Nitrate is the well contaminant most likely to be tied to what happens on the land around you, and you can't detect it yourself. The Minnesota Department of Health puts it plainly: "You cannot taste, smell, or see nitrate in water." The number to know is 10 mg/L measured as nitrogen, the federal limit for public water systems. Private wells are not covered by that rule, so reading your own result, and deciding what to do about it, falls to you.
Baby under six months at home? Don't use untested well water for formula, and don't boil water to "clean" it of nitrate: boiling makes nitrate more concentrated. Use another water source until you have a lab result, and ask your pediatrician or health department what is safe for your baby.
Nitrate and nitrite in one minute
Nitrate (NO3-) and nitrite (NO2-) are forms of nitrogen dissolved in water. In soil, microbes break down nitrogen-containing waste into ammonia, which is then oxidized to nitrite and nitrate. The CDC's toxic-substances agency (ATSDR) explains why your test is mostly about nitrate: "Because nitrite is easily oxidized to nitrate, nitrate is the compound predominantly found in groundwater and surface waters." Nitrate compounds in soil "are generally water soluble and readily migrate with groundwater."
The harm comes mostly from what the body makes of nitrate. EPA's private-well page says "Once taken into the body, nitrates are converted into nitrites," and ATSDR notes that this conversion "significantly enhances nitrates' toxic potency." Nitrite converts hemoglobin to methemoglobin, which limits how much oxygen the blood can carry. That is why federal rules set two limits:
| Contaminant | Federal MCL (public water systems) | Unit |
|---|---|---|
| Nitrate | 10 | mg/L as nitrogen |
| Nitrite | 1 | mg/L as nitrogen |
| Total nitrate + nitrite | 10 | mg/L as nitrogen |
Those values come from 40 CFR 141.62, and EPA sets the health goal (MCLG) at the same numbers. MCLs are legally enforceable for public water systems only. A private well has no federal limit, but state health departments and extension services use 10 mg/L as N as the benchmark.
The unit trap: "as N" versus "as NO3"
This is where well owners most often misread a report. A lab can express the same water two ways:
- Nitrate as nitrogen (written NO3-N, "nitrate-nitrogen" or "nitrate as N") counts only the weight of the nitrogen atom in each nitrate ion.
- Nitrate as nitrate (written NO3 or "nitrate as NO3") counts the whole ion, nitrogen plus three oxygens.
The whole ion weighs more, so the same water produces a bigger number in the second unit. The University of Georgia's water lab gives the factor: "1 mg/L nitrate-nitrogen (NO3-N) = 4.43 mg/L nitrate (NO3)." It also does the conversion for the federal limit: "The EPA's maximum contaminant level (MCL) for NO3-N is 10 mg/L, which is equal to 10 x 4.43 or 44.3 mg/L nitrate (NO3)." Extension publications from Penn State and Virginia Tech round the same limit to 45 mg/L as nitrate.
| Report says (mg/L as N) | Same water in mg/L as NO3 (× 4.43) | Where it sits |
|---|---|---|
| 1 | 4.4 | USGS: above 1 mg/L as N usually indicates human activity in many areas |
| 3 | 13.3 | Minnesota: suggests human-made sources |
| 5 | 22.2 | Half the MCL |
| 10 | 44.3 | The federal MCL |
| 14 | 62.0 | 40% over the MCL (worked example below) |
| 20 | 88.6 | Twice the MCL |
Going the other way, divide by 4.43. A report that says "Nitrate 14 mg/L" with no "-N" may be reporting the whole ion, which works out to about 3.2 mg/L as N. Misread it as nitrate-N and you'll worry over water that is under the limit. Make the opposite mistake with a true nitrate-N result of 14 and water at 1.4 times the limit looks safe.
How to tell which unit you have:
- Look for "-N", "as N" or "nitrogen" next to the result or in the units column. If they're there, compare the number directly with 10.
- Check the "standard" or "limit" column on the report. A lab that prints 10 next to your result is usually reporting as N. One that prints 44 or 45 is reporting as nitrate.
- "Nitrate + nitrite" or "nitrate-nitrite" is a combined measurement. The drinking-water monitoring rule notes that it "refers to a measurement of total nitrate." It's compared with the same 10 mg/L as N limit.
- Still unsure? Virginia Tech's extension service: "If you are unclear about how to interpret the report, contact the laboratory that performed the analysis."
