How to remove nitrates in tap water — and why experts say the EPA's limit is outdated
About 62 million Americans — roughly 1 in 5 people — may be drinking tap water with potentially harmful nitrate levels, according to a recent Environmental Working Group (EWG) analysis of nearly 50,000 public water systems.
The findings are raising new questions about what are nitrates in water, how dangerous high nitrates in water may be and how to remove nitrates from water at home.
Here’s a breakdown of the biggest questions surrounding the contamination concerns and the whole-house filtration systems experts say actually work.
What are nitrates in water and where do they come from?
Nitrates in water are compounds made of nitrogen and oxygen naturally found in soil, plants, air and water, according to the EPA. Problems begin when fertilizer, livestock manure, septic waste and industrial runoff wash into rivers and groundwater. Christopher Glen of The Fertilizer Institute told CNN that contamination can also come from urban stormwater, decomposing organic matter and vehicle emissions.
Why are small communities seeing the highest nitrate levels?
The Environmental Working Group found that nearly all water systems with extremely high nitrate contamination rely on groundwater wells serving communities with fewer than 1,000 residents. Smaller towns often lack advanced treatment infrastructure, making it harder to remove contaminants before water reaches homes. Because nitrates can travel through rivers and streams, even communities far from farmland may still experience contamination.
How dangerous are high nitrates in water?
A 2018 review published in the International Journal of Environmental Research and Public Health linked high nitrates in water to thyroid disease, birth defects, preterm births and several cancers. The cancers associated with nitrate exposure included gastric, kidney, bladder, colon, colorectal and ovarian cancers. Researchers found health effects may occur at levels between 2 and 5 mg/L — below the EPA’s legal limit of 10 mg/L.
Why are experts criticizing the EPA nitrate limit?
The current federal nitrate limit of 10 mg/L was originally established in 1962 and formally adopted by the EPA in 1991. Critics argue the standard no longer reflects newer health research showing potential harm at much lower concentrations. The EWG found more than 6,000 water systems testing at or above 3 mg/L and more than 3,200 systems reaching 5 mg/L or higher.
How many Americans may be exposed to nitrate contamination?
The EWG estimates that roughly 62 million Americans may be drinking water with potentially concerning nitrate levels. Its analysis used data collected from nearly 50,000 public water systems between 2021 and 2023 across all 50 states. Around 3 million people were served by systems exceeding the EPA’s legal limit of 10 mg/L.
Where were the highest nitrate readings found?
The EWG analysis identified 70 water systems with nitrate levels at 20 mg/L — double the federal limit — while 21 systems tested at 30 mg/L or higher. The highest reading came from a small water system near Dinuba, California, which reached 50 mg/L, or five times the EPA limit. That system serves only 31 residents.
Does the report include private well water?
No. The EWG report only analyzed public water systems and did not include private wells. That means homeowners relying on well water must test independently to know whether nitrates are present. Experts recommend regular testing because wells are not regulated by the EPA and may be vulnerable to nearby agricultural runoff or septic contamination.
How do you remove nitrates from water?
The two filtration methods proven to remove nitrates from water are reverse osmosis systems and ion exchange filters, according to the EWG. A reverse osmosis water filter for nitrates pushes water through a semipermeable membrane that traps contaminants, while ion exchange systems replace nitrate ions with less harmful ones during filtration. Both can be installed under a sink or as whole-home filter systems.
Do regular water filters remove nitrates?
Most standard carbon filters and basic pitcher filters do not remove nitrates from water. The PennState Extension also warns against boiling contaminated water as a solution. Boiling may actually increase nitrate concentration because water evaporates while the nitrate compounds remain behind.
How can you check nitrate levels in your tap water?
Consumers can search their local water system using the EWG Tap Water Database, which includes data from nearly 50,000 public systems nationwide. Experts also recommend comparing those results with annual water quality reports provided by local utilities. Private well owners should contact certified water-testing labs or agricultural extension offices for independent testing to determine whether nitrate contamination is present.
This article was created by content specialists using various tools, including AI.
