Coliforms are bacteria that are naturally present in the environment and used as an indicator that other, potentially harmful, bacteria may be present. Coliforms found in more samples than allowed is a warning of potential problems.

Not a health threat in itself; it is used to indicate whether other potentially harmful bacteria may be present5

Trihalomethanes occur when naturally-occurring organic and inorganic materials in the water react with the disinfectants, chlorine and chloramine.

Liver, kidney or central nervous system problems; increased risk of cancer

Haloacetic acids occur when naturally-occurring organic and inorganic materials in the water react with the disinfectants, chlorine and chloramine.

Increased risk of cancer

Arsenic is a semi-metal element in the periodic table. It is odorless and tasteless. It enters drinking water supplies from natural deposits in the earth or from agricultural and industrial practices. Approximately 90 percent of industrial arsenic in the U.S. is currently used as a wood preservative, but arsenic is also used in paints, dyes, metals, drugs, soaps, and semi-conductors. Agricultural applications, mining, and smelting also contribute to arsenic releases in the environment.

Skin damage or problems with circulatory systems, and may have increased risk of getting cancer

Nitrates and nitrites are nitrogen-oxygen chemical units which combine with various organic and inorganic compounds. The greatest use of nitrates is as a fertilizer. Once taken into the body, nitrates are converted to nitrites.

Infants below the age of six months who drink water containing nitrate in excess of the MCL could become seriously ill and, if untreated, may die. Symptoms include shortness of breath and blue-baby syndrome.

Turbidity refers to cloudiness of water. Turbidity has no health effects, but can interfere with disinfection and provide a medium for microbial growth. Turbidity may indicate the presence of disease-causing organisms. These organisms include bacteria, viruses, and parasites that can cause symptoms such as nausea, cramps, diarrhea and associated headaches.

Turbidity is a measure of the cloudiness of water. It is used to indicate water quality and filtration effectiveness (e.g., whether disease-causing organisms are present). Higher turbidity levels are often associated with higher levels of disease-causing microorganisms such as viruses, parasites and some bacteria. These organisms can cause symptoms such as nausea, cramps, diarrhea, and associated headaches.

Copper is a metal found in natural deposits such as ores containing other elements. Copper is widely used in household plumbing materials.

Short term exposure: Gastrointestinal distress

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.

Increase in blood pressure

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.

Infants and children: Delays in physical or mental development; children could show slight deficits in attention span and learning abilities

Di(2-ethylhexyl) phthalate is the most commonly used of a group of related chemicals called phthalates or phthalic acid esters. The greatest use of di(2-ethylhexyl) phthalate is as a plasticizer for polyvinylchloride (PVC) and other polymers including rubber, cellulose and styrene. A number of packaging materials and tubings used in the production of foods and beverages are polyvinylchloride contaminated with phthalic aced esters, primarily di(2-ethylhexyl) phthalate.

Reproductive difficulties; liver problems; increased risk of cancer

Tetrachloroethylene is a colorless organic liquid with a mild, chloroform-like odor. The greatest use of tetrachloroethylene is in the textile industry, and as a component of aerosol dry-cleaning products.

Liver problems; increased risk of cancer

trans-1,2-Dichloroethylene is an odorless organic liquid that has two slightly different forms, a cis form and a trans form. Both the cis and trans forms — usually as a mixture — are used as a solvent for waxes and resins; in the extraction of rubber; as a refrigerant; in the manufacture of pharmaceuticals and artificial pearls; in the extraction of oils and fats from fish and meat; and in making other organics.

Liver problems

Ethylbenzene is a colorless organic liquid with a sweet, gasoline-like odor. The greatest use – more than 99 percent – of ethylbenzene is to make styrene, another organic liquid used as a building block for many plastics. It is also used as a solvent for coatings, and in the making of rubber and plastic wrap.

Liver or kidneys problems

Toluene is an organic liquid with a sweet, benzene-like odor. The largest chemical use for toluene is to make benzene and urethane.

Nervous system, kidney, or liver problems

The gaseous or liquid form of chlorine (CL2) is a water additive used by municipal water systems to control microbes. It is relatively inexpensive and has the lowest production and operating costs and longest history for large continuous disinfection operations. Chlorine is a powerful oxidant.

Eye/nose irritation; stomach discomfort

cis-1,2-Dichloroethylene is an odorless organic liquid that has two slightly different forms, a cis form and a trans form. Both the cis and trans forms – usually as a mixture – are used as a solvent for waxes and resins; in the extraction of rubber; as a refrigerant; in the manufacture of pharmaceuticals and artificial pearls; in the extraction of oils and fats from fish and meat; and in making other organics.

