All sources of drinking water contain some naturally occurring contaminants. As water flows in streams, sits in lakes, and filters through layers of soil and rocks, it dissolves or absorbs the substances that it touches. 

According to its exposure, water transforms in composition and in physical parameters.
Aluminum (Al) Low-level exposure is not thought to be harmful, but long-term intake has been linked to impaired brain function, including Alzheimer’s disease. (Federal Limit 0.05 – 0.2 mg/L)
Arsenic (As) A known human carcinogen. Any exposure to this toxic metal can cause skin and circulatory system damage. (Federal Limit 0.01 mg/L)
Barium (Ba) Symptoms of barium poisoning include increased blood pressure, changes in heart rhythm, stomach irritation, and muscle weakness. (Federal Limit 2.0 mg/L)
Beryllium (Be) One of the most toxic chemicals known, and a probable human carcinogen. Laboratory tests indicate that beryllium can cause cancer and the mutation of animal DNA. (Federal Limit 0.004 mg/L)
Boron (B) Boron is exceptionally toxic to some plants. (No Federal Limit)
Cadmium (Cd) Long-term exposure to low levels can cause kidney disease, lung damage and fragile bones. (Federal Limit 0.005 mg/L)
Calcium (Ca) The most abundant metal in the human body, necessary for bone and tooth formation. It is also an important contributor to water hardness. (No Federal Limit)
Conductivity (s ) Measures resistance to an electrical current passing through water. Useful as a ballpark number for the concentration of dissolved salts. (No Federal Limit)
Chromium (Cr) Exposure above the EPA limit may cause skin ulceration. Long-term contact may damage liver, kidneys, and nerve tissue. (Federal Limit 0.1 mg/L)
Copper (Cu) Imparts a bitter taste to water, stains fixtures, hair, and fabrics, and can cause stomach irritation and vomiting. (Federal Limit 1.3 mg/L)
Fecal Coliform Bacteria and Escherichia coli (E. coli) Present in the intestines of mammals. In the laboratory, coliforms are used as indicators of fecal contamination of ground and surface waters. Water sources containing any coliforms must be treated before consumption. See “Fecal Coliforms.”
Fluoride (F) Helps prevent tooth decay. Long-term overexposure leads to tooth enamel destruction, brittle bones, and joint pain. (Federal Limit 4.0 mg/L, Oregon 2.0 mg/L)
Hardness Usually attributed to calcium and magnesium ions that combine with soap to form an insoluble scum around plumbing fixtures. See “Water Hardness.” (Federal Limit 250 mg/L)
Iron (Fe) Forms rust that stains fixtures. (Federal Limit 0.3 mg/L)
Lead (Pb) Particularly dangerous to children, lead in the body attacks the nervous system and can cause brain and kidney damage. (Federal Limit 0.015 mg/L)
Lithium (Li) Occurs naturally in many areas of the country. When ingested, lithium can cause nausea, vomiting, diarrhea and kidney damage. (No Federal Limit)
Magnesium (Mg) Contributes to water hardness and lime scale. Concentrations greater than 125 mg per liter may have a laxative effect. (No Federal Limit)
Manganese (Mn) High levels are toxic to expectant mothers and young children. (Federal Limit 0.05 mg/L)
Molybdenum: Excessive molybdenum consumption can be associated with enlarged liver, gastrointestinal, and kidney disorders. (USEPA Lifetime Health Advisory: 40 ug/L)

Nickel (Ni) Long-term exposure can cause decreased body weight as well as heart and liver damage. (Federal Limit 0.1 mg/L)
Nitrate/Nitrite (NO2/NO3) Infants younger than 6 months of age are at risk of permanent brain damage or death from exposure. (Federal Limit Nitrate 10 mg/L, Nitrite 1 mg/L)
Pesticides & Herbicides Enter surface and ground water primarily as runoff and can remain in sediment for years. Thousands of chemicals are currently regulated by the EPA and have various hazardous effects on humans. (Federal Limit Per Each Analyte)
pH Ideal pH for drinking water is 7.5. When pH is below 7.0, water is acidic and can cause corrosion of pipes and fixtures. pH above 8.0 indicates alkalinity that can create mineral deposits inside pipes. (No Federal Limit)
Potassium (K) Helps lower blood pressure, and reduces the risk of kidney stones and bone loss. Adults should consume 4.7 grams of potassium per day. (No Federal Limit)
Selenium (Se) An essential nutrient at low levels. Long-term overexposure is harmful to kidneys, liver, and nervous and circulatory systems. (Federal Limit 0.05 mg/L)
Silica: Silica analysis provides useful information for systems that my require water treatment.  Not identified as a health hazard. (No Limit)
Silver (Ag) Poisoning causes a skin discoloration. Fatal to humans in high doses. (Federal Limit 0.1 mg/L)
Sodium & Chloride (Na/Cl2) High levels make water taste salty and also affect plant growth. (Sodium: No Federal Limit, Chloride: Federal Limit 250 mg/L)
Sulfate (SO4) Naturally occurring substance. May cause diarrhea when ingested at high levels. (Federal Limit 250 mg/L)
Thallium (Tl) Long-term exposure may cause hair loss and damage to liver, kidney, intestinal, and testicular tissues. (Federal Limit 0.002 mg/L)
Turbidity:  Turbidity is the lack of clarity or brilliance in water.  This can affect water treatment systems such as UV lights for disinfection, reverse osmosis units, sediment removal systems, and ion exchange treatment systems.
Uranium: naturally occurring substance that is mildly radioactive.  Exposure to high levels of uranium can cause kidney disease. (Federal Limit 0.03 ug/L)
Vanadium: The health effects in humans has not been established.  Studies in pregnant animals showed minor birth defects.  Vanadium ingested over a long period of time also revealed minor kidney and liver changes.  Vanadium is also used for arsenic remove in drinking water treatment systems. (No limit)
Volatile Organics or VOCs are found in gasoline, dry cleaning solvents, degreasing agents and other industrial solutions. The EPA and DEQ monitor thousands of chemicals that fall under this classification. (Federal Limit Per Each Analyte)
Zinc (Zn) Overexposure can lead to anemia. (Federal Limit 5.0 mg/L)
For a complete list of all regulated contaminants and the maximum levels as established by the EPA, see the following page: