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Common Water Contaminants

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This page is intended to provide short, legible descriptions of common water contaminants, with a no-nonsense rundown on what methods might be used to both assess and address the presence of these contaminants. We're aiming to pay special attention to the relative cost and technical expertise required for each method.

For example, some of these contaminants might be readily addressed by simple, cheap home testing kits. Some of them might currently require expensive laboratory testing. For many of them, the EPA and others have published protocols for how to assess the level of these contaminants in a laboratory setting; we'd like to begin to collect links to these protocols, labeling them as "possibly DIY?" or "DIY: implausible", etc ...

Suggested format for entries:

Name of the contaminant

  • Why is it a problem? How does it enter the water supply?

  • How much of this contaminant is safe?

  • How can we measure it? Does it require a "professional" lab? Are there DIY techniques available?

  • What can be done about it? Can I filter it out of my water myself?

  • Links to good relevant resources, helpful agencies, and groups concerned about the issue.

Please help us fill out this list with relevant info about important water contaminants ...


Why is it a problem?

Current studies are finding that arsenic is 17 times more potent of a carcinogen than previously thought. Arsenic is known to cause a variety of cancers and has been linked to heart disease, stroke and diabetes. Recent research has found an association between arsenic levels below 10 parts per billion and IQ deficits in children. Women are especially susceptible to arsenic poisoning.

How does it enter the water supply?

Arsenic makes up part of Earth’s crust and is commonly found in groundwater. In 2001, the U.S. Environmental Protection Agency lowered the drinking water standard from 50 parts per billion of arsenic to 10 parts per billion. The agency initially had proposed a limit of 5 parts per billion but faced criticism that it would be too costly for water companies to hit that target.

Arsenic can be found in groundwater near fracking sites at levels that exceed the EPA's maximum contaminate limit for drinking water.

It is also a common contaminant of oil fields, coal export, and in BP's oil. It's a common concern in the city of New Orleans, which has schools and housing developments built on old landfills.

How much is safe?

Anything below 10 PPB (parts per billion) or micrograms/L, according to current FDA standards. The last big study about arsenic was published in 1988, but more current studies are finding that arsenic is 17 times more potent of a carcinogen than previously thought. That means that even water that meets current federal standards could be dangerous, and the risks it poses to public health can be dire.

How is it tested?

Simple arsenic tests can be found online for about $20 each here. While these tests tell you whether or not you have arsenic in your water supply (by either the PPM or PPB, depending on which you get), it doesn't tell you how much arsenic is in your water.

From Mark Green's work at Plymouth State, conductivity spikes could also indicate pollution or contamination worthy of further testing.

Anodic Stripping Voltammetry with a Potentiostat

(This section could use some more details about the actual chemistry. Anyone else want to weigh in?)

What can be done about it?

By law, water companies are required to post information about arsenic levels in watersheds. I found a map for the probability of arsenic exceeding the public drinking water standard (10 PPB or micrograms/L) here.

Still, this is only for private wells, and only for central/eastern Massachusetts. It doesn't have much data about the Greater Boston area, meaning a lot of data is either not public or nonexistent.

Links to more info

  1. How Politics Derailed the EPA via the Center for Public Integrity

  2. Arsenic contamination podcast segment from the Center for Investigative Reporting + Center for Public Integrity

  3. This map is based on arsenic readings from 45,000 wells collected by the U.S. Geological Survey throughout the country, going back four decades. In addition, the states of Texas and Minnesota provided data gathered on arsenic in private wells. In several other states, few readings were available.

Edit this page to help complete it!


Barium is a lustrous, machinable metal which exists in nature only in ores containing mixtures of elements. It is used in making a wide variety of electronic components, in metal alloys, bleaches, dyes, fireworks, ceramics and glass. In particular, it is used in well drilling operations where it is directly released into the ground.

Why is it a problem?

Some people who drink water containing barium well in excess of the maximum contaminant level (MCL) for many years could experience an increase in their blood pressure. This health effects language is not intended to catalog all possible health effects for barium. Rather, it is intended to inform consumers of some of the possible health effects associated with barium in drinking water when the rule was finalized.

The Department of Health and Human Services (DHHS) and the International Agency for Research on Cancer (IARC) have not classified barium as to its carcinogenicity. The EPA has determined that barium is not likely to be carcinogenic to humans following ingestion and that there is insufficient information to determine whether it will be carcinogenic to humans following inhalation exposure.

