National Drinking Water Database
National Drinking Water Database - Chemical Contaminants
Mercury (total inorganic)
Status: Regulated - EPA has established a maximum legal limit in tapwater for this contaminant.
Mercury is a metal from refinery and factory pollution, coal burning, landfill and agricultural runoff and erosion of natural deposits. [read more]
Mercury occurs naturally in the environment and exists in several forms: metallic (elemental) mercury, inorganic mercury, and organic mercury. Metallic mercury is a shiny, silver-white metal that is a liquid at room temperature, often used in thermometers. Inorganic mercury compounds (also called mercury salts) occur when mercury combines with elements such as chlorine, sulfur, or oxygen. When mercury combines with carbon, the compounds formed are called "organic" mercury compounds (U.S. Geological Survey (USGS) 2009).
By far the most common organic mercury compound in the environment is methylmercury, a known human neurotoxicant linked to adverse health effects in people, especially children. Mercury is converted to methylmercury by naturally occurring microorganisms in the environment. Methylmercury accumulates in certain freshwater and saltwater fish, and marine mammals. People are exposed to methylmercury through mercury-contaminated fish in their diets (Agency for Toxic Substances and Disease Registry (ATSDR) 1999f, 2009a).
In 2009, the U.S. Geological Survey (USGS) published results of an 8-year survey of mercury in fish, riverbed sediment, and water from rivers and streams across the entire country. Sampled settings included stream basins that were agricultural, urbanized, undeveloped (forested, grassland, shrubland and wetland regions), as well as areas of gold and mercury mining (Scudder 2009). Scientists detected mercury contamination in every fish sampled in every stream, many with mercury levels exceeding the criterion for health protection of people consuming fish in their diet or for fish-eating mammals. Atmospheric mercury is the main source of contamination of most of these streams. Coal-fired power plants are the largest source of mercury emissions in the United States; 59 of the mercury-contaminated streams were also potentially affected by gold and mercury mining (Scudder 2009).
Concerns about the neurodevelopmental toxicity of methylmercury in fish form the basis for the Food and Drug Administration (FDA) fish consumption advisory, which instructs women of childbearing age and children to eat no more than 12 ounces of fish a week and to make sure the 12 ounces is a variety of fish (i.e. do not eat two 6 ounce cans of tuna each week). Both FDA and the Environmental Protection Agency (EPA) recommend that pregnant women, women of childbearing age who may become pregnant, nursing mothers and young children not eat shark, swordfish, king mackerel and tilefish because they have high methylmercury levels (FDA 2004; USEPA 2004a). Similar advisories are issued by other public health agencies in the U.S. and abroad (Ginsberg 2009).
In 2004, the U.S. EPA's Toxics Release Inventory (TRI) reported that U.S. industrial facilities in 2002 released 110,487 pounds of mercury and 5,167,183 pounds of mercury compounds into the environment, mostly onto the land (such as landfills, mixed into surface soil, spills and holding ponds). Most of the reported releases are due to discharges from chemical industries, solvent recovery facilities and metal mining (USEPA 2009i).
Drinking water contaminant fact sheets written by EPA note that exposure to inorganic mercury in drinking water above the maximum contaminant level (MCL) of two microgram per liter (parts per billion or ppb) can cause kidney damage (USEPA 2009b). In laboratory animals, inorganic mercury causes damage to the kidney, stomach, immune system, heart and liver, and leads to increased blood pressure and decreased thyroid hormone levels. In people, exposure to inorganic mercury has been linked with nausea, vomiting, diarrhea and kidney failure (ATSDR 1999b).
Mercury (total inorganic) Exposure by State
Water utilities in 36 states have reported detecting Mercury (total inorganic) in treated tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies.
|State||Water Suppliers with Mercury (total inorganic) contamination||Water suppliers reporting Mercury (total inorganic) above health-based limits|
The Most Polluted Communities
958 water utilities reported detecting Mercury (total inorganic) in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies
Ranked by highest average Mercury (total inorganic) level
|Rank||System||Population Served||Positive test results of total reported tests||Average Level|
|1||Generac Power Systems Inc|
|500||1 of 2||1.93 ppb|
(0 to 3.86 ppb)
|2||Clark Rural Water-Kampeska|
|876||1 of 1||1.8 ppb|
|3||Town of Clear Spring|
|499||1 of 3||1.67 ppb|
(0 to 5 ppb)
|4||Country Meadows Comm. Mhp|
|36||1 of 1||1.4 ppb|
|5||Evergreen Trailer Park - System #1|
|63||1 of 1||1.4 ppb|
|6||Brook Lane Psychiatric Center|
|175||1 of 3||1.33 ppb|
(0 to 4 ppb)
|7||Alpine Village Mobile H P|
Buena Vista Twp, NJ
|70||2 of 2||1.1 ppb|
(1 to 1.2 ppb)
|38||1 of 1||1.1 ppb|
|9||Kelso Water Assn|
|350||1 of 1||1 ppb|
|10||Willow Hills S/D|
Fuquay Varina, NC
|89||1 of 2||1 ppb|
(0 to 2 ppb)
Health Based Limits for Mercury (total inorganic)
|California Public Health Goals||Defined by the State of California Office of Environmental Health Hazard Assessment (OEHHA) as the level of contaminant that is allowed in drinking water. For acutely toxic substances, levels are set at which scientific evidence indicates that no known or anticipated adverse effects on health will occur, plus an adequate margin-of safety. PHGs for carcinogens or other substances which can cause chronic disease shall be based solely on health effects without regard to cost impacts and shall be set at levels which OEHHA has determined do not pose any significant risk to health.||1.2 ppb|
|Maximum Contaminant Limit (MCL)||The enforceable standard which defines the highest level of a contaminant that is allowed in drinking water. MCLs are set as close to health-based limits (Maximum Contaminant Level Goals, or MCLGs) as feasible using the best available analytical and treatment technologies and taking cost into consideration. Source: U.S. Environmental Protection Agency.||2 ppb|
|Maximum Contaminant Limit Goal (MCLG)||A non-enforceable health goal that is set at a level at which no known or anticipated adverse effect on the health of persons occurs and which allows an adequate margin of safety. Source: U.S. Environmental Protection Agency.||2 ppb|
|Children's health-based limit for 1-day exposure||Concentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for up to one day of exposure. The One-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.||2 ppb|
|Children's health-based limit for 10-day exposure||Concentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic effects for up to ten days of exposure. The Ten-Day health-based limit (or Health Advisory, HA) is typically set to protect a 10-kg child consuming 1 liter of water per day. Source: U.S. Environmental Protection Agency.||2 ppb|
|Lifetime health-based limit, non-cancer risk||Concentration of a chemical in drinking water that is not expected to cause any adverse, noncarcinogenic health effects for a lifetime of exposure. The Lifetime health-based limit (or Health Advisory, HA) is based on exposure for a a 70-kg adult consuming 2 liters of water per day. Source: U.S. Environmental Protection Agency.||2 ppb|
|Drinking Water Equivalent Level||A lifetime exposure concentration protective of adverse, noncarcinogenic health effects, that assumes all of the exposure to a contaminant is from drinking water. Source: U.S. Environmental Protection Agency.||10 ppb|
Testing Summary for Mercury (total inorganic)
|Are tests routinely required for Mercury (total inorganic) by federal law?||Yes|
|Water suppliers reporting tests for Mercury (total inorganic) (2004-2009):||29,211 of 47,576|
|Average testing rate for water supplier reporting tests (2004-2009):||0.3 per year|
Violation Summary for Mercury (total inorganic)
Data from the U.S. Environmental Protection Agency includes the following violations of federal standards for Mercury (total inorganic) since 2004
|Maximum Contaminant Level Exceedance Violations||4|