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National Drinking Water Database
Thallium (total) in Nevada
Thallium is a highly toxic metal that contaminates the environment due to leaching from ore-processing sites, discharge from electronics, glass, and drug factories and historical use as rodenticide [read more]
Thallium is a naturally occurring metal found in deposits of ores containing other elements. Thallium is used in the manufacture of semiconductors, thermometers, photoelectric cells and optical systems. Thallium is also used in mining operations, as a catalyst in industrial chemical synthesis, and in medical applications for cardiac imaging. Thallium was used as an insecticide and rodenticide (rat poison), but its use for these purposes was banned in the U.S. in 1972 (Agency for Toxic Substances and Disease Registry (ATSDR) 1992e, U.S. Environmental Protection Agency (USEPA) 2002m).
Thallium elicits some of the most complex and serious toxicities in living beings, involving a wide range of organs and tissues. Thallium is more toxic to mammals than mercury, cadmium and lead, and has been responsible for many deliberate, accidental, occupational and therapeutic poisonings of people since its discovery in 1861 (Nriagu 2003). Thallium is absorbed through the skin and gastrointestinal tract. The thallium ion has a similar charge and size as the potassium ion and its toxic effects may result from interference with the biological functions of potassium (ATSDR 1992e).
Thallium contamination of soil and water can occur as a result of coal combustion, cement production and industrial release of thallium from the mining and semiconductor industry. The U.S. EPA's Toxics Release Inventory (TRI) reported that industrial facilities released 98,062 pounds of thallium into U.S. water, land, and air during the year 2002 (USEPA 2009i). The major industries to report thallium releases were the copper smelting industry and the petroleum refining industry (USEPA 2002m). The thallium releases reported are a gross underestimation of the actual volume of thallium released into the environment, however, because thallium releases from coal combustion are generally not reported to the TRI (USEPA 2001a).
Chronic exposure to thallium can also result in a number of symptoms that include gastroenteritis, neurological disorders of the peripheral nervous system (polyneuropathy) and hair loss (alopecia). Residents living near a thallium-contaminated cement plant reported pain in muscles and joints, sleep disorders, and fatigue. Workers exposed to thallium for 16 to 17 years exhibited vascular system disorders and neurological symptoms (California Environmental Protection Agency 1999g). More severe cases of thallium poisoning following long-term exposure have caused hair loss, leg pains, inability to walk, nerve inflammation, blindness, kidney dysfunction, endocrine disorders, brain inflammation and psychoses (California Environmental Protection Agency 1999g). Thallium, in the form of thallium sulfate, was once used as a hair-removal agent in people until its high toxicity was recognized (California Environmental Protection Agency 1999g).
According to EPA, short-term exposure to thallium-contaminated drinking water can result in gastrointestinal irritation and nerve damage. Long-term exposure to thallium can result in hair loss and blood, liver, kidney, intestinal and testicular damage (USEPA 2002m).
In laboratory rats, thallium crosses the placenta and causes developmental toxicity in the fetus, including growth retardation and greater incidences of cleft palates and learning impairments (ATSDR 1992e, California Environmental Protection Agency 1999g). Reproductive effects such as decreased sperm motility and testes alterations have also been reported in rats exposed to thallium (ATSDR 1992e). Other effects seen in animals after high dose exposures include damage to the liver, respiratory tract, eyes and heart. To date, no cancer studies have been conducted for thallium, but it has been shown to damage DNA (ATSDR 1992e, California Environmental Protection Agency 1999g).
The Most Polluted Communities in Nevada
1 water utilities reported detecting Thallium (total) in tap water since 2004, according to EWG's analysis of water quality data supplied by state water agencies
Ranked by highest average Thallium (total) level
|Rank||System||Population Served||Positive test results of total reported tests||Average Level|
Mt Charleston, NV
|126||1 of 1||0.1 ppb|
Health Based Limits for Thallium (total)
|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.||0.1 ppb|
|EPA Human Health Water Quality Criteria||Water quality criteria set by the US EPA provide guidance for states and tribes authorized to establish water quality standards under the Clean Water Act (CWA) to protect human health. These are non-enforceable standards based upon exposure by both drinking water and the contribution of water contamination to other consumed foods. Source: U.S. Environmental Protection Agency.||0.24 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.||0.5 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.||0.5 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|
|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.||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.||7 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.||7 ppb|
Violation Summary for Thallium (total) in Nevada
Data from the U.S. Environmental Protection Agency includes the following violations of federal standards in Nevada since 2004
|Violation Type||Number of Violations|
|Failure to monitor regularly||5|