How does it enter the water supply?

The major sources of barium in drinking water are discharge of drilling wastes; discharge from metal refineries; and erosion of natural deposits. The greatest potential source of barium exposure is through food and drinking water. However, the amount of barium in foods and drinking water are typically too low to be of concern.

What are the EPA's drinking water regulations for barium?

The MCLG for barium is 2 mg/L or 2 ppm. EPA has set this level of protection based on the best available science to prevent potential health problems. EPA has set an enforceable regulation for barium, called a maximum contaminant level (MCL), at 2 mg/L or 2 ppm. MCLsare set as close to the health goals as possible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies. In this case, the MCL equals the MCLG, because analytical methods or treatment technology do not pose any limitation.

The Phase IIB Rule, the regulation for barium, became effective in 1993. The Safe Drinking Water Act requires EPA to periodically review the national primary drinking water regulation for each contaminant and revise the regulation, if appropriate. EPA reviewed barium as part of the Six Year Review and determined that the 2 mg/L or 2 ppm MCLG and 2 mg/L or 2 ppm MCL for barium are still protective of human health.

In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine the level of contaminants in drinking water at which no adverse health effects are likely to occur. These non-enforceable health goals, based solely on possible health risks and exposure over a lifetime with an adequate margin of safety, are called maximum contaminant level goals (MCLG). Contaminants are any physical, chemical, biological or radiological substances or matter in water.

How is it tested?

Barium concentrations in water may be determined by atomic absorption spectroscopy using either direct aspiration into an air–acetylene flame (detection limit 2 µg/litre) or atomization in a furnace (detection limit 100 µg/litre) (US EPA, 1985a). Barium in water may also be determined by inductively coupled plasma atomic emission spectrometry, the detection limits being equivalent or superior to those of flame atomic absorption spectroscopy (OME, 1988).

What can be done about it?

The following treatment method(s) have proven to be effective for removing barium to below 2 mg/L or 2 ppm: ion exchange, reverse osmosis, lime softening, and electrodialysis.

Links to good relevant resources, helpful agencies, and groups concerned about the issue.

  1. Agency for Toxic Substances and Disease Registry ToxFAQs, Barium

  2. WHO barium resource page

sources: produced water


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Hexavalent chromium. Brought into public awareness by Erin Brokovich.

sources: produced water

Endocrine disruptors

Atrazine. A common herbicide. It's probably on your lawn, or a lawn near you.

Edit this page to help complete it!

Fecal Bacteria

Fecal bacteria found in the lower intestines of mammals can sometimes cause illness but are also used as indicators of more difficult to detect enteric diseases such as giardia, cryptosporidium ,hepatitis A & E, Campylobacter, and intestinal worms. Indicators that can be used are Total Coliforms (all cylindrical bacteria), Fecal Coliform, E. Coli, Enterococci (Fecal streptococci) and Salmonella are all used. Total Coliforms, Fecal Coliform, and Enterococci are the most common, and Enterococci is the primary indicator in salt water. Fecal Coliform is, according to the EPA, a poor indicator though. They recommend E.Coli and Enterococci. (Indicator bacteria on Wikipedia). EPA 5.11 governs Fecal Bacterialogical contamination.

DIY Fecal Coliform testing

Art Ludwig has published a non-open source but DIY guide to doing Fecal Coliform tests. His guide costs $15.

There is an open-source DIY Automatic Colony Counter.

See #coliform for more on this topic


Why is it a problem? How does it enter the water supply?

Glyphosate is a commonly used pesticide sold under trademarks such as Monsanto's 'Roundup'. that enters the water supply via agricultural runoff. The EPA information site for glyphosate is here.

How much is safe?

Experts disagree on safe levels; the EPA has set a legally enforceable maximum contaminant level (MCL) for glyphosate of 700 ug/l in drinking water, which is 7,000 times higher than the MCL in Europe.

How is it tested?

