Iowa has the second-highest rate of cancer incidence in the United States, according to the Iowa Cancer Registry. The state is one of only a few in the country with a rising rate of new cancer cases, and this can be blamed in part of the operations of confinement hog farms. Many public health and environmental experts point to water quality as a leading cause of this public health crisis—a 2020 investigation by the Environmental Working Group found that Iowa has among the most widespread nitrate contamination of drinking water in the U.S.

“Something that is very difficult living in Iowa is this constant level of anxiety over the fact that you don’t know what kind of cancer you’re going to get,” says John Gilbert, a fourth-generation family farmer near Iowa Falls. “It’s in the back of your mind all the time that you’re living in dangerous times in a dangerous place.”

Nitrate pollution in Iowa’s water is largely due to overuse and misuse of artificial fertilizer and mismanagement of manure from confined animal feeding operations (CAFOs), particularly confinement hog farms. Iowa is the leading hog producer in the United States, with more than one-third of the nation’s hogs, according to the Economic Research Service. More than 25 million hogs outnumber people in Iowa by a ratio of 7 to 1. And as the state’s pork production nearly doubled from 2000 to 2023, so did its manure production.

“CAFOs have more manure than the crops can reasonably use as fertilizer,” says Michael Schmidt, General Counsel at the nonprofit Iowa Environmental Council (IEC). While information on fertilizer and manure application is not publicly available, “we can assess at a large scale. We know there’s more manure than the crops need and know that synthetic fertilizers are being oversold.”

Almost half of Iowa’s cropland uses tile draining, which removes excess water from fields through a network of underground perforated pipes and releases it into drainage systems. This means that when fertilizer and manure are overapplied to farm fields, excess nutrients are fed straight into water systems. That contaminates drinking water for Iowa residents and fuels algae blooms and dead zones downstream in the Gulf of Mexico.

Read the full article about CAFOs in Iowa by Emily Payne at Food Tank.