Drinking Water From Private Wells and Risks to Children

Approximately 23 million households in the United States obtain their water from private wells.^1,2  Whereas public water supplies (community and noncommunity systems) are within the jurisdiction of the US Environmental Protection Agency (EPA) under the Safe Drinking Water Act (SDWA), with national drinking water regulations providing legally enforceable standards, private wells are not subject to federal regulations and are minimally regulated by states after their construction. All states but 2 require that a well be dug or drilled by a certified contractor. A number of states also require an initial water test before a new private well is put into service. After construction, in most states, the owner of the well is not required to inspect the well or test the water.

Well water is not sterile, nor does it need to be, but it should be free of fecal contamination, usually detected by coliform bacteria counts. Other contaminants, such as metals, solvents, fuel additives, perfluoroalkyl substances, pesticides, and naturally occurring contaminants (eg, arsenic, manganese, radium) also may contaminate private wells. And although recommendations regarding wells note that infants are most susceptible to nitrate-induced methemoglobinemia, other recommendations regarding well water specific to families with children are limited. Similarly, recommendations that address events that might expose a child to untested water, such as the birth or adoption of a child, are not available. As a general principle, children are likely to be more susceptible to waterborne illness than adults, because they drink relatively more water per body weight, develop gastroenteritis more often, and become dehydrated more quickly when they develop gastrointestinal (GI) illness. Thus, even if adults can consume the water without incident, there is not a guarantee that a child can do so. It is also worth noting that most studies, when investigating the adverse health effects of drinking contaminated water, address only the effects of a single toxicant in isolation. However, some contaminated drinking water may contain several impurities with significant health implications. The combination of several chemical contaminants present in drinking water at the same time may produce at least additive, and possibly synergistic, symptoms and signs of illness.^3,4 

Groundwater is water that infiltrates into the ground and exists in the open space between soil particles and fractures in bedrock. As it infiltrates, some is held in the soil, some is taken up by plants, and the rest reaches the water table, where all of the pore spaces and fractures are completely filled (saturated) with water. Below the water table, there may be several additional geologic units that are saturated; some are considered aquifers. An aquifer, which may or may not be the water table, is a geologic unit—either unconsolidated sand and gravel or bedrock—that can provide a useable quantity of water to a well. Aquifers receive recharge through infiltration from the surface or from movement of water between geologic units, including other aquifers. As part of the hydrologic cycle, groundwater is continually moving both into (infiltrated) and out of (discharged to streams, pumping, springs) the ground, and its volume can vary from season to season and year to year. An “artesian well” has a water level that is higher than the top of the artesian aquifer itself because of pressure in the aquifer (Fig 1).

There are 3 main types of water wells: large diameter dug or bored wells, sand and gravel wells, and bedrock wells. Bedrock wells are typically drilled into bedrock, and the fractures in the rock act as a conduit to provide water to the well (Fig 2). Sand and gravel wells are generally either drilled or driven and completed in a geologic unit comprising sand and gravel. Sand and gravel wells typically have a screen at the lower 5 to 10 feet of the well, and water comes into the well through the screen. Driven sand and gravel wells (commonly referred to as sand points) are usually installed where sand is near the surface and the water level is shallow. Sand points do not protect from nearby surface contamination because of the high infiltration attributed to sandy surface soils, allowing surface contaminants to reach the well. Large-diameter dug or bored wells are generally installed when there is no aquifer available at the well location and instead are built to capture water from the shallow water table. Large-diameter wells are typically 3 or 4 feet in diameter to provide more volume in the well casing to store water that slowly infiltrates into the well from finer, less permeable materials. Large-diameter dug and bored wells are typically shallow and, therefore, more susceptible to surface influences (eg, contamination, drought).

The drilling of a new private well or the reconstruction of an existing well should be a 3-part process: permitting by local or state authorities, professional inspection, and water quality testing.⁵  Although the recommended minimum distances vary on the basis of the contaminant, private wells should be as far as feasible from any potential sources of contamination. A state well construction code includes set-back distances for most common sources found near a home, and those distances vary by state. Septic systems, for instance, may be listed as no less than 50 feet, 75 feet, or 100 feet, depending on the state. There are a number of considerations in siting a well. Some examples include septic systems, underground fuel tanks, sheds in which fertilizers or other chemicals are stored, livestock, and cultivated fields. Farms and ranches where animals are raised are also potential sources of groundwater contamination. Large agricultural facilities with livestock, termed concentrated animal feeding operations, which are animal feeding operations housing 1000 animal units or more, are especially likely to be potential sources of groundwater contamination. Thus, when siting a new well or when there is concern about contamination of an existing well, consultation with the local health department should be sought. In addition, the well should be on relatively high ground (for example, uphill from septic tanks). If a homeowner is in doubt about the safety or integrity of the well, inspection by the state or county health department or a licensed well contractor should be arranged. In addition, if there is a flood or if the well housing is damaged, professional inspection is warranted. Finally, the inspection of a private well should be triggered by the sale of a residence, if evidence of a recent previous inspection is unavailable.

What follows is a selective compilation of information and recommendations concerning wells and well water. The more common contaminants are addressed in this technical report. However, the EPA regulates many different chemicals and microbials, and the reader is referred to the EPA websites (see “Resources” at the end of this report) for details on all EPA-regulated agents. For additional information on the safety of drinking water, the reader is referred to Chapter 17 in the American Academy of Pediatrics (AAP) book, Pediatric Environmental Health, Fourth Edition.⁶ 

Arsenic is one of the most common elements in the earth’s crust and is a groundwater contaminant in parts of many states in the United States.^7,8  Arsenic is a colorless, tasteless, odorless metalloid element that occurs in both trivalent (As⁺³; arsenite) and pentavalent (As⁺⁵; arsenate) forms, each having differing toxicities. Whereas organic arsenic as As⁺³ and/or As⁺⁵ occurs mainly in foods, inorganic arsenic can contaminate drinking water from natural sources, as well as from industrial activities such as mining, electronics manufacture, and smelting. The World Health Organization (WHO) has characterized arsenic contamination of food and water as the most toxic pollutant affecting human health worldwide. Arsenic is found in specific rock formations, for example, the “slate belt” in the southeastern United States, and its presence in well water is sometimes predictable from geologic data. In 2001, the EPA reduced the maximum contaminant level (MCL) for arsenic in drinking water from 50 μg/L to 10 μg/L. A few states, such as New Hampshire, have further lowered the MCL to 5 ug/L. Private wells are unregulated with respect to arsenic contamination, and arsenic levels as high as 3100 μg/L have been recorded in the United States.⁹  One National Health and Nutrition Examination Survey (NHANES)-based study showed that, whereas users of municipal water supplies for drinking water experienced a 35% decline in urinary arsenic levels between 2003 to 2004 and 2013 to 2014, users of private wells did not experience a similar trend.¹⁰  Researchers hypothesized that a lack of regulation, monitoring, and prevention made private well users a more vulnerable population for continued arsenic exposure.

