Fertilizer Runoff Contaminates Drinking Water With Nitrate

Trouble in Farm Country Revisited: Fertilizer Runoff Contaminates Drinking Water With Nitrate

October 2019

By Anne Weir Schechinger, Senior Analyst, Economics

A deluge of chemical fertilizer and manure washes off farm fields each year, polluting drinking water supplies nationwide with nitrate, a contaminant linked to cancer and birth defects. Despite billions in federal funds spent annually to encourage farming practices that reduce runoff, new data shows that nitrate contamination is getting worse – especially in small, rural communities that lack the resources to clean it up.

EWG’s newly updated Tap Water Database, which collects test results from 50,000 community water systems across the country, shows that 1,695 systems had two-year average nitrate levels in 2016 and 2017 that were at or above the amount the National Cancer Institute says increases the risk of colon, kidney, ovarian and bladder cancers.

The Environmental Protection Agency’s legal limit for nitrate in drinking water is 10 parts per million, or ppm. It was set in 1962 to protect against blue baby syndrome, a potentially fatal condition that starves infants of oxygen. Since then, evidence has accumulated that links elevated risk of cancer and birth defects to drinking water with nitrate levels of 5 ppm or even lower.

The map below shows all community water systems that served 25,000 people or less and that in 2016 and 2017 averaged nitrate levels at or above 5 ppm. It also shows how many acres in each county were treated with chemical fertilizer or manure. Water systems with elevated nitrate levels tend to be in counties with lots of fertilizer- or manure-treated acres. 

Explore the Map

Nitrate Levels Rising

The 2016-2017 data show that 98 percent of all community water systems with nitrate levels at or above 5 ppm served 25,000 customers or less. These small, mostly rural systems tend to be the least able to afford fixing the problem. Compared to 2014-2015:

Big Ag States Have the Worst Nitrate Levels

In 2016-2017, 69 percent of the systems with nitrate at or above 5 ppm were in just 10 states where agriculture is big business.

StateSystems at or above 5 ppm in 2016-2017Population of systems

More than half of all states had the same or greater number of systems at or above 5 ppm in 2016-2017 compared to 2014-2015. Although nationally there was a net increase of 12 systems whose nitrate levels rose from below five ppm to at or above five ppm, California had 47 more systems at or above 5 ppm in 2016-2017 than in 2014-2015.

Real Solutions for a Growing Problem

Keeping nitrate out of drinking water is much cheaper than removing it through water treatment. But prevention currently relies completely on farmers’ adoption of voluntary conservation practices heavily subsidized by taxpayers. The funds aren’t targeted and this strictly voluntary method is clearly not enough to keep dangerous nitrates out of water. Only mandatory farm standards that include the most effective pollution-prevention practices, in the right places and on the right farms, will stem the tide.

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