Nitrates in Well Water: What Maryland Homeowners Need to Know
Nitrates in Well Water: What Maryland Homeowners Need to Know
Nitrates have no taste, odor, or color — but they are one of the most serious health risks in Maryland well water, particularly for infants. Here's what you need to know.
Why Nitrates Are a Serious Concern
Nitrates are a form of nitrogen that occurs naturally in soil and water, but elevated levels in well water are almost always caused by human activity — primarily agricultural fertilizer and septic systems. Nitrates have no taste, odor, or color, so the only way to know they're present is to test.
For most adults, nitrates at levels below the EPA limit of 10 mg/L are not a health concern. But for infants under 6 months, nitrates interfere with the blood's ability to carry oxygen — a condition called methemoglobinemia, or "blue baby syndrome." This can be fatal. Pregnant women, elderly individuals, and people with certain health conditions are also at elevated risk.
Maryland's agricultural landscape — particularly in Anne Arundel County, Charles County, and parts of Calvert County — means nitrate contamination is a real risk for many private well owners.
Nitrate Levels: What They Mean
Below 3 mg/L
SafeBackground level — typical of wells with no nearby contamination source. Safe for all uses including infant formula.
3–5 mg/L
MonitorElevated but below action levels. Test annually. Some pediatricians recommend caution for infant formula above 5 mg/L.
5–10 mg/L
CautionBelow the EPA MCL but above the level many pediatricians consider safe for infants. Treatment recommended for households with infants or pregnant women.
Above 10 mg/L
Action RequiredAbove the EPA maximum contaminant level. Do not use for infant formula, drinking, or cooking without treatment. Treatment required.
Sources of Nitrates in Maryland Well Water
How to Treat Nitrates in Well Water
Reverse Osmosis (Point-of-Use)
90–96% removalThe most common and cost-effective solution for most households. An under-sink RO system treats drinking and cooking water. Requires pre-filtration for well water (sediment, carbon, iron filter if needed).
Reverse osmosis guide →Ion Exchange (Nitrate-Specific)
95–99% removalA whole-home system that removes nitrates from all water in the house. More expensive than point-of-use RO but treats all water including bathing. Uses a nitrate-selective resin that must be regenerated with salt.
Distillation
95%+ removalEffective but slow and energy-intensive. Not practical for whole-home use. Countertop distillers can treat small volumes of drinking water.
Important: Boiling Does NOT Remove Nitrates
Boiling water concentrates nitrates by evaporating water while leaving the nitrates behind. Never boil water to reduce nitrates — it makes the problem worse.
Frequently Asked Questions
What is the safe level of nitrates in well water?
The EPA maximum contaminant level (MCL) for nitrates is 10 mg/L. For infants under 6 months, many pediatricians recommend not using water above 5 mg/L for formula preparation. Adults can safely consume water up to the 10 mg/L limit.
How do nitrates get into well water in Maryland?
The primary source is agricultural fertilizer — nitrogen leaches through the soil into shallow groundwater. Septic systems are the second most common source. Agricultural areas of Anne Arundel County have elevated nitrate levels in many wells.
Does boiling water remove nitrates?
No — boiling water does not remove nitrates. In fact, boiling concentrates nitrates by evaporating water while leaving the nitrates behind. Never boil water to reduce nitrates. Reverse osmosis or ion exchange are the correct treatment methods.