Arsenic is extremely toxic; exposures in early childhood have been associated with an excess incidence of cancers (eg, skin, lung, bladder) in adulthood.^11–14  Noncancerous toxic effects are seen after chronic ingestion of inorganic arsenic at higher concentrations, including skin lesions, respiratory effects, musculo–neurologic and peripheral neurotoxicity, and vascular abnormalities.¹⁵  Long-term exposures to relatively low doses of arsenic in drinking water may pose neurobehavioral and neurodevelopmental toxic risks for children.^9,16  Excessive intakes of arsenic during pregnancy have been associated with increased rates of stillbirths and other adverse birth outcomes.¹⁷ 

Fluoride is the lightest chemical element from the halogen group on the periodic table. It is naturally occurring in groundwater, although levels vary between wells depending on multiple factors, including geographic region.¹⁸  Fluoride is used as an effective preventive for dental caries.¹⁹  For this reason, public water systems often fluoridate water at the community level.²⁰  The US Public Health Service most recently recommended an optimal fluoride level of 0.7 mg/L (0.7 ppm) within community water systems for the purpose of preventing dental caries.²¹  The AAP recommends that fluoride supplements be considered for children older than 6 months who drink well water that does not contain fluoride.¹⁹  Recommendations for dosing of fluoride supplements vary by age and fluoride level in drinking water.¹⁹  The US Preventive Services Task Force, American Academy of Pediatric Dentistry, and American Dental Association also recommend oral fluoride supplementation for children whose water supply is deficient in fluoride, although the recommendations of the latter two are specific to children at high risk for dental caries.^22–24 

Skeletal fluorosis or dental fluorosis may result from excess fluoride intake. Dental fluorosis is characterized by tooth discoloration or pitting.²⁵  Skeletal fluorosis results in tenderness or pain of bones and joints, although it only occurs in adulthood after years of exposure to elevated levels of fluoride. Given the risk of dental fluorosis in children, all potential sources of fluoride should be assessed before prescribing a supplement, and ingestion of higher-than-recommended doses of fluoride should be avoided.^19,22 

The EPA sets a primary MCL of 4 ppm for prevention of skeletal fluorosis and a secondary MCL of 2 ppm for prevention of tooth discoloration.^26,27  Fluoride concentration in well water should be determined as part of the initial evaluation of a new well or during periodic retesting of water from an established well as indicated. Should fluoride levels in water from a private well exceed 2 ppm, then children younger than 8 years should be provided with an alternative source of drinking water. Several methods can be used to remove excess fluoride from drinking water, such as distillation and reverse osmosis.²⁸ 

Most state health departments and many commercial sources offer testing of drinking water for inorganic compounds including calcium, sodium, fluoride, chloride, iron, manganese, magnesium, pH, hardness, and total dissolved solids. Total dissolved solids usually consist of calcium and magnesium as their bicarbonates. These bicarbonates make water “hard.” Hard water is not toxic; however, the calcium and magnesium precipitate when the water is heated, and this precipitation will eventually cause electric hot water heaters, coffee pots, kettles, and any electrical device in which water is heated repeatedly to fail as the precipitate insulates the heating element. Hard water also forms scum with soaps and detergents. High concentrations of manganese and iron can affect water’s appearance and taste. Water can appear as rust-colored with black flecks, have a bitter or metallic taste, and can stain clothing, plumbing, and fixtures. So-called iron bacteria can grow in such water and form black slimy colonies of microorganisms, sometimes clogging pipes and faucets. They can also form biofilms containing other pathogens that can pose a threat to the family’s health.

Lead is ubiquitous in the environment and can be in groundwater. However, it is most often leached from the brass in a submersible pump, from solder, from faucets and other plumbing fixtures, and in some cases, from old lead pipes if the water is naturally corrosive or made corrosive by treatment.²⁹  Plumbing older than 1986, the year a federal ban was passed on lead use in pipes and solder, is especially likely to contain some lead. So-called “lead-free” pipe fittings, faucets, and other plumbing fixtures could still contain 8% lead by weight until that was reduced to 0.2% by the Reduction of Lead in Drinking Water Act (2011).³⁰ 

Lead in water has no detectable taste, and it does not change the water’s smell or appearance. The best way to identify and quantify lead in water in an older home served by a private well is to test the water first, inside the home and then (and only if it is elevated) closer to the source at the well. In 1991, the EPA set an action level for lead in drinking water from municipal sources of 15 μg/L (or 15 ppb), although this is not a health-based standard.³¹  Others have recommended a lower limit; for example, the current limit for lead in school water fountains recommended by the AAP is 1 ppb.³²  In homes with water lead levels exceeding 15 μg/L, the Centers for Disease Control and Prevention (CDC) specifically recommends that children and pregnant women consume only commercially available bottled water or water that has been treated with a filter that is American National Standards Institute (ANSI)/NSF certified to remove lead.

Manganese is an essential trace element, necessary in small amounts for proper body function.^33–36  Most people achieve adequate intake of manganese from food-based sources. In drinking water, manganese is considered an undesirable contaminant. Manganese may dissolve into groundwater from naturally occurring deposits in soil and rock or may be associated with industrial emissions or pollution.³⁶  Such contamination may be present in drinking water at levels that could lead to excessive consumption. Very high levels of exposure to manganese are associated with neurologic effects, including signs and symptoms similar to Parkinsonism.³⁷  Such disease is generally seen in inhalational exposures in occupationally exposed individuals, such as welders, although there is some concern that oral exposure may also be a cause.^35,37  More subtle neurologic symptoms, including poorer memory and attention, have been found in children exposed to higher levels of manganese in drinking water.^38,39  Individual susceptibility to high levels of manganese is variable; some children have rare genetic manganese transporter defects and suffer serious disabilities related to neurologic dysfunction.⁴⁰  Although the EPA sets no primary drinking water standard for manganese, a secondary MCL is set at 0.05 ppm (0.05 mg/L) because of notable discoloration, black staining, and a bitter metallic taste at higher concentrations.^27,36  Recognizing the potential for health effects, the EPA also sets a nonenforceable health advisory level, recommending manganese levels in water be below 0.3 ppm over a lifetime to protect against potential neurologic effects.^35,36  For infants younger than 6 months, this level of 0.3 ppm should also be applied to acute exposures over 10 days.³⁶  Manganese can be removed from water using a variety of methods such as water softening, oxidation, and filtration.⁴¹  Given its ability to stain, point-of-entry treatment devices are typically desirable for manganese to allow for treatment of all water uses in the home.⁴¹ 

Methyl tertiary butyl ether (MTBE) is a partially oxidized hydrocarbon fuel additive used in the past to oxygenate gasoline, having replaced the previously used toxic chemical: tetraethyl lead. The oxygenation of gasoline during certain seasons was mandated by the Clean Air Act in 1990 (Public Law No. 101–549) to reduce carbon monoxide emissions. Motor vehicle exhausts are the primary source of ambient carbon monoxide levels. Oxygenated gasoline is designed to increase the combustion efficiency of gasoline, thereby reducing carbon monoxide emissions. The tertiary butyl group on MTBE hinders breakdown by sterically protecting the molecule; as a result, uncombusted MTBE can persist in the environment and seep into groundwater. MTBE is neurotoxic and carcinogenic in experimental animals.⁴²  MTBE was found in water supplies throughout the United States in the early 2000s and was subsequently banned by 23 states and phased out of all US gasoline by 2008 to 2009, replaced by ethanol.

