Iowa has the second-highest cancer rate in the nation, and it is the only state where cancer cases are rising. What gives?
For more than 50 years, the Iowa Cancer Registry at the University of Iowa has tracked cancer rates in Iowa. For all that time, Iowa cancer trends tracked the national averages.
That all changed around 2015, when Iowa cancer rates suddenly began rising faster than national averages. And the trend continues.
Iowa now has the second-highest cancer rate in the U.S., behind Kentucky. And cancer rates are growing faster than any other state in the nation, according to the 2024 Cancer in Iowa report.
What’s Driving the Growing Rates?
What’s causing cancer rates in Iowa to outgrow national averages?
One could point to the usual suspects for increasing cancer risk: an aging population, earlier detection, cigarette smoking, obesity, a sedentary lifestyle.
However, these risk factors are at the same levels in Iowa as in other states.
Other factors include radon and arsenic in the drinking water, but these factors haven’t changed for 50 years, so they also can’t account for the growing cancer rates.
Are the high rates of binge drinking in Iowa a factor? This was the claim in the 2024 Cancer in Iowa Report released in February.
However, as many researchers were quick to point out, Iowa binge-drinking rates have not changed significantly in recent years. And other states, like Montana and North Dakota, have higher binge-drinking rates—but no rise in their state cancer profiles, according to a report from the CDC.
To really get to the root cause of the rise in Iowa cancer rates, researchers note that we need to look at what has happened in Iowa that isn’t happening to the same extent in other states.
“What needs to be looked at are things that are probable or possible carcinogens that have increased beginning about 1990, because of the well-recognized latency of environmental cancers,” says James Merchant, a retired professor of occupational and environmental health at the University of Iowa, in an article in the Des Moines Register.
Most notable? The changing agricultural practices over the past two decades could be driving the trend, notes Merchant.
“The carcinogens associated with industrial agriculture are the ones that really need to be looked at very closely,” he says.
Changing Agricultural Practices
Undeniably, growing cancer rates are caused by numerous interacting factors. However, increasingly, health advocates, doctors, and cancer researchers point to a growing body of evidence linking greater exposure to agricultural chemicals to the growing cancer rates.
“If you did an aerial map of Iowa, we are—river to river and north to south—a bath of ag chemicals: herbicides, pesticides, fertilizers, nitrates,” said Dr. Richard Deming, a Des Moines oncologist, at the Cedar Rapids Gazette’s Iowa Ideas conference last fall.
Two things have changed in Iowa agricultural practices since the 1990s: the growth of CAFOs (Concentrated Animal Feeding Operations) and the explosion in the use of herbicides with the introduction of herbicide-resistant genetically modified crops.
Health advocates and environmentalists are quick to point out that Iowa has some of the highest usage of nitrate fertilizers and herbicides like glyphosate, as well as the largest amounts of animal manure from confined feeding operations in the country.
The Growth in Concentrated Animal Feeding Operations (CAFOs)
The growth in CAFOs has increased almost fivefold since the 1990s, from 789 to 3,936, according to a 2020 report from the Environmental Working Group. Ninety-four percent of that growth came from hog operations.
This has exponentially increased the animal manure released in the state. The amount of livestock manure Iowa now generates is equal to the waste produced by 168 million people, or half the entire U.S. population, according to a report on “The Costs of CAFOs—Impacts on Your Wallet and Your Health” released in 2023 by the Iowa Environmental Council.
“Most of this manure is not treated before being applied to cropland as fertilizer, which then can run off fields in stormwater, infiltrate soil, and pollute groundwater, or reach surface waters via tile drainage,” the report notes.
This, along with growing use of fertilizers, has contributed to high levels of nitrate in the Iowa drinking water.
This in turn could be one smoking gun for higher cancer rates.
