MINNEAPOLIS – Nitrate contamination of drinking water has increased across Minnesota’s farm country, an Environmental Working Group analysis of state data has found.

EWG analyzed data from 115 water utilities, serving over 500,000 Minnesotans, with elevated levels of nitrate between 1995 and 2018. About 63 percent, or 72, of these systems saw increases in nitrate during that time, impacting 218,000 people.

The rate was even higher for the community water systems with the worst contamination: 67 percent of the systems with nitrate at or above the federal legal limit of 10 milligrams of nitrate per liter, or mg/L, serving about 48,500 Minnesotans, showed increased contamination over the study period.

“Rapid, strong action is needed to protect Minnesota’s tap water from agricultural pollution,” said Anne Weir Schechinger, EWG senior economic analyst and the report’s author. “The problem is not only widespread, it’s also getting worse at an alarming rate.”

Although nitrate occurs naturally in soil at low levels, a contamination level of 3 mg/L or higher indicates a human cause, according to the Minnesota Department of Health.

The 10 mg/L legal limit for nitrate in drinking water, regulated by the federal Safe Drinking Water Act, is based on a 1962 U.S. Public Health Service recommendation intended to prevent so-called blue baby syndrome, a potentially fatal condition that starves infants of oxygen.

But research from recent decades, including a recent peer-reviewed study by EWG scientists, indicates that nitrate is associated with higher risks of cancer and birth defects at 5 mg/L — half the federal limit — or even less.

In 2018, the average level for nitrate in the 72 systems that have seen worsening contamination was 4.4 mg/L – a 61 percent jump from 1995’s average of 2.7 mg/L

Nitrate is a primary chemical component of fertilizer and manure that can run off farm fields and seep into drinking water supplies. In January, Minnesota began implementing a new Groundwater Protection Rule to address this pollution, but EWG and other watchdog groups have pointed out the regulation’s many shortcomings, including its heavy reliance on voluntary measures to address nitrate pollution from farms.

“For nearly 30 years, Minnesota has relied on a voluntary approach to working with farmers to protect drinking water, but surveys show fertilizers are still overapplied to crop fields,” said Jamie Konopacky, EWG’s Midwest director. “But the state’s new Groundwater Protection Rule includes no immediate and practical requirements for farming operations to ensure communities have safe drinking water.”

EWG’s new analysis, which includes community water systems that rely on groundwater, surface water, or both, is based on Minnesota Department of Health data. Similar comprehensive data for Minnesota’s hundreds of thousands of private wells is unavailable, but it is likely they have seen a similar increase in nitrate contamination, because many draw water from the same sources as public water systems.

In January, EWG released a related report showing widespread nitrate contamination in private wells and groundwater-based water systems across the state between 2009 to 2018.

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