IEC Explainer: Nitrates and Public Health

What is Nitrate and Where Does it Come From? 

Nitrates are naturally occurring chemicals found in soil, water, and air. They contain nitrogen and oxygen, which are required by plants and animals for growth and development. Nitrates are negatively charged particles (ions), so they bond to other substances in the environment and dissolve easily in water. Nitrates are also found in fertilizers, livestock waste, and septic systems. Unfortunately, nitrate compounds are overabundant in Iowa’s environment due to the extensive use of fertilizer and spreading of animal manure. Iowans are directly exposed to nitrate pollution in drinking water supplies when nitrate dissolves in water in high concentrations and runs off the land into Iowa’s streams and seeps into the groundwater. The source of nitrate exposure is important when considering human health, whether the nitrate originates from food, polluted drinking water, chemical products, or trace amounts in dust particles, because ingesting too many nitrates can be harmful for human health. 

Federal Nitrate Standards and Human Health 

Elevated nitrate levels in Iowa’s water have been a source of concern for decades, particularly for the health of the most vulnerable Iowans. The federal nitrate drinking water standard of 10 milligrams per liter (mg/L) was established in 1962 to prevent methemoglobinemia, or blue baby syndrome, a life-threatening condition that decreases the blood’s ability to carry vital oxygen through the body. The Safe Drinking Water Act, enforced by the U.S. Environmental Protection Agency, keeps water utilities accountable to this standard. While blue baby syndrome is now rare, an increasing number of scientific studies are making connections between long-term, low-level nitrate concentrations in drinking water and other health issues, including birth defects, cancers, and thyroid disease. 

When nitrate is ingested, it is reduced within the body to nitrite, which is considered unsafe at much lower levels than nitrate. Nitrite is further reduced in the body to N-nitroso compounds, which are widely considered to cause cancer and contribute to a variety of health problems. 

Addressing Nitrates in Drinking Water Supplies

High nitrate concentrations in public drinking water supplies present a significant challenge for public drinking water systems that are legally required to provide water with nitrate concentrations at or below 10 mg/L. For example, the Central Iowa Water Works (CIWW) — a regionalized water utility serving customers throughout central Iowa – has an advanced treatment technology that costs between $14,000 and $16,000 a day to reduce nitrate loads to a safe threshold. 

While public water systems are required to meet federal drinking water standards, private wells are not. Private well owners are responsible for testing and treating their own wells to ensure the water is safe to drink. These Iowans are at a greater risk of ingesting elevated concentrations of nitrate or other regulated pollutants. Information on county-level programs for private well testing can be found at the Iowa Department of Natural Resource’s website. 

Environmental Impacts of Nitrates

High nitrate concentrations in waterways also have devastating environmental impacts beyond human health. In April, American Rivers designated the Mississippi River as the most endangered river in the nation due to factors like industrial pollution, habitat loss, and most concerning, high amounts of agricultural runoff. Iowa delivers more agricultural nutrient runoff – including nitrate – to the Gulf than any other state along the river. This fuels the Dead Zone in the Gulf, an area of excessive algae growth toxic for aquatic life. 

The consequences of high nitrate runoff are not only found downstream, but also right here in Iowa. Excessive algae growth is monitored by the Iowa Department of Natural Resources and Army Corps of Engineers at Iowa state beaches. These organizations monitor microcystin blooms as they can cause serious health problems if ingested by humans or animals. In wildlife, algal toxins are consumed by small fish and shellfish, impacting other larger predatory animals. Thick algae can also form layers of scum that can harm aquatic life by blocking out sunlight and even clogging fish gills. Nitrates, as well as other fertilizers, contribute to the excessive growth of algae in Iowa waterbodies. High levels of algae growth result in beach closures, negatively impacting local recreation and tourism. 

What’s Next for Iowans Facing High Nitrate Levels

Water use restrictions are top of mind for many Iowans this week as nitrate levels spike in local waterways. The Raccoon River, a key drinking water source for central Iowa residents, recorded nitrate levels above 20 mg/L — the highest measured since 2013. At the same time, the nitrate level in the Des Moines River was 17 mg/L, the Cedar River neared 12 mg/L, the Floyd River spiked to 15 mg/L, and Bloody Run Creek was around 13 mg/L.  

To meet the 10 mg/L standard, water utilities may choose to invest in nitrate treatment technology, blend water from other sources, or enact advisories or restrictions on nonessential water use. In some instances, such as currently implemented by CIWW, all three strategies are necessary to comply with the regulatory limit. Adherence to any water conservation restrictions is important to help the utility reduce nitrate levels for essential water uses, keeping water safe for consumption. Resources are available for Iowans seeking information on their utility’s nitrate status. For example, in central Iowa, Des Moines Water Works provides real-time water quality data for customers’ water from the Saylorville, Fleur, and L.D. McMullen Treatment Plants. Be sure to check your local utility’s website for nitrate alerts affecting your tap water. 

Learn About Iowa’s Water Challenges with IEC

You have the opportunity to learn more about the impacts of high nitrate levels, extreme climate events, and aging infrastructure at our upcoming webinar Understanding Iowa’s Changing Climate: Drought, Deluge, and Drinking Water on July 15. At this webinar, public water utility experts will discuss the many challenges to providing clean, affordable drinking water in the wake of climate change events. 

You can also read our 2024 report, Nitrate in Drinking Water: A Public Health Concern for All Iowans, for an analysis of recent research findings that suggest associations between elevated levels of nitrate in drinking water and human health problems. The report concludes with calls for action to protect our state’s drinking water sources and public health, including increased regulatory action in alignment with Iowa’s Nutrient Reduction Strategy, natural infrastructure to help filter nitrates, and boosted initiatives for the testing and treatment of contaminated wells. 

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