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Water Testing Recommendations for Private Well Owners
Mercury
Mercury is a naturally occurring metal which has several forms. At room temperature, metallic mercury is a heavy, shiny, silver, odorless liquid. When heated, mercury becomes a colorless, odorless gas. Metallic mercury is used to produce chlorine gas and caustic soda. Mercury is also used in thermometers, dental fillings, batteries and switches.
Mercury may enter the body through the respiratory system or by being absorbed through the skin or eyes. It may also be ingested from contaminated drinking water or fish.
Mercury that makes its way into bodies of water builds up in fish tissue and other aquatic life. As bigger fish eat smaller fish, the bigger fish get higher levels of mercury. As a result, many fish consumption advisories related to mercury warn against eating large fish like bowfin or largemouth bass or ocean fish like shark or king mackerel. Learn more about mercury in fish.
The N.C. Department of Environmental Quality (DEQ) routinely monitors water quality and fish tissue for potential problems (Learn more about the DEQ Water Sciences Section). In the event that potentially hazardous levels of chemicals are detected in fish, the N.C. Department of Health and Human Services (DHHS) issues public advisories telling people to either limit consumption or, if necessary, avoid eating those kinds of fish entirely.
Current mercury-related fish advisories in effect for North Carolina are available on the Occupational and Environmental Epidemiology Current Fish Advisories page as well as through the U.S. Environmental Protection Agency. 
Mercury is also a contaminant of concern for private well owners. Mercury levels in North Carolina private well water from 1998 to 2010, for the most part, averaged less than the EPA maximum contaminant level of 2 µg/L. (See Facts & Figures: Mercury in Private Well Water 1998-2010.) Because concentrations of pollutants and groundwater flow are subject to change, private well owners should regularly test their well water for arsenic and other contaminants. See N.C. DPH water testing recommendations for North Carolina private well owners.
Serious respiratory disturbances can result from inhalation exposure to mercury. Mercury can also cause skin and eye irritation. Exposure to high levels of mercury can damage the brains of unborn children and young children. Prenatal exposure to mercury can affect the way children think, learn, and problem-solve later in life. For this reason, mercury-related fish consumption advisories are stronger for pregnant women and young children who are more sensitive to the toxic effects of mercury. See N.C. DHHS recommendations on fish that are safe to eat and which fish are likely to be high in mercury.
In adults, the earliest obvious signs of mercury poisoning are numbness of lips, fingers or toes, fatigue and blurred vision.