Nitrate and nitrite, largely from sewage, fertilizer, animal waste, and natural deposits, remain 2 of the most common contaminants of wells. Nitrite and nitrate, terms describing nitrogen-containing molecules, are frequently confused. Nitrite has 2 oxygen atoms and nitrate has 3. Nitrate ions form nitric acid, which is a strong acid. Nitrite ions form nitrous acid, which is a weaker acid. Nitrite is fairly unstable and easily oxidized to nitrate, but nitrate also turns into nitrite with the help of bacteria in the mouth and body. Nitrite is much less common than nitrate in groundwater and, when detected, is found at much lower concentrations. High levels of nitrates and/or nitrites in well water can result from improper overuse of chemical fertilizers containing nitrogen or from the improper disposal of human and animal waste.⁴³  Contamination by nitrates can be exacerbated by improper well construction or well location near nitrogen sources, such as a farm or concentrated animal feeding operations. The US Geological Survey (USGS)’s National Water Quality Assessment Project 1988 to 2015 tested principal groundwater aquifers used as US public and private drinking water supplies and estimated that 2% of public-supply wells and 6% of private wells exceeded the EPA’s MCL for nitrate; 21% of private wells in agricultural areas exceeded the MCL.⁴⁴ 

In the United States, nitrate is typically reported from the laboratory as nitrate nitrogen (NO₃–N); a level of 3 mg/L or greater indicates contamination, although private wells are not federally regulated.⁴⁵  Water with a nitrate concentration greater than 10 mg/L or nitrite greater than 1 mg/L should not be used to prepare infant formula or other foods or given to a child younger than 1 year to drink.⁴⁵  The presence of nitrate requires testing for coliforms. Nitrate with no coliforms is likely from fertilizer. If possible, neighboring wells should be tested to determine whether the contamination is widespread. Nitrate with coliforms is likely from sewage (livestock or human). Septic fields or tanks, concentrated animal feeding operations, manure fields, or settling ponds also can be sources of contamination.

The toxicity of nitrate to humans is mainly attributable to its reduction to nitrite.^45,46  The MCL for nitrate and nitrite was initially set to protect infants from methemoglobinemia; it is nitrite that actually is involved in the oxidation of hemoglobin to methemoglobin.^45,47  Associations now exist between other adverse health outcomes and drinking water nitrate ingestion, such as colorectal cancer, thyroid disease, and neural tube defects, but there are still too few studies to allow firm conclusions about risk.⁴⁸  Nitrate and nitrite may be successfully removed from water using treatment processes such as ion exchange, distillation, and reverse osmosis.

Perchlorate is an oxidizing anion used in rocket fuels, fireworks, and road flares. It is used in industrial processes and can contaminate ground water at industrial sites. It also occurs naturally and is recognized as a water pollutant. Major sources of exposure in children include foods, drinking water, and human milk. Perchlorate is a well-studied steric inhibitor of the thyroid symporter, which transports iodine across the thyroid gland’s membrane before hormone synthesis. There is evidence that perchlorate interferes with thyroid function in children and adults in the United States, even at background exposures,⁴⁹  and can be detrimental to the fetus during pregnancy.^50,51  In 2011, the EPA announced its intent to regulate perchlorate under the SDWA. The EPA has not yet set an MCL goal for perchlorate, although individual states have established their own guidance. For example, Massachusetts has set its drinking water standard for perchlorate at 2 μg/L and California has set its standard at 6 μg/L.

Perfluoroalkyl and polyfluoroalkyl substances (PFAS) are ubiquitous manmade chemicals; the class may include more than 12 000 different compounds. PFAS are not lipophilic; they are thermally and chemically stable, stain resistant, and have surfactant properties. They have been commonly used in nonstick pots and pans (Teflon), some food packaging, stain-resistant finishes for carpeting, water-resistant coatings for shoes and clothing, and aqueous firefighting foam used especially by firefighters and the military to extinguish airplane and other fires and in training exercises. PFAS have been detected in municipal and private well water, as well as in certain foodstuffs (eg, meat, fish, dairy) and house dust. Some PFAS are environmentally persistent, not easily degraded by natural processes. PFAS have been called “emerging pollutants” by the EPA, which, in 2014, set provisional health advisory limits for 2 such compounds, perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) in drinking water at 70 ppt, either separately or combined.⁵²  Some states have since elected to set their own maximum contaminant levels for PFAS compounds in drinking water at lower levels. In 2022, the EPA further lowered its health advisory limits to 0.004 ppt for PFOA and 0.02 ppt for PFOS. The EPA has also set lifetime, non-cancer health advisory limits for hexaflouropropylene sulfonic acid (a newer GenX PFAS chemical) at 10 ppt and perfluorobutane sulfonic acid at 2100 ppt.

Almost all Americans have detectable PFAS levels in their blood. NHANES data indicate that the concentrations of both PFOA and PFOS have been declining in adults over time; however, levels in the blood of other PFAS compounds still in the commercial stream may be rising, especially in those areas with known groundwater contamination. PFAS can be transmitted to infants in human milk.⁵³  Children and adults drinking water from municipal sources or private wells contaminated with PFAS for long periods of time may have elevated levels in their blood.^54,55  PFAS are believed to cause adverse health effects in humans, although there is much uncertainty about the risks they pose. Chronic exposure to amounts found in food and water may be associated with some types of cancers, effects on lipid metabolism, changes in some hormonal levels, immune effects, small reductions in birth weight, reduced fecundity in adults of childbearing age, and preeclampsia.⁵⁶  Some home treatment systems have been certified to remove PFAS in contaminated drinking water, including granulated activated carbon, ion exchange resins, and reverse osmosis systems. State health departments can be consulted for more information. The PFAS Exchange project also has a fact sheet aimed at treatment options (“PFAS in Drinking Water: What You Should Know”; https://pfas-exchange.org/resources/). The STEEP Superfund Research Program Center has a Web page on tips for private well owners on PFAS (https://web.uri.edu/steep/tips-for-well-owners/).

