Arsenic Found in Groundwater
Study Estimates about 2.1 Million People using Wells High in Arsenic
Arsenic is a naturally occurring element, but long-term exposure can cause cancer in people. There has been a substantial amount of research done to address arsenic in groundwater and drinking-water supplies around the country. The USGS studies local and national sources of arsenic to help health officials better manage our water resources.
Updated Information on U.S. Groundwater: Arsenic among many concerns
Three new fact sheets add to information on groundwater quality in the Nation's most heavily used aquifers. Arsenic is among the constituents that most frequently exceed human-health benchmarks.
Featured: 3-D Models of As and Mn in the Glacial Aquifer System
New 3-D models from the USGS National Water Quality Program predict where high concentrations of arsenic and manganese likely occur in the glacial aquifer system, groundwater supply for 30 million. Redox conditions and pH are controlling factors.
BACKGROUND
Arsenic occurs naturally as a trace component in many rocks and sediments. Whether the arsenic is released from these geologic sources into groundwater depends on the chemical form of the arsenic, the geochemical conditions in the aquifer, and the biogeochemical processes that occur. Arsenic also can be released into groundwater as a result of human activities, such as mining, and from its various uses in industry, in animal feed, as a wood preservative, and as a pesticide. In drinking-water supplies, arsenic poses a problem because it is toxic at low levels and is a known carcinogen. In 2001, the USEPA lowered the MCL for arsenic in public-water supplies to 10 micrograms per liter (µg/L) from 50 µg/L.
DANGEROUS GROUNDWATER SUPPLIES
The USGS plays an active role in protecting human health from potential issues related to our Nation's natural resources. One vital aspect is assessing the water quality of groundwater supplies. Whether across the U.S. or around the world, the USGS helps measure and monitor drinking water supplies for contaminants like arsenic. For example, dangerously high levels of arsenic have been found in drinking water wells in more than 25 states in the United States, potentally exposing 2.1 million people1 to drinking water high in arsenic. Possibly the worst case ever of arsenic poisoning occurred in Bangladesh, where over 100 million people2 were poisoned by arsenic in groundwater supplies.
In a national study of groundwater quality, the USGS found that arsenic was detected in nearly half of the wells sampled in parts of aquifers used for drinking-water supply at a concentration of 1 µg/L or greater. Detections were more common and concentrations generally were higher in the west than in the east. About 7 percent of the wells sampled contained arsenic at a concentration that exceeded the MCL of 10 µg/L, indicating a potential health risk. The greatest concern was in the Southwest, where concentrations of arsenic exceeded the MCL in about 16 percent of drinking-water wells sampled. Other Principal Aquifers with concerns for arsenic included the Glacial aquifer system (northern U.S.), the crystalline rock aquifers of the Piedmont, Blue Ridge, and Valley and Ridge Aquifers (northern U.S.), and the Mississipppi Embayment–Texas Coastal Uplands Aquifer System and Mississippi River Valley Alluvial Aquifer (southeastern U.S.).
In the Southwest basin-fill aquifers, arsenic concentrations in drinking-water wells exceeded the MCL more than twice as frequently as in drinking-water wells nationwide. The source is the volcanic and granitic rocks through which that groundwater moves. [maybe use photo from p. 18] Factors that contribute to elevated concentrations of arsenic in these aquifers include long groundwater residence times, rock type, high pH, arid climate, and irrigation practices.
The USEPA estimated in 2001 that the annual cost to reduce arsenic concentrations to below the MCL would range from $0.86 to $32 per household for customers of large public water systems (more than 10,000 people) to $165 to $327 per household for very small systems (25–500 people). Understanding the factors that affect concentrations of arsenic and other contaminants with geologic sources in groundwater can help water suppliers prioritize areas for new groundwater development and reduce treatment costs.
RELATED USGS RESEARCH
The unique hydrogeologic character of this health hazard makes USGS research crucial for understanding this hazard and helping water-supply and public-health authorities implement strategies to mitigate this risk. The USGS investigates the presence and effect of arsenic in drinking water supplies, monitors the worldwide distribution of arsenic in groundwater, and assesses the impact of arsenic on local stream sediment chemistry.
