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Safety & Prevention

Well Water Safety & Testing: AAP Policy Explained

​​By: Alan Woolf, MD, MPH, FAAP, FACMT, FAACT

In the United States, more than 23 million households get their drinking water from private wells. Unlike public drinking water systems, these wells are not regulated for safety by federal or state government. They can become polluted by many substances and cause kids to get sick.

If your family drinks water from a private well, it's important to test the water regularly to make sure it's safe. It's also a good idea to ask about testing if your children drink well water at child care, school, camps or when your family travels.

How often should your well water be tested?

The American Academy of Pediatrics (AAP) recommends that if your family drinks well water, the well should be tested once a year for coliform bacteria and nitrates.

You may need to test your well water more often if:

  • ​Someone in your household is pregnant or nursing

  • There is a new infant or a child under 1 year of age in the home

  • You've had unexplained illnesses in your household

  • Your neighbors find a dangerous contaminant in their well water

  • The smell or taste of your well water changes

  • There's a chemical spill near your well

  • There are new fracking operations, underground chemical storage tanks or other industrial operations in your area that could contaminate the ground water

  • You had a major repair or replacement in your well

  • There was flooding or another disaster that may have contaminated your well

Are children at higher risk from contaminated well water?

Kids are more likely to pick up an illness from contaminated water than adults. This means that just because adults can drink the water without any problems, that doesn't mean a child can.

Types of well water contaminants

The main types of contaminants that can pollute wells come from chemicals and microorganisms (bacteria, viruses, fungi and parasites). You can find a list of all the regulated drinking water contaminants here.

How do contaminants get into well water?

All water naturally contains chemical elements. The natural chemical composition of well water varies with region, underlying geology and type of aquifer

The problem is when the water becomes polluted with potentially toxic chemicals. This can happen from naturally occurring chemicals in the well, such as arsenic, manganese and radium. It can also be caused by runoff from nearby industry, farms or businesses. Pollutant chemicals in well water may include nitrate and nitrite, heavy metals, organic chemicals including pesticides and per- and polyfluoroalkyl substances (PFAS) and radioactive particles.

Microorganisms (bacteria, viruses, fungi and parasites) can also pollute groundwater that supplies wells and cause illness. The biggest source of these microorganisms is solid waste from animals and humans. In 2013-2014, the Centers for Disease Control and Prevention reported 42 U.S. waterborne disease outbreaks, causing 1,006 cases of illness, 124 hospitalizations and 13 deaths.

Other factors that can affect well water safety

  • Climate change & disasters can affect drinking water, including private wells. Extreme weather events such as hurricanes, droughts and flooding can pollute groundwater with chemicals or microorganisms. Disasters such as industrial spills, wildfires, war and terrorist attacks can also result in wells becoming contaminated. For example, radioactive substances can be released due to an earthquake or a tsunami.

  • Hydraulic fracturing, also known as fracking, is another potential threat to drinking water. Fracking is a process of extracting oil or gas from underground rock. The fluids used in fracking can affect groundwater.

Chemicals in well water

Too much of these chemicals in drinking water can cause side effects:



Possible Effects

Target Range/Goal


  • Rock formations specific to the southeastern U.S. "slate belt," Nevada, Alaska, and other areas of the western U.S.

  • Bladder, skin and lung cancer in humans

  • Miscarriage, stillbirth and low birth weight

  • Skin pigmentation, melanosis and keratosis

  • Gastrointestinal, pulmonary, cardiovascular, endocrine, immune and neurotoxicity

10 ug/L maximum

Chromium VI

  • Used in electroplating and other industries

  • Toxic to and causes cancer in laboratory animals



  • Naturally in water in a few parts of the U.S.