Pesticides, a class of anthropogenic compounds along with volatile organic compounds, are chemicals used to kill weeds (herbicides), insects (insecticides), vermin (rodenticides), and fungus (fungicides). They are ubiquitous. There are 50 000 different pesticide products used in this country, composed of more than 600 active ingredients.⁵⁷  A billion pounds of pesticides are used every year.⁵⁸  The permissible US limit for pesticide concentration in drinking water varies by each specific chemical. Some pesticides have had a designated MCL in drinking water set by the EPA, but many have not.^59,60  In one 2009 USGS study of more than 2000 wells, approximately half of the pesticides were measured in nearly all (about 90% or more) of the sampled wells; other pesticides were measured in about 60%.⁶¹  A more recent study tested 1204 wells (in aquifers representing 70% of the volume pumped for drinking water) for 109 pesticides and 116 pesticide residues. Results showed pesticides and/or pesticide residues in 41%, with the most common (>5% of wells) being atrazine, hexazinone, prometon, tebuthiuron, and metolachlor residues.⁶²  Atrazine and glyphosate are the first and second most common pesticides used in the United States. Glyphosate is a primary drinking water contaminant of the federal SDWA, with an MCL for drinking water of 0.7 mg/L. As of January 2020, the EPA continues to find that there are no risks of concern to human health when glyphosate is used in accordance with its current label.⁶³  The EPA’s dietary (food plus water) risk assessments did not identify any potential acute, 4-day, chronic, or cancer risks of concern. However, evidence has demonstrated that even low concentrations of glyphosate may lead to the stimulation of hormone-dependent cancers in humans.⁶⁴  The International Agency for Research on Cancer (IARC), an arm of the WHO that conducts expert reviews of exposures that potential carcinogenic hazards to humans, in 2015 concluded that glyphosate is a “probable” carcinogen.⁶⁵  The EPA classified atrazine as “not likely to be carcinogenic” in 2000.⁶⁶  However, the Agency for Toxic Substances and Disease Registry notes that atrazine may affect reproduction.⁶⁷  In agricultural areas, neonicotinoid insecticides are sometimes used as seed treatments. In animal studies, neonicotinoids have been shown to have reproductive toxic effects, neurotoxicity, and potential carcinogenicity.⁶⁸  Point-of-use devices like charcoal filters and reverse-osmosis treatments can be used to remove or minimize pesticides in drinking water (for details on pesticides in private well water, see http://npic.orst.edu/envir/dwater.html).

Gross α radiation is a type of energy released when certain radioactive elements in the earth’s crust, such as uranium and thorium, decay or breakdown. The overall amount of radioactivity in water, representing contributions from all of the radionuclides present, is measured as “gross alpha,” because naturally occurring radioactive elements emit α particles as they decay. Usually, uranium, radium, and radon isotopes and other isotopes constitute the gross α radiation in groundwater. The SWDA Amendments in 2001 list standards for combined radium 226/228 of 5 pCi/L and a gross α standard for all alphas of 15 pCi/L (not including radon and uranium).⁶⁹  When β particle radioactivity is greater than 50 pCi/L, minus the naturally occurring potassium-40 in public water supplies, the individual radionuclide species must be evaluated. Exposure to background levels of radionuclides can pose unknown health issues for pregnant women, infants, children, and other vulnerable groups.⁷⁰ 

The highly radioactive element, radium, is the product of the radioactive decay of uranium and thorium in rocks and soils. It is naturally occurring, and radium levels tend to be higher in groundwater (wells, aquifers) than surface water. Water from wells and air near factories using fossil fuels also have higher amounts of radium. The Environmental Working Group maintains a map of radium contamination in public water systems.⁷¹  Radium dissolved in drinking water is a human-health concern, because it affects different parts of the body than radon, accumulating largely in bone and other tissues, increasing lifetime cancer risks. The SDWA Amendments in 2001 list the standard for combined radium 226/228 of 5 pCi/L.⁶⁹  About 2.2% of private wells tested above this limit in 2009.⁶¹  Reverse osmosis (cationic ion exchange) has been identified by the EPA as a “best available technology” for uranium, radium, gross α, and β particles and photon emitters. It can remove up to 99% of these radionuclides.⁷²  Activated charcoal filters are more effective against radon.

Radon-222 is a naturally occurring colorless, odorless, water-soluble, radioactive gas formed as uranium-238 decays. Radon emits α particles as it decays. Radon gas can dissolve and accumulate in water from underground sources such as wells. When water that contains radon is used in the home for showering, washing dishes, and cooking, radon gas escapes from the water and enters the air.⁷³  When living in an area with high radon in groundwater, generally the northern United States,⁷⁴  radon can enter private wells. The CDC notes that showering, washing dishes, and doing laundry can disturb the water and release radon into the air.⁷⁵  A 2009 USGS report found concentrations greater than the proposed MCL from the EPA occurred in every major aquifer in the United States. Radon concentrations averaged 434 pCi/L and were greater than the lower of 2 proposed MCLs (300 pCi/L) in 65% of the wells and greater than the higher proposed MCL (4000 pCi/L) in 4% of wells.⁶¹  There is currently no federally enforced drinking water standard for radon, but the EPA recommends that homes with indoor air concentrations at or above 4 pCi/L be remediated to reduce concentrations.^76,77  Approximately 2% of radon in the air in homes that use well water is from the water. Radon emits strongly ionizing particles that do not penetrate far into tissue or other substances but are carcinogens.⁶¹  Breathing radon in indoor air is a cumulative risk that can cause lung cancer. Drinking water containing radon also presents a (smaller) risk for developing internal organ cancers, primarily stomach cancer.^76,77  The National Academy of Sciences (now known as The National Academies of Sciences, Engineering and Medicine) estimated that radon in drinking water causes about 168 cancer deaths per year, 89% from lung cancer caused by breathing radon released from water, and 11% from stomach cancer caused by drinking radon-containing water.⁷⁸  Radon testing can easily be performed, and homes should be remediated if indoor air levels are 4 pCi/L or higher.⁷⁶ 

Sea salt is a problem near the ocean and in areas where there was formerly saltwater.

The sodium content of drinking water is extremely variable, and 1 national survey found that the sodium content of drinking water varies from 4 to 80 mg/L, with a mean concentration of 28 mg/L. The estimated adequate and safe intake of sodium for adults ranges from 1100 to 3300 mg/day, although the Dietary Guidelines for Americans recommends adults limit sodium intake to less than 2300 mg/day. Infant requirements vary from 115 to 750 mg/day, although some sources recommend sodium intake for infants at less than 200 mg/day. Although the EPA does not mandate a maximum level of sodium permitted in public water supplies, the Drinking Water Equivalence Level, or guidance level, recommends that sodium levels not exceed 20 mg/L.²⁷  Chloride is one of several of the total dissolved solids included in the EPA National Secondary Drinking Water Regulations. Deemed as not threatening to health, the National Secondary Drinking Water Regulations are established as guidelines to assist public water systems in managing their drinking water for aesthetic considerations, such as taste, color, and odor. The secondary MCL for chloride is 250 mg/L.²⁷  In coastal areas, saltwater intrusion into coastal rivers and aquifers can be exacerbated by sea level rise. With continued sea level rise and coastal saltwater intrusion into aquifers occurring worldwide as a result of climate change, coastal wells can be expected to see an increase in salinity. Saltwater intrusion (into aquifers and, therefore, into wells) is a US problem largely in south Florida as of 2012.⁷⁹  A 2019 study by the Maryland Extension Service in the coastal plains of Maryland found the average level of sodium in homes using well water was 92.6 mg/L, which could represent 15% of the recommended daily intake of sodium.⁸⁰  Most people cannot or will not drink enough saltwater to become acutely toxic, but hypertension is associated with increased daily sodium intake. Additionally, a link between salinity in drinking water in late pregnancy and the risk of preeclampsia and gestational hypertension and infant mortality was noted in coastal Bangladesh.⁸¹  A 2015 World Bank Report postulated a role of increased salinity in infant mortality as a result.⁸²  Road salt can also contaminate public and private wells; New Hampshire has dug hundreds of new wells because of such contamination.⁸³  With water scarcity, saltwater intrusion, and climate change predictions, domestic desalinization is being studied worldwide and is becoming economically feasible. Home reverse osmosis units can remove sodium and chloride.