How nitrate gets into a well
EPA lists the sources for nitrate as "Runoff from fertilizer use; leaking from septic tanks, sewage; erosion of natural deposits." Natural levels are low, and the USGS writes that concentrations above 1 mg/L as N "usually are indicative of human activities, such as fertilizer application, animal production, and septic systems, in many parts of the United States."
Just as important as the source is how easily it reaches the water you pump. MDH lists the wells most vulnerable to nitrate:
- Shallow wells.
- Wells in sand, karst and fractured rock aquifers.
- Dug wells with casings that are not watertight.
- Wells with damaged or leaking casings or fittings.
The Wisconsin DNR says the same about the land itself: "Areas with sandy soils or fractured bedrock near the surface can make areas more prone to groundwater contamination." The mechanism is simple. Virginia Tech's extension service explains that once nitrate is dissolved "it moves easily through the soil and into groundwater," and that the risk rises "where the water table is near the soil surface and/or soils are sandy." The USGS national study found the same pattern: high nitrate goes with "well-drained soils, fractured or porous-rock aquifers, and oxygenated ground water."
Why your neighbor's result may not match yours
Nearby wells can give very different numbers. In oxygen-rich ("oxic") groundwater nitrate persists. In groundwater low in oxygen it can be converted to harmless nitrogen gas, a process called denitrification. The USGS nutrient fact sheet reports that the median nitrate concentration in agricultural-area wells "was 5.5 mg/L in oxic water, but was almost undetectable in less oxygenated (or 'reduced') water despite similar nitrogen inputs at the land surface." It also found that concentrations above the MCL "were never found in groundwater with low dissolved-oxygen concentrations and recharged prior to 1950."
EPA MCL 10
Show the numbers
| Item | Value | Note |
|---|---|---|
| Shallow agricultural wells, oxic water | 5.5 mg/L as N (median) | |
| Shallow agricultural wells | 3.1 mg/L as N (median) | |
| Shallow urban wells | 1.4 mg/L as N (median) |
Fact sheet figure, axis in mg/L as N. In agricultural-area wells with low-oxygen ("reduced") water, USGS found the median was almost undetectable despite similar nitrogen inputs. Source: USGS Fact Sheet 2010-3078, Nutrients in the Nation's Streams and Groundwater: National Findings and Implications (Dubrovsky and Hamilton, 2010), accessed 2026-11-01.
Depth matters too. The USGS found MCL exceedances less common in public-supply wells and pointed partly to "greater depths and hence age of the groundwater." So a test from the well next door can't stand in for yours: depth, casing and the water each well draws from can all differ.
Nitrate can be decades old
The same fact sheet warns that "Nitrate can persist in groundwater for years and even decades and may still be present because of previous land uses and management practices." A house surrounded by lawns today can sit over groundwater that soaked in under farmland. The USGS recommends testing "particularly for wells associated with current or previously farmed land."
How common is nitrate in U.S. domestic wells?
The best national picture comes from the U.S. Geological Survey's study of private domestic wells, which sampled about 2,100 wells in 48 states between 1991 and 2004 (USGS Circular 1332). The findings for nitrate:
- Nitrate exceeded the MCL of 10 mg/L as N "in 4.4 percent of all wells."
- Concentrations above 1 mg/L as N were found "in about 40 percent of wells."
- Nitrate was "the only contaminant derived primarily from man-made sources" found above a human-health benchmark in more than 1 percent of wells.
- Concentrations "were highest in the upper Midwest, Great Plains, and the Central Valley in California" and occurred "least commonly in the Southeast," where the USGS says low values "may result from aquifer and soil conditions that promote denitrification."
- In a separate sample of 436 domestic wells in shallow groundwater under intense agriculture, nitrate was above 10 mg/L as N "in nearly 25 percent of the sampled wells."
Show the numbers
| Item | Value | Note |
|---|---|---|
| All domestic wells | 4.4 % of wells above 10 mg/L as N | |
| Agricultural | 7.1 % of wells above 10 mg/L as N | |
| Mixed land use | 3.7 % of wells above 10 mg/L as N | |
| Urban | 3.1 % of wells above 10 mg/L as N |
USGS national sample of about 2,100 domestic wells, 1991–2004; land use within 500 m of the well. Undeveloped areas: less than 1 percent. A separate sample of 436 shallow wells under intense agriculture: nearly 25 percent. Source: USGS Circular 1332, Quality of Water from Domestic Wells in Principal Aquifers of the United States, 1991–2004 (DeSimone, Hamilton, Gilliom, 2009), accessed 2026-11-01.