  • Preventive for dental cavities

  • Supplement if concentration is low

  • Too much can cause dental fluorosis

Optimum level = 0.7 mg/L

Maximum contaminant level = 4 mg/L

Fracking chemicals

  • Natural gas extraction




  • Leached from brass in a submersible pump, from solder or from old lead pipes

  • Learning and behavior problems

  • Hearing and speech challenges

  • Red blood cell, kidney and bone toxicity

EPA maximum contaminant level for lead is 15ppb; the AAP has recommended a lower maximum safe lead level of 1 ppb for school drinking fountains



  • Naturally in water

  • Waste slag from smelting, refining or other mining operations

  • Parkinson syndrome-like symptoms

  • May affect childhood development and learning

Under 0.3 mg/L

Methyl tertiary butyl ether

  • Fuel additive in gasoline

  • Causes cancer in laboratory animals


Nitrate and nitrite

  • Sewage

  • Fertilizer

  • Animal waste

  • A blood disorder called methemoglobinemia

  • Enables carcinogens (substances that can cause cancer) to form in the body

Maximum contaminant level = 10 mg/L for nitrate

Maximum contaminant level = 1 mg/L for nitrite

Perchlorate nitrate

  • Used in rocket fuel, fireworks, airbag inflators and other items

  • Can occur naturally

  • Restricts thyroid hormone processes

Only certain states have guidance; in Massachusetts, it's 2 ug/L maximum, in California, it's 6 ug/L maximum

Perfluoroalkyl and polyfluoroalkyl substances (PFAS)

  • Landfills, military or industrial sources

  • Consumer products such as nonstick cookware and stain repellents

  • May be linked to health problems such as cancer, low birth weight, reduced fertility, impaired immune response, thyroid abnormalities, increased cholesterol and uric acid

Depends on specific chemical


  • Naturally occurring

  • Lung cancer in humans

No enforced drinking water standard


  • Naturally occurring in western mountains in the U.S. and areas with visible granite formations in the eastern U.S.

  • High dose is extremely toxic

  • Linked to kidney disease

  • A source of ionizing radiation, which causes cancer

Maximum contaminant level = 30 ug/L

Volatile organics and pesticides

  • Dry cleaning, gasoline, agriculture, etc.

  • Often unable to be identified

  • Effects depend on the compound


A word about nitrates

Studies show that a substantial number of private wells contain levels of nitrates that are too high. Nitrates are a natural part of plants and nitrate-containing fertilizers. They can seep into well water and can pose toxic risk to humans. In the body, they can be converted to nitrites, which are also potentially hazardous. Boiling doesn't remove them.

In infants, nitrates can lead to a dangerous condition called methemoglobinemia. This is a blood disorder that interferes with the circulation of oxygen in the blood. Formula that is prepared with well water may put babies at risk of nitrate poisoning.

If your well water contains a level above 10 mg/L, it should not be used in infant formula or food. Instead, use purchased water, public water supplies or water from deeper wells with minimal nitrate levels.

Bacteria & other microorganisms in well water

To check for microorganisms, test your water for "total coliform bacteria." Most coliform bacteria don't cause disease. But if they're in your well water, this means that your water might be contaminated with microorganisms.

Examples of harmful microorganisms that may be found in well water include:




Escherichia coli (E coli), including O157:H7

Norovirus and sapovirus

Giardia duodenalis

Salmonella species


Cryptosporidium parvum

Shigella species



Campylobacter jejuni

Hepatitis A and E


Yersinia enterocolitica


Mycobacterium avium-intracellulare

Legionella species

Talk with your pediatrician

If you have concerns about contamination of your private well, stop using the water and consult your local or state health department and local individuals with known expertise in private well construction and remediation. Your pediatrician can also be a resource. In addition, your regional Pediatric Environmental Health Specialty Unit (PEHSU) have staff who can also talk to you about your concerns.

You can find information about private drinking water well programs on the U.S. Environmental Protection Agency (EPA) website.

More information

About Dr. Woolf

Alan Woolf, MD, MPH, FAAP, FACMT, FAACT​ is a pediatrician and a professor of pediatrics at Harvard Medical School. He serves as the associate chief medical education officer at Boston Children’s Hospital (BCH) and the director of its Pediatric Environmental Health Center and its fellowship training program in pediatric environmental health. He also directs the Region 1 New England Pediatric Environmental Health Specialty Unit. Dr. Woolf is a member of the Executive Committee of the AAP’s Council on Environmental Health & Climate Change.

Last Updated
American Academy of Pediatrics (Copyright © 2023)
The information contained on this Web site should not be used as a substitute for the medical care and advice of your pediatrician. There may be variations in treatment that your pediatrician may recommend based on individual facts and circumstances.
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