Selenium is an essential trace element that can be found in many foods. Selenium may also be present in groundwater naturally, from erosion of natural deposits, or as a pollutant by discharge from mines or from petroleum or metal refineries.^26,84,85  Small amounts of dietary intake of selenium are required for protein production, reproduction, thyroid hormone metabolism, DNA synthesis, and protection from oxidative damage.⁸⁴  However, excessive selenium exposure can have negative health effects. Acute oral exposure to high levels of selenium can lead to nausea, vomiting, and diarrhea.⁸⁵  Long-term exposure to high levels of selenium can causes selenosis, a condition characterized by hair loss, nail loss, and neurologic symptoms such as numbness of hands or feet.⁸⁵  The EPA sets a primary drinking water standard for selenium at an MCL of 0.05 ppm.²⁶  Reverse osmosis, ion exchange, and alumina adsorption can reduce levels of selenium in water.⁸⁶ 

Uranium in groundwater is mostly found in the western mountains in the United States. However, uranium can also be found in areas that have granite outcrops, the result of granite intrusion into existing subterranean strata and subsequent weathering. There have also been reports of high uranium concentrations in waters of Connecticut and South Carolina.^87,88  Levels of radon and uranium are positively correlated.⁶¹  Those who drink uranium-containing water absorb and then excrete it; urinary concentrations as high as 25% of peak can be present 6 months after exposure has ceased.⁸⁷  The EPA established an MCL for uranium of 30 μg/L.²⁶  A USGS report of more than 2000 US wells in 2009 found uranium greater than the MCL in 1.74% of wells. Isolated regions contain much higher levels—14.1% of wells in southeast Montana tested by the USGS exceeded the threshold.⁶¹  Exposures likely to be encountered in drinking water have not resulted in acute toxicity. Radiation carcinogenesis, however, is currently believed to have no threshold. Reports on the biological effects of ionizing radiation estimated that some cancer may be attributable to background uranium exposure, including uranium in water, even though uranium has not been classified with respect to carcinogenicity.⁸⁹  More recently, preliminary research suggests a link between uranium and diabetes mellitus prevalence in a 2016 study of adults using NHANES data even at the relatively low levels observed in the US general population.⁹⁰  Kidney damage has been observed in humans and animals after inhaling or ingesting uranium compounds, and the EPA cites kidney damage as a potential health effect from long-term exposure to uranium above the MCL.²⁶ 

Compounds that are prepared by reaction of other compounds are known as “synthetic.” They enter the environment and eventually the water from agricultural practices, industrial sites, petroleum industries, landfills, and incinerators. These are sometimes grouped under “total organic compounds” on water analyses. The most common ones found in US water supplies are pesticides, PFAS, dioxins such as polychlorinated biphenyls, solvents, and volatile organic compounds (VOCs). Thousands of volatile organic chemicals, from gasoline to pesticides to cleaning fluids, are used in agriculture, industry, and transportation and around the home daily. Whereas they readily vaporize and dissipate in open air and in surface water, they persist when they seep into the ground and contaminate groundwater. Although some VOCs may be degraded there by bacteria, others remain in the aquifer for some time and can migrate with movement of the water into supply wells.⁹¹  Although individual sources of these compounds are sometimes identified, such as abandoned gas stations with leaking underground storage tanks, these compounds are very mobile in an aquifer and can appear without specific sources. The USGS evaluated studies of 3500 water samples from domestic wells representing more than 100 aquifers collected between 1985 and 2001.⁹²  Water samples were tested for 55 different VOCs. Common VOCs present in 1% of more of samples at an assessment level of 0.2 μg/L included chloroform (trihalomethane), perchloroethylene (solvent), MTBE (gasoline oxygenate), trichloroethene (solvent), toluene (gasoline hydrocarbon), dichlorofluoromethane (refrigerant), 1,1,1-trichloroethane (solvent), chloromethane (solvent), bromodichloromethane (trihalomethane), and trichlorofluoromethane (refrigerant). Public wells were more likely to contain VOCs than private wells, perhaps because of the larger withdrawal rates and their closer proximity to industrialized areas of the country. Wells were more likely to be contaminated if they were shallow, were in a more urban area, or if they drew water from an aquifer with no impermeable layer between the surface and the water (Fig 2). Although exposure of children to VOCs in water is most often presumed to be by ingestion, skin absorption and/or inhalation are other possible routes of exposure. VOCs vary in their toxicity profiles; some, such as benzene, are known carcinogens. VOCs also are associated with a variety of noncancer health effects, ranging from skin, eye, and mucous membrane irritation to target end-organ damage. Point-of-entry filtration systems can be installed in the home that remove VOCs from contaminated water.

Much of the information describing the pathogens that may be present in well water has been obtained from prospective water quality studies and investigations of waterborne outbreaks.^93–95  There were 42 waterborne disease outbreaks reported in the United States in 2013 to 2014, causing 1006 cases of illness, 124 hospitalizations, and 13 deaths.⁹⁶ Legionella species was associated with 24 (57%) outbreaks and all the deaths. Mycobacterium avium-intracellulare and Cryptosporidium species may be found in well water, producing systemic or pulmonary disease in specific vulnerable populations. Disease from Legionella species typically results from inhalation rather than ingestion of bacteria. Outbreaks caused by Legionella species typically occur in large buildings after colonization of the water distribution system and have not often been identified as a result of contamination of well water. Antibiotic-resistant bacteria have been identified in sources of drinking water and can be a concern.⁹⁷  Iron and sulfur bacteria also may be present in well water. Although these bacteria do not pose a health threat, they can cause the water to smell (like “rotten egg”) and taste bad; they also increase the likelihood that plumbing equipment will become plugged or corroded. Iron bacteria also are known to form biofilms that can harbor other, harmful bacteria. Detailed information about illnesses produced by these organisms and how to treat them can be found in the AAP Red Book⁹⁸  and other sources.

