamed source. The Iowa Corn Growers Association confirmed its opposition to regulation but said it supports conservation practices.
Farmers and local officials who spoke with APM Reports said the state does not follow up to monitor the saturated buffers installed through Batch and Build, despite a legislative advisory committee recommendation that it do so. When asked how the state evaluates success, or if it will test the devices to assess their impact, McDowell sent a link to a dashboard with two-year-old data. It tracks the number of acres treated – not the amount of nitrate removed by the devices.
Even supporters of the program question the lack of data.
"We probably owe the taxpayer some results," said Lee Tesdell, a farmer, landowner, and early adopter of saturated buffers and other conservation technologies. "What good are they doing, if we don't know the data?"
One of the biggest boosters of saturated buffers is John Swanson, the Polk County official who leads Iowa's largest Batch and Build.
Swanson said in a state where farmers are not obligated to mitigate nutrient pollution, many different voluntary practices need to be adopted, and they need to be adopted en masse. "It's kind of like, do nothing or do the best we can."
But Laura Krouse, a farmer and Linn County, Iowa, soil and water commissioner, said she fears the point of the program is to make the state look like it's addressing water pollution without fundamentally changing farming practices.
"My main criticism of the Batch and Build program is that it's being used for somebody to look good," said Krouse, adding that it allows IDALS to "look like they're doing something far more than they actually are to improve water quality."
When asked to respond to that criticism, IDALS did not provide a comment.
There are more effective ways to clean up pollution, Krouse said, including addressing it directly at the source. Farmers can use less fertilizer, she pointed out. They can limit tilling so nitrates seep through the soil less easily.
Rotating other crops with corn and soybeans is also an effective practice, though it would challenge Iowa's dominant corn-soy economy.
"There's lots of things you could do to keep the nitrate out of the water, but they're all hard," Krouse said. "Because they all require change from this perfectly tuned system that we have in Iowa to grow a lot of corn."
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