A companion USGS nutrient analysis covering 1992 to 2004 counted a different set of wells and found that concentrations "exceeded the MCL in about 7 percent of 2,388 domestic wells," and were "most common in domestic wells that are shallow (less than 100 feet deep) and located in agricultural areas." Different well sets, same pattern: a few percent nationally, much more under farmland and in shallow wells.
State data are uneven:
- Minnesota. MDH says about 4 percent of new wells have nitrate above 3 mg/L, that "Concentrations above 10 mg/L are mainly in central and southwestern Minnesota," and that the state agriculture department's township testing found more than 10 percent of private wells sampled in some townships above 10 mg/L. See certified labs in Minnesota.
- Wisconsin. The Wisconsin Department of Health Services says "Studies estimate that at least 10% of private wells in Wisconsin have high levels of nitrate." The DNR adds that higher levels occur "in areas with a larger agricultural presence or a concentration of septic systems," and that "almost one-third of private well owners have never had their water tested for nitrate." See certified labs in Wisconsin.
Who is at risk, and why infants come first
The federal nitrate limit was built around one group. EPA's health-effects note for nitrate reads: "Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome." EPA's private-well page adds that this "acute condition can occur rapidly over a period of days."
ATSDR's course for clinicians explains why young babies are more vulnerable. Three things stack up:
- Stomach chemistry. An infant's digestive tract is less acidic, which "favors the growth of nitrate-reducing bacteria." In adults the stomach is usually too acidic for much nitrate to become nitrite there.
- Fetal hemoglobin. Much of a young infant's hemoglobin is the fetal form, which is "more readily oxidized to MetHb by nitrites than is adult hemoglobin."
- A slow repair enzyme. The enzyme that turns methemoglobin back into working hemoglobin "has only about half the activity it has in adults" at birth and does not reach adult levels "until at least 4 months of age."
Illness makes it worse. ATSDR notes that gastroenteritis with vomiting and diarrhea "can exacerbate nitrite formation in infants," and singles out infants "fed formula diluted with water from untested rural domestic wells." That's the formula connection. MDH says "Bottle-fed babies under six months old are at the highest risk," that the bluish color of lips and skin "may be difficult to detect in infants," and that "Symptoms will often resolve once the nitrate source is removed." ATSDR names infants under four months as most at risk, listing the slow enzyme among several reasons. EPA and MDH use six months in their advice.
Adults with certain conditions may also be at higher risk. MDH says these conditions "may also put people at higher risk": "anemia, cardiovascular disease, lung disease, sepsis, glucose-6-phosphate-dehydrogenase deficiency, and some metabolic problems."
Pregnancy and long-term exposure: what the research says
Here the evidence is still developing, and agencies word it differently:
- ATSDR says "the pregnant woman and her fetus might be more sensitive to toxicity from nitrites or nitrates at or near the 30th week of pregnancy."
- MDH says recent science describes "associations with thyroid problems, adverse pregnancy outcomes, and cancers (particularly colorectal)" at levels below the standard, and that "Further research is necessary to confirm these observations."
- A 2018 review of more than 30 newer studies (Ward et al., Int. J. Environ. Res. Public Health) found the strongest evidence for colorectal cancer, thyroid disease and neural tube defects, and reported that "five of six studies of neural tube defects showed increased risk with exposure to drinking water nitrate below the MCL."
- Wisconsin DHS goes furthest and states that nitrate "can increase the risk of neural tube defects," which form "very early in pregnancy often before a person even knows that they are pregnant."
If you're pregnant or planning to be, MDH and Wisconsin DHS both advise testing for nitrate first. What level is acceptable for you is a question for your doctor or your state health department. Show them the actual report, with its units.
Why one test is not enough
A single result is a snapshot. Levels shift with the seasons and can drift upward over years.
- Spring tends to be the high point. Virginia Tech's extension service says nitrate "can vary seasonally" and that "Testing during the spring months can give an indication of nitrate levels at their highest annual concentration in your area."
- Snowmelt and drought both push it up. ATSDR notes that "During spring melt or drought conditions, both domestic wells and public water systems using surface water can show increased nitrate levels."
- Trend matters. MDH treats 3 mg/L as a warning sign because human-made sources have reached the water and "the level could increase over time."
The rule for public systems is a useful model. Under 40 CFR 141.23, public groundwater systems must test nitrate "quarterly for at least one year following any one sample in which the concentration is ≥50 percent of the MCL," which is 5 mg/L as N. No law requires this for your well, but it's a sensible way to find its seasonal peak once a result comes back near 5 or higher.