The major source of Campylobacter jejuni is fecal material from animals and humans. For example, a large outbreak of campylobacteriosis was traced to livestock wastewater that accumulated in a roadside ditch, contaminating 2 city wells that distributed water through the well system without any disinfection or filtration.⁹⁹ 

Although there are no confirmed reports of well water contamination with Clostridioides difficile, contamination of a tap water distribution system with C difficile has been found, and an association of recent flooding with an increase in emergency department and outpatient visits for C difficile infection has been reported.^100,101 

Cryptosporidium species, a leading cause of outbreaks associated with exposure to recreational water, is extremely tolerant to chlorine and has oocysts that are infectious at excretion and are excreted in numbers well above the infectious dose.¹⁰² 

The microorganisms listed in Table 1 typically cause a GI illness, but there are notable exceptions. Enterovirus exposure may be asymptomatic but may also result in a febrile illness associated with sore throat, rash, myalgia, or less commonly, aseptic meningitis syndrome.

Microorganisms, including bacteria, viruses, fungi, and parasites, may contaminate an improperly constructed or improperly sealed water well (Table 1). The major source of these organisms is fecal material from animals and humans. Analyzing well water at its point of use for “total coliforms” is the most common way of detecting fecal contamination of the water. Coliform bacteria may be pathogenic or nonpathogenic and are termed an “indicator” contaminant of well water. Coliforms include many species of gram-negative bacteria found in the intestinal tract of animals and humans, in the soil, on vegetation, and in surface water runoff. Although coliforms do not reproduce in water, they can survive there for extended periods of time. Assessing total coliforms in a water sample is a useful, inexpensive screening tool, one that does not require sophisticated technology. No coliforms should be detectable in 100 mL of water. Presence of coliforms does not mean that pathogens are present, but it does make fecal contamination and contamination by pathogens much more likely. Samples that contain any coliforms should be retested to determine whether they are fecal coliforms; specimens that test positive should be examined for presence of Escherichia coli or other pathogens. Some organisms, such as Legionella species and M. avium-intracellulare, are present naturally in water and do not represent fecal contamination. Lack of correlation between detection of coliforms and presence of the environmental pathogens Mycobacteria, Legionella, and Helicobacter species has been demonstrated.¹⁰³ 

Most outbreaks (83%) of Cryptosporidium and Giardia duodenalis contamination were associated with regulated, public water systems; 3 (7%) were associated with unregulated, individual systems.⁹⁶  Organisms associated most commonly with water-associated outbreaks often have properties that facilitate spread through water sources. Giardia organisms are able to survive in inadequately chlorinated or untreated drinking water and have a low infectious dose. Individual water systems such as private wells were associated with about 8% of drinking water-associated Giardia outbreaks in one analysis.¹⁰⁴ 

One type of well water-associated outbreak has become less frequent: there have been no water-associated hepatitis A outbreaks since 2009, likely because of a combination of increased use of hepatitis A vaccines and the EPA public groundwater system regulations.¹⁰⁵ 

The efficiency of the sand filter of on-site wastewater treatment systems may be lower for removal of norovirus during the transport through the soil to the underground well than for certain coliforms and other bacteria.¹⁰⁶ 

It is estimated that about 87% of rotavirus emissions are produced by urban populations; global modeling of these emissions and a discussion of implications of their effect on surface water was published recently.¹⁰⁷ 

Biofilms may facilitate survival of Salmonella species in irrigation water, and Salmonella species, along with other bacteria, may be able to enter a viable but nonculturable state under stress conditions.¹⁰⁸ 

Shigella species may cause waterborne outbreaks, but most often these are associated with recreational water use rather than drinking water.

Yersinia infection can occur from drinking contaminated water, but most infections are transmitted through contaminated food.

Global climate change has far-reaching impacts on children’s health.¹⁰⁹  Among these many impacts is the effect on drinking water quality and availability. Climate change can affect drinking water, including groundwater, through a variety of mechanisms. Impacts vary by location across the United States.¹¹⁰ 

The most recent National Climate Assessment from 2018 expects climate change to reduce groundwater availability in some areas because of drought, changing water demand, withdrawal of groundwater, and altered recharging of aquifers.¹¹⁰  Depletion of aquifers and decreased groundwater availability not only threaten the availability of water, but also can lead to changes in water quality.¹¹¹  In addition, locally variable changes in precipitation, as well as temperature, can affect surface runoff and leaching of pollutants and pesticides, leading to impacts on groundwater.^110,112  Sea level rise and storms can affect coastal areas through altered water tables and saltwater intrusion into coastal aquifers, leading to increased salinity and poor water quality.¹¹⁰  Heavy rain and droughts have been associated with GI illness from contamination of water systems.¹¹³  In North America, most waterborne disease outbreaks occur after extreme precipitation events. Such events have been increasing in frequency and severity and are expected to continue increasing.¹¹³  Well owners can monitor their well for contaminants after extreme weather events, as well as periodically in response to climactic changes over time.

Disasters can occur naturally or as the result of human activity and include floods, earthquakes, tornadoes, hurricanes, wildfires, radiologic emergencies, warfare, and terrorist attacks.^114–117  Well water can become contaminated with chemicals, radioactive substances, or microorganisms as a result of disasters. For example, radioactive substances can contaminate groundwater after radiologic or nuclear emergencies, as occurred after the Chernobyl accident.¹¹⁸  Floods can lead to contamination of wells by infectious organisms and/or chemicals.¹¹⁹  Storm surges from hurricanes can also lead to saltwater intrusion of wells.¹²⁰  There are examples of impacts on water quality associated with major earthquakes, which can lead to rapid fluctuations in water levels, cause increased turbidity, or result in hydrogeochemical changes such as natural gas seepage.^121,122  Wildfires can damage well systems, leading to contamination.¹²³ 

Processes for handling contaminated wells and well water from disasters differ depending on the contaminants of concern. For example, although well disinfection may resolve concerns for coliform bacteria contamination resulting from flooding, it will not make water contaminated with toxic chemicals safe.¹¹⁹  The CDC and EPA provide general guidance for well owners after disasters but recommend contacting local, state, or tribal health departments or environmental agencies for specific advice regarding inspecting and testing wells after a natural disaster or emergency of concern.^119,124  Until the water is known to be safe, commercially available bottled water or some supply of water known to be safe can be used.¹¹⁹ 

Hydraulic fracturing, otherwise known as “fracking,” is a technique used to extract oil or gas from underground rock formations.¹²⁵  The technique involves injecting hydraulic fracturing fluid into oil or gas production wells under high pressure to fracture oil- or gas-bearing rock. These fractures are propped open with various components of the hydraulic fracturing fluid known as proppants. Once pressure is removed, oil and gas are then free to move through the fractures and through the well to the surface for collection. Hydraulic fracturing fluids are typically made of water, proppants, and chemical additives. The composition of hydraulic fracturing fluids is variable from well to well. Numerous chemical additives are used in hydraulic fracturing fluids, many of which are toxic to humans, including known carcinogens and endocrine disruptors.^125,126  Further, many of the components of fracking fluids are unknown, because companies are not required to disclose all of the contents of the fracking fluids they use.

