WaterAnswer.com
Health information notice: This page covers potential health effects associated with water contaminants. It's general information, not medical advice. Ask your doctor about risks specific to your health history.

Medical disclaimer: Nitrate contamination in private well water is a documented public health hazard. The information on this page is general in nature and isn’t a substitute for professional water testing or medical advice. If you have concerns about infant health or exposure, contact your pediatrician.

Private well water doesn’t get tested by anyone except you. There’s no utility monitoring it, no inspector running quarterly checks. That’s the core problem with nitrates. They’re odorless, colorless, and tasteless, and in high enough concentrations, they can kill an infant within hours.

Emergency: If an infant under 12 months shows bluish skin, rapid or labored breathing, or unusual fatigue after drinking well water, call 911 immediately. These may be signs of nitrate poisoning (methemoglobinemia).

This isn’t a theoretical risk. The CDC has documented cases of infant methemoglobinemia, “blue baby syndrome,” traced to nitrate-contaminated private wells across the US. If you have a well and an infant or pregnant person in your home, you need to read this page and then schedule a test.

Where Nitrates Come From

Nitrogen is everywhere in the environment. Nitrates form when nitrogen compounds break down in soil and water. That’s natural. The problem is scale.

Agricultural activity is the dominant driver of elevated nitrate levels in private wells. Fertilizer applied to cropland, both synthetic and organic, releases nitrogen into the soil. Rain and irrigation carry it down through the ground and into aquifers. Manure from concentrated livestock operations adds enormous nitrogen loads. Leaking septic systems contribute too, especially in older rural housing.

The USGS National Water Quality Assessment program has mapped nitrate contamination in groundwater across the country for decades. The pattern is consistent: the highest concentrations cluster in agricultural regions. Iowa, Illinois, Indiana, Nebraska, and Kansas regularly show elevated nitrate levels in private well water. The USGS also documented that rainfall following drought conditions can spike nitrate concentrations dramatically as stored nitrogen flushes through soil into waterways and groundwater.

Well depth matters. Shallow wells draw from water that’s been in the ground for months or a few years. Deeper wells tap older aquifers where water has been filtering for decades. Shallower wells face higher contamination risk from surface agricultural activity, but even some deep wells in heavily farmed areas show elevated nitrates.

The Blue Baby Syndrome Mechanism

Infants under 12 months are uniquely vulnerable to nitrate poisoning. Here’s why.

When nitrates enter the digestive system, bacteria in the gut convert them to nitrites. In adults, stomach acid limits this conversion. Infant stomachs have higher pH levels, less acidic, so the conversion happens much more readily. The resulting nitrites bind to hemoglobin in the blood, converting it to methemoglobin. Methemoglobin can’t carry oxygen effectively.

The result is methemoglobinemia. The infant’s blood loses its ability to deliver oxygen to tissues. Skin turns bluish, especially around the lips and fingernails. The infant may seem lethargic or show labored breathing. Without treatment, the condition can progress to coma and death.

A study published in Environmental Health Perspectives and indexed by PubMed documents the connection between nitrate-contaminated private well water and infant methemoglobinemia cases (PMC1638204). The risk is real, it’s documented, and it’s concentrated in rural families using private wells in agricultural areas.

Pregnant women face a different but also serious risk. Emerging research links high nitrate exposure during pregnancy to adverse birth outcomes including preterm birth and low birth weight. The evidence is still developing, but the precaution is the same: if you’re pregnant and on a private well, test your water.

Boiling Water Does Not Help

This section deserves its own heading because the mistake is common and dangerous.

Boiling does not remove nitrates. It makes the problem worse.

When you boil water, some of the water evaporates as steam. The nitrates don’t evaporate. They stay in the remaining liquid. That means the concentration of nitrates in the water you’re left with is higher than what you started with.

Never boil well water as a treatment for nitrate contamination. Never use boiled well water to prepare infant formula if nitrates are a concern. If you’re unsure about your well’s nitrate level and you have an infant in the home, use bottled water with confirmed low nitrate levels for formula preparation until you can get a certified lab test back.

The EPA Limit and Why It Doesn’t Protect Well Owners

The EPA’s National Primary Drinking Water Regulations set the Maximum Contaminant Level (MCL) for nitrates at 10 mg/L as nitrogen. The Maximum Contaminant Level Goal (MCLG) is also 10 mg/L. Unlike lead, where the MCLG is zero, the nitrate standard was set specifically to prevent blue baby syndrome in infants. It’s an acute standard, not a long-term cancer risk threshold.

Public water utilities are legally required to test for nitrates and stay below 10 mg/L. If they exceed it, they must notify customers.

Private well owners get none of that protection. The EPA doesn’t regulate private wells. Your state may have voluntary testing recommendations, but no one will knock on your door and hand you a test kit. Testing is your responsibility.

About 13 million households in the US rely on private wells as their primary water source. Studies estimate that roughly 4 percent of private wells exceed the EPA’s 10 mg/L nitrate limit. In heavily agricultural areas, that percentage climbs. Your location matters.

