Iowa Has a Cancer Problem—and Nobody Can Explain Why

 

Iowa has a cancer problem.

The state has the second-highest cancer rate in the country. From 2018 through 2022, it averaged 499 new cases for every 100,000 people. The national average was 449.

If you packed 100,000 people into a football stadium, 50 more Iowans would get cancer than the average American crowd.

Only Kentucky has a higher rate.

Here’s what should really bother Iowans. Cancer rates have been dropping across much of the country, but Iowa is going the other way.

The 2026 Cancer in Iowa report estimates 21,700 Iowans will be diagnosed with invasive cancer this year—6,400 will die from it. Five years ago, the state estimated 18,900 new cases.

Iowa is getting older, and cancer is more common as people age. Researchers know that. That’s why cancer rates are adjusted for age, making it possible to compare Iowa fairly with younger states.

Even after that adjustment, Iowa is still near the bottom of the pack.

Researchers know which cancers are driving the numbers. Figuring out why is proving much harder.

Melanoma is one of the biggest problems.

In 2022, 400 more Iowans were diagnosed with melanoma than you’d expect based on the national rate. That’s over 15 percent of Iowa’s extra cancer cases.

Iowa’s melanoma rate is about 34 cases per 100,000 people. The national rate is closer to 24. For every five melanoma cases you’d expect nationally, Iowa has seven.

The obvious suspect is the sun. Iowa has a large white population and generations of farmers, roofers, construction workers, and others who have spent their lives outdoors. Tanning beds may also play a role, especially among women.

But melanoma isn’t the entire story.

Prostate, breast, and melanoma cancer rates are rising in Iowa. The state also has the highest rate of oropharyngeal cancer in the country. That’s cancer of the back of the throat, tonsils, and base of the tongue. Many cases are linked to HPV.

Lung cancer remains one of Iowa’s biggest killers.

Iowa had 376 more lung cancer cases than expected in 2022. Prostate cancer added another 331. Colorectal cancer accounted for 189 extra cases, and female breast cancer another 141. Add melanoma, and those five cancers account for more than half of Iowa’s extra cancer cases.

If Iowa could bring those five cancers down to national rates, 1,400 Iowans a year might avoid a cancer diagnosis. That’s almost four people every day.

Prostate cancer is especially puzzling.

Iowa’s rate was 129.5 cases per 100,000 men from 2018 through 2022, compared with 116.4 nationally. Iowa’s prostate cancer rate has also been climbing about 3.3 percent a year.

Researchers found unusually high numbers of cases in 18 western and northwestern Iowa counties. Another 16 counties in eastern and northeastern Iowa had the same problem.

Then they ran through the usual explanations. Obesity. Drinking. Smoking history. Medical checkups. PSA testing. Insurance. Race. The gap got smaller, but it didn’t go away. Several northwest Iowa counties still had more prostate cancer than the models predicted. Linn County did, too.

If you look at northwest Iowa on a map, an obvious question pops up. This is serious farm country. Hogs, cattle, corn, soybeans, fertilizer, manure, and pesticides are part of everyday life.

That doesn’t mean farming causes prostate cancer. If it were that simple, researchers would have solved this years ago. But it raises a fair question. What are Iowa men being exposed to that researchers haven’t measured yet?

The Agricultural Health Study has been trying to untangle questions like that since the 1990s. It follows farmers, pesticide applicators, and their spouses in Iowa and North Carolina.

Here’s where things get weird.

Iowa farmers developed 13 percent fewer cancers overall than expected. They had less lung, colorectal, and bladder cancer.

Then you get to prostate cancer.

Iowa farmers had 20 percent more prostate cancer than expected. Over 22 years, 1,928 Iowa farmers in the study were diagnosed with it.

Researchers have also connected heavy exposure to certain pesticides with higher risks for specific cancers. That doesn’t prove pesticides are causing Iowa’s prostate cancer problem. Farmers may get tested more often. Genetics could matter. Other workplace exposures may be involved.

Still, when prostate cancer keeps popping up in farm country, and farmers already have more of it than expected, it’s hard not to ask questions.