How often to test as a baseline:
- CDC: "Test your well water at least once each year for total coliform bacteria, nitrates, total dissolved solids, and pH levels," and again if someone in the home becomes pregnant, if there's flooding or land disturbance near the well, or if the water changes.
- MDH: "Test for nitrate every year," and also "if you planning on becoming pregnant or if infants will be using the water."
- Wisconsin DHS: at least once a year, before water is given to a baby or someone who is or may become pregnant, and right away if color, taste or smell changes.
Pair nitrate with a bacteria test. Virginia Tech notes that elevated nitrate "may be an indicator of other water quality problems, such as contamination by bacteria or pesticides." Our coliform bacteria explainer covers that test. For a full first-time panel, see the guide to testing well water.
How to take a nitrate sample
- Use a state-certified lab and its bottle. CDC says to "Use a state-certified laboratory to test your water." MDH advises contacting an accredited lab "to get sample containers and instructions." Federal rules allow combined nitrate-nitrite samples to be preserved with acid, so ask whether your bottle contains a preservative and follow the lab's filling instructions exactly.
- Know the clock. In the federal monitoring rule for public systems, an unpreserved nitrate sample kept at 4 °C must be analyzed within 48 hours. A combined nitrate-nitrite sample preserved with sulfuric acid can be held 28 days. Ask your lab which bottle you have, and mail or drop off early in the week so it doesn't sit over a weekend.
- Decide what you're testing. To learn what's in the well, sample a tap that bypasses any treatment. To check that a treatment unit works, sample the treated tap too. Wisconsin DHS advises testing treated water after a device is installed.
- Write down the date and conditions. Note the season, recent heavy rain or snowmelt, and nearby fertilizer or manure spreading. Keep every report: a five-year trend tells you more than any single number.
Find certified labs with the nitrate lab finder.
Reading your result: a decision table
Every threshold below comes from the agency named next to it. Convert to mg/L as N first.
| Nitrate (mg/L as N) | What sources say | Sensible next step |
|---|---|---|
| Below 1 | Natural range. MDH: natural levels in Minnesota are "usually quite low (less than 1 milligrams per liter [mg/L])." | Retest yearly as CDC recommends. |
| 1 to under 3 | USGS: above 1 mg/L usually indicates human activity in many areas. Below the health-based thresholds in this table. | Retest yearly, ideally in spring. Look at what's near the well. |
| 3 to under 5 | MDH: 3 mg/L "suggests human-made sources of nitrate have contaminated the water and the level could increase over time." Virginia Tech: at a level "approaching 3-5 mg/L," don't use the water for formula or for infants under six months. | If there's an infant in the home, ask the pediatrician. Retest in spring. Check septic and well casing. |
| 5 to under 10 | Half the MCL or more. Public groundwater systems must switch to quarterly testing for a year at this level (40 CFR 141.23). | Consider testing quarterly for a year to find the peak. Same infant caution as above. |
| 10 or higher | At or above the EPA MCL. MDH: switch to another drinking source, keep babies under six months off the water, don't boil, have a licensed contractor inspect the well. Wisconsin DHS: anyone who is or may become pregnant should use other water at once; retest to confirm. | Stop using it for drinking, formula and cooking now. Retest. If it's confirmed, plan a long-term fix. |
| Nitrite 1 or higher | At or above the nitrite MCL. Wisconsin DHS: anyone who is or may become pregnant should switch water at once and the well should be retested; if it's still high, everyone should use another source. | Switch water for infants and pregnancy now. Retest. Ask the lab and health department why: ATSDR notes nitrate, not nitrite, is the form usually found in groundwater. |
The lower thresholds (3 and 5 mg/L) are not legal limits for private wells. They're early warnings, and the agencies that publish them use them that way.
What removes nitrate, and what doesn't
MDH's advice is to fix the source first: "Before treating for nitrate, MDH encourages you to first try to get rid of potential sources of nitrate on your property and get your well inspected and repaired." Penn State suggests diverting surface water from the well and a casing at least a foot above ground with a suitable cap. Virginia Tech recommends keeping the well at least 100 feet from and upslope of contaminant sources (check your state's well code for the exact setbacks). When the source is off your property, such as surrounding fields, treatment or a new well may be the realistic fix.
