Public Lab Wiki documentation

Common Water Contaminants

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Purpose of this wiki

This wiki 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? 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: a) 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. b) spectroscopy (see Public Lab's Spectroscopy Kit). 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.
c) conductivity (see Public Lab's Riffle) (links more info). 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) (links to more info)

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.

Endocrine disruptors

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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


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sources: produced water


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sources: produced water


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.

_(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

How Politics Derailed the EPA via the Center for Public Integrity

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

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.

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sources: produced water

Oil and Grease

-TPH Volatiles -TPH Gasoline -TPH Diesel and Oil

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.

Ammonia (NH3) and ammonium ion (NH4+) are related chemically by an acid / base reaction: NH3 + H+ <=> NH4+ The equilibrium between ammonia and ammonium is pH dependent, with the two species being at the same concentration only under fairly alkaline conditions, pH = 9.25. At neutral pH, the concentration of free NH3 is less than 1% that of NH4+. Since this is the case, the concentration of ammonia is usually not significant and can be determined from the concentration of ammonium and the pH.

Assaying Nitrogen

The wet lab Kjeldahl Method is often used to get the measurement TKN, or Total Kjeldahl Nitrogen.

EPA Method 353.2 involves a cobalt catalyst and spectroscopy in the visible range.

UV Spectroscopy

In Situ Underwater Spectroscopy (UV in the ocean):

Ultraviolet spectrophotometric determination of nitrate: detecting nitrification rates and inhibition. Kelly RT 2nd, Love NG. Water Environ Res. 2007 Jul;79(7):808-12.

TSS, BOD, and Nitrate with a single 200nm-720nm spectrometer ON-LINE NITRATE MONITORING IN SEWERS USING UV/VIS SPECTROSCOPY F. Hofstaedter, T. Ertl, G. Langergraber, W. Lettl, A. Weingartne

Potentiometric Measurements of Nitrate and Ammonium using Ion Selective Electrodes

Ion selective electrodes (discussed here) can be used to conveniently measure ammonium and nitrate. These electrodes behave similarly to commonly used pH electrodes. The main difference between a pH electrode and an ion selective electrode (ISE) is that the former has a glass surface that is electrically polarized by protons and the latter has a membrane that is responsive to the ion in question. Like a pH electrode, an ion selective electrode responds to changes in analyte concentration by a measurable change in voltage. Ion selective electrodes can be measured with most pH meters. These electrodes can be purchased from a variety of sources (VWR, Fisher, etc) but are somewhat more expensive than pH electrodes. Vernier sells ammonium and nitrate sensitive electrodes (here) for $179 each.

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. In Stoney Creek in Burnaby, BC, conductivity follows a linear relationship to chloride concentration. Chloride in mg/L=(0.3013 x SpCond - 16.095)

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.