Horizontal drilling, which started in about 2000, led to a surge in fracking production.¹²⁵  As of 2016, approximately 1 million wells had been hydraulically fractured in the United States.¹²⁵  Fracking operations are often located within or in close proximity to residential areas. Approximately half of hydraulically fractured wells are located within 2 to 3 km of a private groundwater well.¹²⁷  Between 2000 and 2013, approximately 3.6 million people obtained their drinking water from private wells in counties with at least 1 hydraulically fractured well.¹²⁵  About 17.6 million people in the United States live within 1 mile of any active oil or natural gas well.¹²⁸ 

The EPA issued a report in 2016 assessing impacts from the hydraulic fracturing water cycle on drinking water resources in the United States. The report listed 5 steps in the hydraulic fracturing water cycle: (1) water acquisition, (2) chemical mixing, (3) well injection, (4) produced water handling, and (5) wastewater disposal and reuse, and concluded that fracking can impact groundwater resources at any of these steps under certain circumstances.¹²⁵  Such conclusions were based, in part, on specific examples in which such impacts were documented.

Epidemiologic studies have shown a link between proximity to fracking operations and numerous health effects such as pregnancy and birth outcomes, headaches, and asthma.¹²⁶  Certain other health outcomes such as cancer and neurodegenerative diseases are less well characterized given the long latency to such health effects.¹²⁹  Fracking has the potential to impact groundwater and has done so in documented cases. Many fracking fluids have known toxicities and some of these fluids may contain unknown chemicals. There is epidemiologic evidence of health effects associated with proximity to fracking operations, so there is a serious concern for the potential for other health effects not yet characterized.

Little guidance exists for owners of private wells near hydraulic fracturing operations. Several organizations have compiled information for concerned well water users. For example, the Colorado Water and Energy Research Center recommends testing well water comprehensively before the initiation of drilling by fracking operations and then testing with key indicator analytes periodically thereafter to look for changes. The suggested indicator analytes, which may be the first to change in an oil- or gas-related groundwater impact, include conductance, pH, dissolved organic carbon, chloride, potassium, sodium, sulfate, barium, and methane.¹³⁰  Although not a comprehensive list, the Texas A&M AgriLife Extension Service suggests that presence of increased total dissolved solids, dissolved methane, or total petroleum hydrocarbons may be indicative of groundwater contamination.¹³¹ 

Wells should be tested annually for coliform bacteria and more frequently if there is an outbreak of GI illness among users of the well water or if the water changes in appearance, taste, or odor. If test results confirm bacterial contamination, the well must be inspected to identify any structural defects.¹³²  The water should not be ingested and commercially available bottled water should be used; water may be boiled if bottled water is not available. After structural defects are repaired, the well must be treated to eliminate pathogenic bacteria immediately, usually by “shock chlorination,” which uses concentrations of chlorine that are 100 to 400 times the amount found in municipal water supplies. Should shock chlorination be necessary, consultation with the health department or other experienced individuals is advisable. The highly chlorinated water needs to be held within the water system pipes for 12 to 24 hours before it is completely flushed out of the system. The water should be retested in 1 to 2 weeks. If shock chlorination does not eliminate the bacteria, a continuous disinfection system or further repairs to the well are needed. Consultation with the local health department and professionals with expertise in the remediation of private wells can help the well owner understand which additional treatment measures are required.

If the contamination is ongoing but under the control of the homeowner, such as from a failing septic field, that problem must be fixed before the well can be used for drinking water again. Successful, lasting decontamination of a well may require more persistent efforts. Swistock and Sharpe¹³²  disinfected and installed sanitary well caps on 16 wells with coliform contamination; coliforms were again present in 7 of the wells within 60 days and in all but 2 within a year. The 2 wells that did not have coliforms after 1 year had low initial coliform counts and no E. coli. The authors suggested that contamination may occur far from the well head and may commonly be an aquifer problem. Such a problem is beyond the scope of the homeowner. If the well cannot be used, it should not be ignored, because it would still provide access for contamination of groundwater. A certified well contractor should properly “abandon” the contaminated well.

Chemical contaminants are approached by investigating the possibility that the contamination from fertilizers, pesticides, or fuel from leaking tanks exists on the homeowner’s or on an adjacent homeowner’s property. Remediation may be inconvenient and/or expensive. If the water supply cannot be remediated and the well is still contaminated or the chemicals in question are naturally occurring, it is possible to treat for or filter most chemicals. An illustration of the relative sizes of filterable contaminants versus filter pore size is provided in Table 2. Most treatment measures for private wells require the service of a trained home water-treatment professional, at least for initial installation. Chemical disinfection with chlorine, ozone, or hydrogen peroxide; distillation; and UV light can remove or kill many microorganisms. Chlorine is effective at killing bacteria and viruses but is less effective against Giardia species and not effective against Cryptosporidium species. Reverse-osmosis filters, usually used in conjunction with activated charcoal and mechanical filtration, can remove inorganic materials, microorganisms, and all but a few organic compounds; however, they are expensive.

Treatment systems must be properly maintained to ensure safe water. Most filters, membranes, or UV lights need to be replaced at least once per year and more frequently if damaged or not working properly. NSF International (www.nsf.com) is a not-for-profit, nongovernmental, independent agency that tests and certifies consumer products, including water- treatment devices. The NSF website allows the consumer to pick the contaminants that are present, and the NSF will provide names of appropriate products and manufacturers. NSF certification is a voluntary program paid for by the manufacturer of the devices. Some states and universities provide descriptions of water-treatment devices. All sites recommend that the water first be tested and then the treatment device or devices selected to deal with the contaminants that are present.

Because there are no standards for private wells for many contaminants of concern, those seeking a specific concentration to indicate potability have little choice but to apply the same standards that municipalities do under the SDWA Amendments of 1996 (Public Law No. 104–182). For the current list of drinking water contaminants, see the Resources at the end of this report. Municipalities regard water that is persistently above these federal standards as not potable. Nonetheless, well owners or home occupants are under no obligation to apply this same standard to their well water.

Pediatric care providers can be effective communicators when they partner with local and state public health authorities in counseling families about routine and periodic well water testing.^133,134  The states, the Navajo Nation, and the EPA offer suggested inspection and testing schedules on their websites. Testing can be expensive, and the AAP encourages states and counties to provide free or low-cost testing to families who need their water tested and cannot afford it. Pediatric care providers can also counsel families about other household practices to ensure safe drinking water, such as running the first morning draw of tap water for several minutes before it’s used for cooking, drinking, and/or making baby formula to clear any lead that may have leached into it from older household plumbing overnight.

Carafe style, refrigerator-installed, and faucet-mounted filters usually are designed to reduce lead and other inorganic minerals, some organic materials, Giardia and Cryptosporidium cysts, and sediment. These units are intended for municipal water and would not be suitable for more heavily contaminated well water. Although historically, such point-of-use filters have focused on microorganisms, lead, and particulates, some newer point-of-use devices can also at least partially filter out some chemicals.¹³⁵  All point-of-use devices available to the public should first undergo rigorous third-party, independent laboratory testing to verify their effectiveness in filtering out impurities. Laboratories meeting such requirements are accredited by the ANSI as meeting NSF/ANSI Standards 42 and 53. Devices with carbon cartridge-type filters will gradually lose their effectiveness over time as the filters become saturated; disposable filters should be changed periodically according to manufacturers’ instructions. Information about point-of-use filters certified to filter lead from drinking water is available at the EPA website.