Technologies that work
For public water systems, the federal rule names three best available technologies for nitrate: ion exchange, reverse osmosis and electrodialysis (40 CFR 141.62(c)). For homes, the extension guides from Penn State and Virginia Tech describe reverse osmosis, ion exchange and distillation:
| Technology | How it removes nitrate | Catches |
|---|---|---|
| Reverse osmosis (RO) | Water is forced through a membrane that holds back dissolved ions. | Penn State puts nitrate rejection at "around 83 to 92 percent." It can waste "up to 90 percent of the incoming water." Usually installed at one tap. Membranes need replacing. |
| Anion exchange | Resin trades chloride for nitrate (and sulfate) as water flows through. | The resin prefers sulfate. If saturated, Penn State warns, "it releases the nitrates in place of sulfates, resulting in an increased nitrate concentration in the 'treated' water." Can make water more corrosive. Brine waste is high in nitrate. |
| Distillation | Water is boiled, the steam is collected and condensed, and nitrate stays behind. | Slow: Penn State says a typical home unit makes "about a gallon of water every four to five hours." Uses a lot of energy. |
You don't need to treat every drop. Virginia Tech notes that "only water to be used for drinking and cooking needs to be treated," which is why RO and distillation units usually serve a single tap. Wisconsin DHS says high-nitrate well water is still fine for bathing, brushing teeth and washing dishes.
What does not work
- Boiling. Boiling makes it worse. MDH: "Boiling will make nitrate more concentrated." Nitrate doesn't evaporate, so the water that boils off leaves the same nitrate in less water. Boil 4 cups down to 3 and a 14 mg/L sample becomes about 18.7 mg/L.
- Chlorination and mechanical filters. Virginia Tech: these "will NOT remove nitrate."
- Carbon filters and water softeners. Wisconsin DHS's certified-device table covers only carbon filtration, reverse osmosis and softeners (not anion exchange or distillation). Of those three, only reverse osmosis is listed for nitrate. Carbon filtration and softeners are listed for other contaminants (softeners for manganese, for example), not nitrate.
Look for independent certification
Wisconsin DHS recommends choosing a device certified to NSF/ANSI standards and lists NSF/ANSI 58 (reverse osmosis) for nitrate. NSF's public listings for that standard show a "Nitrate/Nitrite Reduction" claim on some units, not all, so check that the specific model lists it. Even a certified unit has limits. Penn State warns that at very high nitrate-nitrogen levels, remaining nitrate "may still result in drinking water that exceeds the standards." Test the treated water after installation and on a schedule after that. MDH adds one more safeguard: even with home treatment, it recommends that no babies under six months drink the water, "a safety precaution in the event the water treatment fails."
While you wait for results or a fix
- Use bottled water or another tested source for drinking, formula and cooking. ATSDR lists FDA's bottled-water limit as the same 10 mg/L as N.
- Wisconsin DHS adds "foods that take up a lot of water (like rice, oatmeal and gelatin)" to that list. Bathing and dishwashing are fine.
- For infant feeding, Virginia Tech lists breastfeeding, premixed formula or bottled water as alternatives. Your pediatrician can tell you which suits your baby.
- If anyone in the home, especially an infant, shows bluish lips or skin (MDH), shortness of breath (EPA), or weakness and fatigue (Wisconsin DHS), get medical care right away and mention the well water.
Worked example: "Nitrate-N 14 mg/L"
Say your report shows Nitrate-N: 14 mg/L, with a standard of 10.
- Units. "-N" means nitrate as nitrogen, so you're at 1.4 times the 10 mg/L MCL. In whole-ion units that's about 62 mg/L as NO3 (14 × 4.43).
- Immediate steps. This is above every threshold in the decision table. Following MDH and Wisconsin DHS, switch drinking, formula and cooking water now, especially for an infant or anyone pregnant. Don't boil.
- Confirm. Wisconsin DHS advises retesting to verify a high result. Collect the retest from the same tap and note the date. A spring sample may be close to your yearly peak. If you sampled at another time of year, the spring level could be higher.
- Look for a cause. Have a licensed well contractor check the casing, cap and grading. Look at septic drainfield location and condition, and at nearby fertilizer or manure. Test for coliform bacteria at the same time: Virginia Tech notes high nitrate can be a sign of other problems, including bacteria.
- Size the fix. An RO unit rejecting 83 to 92 percent (Penn State's range) would bring 14 mg/L down to roughly 1.1 to 2.4 mg/L as N, well under the MCL. But that's only true if the specific unit is certified for nitrate and maintained. Confirm with a treated-water test after installation.
- Monitor. Using the public-system rule as a model, test quarterly for a year to learn the range, then at least yearly.