Breast cancer is a mystery of its own.

Eleven Iowa counties had more postmenopausal breast cancer cases than expected. Six formed a cluster in central Iowa. Again, researchers ran through the usual suspects: obesity, drinking, mammograms, education, insurance, and demographics.

Harrison, Warren, and Washington counties still had more postmenopausal breast cancer than predicted. Tama and Johnson counties showed higher-than-expected rates of premenopausal breast cancer.

Nobody knows why.

The overall county numbers are even harder to ignore. Researchers compared Iowa’s 99 counties with national cancer rates and found 87 had more cancer cases than expected.

Imagine a classroom with 99 kids. The teacher gave everyone the same test, and 87 came back with the same red warning mark. At some point, you stop blaming individual students and start asking if there’s a bigger problem.

In 2022 alone, Iowa had about 2,582 more cancer cases than expected based on national rates. That’s seven extra cancer diagnoses every day.

Researchers fed smoking, obesity, binge drinking, medical checkups, insurance, screening, race, and other factors into their models. They explained some of Iowa’s cancer problem, but not all of it.

Thirteen counties still had overall cancer rates significantly higher than predicted: Linn, Jackson, Clinton, Tama, Des Moines, Wapello, Appanoose, Marion, Cass, Woodbury, Cherokee, Palo Alto, and Floyd.

Researchers found 13 counties doing worse than expected. Zero were doing better.

The counties don’t line up in a neat row on a map. Some are in northwest Iowa. Others sit along the Mississippi River or in southern Iowa. Linn County includes Cedar Rapids, one of the state’s biggest cities.

Some are heavily agricultural. Some have industry. Some are rural. Some aren’t. There’s no giant X on the map telling researchers where to dig.

Palo Alto County may be the scariest example.

The northwest Iowa county has fewer than 9,000 people, but its cancer rate was far above the national average in one five-year analysis: 658 cases per 100,000 people, compared with about 442 nationally.

Put another way, in a town of 10,000 people, the national rate would mean about 44 new cancer cases a year. Palo Alto County’s rate is 66.

That’s 22 extra people hearing the words, “You have cancer.” In a small town, that’s not a statistic. That’s your former teacher, the guy who fixed your truck, or somebody you sat next to at a basketball game.

At one point, Palo Alto County ranked second among all U.S. counties for cancer incidence. People there started asking the obvious question. What the hell is going on?

Palo Alto is farm country. So are Cherokee, Woodbury, Cass, Marion, Tama, Appanoose, and Floyd counties.

It’s tempting to point at agriculture and say, “There’s your answer.” But Iowa is covered in farmland. If farming alone caused the state’s cancer problem, the map should light up almost everywhere.

It doesn’t.

Nitrates are another suspect. Fertilizer and manure can push nitrates into Iowa’s rivers and groundwater. A 2025 study examined 871 public water systems across the state. About 7.4 percent of the people served by those systems had been consistently exposed to nitrate levels above 5 milligrams per liter.

The federal limit is 10.

That means water containing 6, 7, or 8 milligrams can still be perfectly legal. The question researchers are asking is whether legal means safe over a lifetime.

Think of an old bridge with a posted weight limit. The limit may keep the bridge from collapsing today. That doesn’t tell you what happens after thousands of heavy trucks cross it for 40 years.

That’s basically the nitrate debate.

The federal nitrate limit prevented an immediate health problem known as blue baby syndrome. It wasn’t created to answer what happens when someone drinks lower levels of nitrate for decades.

Some studies have found links between long-term nitrate exposure and colorectal cancer. Iowa had 189 more colorectal cancer cases than expected in 2022.

That doesn’t prove nitrate caused them, but it’s enough to keep researchers looking.

Then there’s radon.

Every Iowa county is considered at high risk for radon exposure. The radioactive gas comes naturally from the ground and can collect inside homes. You can’t see it or smell it. Your basement can look exactly like your neighbor’s, while one has a serious radon problem and the other doesn’t.

Radon is the leading cause of lung cancer among nonsmokers.

