COMMON CONTAMINANTS IN YOUR WATER SYSTEM
COMMON CONTAMINANTS IN DRINKING WATER SOURCES
The溶解能力 of water to dissolve or suspend a wide variety of substances means that obtaining entirely “pure” water (simply H2O) from your tap is not feasible. All water, with the exception of that found in research laboratories, contains some degree of impurities. Even commercially purchased distilled water will eventually absorb atmospheric carbon dioxide (CO2), transforming into a weak acid known as carbonic acid, and may also contain minute amounts of dissolved plastic. Not every contaminant found in water is harmful to health; many natural substances present in water are either harmless or beneficial. Certain minerals, such as calcium and magnesium, are essential for human health, and some research indicates that these minerals can be ingested via drinking water. The following discussion mainly focuses on harmful or undesirable contaminants. The Environmental Protection Agency (EPA) has established Maximum Contaminant Levels (MCLs) for numerous common and/or dangerous water pollutants that have been identified to date. The non-H2O substances that could be present in your drinking water can be categorized as follows, with only the most common or severe examples listed due to the nearly infinite number of potential contaminants.
This is a significantly condensed list that encompasses complex chemistry and technical information. These are not necessarily the contaminants present in your water supply (hopefully, very few will be detected). Furthermore, this list is not comprehensive (additional contaminants not listed might be present in your water). Accurate identification of contaminants in your water requires testing. Where relevant, the Maximum Contaminant Levels (MCLs) set by the EPA are noted in {brackets} next to the contaminant names, usually measured in milligrams per liter of water.
Dissolved Substances in Water:
Inorganic Compounds – Generally carbon-free compounds that dissolve in water from natural sources or human activities.
Dissolved Gases (oxygen, carbon dioxide, nitrogen, radon, methane, hydrogen sulfide, etc.) – These typically do not have significant health impacts, with the exception of hydrogen sulfide and radioactive gases like radon. Both methane and hydrogen sulfide are flammable. Carbon dioxide in water creates carbonic acid, a weak acid that gives carbonated water its distinct taste and contributes to the erosion of limestone and other carbonate rocks.
Metals and Metalloids – (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 can be hazardous at low levels and may enter drinking water through natural processes or human activities. Others, including calcium, magnesium, sodium, and potassium, are essential for human health when consumed in appropriate amounts. Calcium and magnesium are notable for contributing to hard water and are considered undesirable by those who deal with calcium carbonate buildup on their fixtures (as well as in their pipes and water heaters) or have difficulty producing lather with soap.
Anions – (fluoride {MCL=4.0}, chloride, nitrate {MCL=10.0}, nitrite {MCL=1.0}, phosphate, sulfate, carbonate, cyanide {MCL=0.2}) Similar to cations, some anions are vital for life in the right amounts, others are moderately harmful at certain levels, and some are toxic even at low concentrations. Fluoride, for example, has been controversial as an additive to drinking water to combat tooth decay, particularly in children.
Radon – A radioactive gas that originates from the natural decay of radium, a byproduct of uranium decay. The primary source of radon in homes is the soil and bedrock beneath, although water supplies, especially private wells or small systems, can also be a source.
Organic Compounds – These contain carbon and are either produced by living organisms or created by natural processes acting on the remains of once-living organisms.
Synthetic Organic Chemicals – These are laboratory or industrially manufactured organic compounds, such as pesticides, plastics, synthetic fabrics, dyes, gasoline additives like MTBE, solvents like carbon tetrachloride {MCL=0.005}, and many more. Numerous synthetic organics, like benzene {MCL=0.005}, carbon tetrachloride, and vinyl chloride {MCL=0.002}, easily evaporate and are classified as volatile organic chemicals (VOCs). Methyl tertiary butyl ether (MTBE) has been used as a gasoline additive and received national attention in January 2000 due to its potential to contaminate water supplies from leaking storage tanks. Denver Water, which provides municipal water to the Denver area, screens for 54 VOCs (21 with MCLs), 73 pesticides (23 with MCLs), 25 synthetic organic compounds (5 with MCLs), and 7 non-specific organics, with nearly all chemicals detected below detectable levels. It is concerning that Denver Water only tests for approximately 150 of the thousands of synthetic organic chemicals used in manufacturing, with even fewer having established MCLs by the EPA.
These chemicals are unwanted in your water supply; many are suspected to elevate the risk of cancer with prolonged exposure, affect the nervous system, or disrupt hormonal balance. Most studies on the effects of these chemicals use individual substances, yet water sources may contain a mixture of organic contaminants. Scientists are acknowledging that exposure to a blend of organic chemicals may present greater health risks than individual contaminants by themselves.