“High levels of nitrate in the drinking water has been linked to a long range of health issues,” notes the Iowa Environmental Council in a 2024 report on “Nitrates in Drinking Water.” “This includes increased risk of bladder, colorectal, kidney, ovarian, and thyroid cancers, as well as increased risk of childhood cancers.
The Exponential Rise in Herbicide Use in Iowa
Another factor that has changed significantly in Iowa agriculture since 1990?
The exponential growth in the use of herbicides, particularly glyphosate, the main ingredient in the herbicide Roundup.
Roundup has been around since the early 1970s. However, in 1996, biotech company Monsanto introduced genetically engineered crops formulated to be resistant to Roundup.
Today, almost 90 percent of corn, cotton, and soybean seeds planted are modified to be tolerant to glyphosate, and the use of Roundup has risen more than tenfold, U.S. Department of Agriculture data shows.
Agricultural Success Story or Public Health Peril?
The introduction of GMO crops has long been touted as a great success story, reducing pest issues and increasing farmers’ yields and profits. More recent studies have questioned whether this actually is the case, however.
A 2020 study funded by the German government and published in Crop Protection sorted through 11,900 published studies on glyphosate use to find studies showing evidence of increased yields. Only a small number of those studies actually looked at yields, and the study authors note that “based on the studies we found, we conclude that there is no scientific basis for published economic calculations on glyphosate benefits.”
At the same time, increasing research is questioning the safety of the extensive glyphosate use on the health of humans and the environment.
In 2015, the International Agency for Research on Cancer (IARC), a subdivision of the World Health Organization, classified glyphosate as “probably carcinogenic to humans.”
The IARC conclusion was based on numerous scientific studies that found an association between glyphosate exposure and non-Hodgkin’s lymphoma (NHI).
The IARC classification triggered a wave of lawsuits against Monsanto from people with some type of non-Hodgkin’s lymphoma who had used Roundup, the main herbicide containing glyphosate.
In March 2024, Monsanto (now owned by giant Swiss biomedical company Bayer) agreed to pay out $11 billion to settle nearly 100,000 Roundup lawsuits. Monsanto estimates that more than 54,000 active Roundup lawsuits remain.
Glyphosate has been linked to other cancers, including acute myeloid leukemia and large B-cell lymphoma.
Beyond Cancer: Charting the Neurotoxic Effects of Glyphosate
Glyphosate has the ability to cross the blood-brain barrier, and recent studies have linked urinary levels of glyphosate to neurological effects.
A 2023 study in Environmental Research reported that higher urinary glyphosate levels were linked to lower cognitive ability on a test for Alzheimer’s as well as greater odds of depressive symptoms and risk of serious hearing difficulty.
Childhood exposure to glyphosate may be linked to liver inflammation and metabolic disorders in early adulthood. These are issues that could lead to liver cancer, diabetes, and cardiovascular disease later in life, according to a study by the UC Berkeley School of Public Health.
Beyond Humans: Ecological Impacts of Glyphosate
Roundup has been touted as being benign to non-target plants, soil, and animals. However, a growing number of studies are finding that glyphosate can have much greater ecological impact than previously assumed, including on the microorganisms in the soil, aquatic creatures, and bees.
A 2022 meta-analysis of 16 studies published in Science of the Total Environment found a link between glyphosate exposure and increased bee mortality.
Environmental researchers warn that the ecological impacts can have serious consequences as glyphosate levels build up in the environment and affect the tiny organisms at the base of the food chain.
“No herbicide in the history of the world has ever been used this heavily. It’s a completely unprecedented case,” says researcher Charles Benbrook in an Environmental Health News article.
Given growing concerns about the health and environmental risks, will glyphosate use get regulated any time soon? For comparison, it took more than 20 years before evidence of the adverse environmental effects of DDT led to the EPA banning its use in 1972.
The GOP-led Iowa Senate is currently working on legislation to ban lawsuits claiming damage from Roundup use.
Fortunately, there are many things you can do to mitigate your personal risk to issues created by both nitrate and glyphosate.