Iowa had 376 more lung cancer cases than expected in 2022. Smoking explains many of them. Iowa has a long history of tobacco use, and cancer can show up decades after someone quits.

But Iowa also has a known cancer-causing gas collecting in homes across the state. Nobody knows how much it’s adding to the total.

A recent Lynn County cancer report found its overall cancer rate was higher than both Iowa’s and the national rates. Prostate cancer was a major concern among men, and the incidence of advanced lung cancer was unusually high.

Researchers mapped industrial air emission facilities against cancer patterns. They didn’t find a smoking gun.

A factory sitting near a cancer cluster doesn’t prove the factory caused the cancer. Cancer isn’t a pothole. You can’t point to the spot where the damage happened.

A cancer diagnosed today may have developed 20 years ago. The person may have moved three times. They may have drunk well water as a child, city water as an adult, and bottled water at work.

Maybe they sprayed chemicals on a farm. Maybe they worked in a factory, smoked for ten years, quit, and lived in a house with high radon.

Now try to figure out which exposure mattered.

That’s the job Iowa cancer researchers are facing. The list of possible suspects keeps growing: pesticides, nitrates, radon, industrial air pollution, PFAS chemicals, alcohol, smoking, obesity, sun exposure, HPV, and genetics.

Maybe one is the major problem.

More likely, Iowa’s cancer problem is a stew. A little of this. A little of that. Decades of exposure piling on top of one another until something finally goes wrong.

The young adult numbers make that possibility especially uncomfortable.

Between 2018 and 2022, 4,006 Iowans between the ages of 20 and 39 were diagnosed with cancer. That’s about 801 young adults every year, or over two every day.

Iowa ranks second in the nation for cancer incidence among people in that age group. The good news is they aren’t dying at a higher rate than young adults nationally. More cancers are being caught early, and treatments have improved.

But that dodges the bigger question.

Why are so many young Iowans getting cancer in the first place?

Researchers don’t know.

Iowa is spending millions of dollars trying to find out. The state’s Key Drivers of Cancer in Iowa project began in 2025, digging into lung cancer, melanoma, colorectal cancer, HPV-related cancers, environmental exposures, and genetics.

The early findings have already knocked down one easy explanation.

Iowans don’t simply have more cancer because they smoke too much, drink too much, and weigh too much. Those things matter, but they don’t explain everything.

The 13 counties with higher-than-predicted cancer rates are obvious places to look harder. So are the northwest Iowa counties with unexplained prostate cancer and the counties showing unusual breast cancer patterns.

Researchers need better information about environmental exposures, genetics, and healthcare. They need to find what isn’t showing up in the spreadsheets yet.

There’s another question hanging over Iowa.

Will any of this affect the state’s population?

So far, there’s no solid evidence people are leaving Iowa because of cancer rates or environmental concerns. But until recently, most Iowans probably couldn’t tell you that the state ranked second in the nation for cancer incidence.

Now that information is everywhere.

People know that 87 of Iowa’s 99 counties had more cancer than expected. They know 13 remained unusually high after researchers accounted for many of the obvious explanations.

They know Iowa farmers have more prostate cancer than expected and young adults have the second-highest cancer incidence rate in the country. They know researchers are looking at the water, the air, the soil, and even the basements of Iowa homes.

That’s not exactly the picture Iowa likes to sell. For generations, Iowa has presented itself as a healthy place to live. Clean air. Open spaces. Small towns. A good place to raise kids.

The cancer numbers muddy that picture.

Maybe it never hurts population growth. Maybe it does. Right now, nobody knows.

What Iowa knows is that roughly 21,700 people are expected to be diagnosed with invasive cancer this year. That’s about 59 Iowans every day.

Fill a school bus with people in the morning. By the end of the day, that’s roughly how many Iowans will have received a cancer diagnosis.

Tomorrow, fill another bus.

Iowa knows which cancers are causing much of the damage. Researchers have found counties where the numbers are worse than they should be and tested many of the easy explanations. The math still doesn’t work.

Now Iowa has to figure out what’s missing.

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