Possible testing methods include:

  1. laboratory tests, for $110 - $300 (links to more info here). Most likely, these tests use a technique called ELISA. ELISA is an acronym for Enzyme Linked Immunosorbent Assay. This type of assay uses antibodies to bind the analyte (glyphosate) and an enzyme reaction to generate a color change. This type of assay is routinely used in pregnancy and drug tests. A discussion of ELISAs can be found here. Various companies make these kits, such as here.
  2. spectroscopy (see Public Lab's #Spectroscopy Kits). Since glyphosate is colorless, direct measurement cannot be done via visible spectrometry. The ultraviolet spectrum at neutral pH (found here) shows an absorbance maximum at ~200 nm with an extinction coefficient of ~62. The same source shows that this value is similar to other carboxylic acids, such as acetic acid. Since common acids and other organic materials will interfere with detection by UV spectroscopy, this is not a recommended method. An indirect spectroscopic method has been proposed here under "experiment 5": This method relies on chemistry established for determining inorganic phosphate (PO43-) and measures the visible absorbance of a reaction product (This method is probably the molybdenum blue method, described on page 672 of Vogel's textbook of quantitative chemical analysis, 6th edition). Unfortunately, the citation does not claim that the method has been tested for glyphosate and shown to give the colored product. Since glyphosate is not inorganic phosphate (it is an organic phosphonate, having a carbon-phosphorus bond), the test needs to be run to ensure that it reacts to give the colored product.
  3. conductivity (see Public Lab's #Coqui). Glyphosate is a polyanion at neutral pH and will affect electrical conductivity of water. Unfortunately, the effect of glyphosate will likely be masked if other common electrolytes (salts) are present at higher concentrations. d) paper chromatography tests (see the following four kits, available online)

What can be done about it?

Links to more info

There has been a controversial report on the internet that measurable amounts of glyphosate have been detected in breast milk: The results in this report do not appear to have been published in the peer reviewed literature. The chair of the pediatrics department at Mass General Hospital subsequently published an online piece addressing findings in the report. In his piece (found here.), Dr Ron Kleinman argues that glyphosate poses no threat to the health of breastfeeding infants and that mothers should continue breast feeding their children.

See #glyphosate for more on this topic


Lead is a toxic metal that was used for many years in products found in and around homes. Even at low levels, lead may cause a range of health effects including behavioral problems and learning disabilities. Children six years old and under are most at risk because this is when the brain is developing. The primary source of lead exposure for most children is lead-based paint in older homes. Lead in drinking water can add to that exposure.

Why is it a problem?

Infants and children who drink water containing lead in excess of the action level could experience delays in their physical or mental development. Children could show slight deficits in attention span and learning abilities. Adults who drink this water over many years could develop kidney problems or high blood pressure. This health effects language is not intended to catalog all possible health effects for lead. Rather, it is intended to inform consumers of the most significant and probable health effects, associated with lead in drinking water.

How does it enter the water supply?

The major sources of lead in drinking water are corrosion of household plumbing systems; and erosion of natural deposits. Lead enters the water (“leaches”) through contact with the plumbing. Lead leaches into water through corrosion – a dissolving or wearing away of metal caused by a chemical reaction between water and your plumbing. Lead can leach into water from pipes, solder, fixtures and faucets (brass), and fittings. The amount of lead in your water also depends on the types and amounts of minerals in the water, how long the water stays in the pipes, the amount of wear in the pipes, the water’s acidity and its temperature.

Although the main sources of exposure to lead are ingesting paint chips and inhaling dust, EPA estimates that 10 to 20 percent of human exposure to lead may come from lead in drinking water. Infants who consume mostly mixed formula can receive 40 to 60 percent of their exposure to lead from drinking water. Lead is sometimes used in household plumbing materials or in water service lines used to bring water from the main to the home.

How much is safe?

The term “lead free” means that solders and flux may not contain more than 0.2 percent lead, and that pipes and pipe fittings may not contain more than 8.0 percent lead. Faucets and other end use devices must be tested and certified against the ANSI – NSF Standard 61 to be considered lead free. A prohibition on lead in plumbing materials has been in effect since 1986. The lead ban, which was included in the 1986 Amendments of the Safe Drinking Water Act, states that only “lead free” pipe, solder, or flux may be used in the installation or repair of (1) public water systems, or (2) any plumbing in a residential or non-residential facility providing water for human consumption, which is connected to a public water system. But even “lead free” plumbing may contain traces of lead.

How is it tested?

  1. $10.86 kit from Amazon
  2. $10 kit from Home Depot
  3. Anodic Stripping Voltammetry with a Potentiostat
  4. WheeStat from Public Lab

What can be done about it?