Well water can be used safely by families, but regular testing is recommended by all relevant authorities. A recommended approach to testing is provided in the accompanying policy statement and outlined as a flowchart in the Supplemental Information of that statement.¹³⁶  In much of the United States, well water is hard and must be softened to prevent damage to hot water heaters, kettles, and other devices, but softening per se does not remove most other contaminants or microorganisms. Whether and how water is treated should be guided by the results of testing. Water contamination is inherently local, and families with wells and pediatricians are encouraged to keep in contact with state and any local programs. Within states, private well water programs, resources, guidance, testing groups, and regulations are found in a variety of state departments of health, public health, environment, natural resources, licensure, or water, and sometimes within multiple departments within a state. Many states also have university-based cooperative extension services with private well water resources. Commercially available bottled water should be considered for travel or other circumstances in which an infant might need water and the source of the water is unknown.

1. Safe Drinking Water 1-800-426-4791

2. CDC Information 1-800-232-4636

1. List of EPA-regulated chemicals, microorganisms, and radionuclides in drinking water https://www.epa.gov/ground-water-and-drinking-water/national-primary-drinking-water-regulations

2. Instructions for disinfecting well water https://www.water-research.net/index.php/shock-well-disinfectionhttps://www.cdc.gov/disasters/wellsdisinfect.html

3. EPA’s tool for identifying certified point-of-use filtering devices https://www.epa.gov/water-research/consumer-tool-identifying-pou-drinking-water-filters-certified-reduce-lead

4. EPA’s private wells guidance https://www.epa.gov/privatewells/learn-about-private-water-wells#keeping

5. CDC’s website on maintenance of private wells https://www.cdc.gov/healthywater/drinking/private/wells/maintenance.html. Accessed August 14, 2020.

6. EPA’s basic information about lead in drinking water https://www.epa.gov/ground-water-and-drinking-water/basic-information-about-lead-drinking-water

7. EPA’s Web page on water topics related to the SDWA and Clean Water Act https://www.epa.gov/environmental-topics/water-topics

8. EPA’s Web page on certification of laboratories that test drinking water https://www.epa.gov/dwlabcert

9. EPA’s drinking water regulations for states and municipalities https://www.epa.gov/dwreginfo

10. Other well-water publications https://www.epa.gov/privatewells/publications-support-private-water-well-safety

11. EPA’s drinking water standards US EPA 2018 edition of the Drinking Water Standards and Health Advisories tables https://www.epa.gov/sites/production/files/2018-03/documents/dwtable2018.pdf

12. IARC listing of carcinogens WHO 2020. IARC monographs on the identification of carcinogenic hazards to humans https://monographs.iarc.fr/list-of-classifications

Alan D. Woolf, MD, MPH, FAAP Bryan D. Stierman, MD, FAAP Elizabeth D. Barnett, MD, FAAP Lori G. Byron, MD, FAAP

Aparna Bole, MD, FAAP, Chairperson Sophie J. Balk, MD, FAAP Lori G. Byron, MD, FAAP Gredia Maria Huerta-Montañez, MD, FAAP Philip J. Landrigan, MD, FAAP Steven M. Marcus, MD, FAAP Abby L. Nerlinger, MD, FAAP Lisa H. Patel, MD, FAAP Rebecca Philipsborn, MD, FAAP Alan D. Woolf, MD, MPH, FAAP Lauren Zajac, MD, MHP, FAAP

Kimberly A. Gray, PhD – National Institute of Environmental Health Sciences Jeanne Briskin – US Environmental Protection Agency Nathaniel G. DeNicola, MD, MSc – American College of Obstetricians and Gynecologists CDR Matt Karwowski, MD, MPH, FAAP – CDC National Center for Environmental Health and Agency for Toxic Substances and Disease Registry Aaron Briggs, MD – Section on Pediatric Trainees Mary H. Ward, PhD – National Cancer Institute

Paul Spire

Yvonne A. Maldonado, MD, FAAP, Chairperson

Sean T. O’Leary, MD, MPH, FAAP, Vice Chairperson Monica I. Ardura, DO, MSCS, FAAP Ritu Banerjee, MD, PhD, FAAP Kristina A Bryant, MD, FAAP James D. Campbell, MD, MS, FAAP Mary T. Caserta, MD, FAAP Chandy C. John, MD, MS, FAAP Jeffrey S. Gerber, MD, PhD, FAAP Athena P. Kourtis, MD, PhD, MPH, FAAP Adam J. Ratner, MD, MPH, FAAP José R. Romero, MD, FAAP Samir S. Shah, MD, MSCE, FAAP Kenneth M. Zangwill, MD, FAAP

David W. Kimberlin, MD, FAAP, Red Book editor Elizabeth D. Barnett, MD, FAAP, Red Book associate editor Ruth Lynfield, MD, FAAP, Red Book associate editor Mark H. Sawyer, MD, FAAP, Red Book associate editor Henry H. Bernstein, DO, MHCM, FAAP, Red Book Online Associate Editor

Karen M. Farizo, MD, US Food and Drug Administration Lisa M. Kafer, MD, FAAP, Committee on Practice Ambulatory Medicine David Kim, MD, HHS Office of Infectious Disease and HIV/AIDS Policy Eduardo López Medina, MD, MSc, Sociedad Latinoamericana de Infectologia Pediatrica Denee Moore, MD, FAAFP, American Academy of Family Physicians Lakshmi Panagiotakopoulos, MD, MPH, FAAP, Centers for Disease Control and Prevention Laura Sauvé, MD, MPH, FRCPS, Canadian Pediatric Society Neil S. Silverman, MD, American College of Obstetricians and Gynecologists Jeffrey R. Starke, MD, FAAP, American Thoracic Society Kay M. Tomashek, MD, MPH, DTM, National Institutes of Health

Melinda Wharton, MD, MPH, Centers for Disease Control and Prevention

Jennifer M. Frantz, MPH

The authors would like to acknowledge with gratitude the contributions of Mr Steven Wilson, a groundwater hydrologist, who reviewed the manuscript, offered advice on needed revisions, and provided invaluable insights.

AAP

American Academy of Pediatrics

ANSI

American National Standards Institute

CDC

Centers for Disease Control and Prevention

EPA

US Environmental Protection Agency

GI

gastrointestinal

IARC

International Agency for Research on Cancer

MCL

maximum contaminant level

MTBE

methyl tertiary butyl ether

NHANES

National Health and Nutrition Examination Survey

PFAS

perfluoroalkyl and polyfluoroalkyl substances

PFOA

perfluorooctanoic acid

PFOS

perfluorooctane sulfonate

SDWA

Safe Drinking Water Act

USGS

US Geological Survey

VOC

volatile organic compounds

WHO

World Health Organization