Who Else Is at Risk

Healthy adults generally don’t face acute danger from nitrates at levels below 10 mg/L. But “generally” isn’t “always.”

Infants under 12 months are the most vulnerable group. The EPA’s standard was set with them as the primary concern.

Pregnant women are the second group to watch. Research continues, but enough evidence exists linking elevated nitrate exposure to birth complications that caution is warranted.

Immunocompromised individuals are more susceptible to nitrite conversion in the gut. This includes people undergoing cancer treatment, those with certain GI conditions, and people taking medications that raise stomach pH. If you’re in this group, talk to your doctor about your water quality.

Testing: Only a Certified Lab Will Do

Home nitrate test strips exist. Don’t rely on them for infant safety decisions. Strip tests can give a rough indication, but their accuracy isn’t consistent enough when the stakes are this high.

A certified lab test is the right call. It costs between $20 and $50 at most water testing labs. Your state health department may offer free or subsidized testing for private well owners. Some counties in agricultural states run annual testing programs specifically because nitrate contamination is widespread in their area.

For lab options and a full breakdown of what to test for, see Best Mail-In Water Tests.

When to test:

  • At least once a year if you have a private well
  • Immediately if you have or are expecting an infant
  • After a major rain event or flooding near agricultural land
  • After a drought breaks and rain returns (nitrate flush risk)
  • If anyone in the household has unexplained illness

Treatment That Actually Works

Once you know your nitrate level, here’s what removes it.

Reverse osmosis (RO) is the most practical option for most households. An RO system certified to NSF/ANSI 58 removes 85 to 95 percent of nitrates at the point of use. Under-sink systems treat water at one tap, typically the kitchen sink, which is the most important point for drinking and cooking. If you use that tap for formula preparation and drinking, an under-sink RO system gives you reliable protection. See Best Under-Sink RO Systems for vetted options.

Anion exchange (not a regular water softener) can also remove nitrates. A standard water softener uses cation exchange to address hard water minerals. It doesn’t touch nitrates. Anion exchange systems are specifically designed for nitrate removal and can treat water at the whole-house level, which is useful if you want to address every tap. These systems require periodic regeneration with salt.

Distillation removes nitrates effectively. Home distillation units are slower and more expensive to operate than RO, but they work.

What doesn’t work: carbon filters, pitcher filters (Brita, Pur, ZeroWater without RO), and standard water softeners. Don’t waste money on these for nitrate removal.

For a full breakdown of treatment methods and what they do and don’t address, see the Treatment hub.

The Direct Recommendation

If you have a private well and an infant under 12 months, or a pregnant person, in your home: test your water now. Not next month. Now. Until you have results back from a certified lab, use bottled water for formula and infant drinking water.

If your test comes back above 10 mg/L, install an RO system at your kitchen tap or switch to bottled water. Don’t boil. Don’t assume it’ll be fine.

For help finding a certified lab in your area, see Well Water Testing Guide.

Sources:

Medical disclaimer: WaterAnswer.com provides general information only. If you have health concerns related to nitrate exposure, contact your healthcare provider. For infant health emergencies, call 911.

Frequently Asked Questions

What is the safe level of nitrates in well water?
The EPA sets the Maximum Contaminant Level (MCL) for nitrates at 10 mg/L as nitrogen. For regulated public water systems, that's a hard legal limit. Private wells aren't regulated by the EPA, so there's no automatic enforcement. If your well tests above 10 mg/L, don't use that water to prepare infant formula or for any infant feeding. For pregnant people or immunocompromised individuals, the same caution applies.
Can you taste or smell nitrates in water?
No. Nitrates are colorless, odorless, and tasteless. You can't detect them without a test. Water that looks and smells clean can still have dangerously high nitrate levels. The only way to know your well's nitrate concentration is to test it with a certified lab.
Does boiling water remove nitrates?
No. Boiling makes nitrate contamination worse. As water evaporates, the remaining water becomes more concentrated with nitrates. Never boil water as a treatment for nitrates. This is especially important for infant formula preparation. Use a reverse osmosis filter or distillation, or switch to bottled water certified for low nitrates.
What water filter removes nitrates?
Reverse osmosis systems certified to NSF/ANSI 58 remove roughly 85 to 95 percent of nitrates. Anion exchange systems (specifically designed for nitrate removal) are also effective. Distillation removes nitrates as well. Carbon filters, pitcher filters, and standard water softeners do not remove nitrates. Always check NSF certification before buying a filter for nitrate reduction.
How often should I test my well water for nitrates?
The EPA recommends testing private wells for nitrates at least once a year. Test more often if you live near farmland, a feedlot, or a septic system, or after a heavy rain following a drought. Test immediately if you have an infant in the home or a pregnancy. Some states offer free or low-cost well testing programs through their department of environmental quality.
Medical disclaimer: WaterAnswer.com provides general information only. Nothing here is medical advice. Consult a licensed healthcare provider before making decisions about your health.