Have your water tested for lead. A list of certified laboratory of labs are available from your state or local drinking water authority. Testing costs between $20 and $100. Since you cannot see, taste, or smell lead dissolved in water, testing is the only sure way of telling whether there are harmful quantities of lead in your drinking water. You should be particularly suspicious if your home has lead pipes (lead is a dull gray metal that is soft enough to be easily scratched with a house key) or if you see signs of corrosion (frequent leaks, rust-colored water). Your water supplier may have useful information, including whether the service connector used in your home or area is made of lead. Testing is especially important in high-rise buildings where flushing might not work. See EPA's public notification requirements for public water systems. If your water comes from a household well, check with your health department or local water systems that use ground water for information on contaminants of concern in your area. For more on wells, go to EPA's website on private wells.

How can I reduce lead in drinking water at home?

Flush your pipes before drinking, and only use cold water for consumption. The more time water has been sitting in your home's pipes, the more lead it may contain. Anytime the water in a particular faucet has not been used for six hours or longer, "flush" your cold-water pipes by running the water until it becomes as cold as it will get. This could take as little as five to thirty seconds if there has been recent heavy water use such as showering or toilet flushing. Otherwise, it could take two minutes or longer. Your water utility will inform you if longer flushing times are needed to respond to local conditions.

Use only water from the cold-water tap for drinking, cooking, and especially for making baby formula. Hot water is likely to contain higher levels of lead. The two actions recommended above are very important to the health of your family. They will probably be effective in reducing lead levels because most of the lead in household water usually comes from the plumbing in your house, not from the local water supply.

What are the EPA's drinking water regulations for lead?

What are EPA’s drinking water regulations for lead? In 1974, Congress passed the Safe Drinking Water Act. This law requires EPA to determine the level of contaminants in drinking water at which no adverse health effects are likely to occur with an adequate margin of safety. These non-enforceable health goals, based solely on possible health risks are called maximum contaminant level goals (MCLG) The MCLG for lead is zero. EPA has set this level based on the best available science which shows there is no safe level of exposure to lead.

For most contaminants, EPA sets an enforceable regulation called a maximum contaminant level (MCL) based on the MCLG. MCLs are set as close to the MCLGs as possible, considering cost, benefits and the ability of public water systems to detect and remove contaminants using suitable treatment technologies. However, because lead contamination of drinking water often results from corrosion of the plumbing materials belonging to water system customers, EPA established a treatment technique rather than an MCL for lead. A treatment technique is an enforceable procedure or level of technological performance which water systems must follow to ensure control of a contaminant. The treatment technique regulation for lead (referred to as the Lead and Copper rule) requires water systems to control the corrosivity of the water. The regulation also requires systems to collect tap samples from sites served by the system that are more likely to have plumbing materials containing lead. If more than 10% of tap water samples exceed the lead action level of 15 parts per billion, then water systems are required to take additional actions including:

  • Taking further steps optimize their corrosion control treatment (for water systems serving 50,000 people that have not fully optimized their corrosion control).

  • Educating the public about lead in drinking water and actions consumers can take to reduce their exposure to lead.

  • Replacing the portions of lead service lines (lines that connect distribution mains to customers) under the water system’s control.

  • EPA promulgated the Lead and Copper Rule in 1991 and revised the regulation in 2000 and 2007. States may set more stringent drinking water regulations than EPA.

Links to more info

  1. See EPA lead info page
  2. CDC resource on lead
  3. Children and Drinking Water Standards

See #lead for more on this topic


Ask a question about mercury or Sign up to answer questions on this topic

Why is it a problem?

Mercury is a neurotoxin - most harmful to the unborn.

How does it enter the water supply?

Coal-fired power plants are the largest emitters of mercury. Bacteria transforms the mercury (Hg) into another form, methylmercury (MeHg), which then significantly bio-accumulates in the tissue of living creatures. For most people, the primary exposure to methylmercury comes from eating predatory fish such as pike, walleye, large-mouth bass, and tuna. The EPA has issued fish consumption advisories for forty-four states warning people to limit their consumption of certain kinds of fish. Canned white (albacore tuna) has been shown to contain about four times as much mercury as chunk light tuna.

sources: produced water, aerial deposition into wetland ecosystems, aerial deposition downwind of coal-fired power plants

See #mercury for more on this topic

Nitrogen: Nitrates, Nitrite, Ammonia, & Ammonium

Nitrates, Nitrite, Ammonia, & Ammonium are "fixed" forms of nitrogen available to living organisms, and represent different stages of nitrogen in the nitrogen cycle.

