Report Linking Nitrates to High Iowa Cancer Rates Carries Lessons for Agricultural Communities Across the United States

According to the IEC-Harkin report, in some areas of Iowa, agricultural sources are responsible for 80% of water nitrate contamination. The findings have sweeping implications for communities across the country where excess fertilizer, manure, and other agricultural runoff threaten water quality and pose risks to public and environmental health.

An earlier report by the Union of Concerned Scientists (UCS) found that in the United States, corn and soybean producers alone overapply millions of metric tons of fertilizer each year. The UCS report also quantified the significant harms that fertilizer overapplication causes for the environment, atmosphere and farmers' operating margins.

Fertilizers provide nutrients like nitrogen and phosphorus that crops need to grow and thrive. But today's agricultural system, shaped by a powerful fertilizer industry and other corporate interests, pressures farmers to apply far more fertilizer than crops can use.

Dr. Stacy Woods, research director for the Food and Environment Program at UCS, explains how excess fertilizer pollutes U.S. drinking water supplies in places like Iowa and across the Midwest.

"Only about half of the fertilizer applied to fields is actually used by plants, while the rest builds up in soil, pollutes the air, leaches into groundwater, and washes into streams and other waters," said Dr. Woods. "As the joint report on cancer in Iowa shows, fertilizer runoff entering our water supplies can carry a hidden but devastating cost to our health."

In Polk County Iowa, in particular, agriculture is responsible for about 80% of nitrate contamination in Des Moines and Raccoon rivers and has made its way into the state's drinking water supply. Low-income residents, older adults, very young children and people of color in Iowa may face even greater nitrate exposure than the general population.

While Iowa has taken some action to cut nitrogen and phosphorus pollution, the problem persists. The IEC-Harkin report found that only 4 percent of community water systems in the state have the capability to remove nitrate from water supplies.

"Much of the cost of nitrate pollution currently falls at the faucet, as communities and households pay high prices to remove it from their drinking water," writes Dr. Woods. "But preventing nitrate pollution at the field before it enters the water supply is the most effective way to reduce the public health risks of nitrate pollution."

According to Dr. Woods, robust and well-funded conservation programs can help farmers adopt agricultural practices that can dramatically reduce fertilizer runoff and nitrate pollution in wetlands, rivers, streams and groundwater. These sustainable farming practices include planting native plants, using cover crops, and preserving wetlands to limit runoff, as well as utilizing crop rotation and diversification strategies to maintain healthier soils. Federal conservation programs and subsidy rules can incentivize water- and soil-friendly farming practices to better protect water quality and provide real public health benefits for communities.