Liver problems

Benzene, a volatile organic chemical, is a clear, colorless aromatic liquid. It is highly flammable. It is formed through natural processes, such as volcanoes and forest fires. It is also formed from industrial processes. Benzene is also a natural part of crude oil, gasoline and cigarette smoke. The greatest use of benzene is as a building block for making plastics, rubber, resins and synthetic fabrics like nylon and polyester. Other uses include: as a solvent in printing, paints, dry cleaning, etc.

Anemia; decrease in blood platelets; increased risk of cancer

Cadmium is a metal found in natural deposits such as ores containing other elements. Cadmium is used primarily for metal plating and coating operations, including transportation equipment, machinery and baking enamels, photography, and television phosphors. It is also used in nickel-cadmium solar batteries and pigments.

Kidney damage

Fluoride compounds are salts that form when the element, fluorine, combines with minerals in soil or rocks. Many communities add fluoride to their drinking water to promote dental health.

Bone disease (pain and tenderness of the bones); Children may get mottled teeth

Asbestos is a fibrous mineral occurring in natural deposits. Because asbestos fibers are resistant to heat and most chemicals, they have been mined for use in more than 3,000 products, including roofing materials, brake pads, and cement pipe often used in distributing water to communities.

Increased risk of developing benign intestinal polyps

Chlorite occurs when chlorine dioxide breaks down.

Anemia; infants & young children: nervous system effects

Dichloromethane, also known as DCM and methylene chloride, is a volatile organic and colorless liquid chemical with a sweet, pleasant odor like chloroform. The greatest use of DCM is as a paint remover. Other uses include: solvent and cleaning agent in chemical manufacture, textiles, electronics, metals and plastics, pesticides industries; blowing and cleaning agent in the urethane foam industry; fumigant for strawberries and grains, and as degreener for citrus fruits; in pharmaceuticals and as an anesthetic; in extraction of caffeine, cocoa, fats, spices and beer hops; as a heat transfer agent in refrigeration products.

Liver problems; increased risk of cancer

Trichloroethylene, a volatile organic chemical, is a colorless or blue liquid with a chloroform-like odor. Trichloroethylene is primarily used to remove grease from fabricated metal parts and in the production of some textiles.

Liver problems; increased risk of cancer

A radionuclide is an atom with an unstable nucleus which, to become more stable, emits energy in the form of rays or high speed particles. This is called ionizing radiation because it can create ions by displacing electrons in the body e.g. in the DNA, disrupting its function. The three major types of ionizing radiation are: alpha particles, beta particles and gamma rays. Approximately 80% of our exposure to radioactivity is natural and another 20% is from man made sources, although more frequent use of diagnostic imaging involving radiation (x-rays, CT scans) is increasing exposure from this source. We are exposed to naturally occurring radiation for example from radon gas emanating from rocks and soil, and cosmic radiation from space. We also carry small amounts of potassium-40 in our bodies from the foods containing potassium. Depending on the type of rocks where you live, 55 to 70% of natural exposure comes from radon gas, while cosmic radiation (which is greater at higher altitude) represents about 11%, and potassium-40 about 5%. Radiation may exist in drinking water from nuclides dissolved in the water from natural sources in the earth or occasionally from releases from laboratories or nuclear power plants. EPA regulates the following radionuclides in drinking water: (Adjusted) Gross Alpha Emitters, Beta Particle and Photon (gamma) Radioactivity, Radium 226 and Radium 228 (Combined) and Uranium.

Increased risk of cancer

Carbon tetrachloride is a clear heavy organic liquid with a sweet aromatic odor similar to chloroform. Most carbon tetrachloride is used to make chlorofluorocarbon propellants and refrigerants, though this has been declining steadily. It has also been used as a dry cleaning agent and fire extinguisher; in making nylons; as a solvent for rubber cement, soaps, insecticides, etc.

Liver problems; increased risk of cancer

Antimony is a metal found in natural deposits such as ores containing other elements. The most widely used antimony compound is antimony trioxide, used as a flame retardant. It is also found in batteries, pigments, and ceramics/glass.

Increase in blood cholesterol; decrease in blood sugar

Beryllium is an inorganic metallic element in the periodic table. Because it is an element, it does not degrade nor can it be destroyed. Compounds of beryllium are either white or colorless and do not have a particular smell. The greatest use of beryllium is in making metal alloys for nuclear reactors and the aerospace industry. Other uses are as an alloy and oxide in electrical equipment and microwave ovens.

Intestinal lesions

Atrazine is a white, crystalline solid organic compound. Atrazine is a widely used herbicide for control of broadleaf and grassy weeds. Effective in 1993, its uses were greatly restricted.

Cardiovascular system or reproductive problems