Nitrogen is a major limiting nutrient in plant growth-- when nitrates occur in large quantities in water from fertilizers, manure, or sewage runoff, they can cause algal blooms that create dead zones. Nitrates have also been linked to increased risks of cancer, and complications with a number of diseases, including asthma. The EPA limits drinking water concentrations of Nitrates to 10mg/L or lower, however, health threats can occur even at those levels.

Read more on the Nitrogen page.

Oil and Gas

-TPH Volatiles -TPH Gasoline -TPH Diesel and Oil

See #oil-and-gas for more on this topic

Road salt

Road salt is detrimental both to aquatic life and to plants. In Canada, it was classified as a toxic substance, but then, since so much was being used to keep roads safe, they did not carry through with measures to reduce it, only voluntary guidelines. Conductivity is a surrogate for chloride content (see Conductivity, below). In Stoney Creek in Burnaby, BC, conductivity follows a linear relationship to chloride concentration. Chloride in mg/L=(0.3013 x SpCond - 16.095)

Water parameters

These aren't contaminants, but they are ways to measure contaminants:


"Conductivity is a measure of water’s capability to pass electrical flow. This ability is directly related to the concentration of ions in the water. These conductive ions come from dissolved salts and inorganic materials (...). The more ions that are present, the higher the conductivity of water. Likewise, the fewer ions that are in the water, the less conductive it is. Distilled or deionized water can act as an insulator due to its very low (if not negligible) conductivity value. Sea water, on the other hand, has a very high conductivity."[2]

Conductivity is an indirect way to measure pollutant concentration, and changes in it’s level indicates changes in water composition.[3] Water within the EC range between 0 - 2500 μS/cm can be consumed by humans, although most would prefer water in the lower half of this range if available.[4]

See #conductivity for more on this topic


"pH is a measure of how acidic/basic water is."[5] A pH level of 7 is neutral, values "of less than 7 indicate acidity, whereas a pH of greater than 7 indicates a base. pH is really a measure of the relative amount of free hydrogen and hydroxyl ions in the water. Water that has more free hydrogen ions is acidic, whereas water that has more free hydroxyl ions is basic. Since pH can be affected by chemicals in the water, pH is an important indicator of water that is changing chemically."[5]

"The optimum pH will vary in different supplies according to the composition of the water and the nature of the construction materials used in the distribution system."[6] The Brazilian government recommends to keep pH in distributions systems in the range 6.0–9.5.[7]

See #ph for more on this topic


"Just as the transfer of hydrogen ions between chemical species determines the pH of an aqueous solution, the transfer of electrons between chemical species determines the"[8] oxidation–reduction potential (ORP, or redox potential) "of an aqueous solution. Like pH, the reduction potential represents how strongly electrons are transferred to or from species in solution."[8]

ORP measures the ability of the water "to cleanse itself or break down waste products, such as contaminants and dead plants and animals. When the ORP value is high, there is lots of oxygen present in the water. This means that bacteria that decompose dead tissue and contaminants can work more efficiently. In general, the higher the ORP value, the healthier the"[9] water is.

"It is possible to define a minimum level of ORP necessary to ensure effective disinfection. This value has to be determined on a case-by-case basis; universal values cannot be recommended. Further research and evaluation of ORP as an operational monitoring technique are highly desirable."[10]

See #orp for more on this topic


"Temperature is an important factor to consider when assessing water quality. In addition to its own effects, temperature influences several other parameters and can alter the physical and chemical properties of water. In this regard, water temperature should be accounted for when determining"[11] (between others):

See #temperature and #thermal-flashlight for more on this topic



An ion is "any atom or group of atoms that bears one or more positive or negative electrical charges. (...) Ions are formed by the addition of electrons to, or the removal of electrons from, neutral atoms or molecules or other ions; by combination of ions with other particles; or by rupture of a covalent bond between two atoms in such a way that both of the electrons of the bond are left in association with one of the formerly bonded atoms."[1]


A non-complete list of sources for some of this information.

  3. (in Portuguese)
  7. (in Portuguese)