Iowa factory farms drive nitrate pollution and rising cancer rates

Iowa contains 10,830 factory farms, the highest number of any U.S. state. The massive scale of animal agriculture produces manure levels that exceed the absorption capacity of local crops, leading to significant nitrate runoff into groundwater, streams, and lakes.

In 2024, more than half of Iowa’s rivers and streams and over 60% of its lakes and reservoirs failed water quality standards. This pollution poses a public health threat, as high nitrate levels in drinking water are linked to increased risks of colorectal, kidney, thyroid, prostate, and breast cancers. Iowa currently has the fastest-growing cancer rate in the nation, with rates for these specific cancers exceeding the national average.

Des Moines manages a large-scale system to remove nitrate pollution at a cost of $10,000 per day. While the crisis is most acute in Iowa, similar dynamics are observed in other agricultural states like North Carolina, Minnesota, and Georgia. An Environmental Working Group analysis suggests nearly 20% of Americans have high levels of nitrates in their drinking water. Currently, the Iowa Department of Natural Resources does not collect records on where companies apply manure, as such information is legally confidential in the state.