When it comes to the chemical free-for-all that generally characterizes industrial agriculture’s approach to modern farming, there’s no doubt that the public has become increasingly wary of pesticides. But what about all that fertilizer?

Somehow, the chemicals used to feed crops don’t seem to have aroused quite the same level of suspicion as those used to kill weeds and pests. Most of us are at least vaguely aware that fertilizer-laden runoff—not to mention waste seeping from huge factory farms—has been blamed for today’s toxic algae blooms and the 6,000-square-mile “dead zone” in the Gulf of Mexico, which sounds like a sci-fi ecological horror film that happens to be true.

But a report released this week from the heartland—which is to say, the heart of industrial farming—suggests that we might do well to start worrying about what the deluge of fertilizers is doing to our bodies too.

Just as it has taken years for the public to begin to accept that carbon dioxide, of all things—the stuff we exhale—could possibly be a pollutant and responsible for global warming, the same might be said for the nitrogen found in fertilizers. After all, nitrogen comprises nearly 80 percent of our atmosphere. How bad could it be?

Well, in addition to those toxic algae blooms, the folks at the Iowa Environmental Council found in a review of prior research that consumption of drinking water containing higher levels of nitrates—nitrogen-based compounds often associated with fertilizer runoff—has been linked to a number of human health effects. Those include birth defects related to brain and spinal development as well as bladder and thyroid cancers.

“While more research is needed, the current findings offer compelling reasons to accelerate efforts to reduce pollution from nitrate flowing into our surface and groundwater from farm fields, urban yards, livestock facilities, water treatment plants, and other sources,” Ann Robinson, an agriculture policy specialist with the group and lead author of the study, said in a statement.

Medical science has known for years that excess nitrate consumption is especially dangerous for infants. It’s tied to a terrifying condition known as blue baby syndrome. Babies fed formula made with nitrate-contaminated water could develop a potentially fatal condition when the contaminants interfere with the body’s ability to circulate oxygen in the blood, turning the skin blue.

The Environmental Protection Agency sets the limit for nitrates in drinking water at 10 milligrams per liter, a threshold shown to prevent blue baby syndrome. But the review conducted by the Iowa group raised new concerns over potential health risks from water containing levels of nitrates below the federal standard—especially if other agricultural chemicals are present as well. In one study, for example, a higher prevalence of bladder cancers was found in women who were exposed to water for four years or more with nitrate concentrations greater than half the EPA’s limit.

While the public may not yet be clamoring for answers about nitrate pollution, public water utilities have been grappling with the problem for years. It’s an imperative for them in more ways than one: Getting nitrates out of drinking water is expensive. In Iowa, the Des Moines Water Works is suing three of the state’s “drainage districts”—essentially industrial ag strongholds—to recoup costs associated with nitrate contamination of the municipal water supply. The utility has said it may have to build a new $183.5 million nitrate-removal facility in the next four years.

Iowa is by no means alone. Although the state is home to plenty of big farms, a map produced by the U.S. Geological Survey shows a moderate to high level of risk for nitrate contamination of groundwater across a huge swath of the Midwest—from Minnesota and North Dakota to the tip of Texas. There are also high-risk clusters in ag-heavy regions such as California’s Central Valley, southeastern Washington state, and poultry-dense North Carolina and Maryland.