Now the reverse case. Your report says Nitrate: 14 mg/L with a standard of 45 and no "-N". That's whole-ion nitrate, about 3.2 mg/L as N. It's below the MCL, but it's above MDH's 3 mg/L human-source signal and inside Virginia Tech's 3-to-5 caution band for infants. The same printed number calls for a very different response.
Next step
If you haven't tested in the past year, or ever, start with nitrate and coliform bacteria from a state-certified lab, the pair CDC puts in its yearly list. Minnesota's health department also recommends testing at least once for arsenic, lead and manganese. Find a certified lab with the nitrate lab finder, and keep the report so the next test has something to compare against.
Questions people ask
What is a safe nitrate level in well water?
Can I use well water with nitrate to make baby formula?
Does boiling water remove nitrate?
How do I remove nitrate from well water?
What's the difference between nitrate and nitrate-nitrogen on my report?
How often should I test my well for nitrate?
Is it safe to shower in water with high nitrate?
- U.S. EPA, National Primary Drinking Water Regulations (nitrate and nitrite MCL/MCLG, health effects, sources) (accessed 2026-11-01)
- 40 CFR 141.62, Maximum contaminant levels for inorganic contaminants (incl. best available technology) (accessed 2026-11-01)
- 40 CFR 141.23, Inorganic chemical sampling and analytical requirements (nitrate monitoring, holding times) (accessed 2026-11-01)
- U.S. EPA, Potential Well Water Contaminants and Their Impacts (updated July 6, 2026) (accessed 2026-11-01)
- USGS Circular 1332, Quality of Water from Domestic Wells in Principal Aquifers of the United States, 1991–2004: Overview of Major Findings (DeSimone, Hamilton, Gilliom, 2009) (accessed 2026-11-01)
- USGS Fact Sheet 2010-3078, Nutrients in the Nation's Streams and Groundwater: National Findings and Implications (Dubrovsky and Hamilton, 2010) (accessed 2026-11-01)
- CDC/ATSDR, Nitrate/Nitrite Toxicity (CSEM): Where Are Nitrates and Nitrites Found? (last reviewed May 24, 2023) (accessed 2026-11-01)
- CDC/ATSDR, Nitrate/Nitrite Toxicity (CSEM): Who Is at Most Risk (last reviewed May 24, 2023) (accessed 2026-11-01)
- CDC/ATSDR, Nitrate/Nitrite Toxicity (CSEM): U.S. Standards and Regulations (last reviewed May 24, 2023) (accessed 2026-11-01)
- CDC, Guidelines for Testing Well Water (updated July 1, 2024) (accessed 2026-11-01)
- Minnesota Department of Health, Nitrate in Well Water (updated October 19, 2026) (accessed 2026-11-01)
- Wisconsin Department of Health Services, Drinking Water: Nitrate and Nitrite (revised February 27, 2026) (accessed 2026-11-01)
- Wisconsin Department of Health Services, Treatment Devices for Private Well Contaminants, P-03494 (11/2024) (accessed 2026-11-01)
- Wisconsin DNR, DNR Offering Free Well Water Screening At Farm Technology Days (news release, July 6, 2022) (accessed 2026-11-01)
- University of Georgia Agricultural & Environmental Services Laboratories, Drinking Water Interpretation and Recommendations (accessed 2026-11-01)
- Virginia Cooperative Extension (Virginia Tech), Virginia Household Water Quality Program: Nitrate in Household Water, Publication 442-659 (BSE-363P) (2024) (accessed 2026-11-01)
- Penn State Extension, Nitrates in Drinking Water (updated May 29, 2025) (accessed 2026-11-01)
- Ward MH et al., Drinking Water Nitrate and Human Health: An Updated Review, Int. J. Environ. Res. Public Health 15(7):1557 (2018) (accessed 2026-11-01)
- NSF, Certified Drinking Water Treatment Units: NSF/ANSI 58 listings (Nitrate/Nitrite Reduction claims) (accessed 2026-11-01)
Find nitrate testing labs by state
Labs each state lists as certified for nitrate, with the ones that take homeowner samples first.
Got a bad result?
- Confirm the result: re-test with a state-certified lab (find one in the finder on this site) and ask how to collect the sample.
- If an infant under six months drinks the water, ask your doctor or health department what to do in the meantime.
- Call your state or county health department and ask what is known about this contaminant in your area and what it recommends.
- If you consider treatment, ask for proof that the system is independently certified for your specific contaminant, and re-test the treated water afterwards.