You turn on the faucet and fill a glass. Simple enough. But a new report is raising questions about whether that water is as safe as we assume.
The nonprofit Environmental Working Group, known as the EWG, analyzed drinking water data from more than 6,100 water systems across the country between 2021 and 2023. What they found: the tap water delivered to about 62.1 million Americans, that is roughly 18 percent of the U.S. population, had nitrate levels of 3 milligrams per liter or higher at least once during that three-year period. At those levels, the EWG says the risk of certain cancers and birth defects increases.
That is a lot of people. And it is worth understanding what it actually means for you.
What Are Nitrates, Exactly?
Nitrate is a compound made of nitrogen and oxygen. It occurs naturally in air, soil and water, and both humans and animals need it in small amounts. The problem is when it shows up in drinking water at elevated levels.
The Environmental Protection Agency set its official limit at 10 milligrams per liter back in 1991. That standard came from a 1962 public health recommendation aimed at protecting infants from a serious condition called blue baby syndrome, caused by too much nitrate. The EWG’s analysis focuses on a much lower threshold (3 mg/L) which some newer research links to cancer risk and birth defects.
Where Is It Coming From?
Mostly from human activity. Agricultural fertilizer runoff, animal manure, leaking septic systems, sewage, wastewater treatment discharge, and urban stormwater all contribute. Nitrates seep into groundwater or wash into rivers and reservoirs, especially after rain or heavy irrigation.
Celina Phillipson, a PhD candidate who researches drinking water at the University of California Irvine, notes that scientists consider levels above 3 mg/L unlikely to occur naturally. In other words, if the number is that high, it is almost certainly coming from human-caused contamination.
The EWG also points to climate change as a factor, as weather increasingly swings between long droughts and heavy storms, which worsens runoff.
Which States Have the Highest Levels?
The highest concentrations of elevated nitrate levels were found in California, Pennsylvania, Nebraska, Kansas, Oklahoma, Minnesota, Washington, New York, North Carolina, Texas, Arizona and Wisconsin. Many of these are top agricultural states, but the problem is not limited to farm country.
Pennsylvania’s biggest concentration is around Philadelphia. In Washington state, it is the Puget Sound Basin, a region with shallow wells and heavy urban, industrial and agricultural land use. In Nebraska, Wisconsin, Oklahoma and Kansas, elevated levels are spread more broadly across entire states, and some water systems there reach or exceed the EPA’s 10 mg/L limit.
How Worried Should You Actually Be?
That is where things get a little more nuanced. Daniele Lantagne, PhD, a research professor at Tufts University who focuses on water and sanitation, says the science is still developing. Some studies show an association between nitrates in drinking water and certain cancers. Others find little or no connection.
“The evidence on long-term cancers is emerging,” Lantagne says. She also points out that other factors such as exposure to agricultural products or eating a diet high in red meat are known cancer risks and can make it hard to isolate nitrates as the cause.
Phillipson adds that certain people face greater concern than others. Infants under six months old, pregnant people, and those with underlying metabolic or cardiovascular conditions are considered more vulnerable populations.
Can a Water Filter Help?
Some filters work. Many do not. Your standard pitcher filter will not remove nitrates. Activated charcoal does not work either. And here is something surprising: boiling your water actually makes it worse, because it concentrates the nitrates rather than removing them.
What does work? Both experts point to high-quality reverse osmosis systems, ion exchange systems, or distillation. These vary in cost depending on the product.
What Should You Do Right Now?
The only way to know if your water has elevated nitrate levels is to have it tested. Nitrates are odorless, colorless and tasteless, you cannot detect them on your own.
If you get your water from a private well, Phillipson recommends having it tested by an accredited lab. If you are on a public water system, you can look up your system’s Consumer Confidence Report, an annual water quality report, through the EPA’s CCR database online.
If your water tests above 10 mg/L, Phillipson says to stop using it for drinking, cooking or infant formula and switch to bottled water. If it comes back above 3 mg/L, she recommends installing a filter system capable of removing nitrates.
The bottom line: this report is worth paying attention to, but it is not a reason to panic. A simple test can tell you exactly where your water stands, and from there, you will know exactly what, if anything, to do about it.