Since water is capable of dissolving or suspending a tremendous variety of materials there is simply no way to get "pure" water (H2O and nothing but H2O) out of your faucet. All water, outside of a research laboratory, will have some other stuff in it. Even distilled water you purchase in plastic bottles at the store will eventually have some carbon dioxide (CO2) from the air dissolved in it forming a weak acid (carbonic acid), and worse, there will probably be some dissolved plastic molecules in it as well.
Are all water contaminants bad for our health? Not at all. Many of the naturally occurring compounds in water are benign or even good for our health. Some minerals, like calcium and magnesium are essential to human health, and some reports indicate that drinking water can provide a dietary source for these minerals. Most of the discussion below will focus on the undesirable or dangerous water contaminants. The environmental Protection Agency has established Maximum Contaminant Levels (MCLs) for some of the most common and/or potentially dangerous of the identified water pollutants. The materials besides H2O that might be in your drinking water can be categorized as shown below (only the most common or dangerous examples in each group are listed here, since there is a nearly infinite number of possible contaminants).
This is a highly simplified list, let's into a lot of chemistry and technical ideas and terms here. These are not necessarily the contaminants that will be in your water (hopefully most will not be present). Nor, as I mentioned, will this be a comprehensive list (some contaminants not mentioned below may, in fact, be in your water). The only way to determine for sure what contaminants are in your water is to test for them. Where appropriate, in the lists of contaminants below, it is been indicated in {MCL=} the Maximum Contaminant Level (MCL) established by the Environmental Protection Agency (EPA). The units are usually milligrams of the contaminant per liter of water.
Materials dissolved in water:
- Inorganic Compounds - Compounds that typically do not contain the element Carbon. They can become dissolved in water from natural sources or as the result of human activity.
- Dissolved gases (oxygen, carbon dioxide, nitrogen, radon, methane, hydrogen sulfide, etc.) - no appreciable health effects, except for hydrogen sulfide and dissolved radioactive gases like radon. Both methane and hydrogen sulfide can be inflammable. Carbon dioxide dissolved in water creates carbonic acid - a weak acid that gives carbonated water its "bite" and plays an important role in the weathering of limestone and other carbonate rocks. Caverns are a product of eons of erosion by carbonic acid-laced water.
- Metal and metalloid positive ions - (aluminum, arsenic {MCL=0.05}, lead {MCL=0.015}, mercury {MCL=0.002}, calcium, magnesium, sodium, potassium, zinc, copper {MCL=1.3}, etc.) Some of these ions (lead, mercury, and arsenic) are dangerous at extremely low concentrations and can be introduced into drinking water either through natural processes or as a result of human activity. Other ions in this group (for example, calcium, magnesium, sodium, and potassium) are essential to human health - in the correct amounts. Calcium and magnesium are interesting ions. Although their presence in drinking water is actually a health benefit, they are the prime culprits in most hard water and are considered undesirable contaminants by those who must live with scaly deposits of calcium carbonate on their faucets (and in their pipes and water heaters) or who can not get their soap to lather.
- Negative ions - (fluoride {MCL=4.0}, chloride, nitrate {MCL=10.0}, nitrite {MCL=1.0}, phosphate, sulfate, carbonate, cyanide {MCL=0.2}) As with the positive ions, some of these negative ions are necessary to life in proper concentrations (chloride and carbonate), others can be dangerous to health at moderate concentrations (nitrates and nitrites - look at the ingredients in the next slice of ham, bacon, or hot dog you eat), and others are dangerous at even small concentrations (cyanide).Some, like fluoride, have raised quite a controversy over its safety as an additive (in many areas) to drinking water in an effort to lessen tooth decay, particularly in children.
- Radon - Radon is a radioactive gas that comes from the natural breakdown (radioactive decay) of radium, which is it a decay product of uranium. The primary source of radon in homes is from the underlying soil and bedrock. However, an additional source could be the water supply, particularly if the house is served by a private well or a small community water system.
- Organic Compounds - These compounds all contain the element Carbon. Although there are many exceptions, naturally occurring organic compounds (sugars, proteins, alcohols, etc.) are synthesized in the cells of living organisms, or like raw petroleum and coal, formed by natural processes acting on the organic chemicals of once-living organisms.
- Synthetic Organic Chemicals - Organic chemicals can also be synthesized in laboratories and by chemical companies. A growing number of these synthetic organic compounds are being produced. They can include pesticides used in agriculture, plastics, synthetic fabrics, dyes, gasoline additives like MTBE, solvents like carbon tetrachloride {MCL=0.005}, and many other chemicals. Many synthetic organic chemicals, like benzene {MCL=0.005} carbon tetrachloride, and vinyl chloride {MCL=0.002}, vaporize easily in air and are grouped under the category of volatile organic chemicals (VOCs). Methyl tertiary butyl ether (MTBE) is a common synthetic organic chemical used for a number of years as a gasoline additive.
In January 2000 it received national notoriety on CBS' 60 Minutes because of its ability to contaminate water supplies after leaking from storage tanks. The potential for water contamination by synthetic organic chemicals can be understood by the fact that Denver Water (the company that supplies municipal water to much of the metro Denver area) tests for 54 VOCs (21 with MCLs established by the EPA), 73 different pesticides (23 with MCLs), 25 different chemicals classified as synthetic organic compounds (5 with MCLs), and 7 as non-specific organics. Nearly all of these chemicals tested below the levels of detectability. It is somewhat disconcerting to realize that Denver water tests for only 150 or so of the thousands of synthetic organic chemicals manufacturing, and the EPA has established MCLs for even fewer.
As you read through the information provided on our site, you will find that these are not nice chemicals to have in your water, many of them are presumed to increase the risk of various cancers in humans, often after many years of low-level exposure, others may affect the nervous system. Some researchers are reporting that yet other synthetic chemicals can cause hormonal disruptions. Most laboratory tests of the effects of these chemicals are done using a single chemical, but there may be several organic contaminants together in a water source. Scientists are just beginning to realize that exposure to multiple organic chemicals seems to increase the risk of health problems much more than any of the chemicals would separately.