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    Published: March 8, 2017

    5 Contaminants Commonly Found in Arizona’s Water Supply

    Arizona’s geology is rich in a wide variety of minerals, metals, and radioactive elements, making the state a gold mine (often literally) for mining companies. This richness comes at a cost. Contaminants dissolve into groundwater, where they can have serious effects on water quality and health. Add in agricultural runoff and industrial waste, and the state’s water quality looks grim.

    How bad is it? In a survey from 2005 the Environmental Working Group discovered 141 unregulated chemicals and 119 chemicals with EPA-set limits in Arizona water. Only California and Wisconsin ranked worst.

    Five contaminants crop up in Arizona groundwater with alarming regularity:

    • Arsenic
    • Chromium-6
    • Fluoride
    • Nitrate
    • Radioactive elements


    Arizona has elevated levels of arsenic in groundwater across the state, especially in geologic areas made up of granite bedrock and gold ore. The Colorado Plateau, Big Chino and Verde Valley have the highest levels of arsenic in their groundwater.

    High concentrations of arsenic in drinking water can cause cancer, affect the vascular system, and is linked to diabetes. The EPA sets the Maximum Contaminant Level (MCL) for arsenic in water at 0.010 parts per billion. Testing of a domestic well near Paulden in the Verde Valley once found arsenic at levels of 2,900 parts per billion.


    Chromium-6 occurs naturally in the environment, and has several industrial applications. The compound is used in chrome plating, steel production and electric power plant cooling towers. Chromium-6 may also be released into the environment in ash from coal-burning power plants.

    Capable of causing stomach cancer, liver damage, reproductive problems, and impaired brain development, chromium-6 is found naturally in Paradise Valley, just north of Phoenix, and the Detrital Valley near Kingman. In 2016, the Environmental Working Group claimed chromium-6 levels in Phoenix drinking water were 400 times the amount recommended as a health goal by California scientists. The city disputed the claim, noting the report was an average, and did not accurately represent the true level of the compound in municipal water. 


    A common mineral, fluoride occurs in high concentrations in Cochise, Mohave, Graham, and Greenlee counties, and along the lower Gila River in Yuma county.

    In small amounts, fluoride encourages bone and teeth development. High concentrations can cause discolored or mottled teeth.


    Nitrates occur naturally due to decaying plant and animal material. Agricultural and industrial runoff can also add nitrates to water supplies.

    In Arizona, high nitrate levels can be found in water supplies throughout the state. Some aquifers in and around Glendale, Mesa, Chandler, and Phoenix contain nitrates in high enough concentrations the water is unusable for potable purposes.

    Odorless, colorless, and tasteless, nitrates cannot be detected without water testing. Nitrate ingestion is associated with “blue baby” syndrome, cancer, birth defects and thyroid enlargement.

    Radioactive Elements

    The most common radioactive elements found in Arizonan bedrock aquifers are uranium, radium, and dissolved radon gas. The Supai Sandstone Formation in the Colorado Plateau is home to several uranium mines, and well water in that area often tests positive for uranium in excess of the MCL of 30 parts per billion.

    Uranium decays and breaks down into radium, which in turn decays into radon. The expression “gross alpha” refers to the measure of radioactivity in water due to radioactive decay. Gross alpha is a common water contaminant in Arizona.

    Other Threats

    Arizona’s rich geologic makeup presents even more challenges to water quality. Lithium, selenium, and boron, all known to present health risks in high concentrations, have been found in groundwater in parts of the state. Iron, manganese, and sulfates are also common in water supplies, increasing water hardness and encouraging the growth of iron bacteria in private wells.

    While private wells are at higher risk of contaminants, Phoenix’s chromium-6 issue proves public water supplies are not immune to Arizona’s many waterborne contaminants. Protect yourself and your family from contaminants lurking in your water with an NSF-certified Reverse Osmosis Water Filter. For more information on filtration options, call one of Pelican Water’s water experts—we can help you decide if your water supply is safe—and offer solutions if it isn’t.