10 Parts Per Million

Aug. 1, 2018

For decades, nitrates have boosted the productivity of America’s farmland. However, the crop-plumping substance has also produced negative effects by contributing to algae blooms and endangering humans as a potential carcinogen that accumulates in groundwater sources and soils.

The US drinking water standard for nitrate—10 parts per million—was set in 1991. But recent studies offer evidence of potential long-term health problems related to exposure to low levels of nitrates, indicating that the EPA’s nitrate limit should possibly be reevaluated.

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Nitrate exists naturally in soils and air. But the rise in concentrations in the nation’s waterways and aquifers is most often the result of fertilizer usage. And nitrate that has been applied on farm fields and not taken up by the crop can remain in the soil for extended periods of time until eventually absorbed by rivers and aquifers.

Researchers consider the buildup of nitrate in soil layers above the groundwater table a serious global issue.

On its own, nitrate is not a carcinogen, explains Circle of Blue’s Brett Walton. But in the body, it’s converted to nitrite, which then reacts to form carcinogenic nitroso compounds. Nitrite reduces the blood’s ability to transport oxygen.  

The EPA’s nitrate standard was originally determined with infant health in mind. Because newborns that ingest water with high levels of nitrate can suffer from methemoglobinemia, or blue baby syndrome, it was set based on the average water consumption of a three-month-old baby. 10 parts per million, it was determined, would keep them safe.

However recent studies such as the Iowa Women’s Health Study have pointed to a higher risk of bladder, ovarian, and colorectal cancer from nitrate levels at half the legal limit. Although researchers explain that further research will be needed before making any definitive claims about the health risk at lower levels of nitrate in drinking water, the data is compelling.

The EPA and its Integrated Risk Information System (IRIS) have expressed interest in reevaluating the health risks of nitrate and nitrite and adjusting the standard levels. Because it is a Safe Drinking Water Act regulation, the consequences of a lower nitrate limit would impact water utilities, many of which may have to install nitrate-removal systems.

What are your thoughts? Is nitrate a problem in your community? What steps has your municipality taken to mitigate its accumulation in water sources? How would your utility be affected by lower nitrate limits?
About the Author

Laura Sanchez

Laura Sanchez is the editor of Distributed Energy and Water Efficiency magazines.

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