- Groundwater Quality—Current Conditions and Changes Through Time
- Predicting Groundwater Quality in Unmonitored Areas
ADDITIONAL RESOURCES
- Drinking water requirements for arsenic (U.S. Environmental Protection Agency)
- In Small Doses: Arsenic (Dartmouth University)
- Arsenic (Agency for Toxic Substances and Disease Registry)
- Map of Arsenic concentrations in groundwater of the United States (DATA.GOV)
Drinking Water and Source Water Research
Metals and Other Trace Elements
Public Supply Wells
Domestic (Private) Supply Wells
Groundwater Quality in Principal Aquifers of the Nation, 1991–2010
Groundwater Quality—Current Conditions and Changes Through Time
Predicting Groundwater Quality in Unmonitored Areas
Groundwater Age
Oxidation/Reduction (Redox)
Study to Test a Novel Shallow Well Design that May Provide Contaminant-Free Water Supply to Domestic Well Users in Arsenic-Prone Parts of the United States
Towards Understanding the Impact of Drought on the Arsenic Hazard for the Private Domestic Well Population in the United States
Mapping and Characterizing the Arsenic Hazard in Private Well Water Across the Nation
Stay informed of media alerts and news stories about when and where arsenic is being discovered in water supplies across the country.
Study Estimates about 2.1 Million People using Wells High in Arsenic
Arsenic is a naturally occurring element, but long-term exposure can cause cancer in people. There has been a substantial amount of research done to address arsenic in groundwater and drinking-water supplies around the country. The USGS studies local and national sources of arsenic to help health officials better manage our water resources.
Updated Information on U.S. Groundwater: Arsenic among many concerns
Three new fact sheets add to information on groundwater quality in the Nation's most heavily used aquifers. Arsenic is among the constituents that most frequently exceed human-health benchmarks.
Featured: 3-D Models of As and Mn in the Glacial Aquifer System
New 3-D models from the USGS National Water Quality Program predict where high concentrations of arsenic and manganese likely occur in the glacial aquifer system, groundwater supply for 30 million. Redox conditions and pH are controlling factors.
BACKGROUND
Arsenic occurs naturally as a trace component in many rocks and sediments. Whether the arsenic is released from these geologic sources into groundwater depends on the chemical form of the arsenic, the geochemical conditions in the aquifer, and the biogeochemical processes that occur. Arsenic also can be released into groundwater as a result of human activities, such as mining, and from its various uses in industry, in animal feed, as a wood preservative, and as a pesticide. In drinking-water supplies, arsenic poses a problem because it is toxic at low levels and is a known carcinogen. In 2001, the USEPA lowered the MCL for arsenic in public-water supplies to 10 micrograms per liter (µg/L) from 50 µg/L.
DANGEROUS GROUNDWATER SUPPLIES
The USGS plays an active role in protecting human health from potential issues related to our Nation's natural resources. One vital aspect is assessing the water quality of groundwater supplies. Whether across the U.S. or around the world, the USGS helps measure and monitor drinking water supplies for contaminants like arsenic. For example, dangerously high levels of arsenic have been found in drinking water wells in more than 25 states in the United States, potentally exposing 2.1 million people1 to drinking water high in arsenic. Possibly the worst case ever of arsenic poisoning occurred in Bangladesh, where over 100 million people2 were poisoned by arsenic in groundwater supplies.
In a national study of groundwater quality, the USGS found that arsenic was detected in nearly half of the wells sampled in parts of aquifers used for drinking-water supply at a concentration of 1 µg/L or greater. Detections were more common and concentrations generally were higher in the west than in the east. About 7 percent of the wells sampled contained arsenic at a concentration that exceeded the MCL of 10 µg/L, indicating a potential health risk. The greatest concern was in the Southwest, where concentrations of arsenic exceeded the MCL in about 16 percent of drinking-water wells sampled. Other Principal Aquifers with concerns for arsenic included the Glacial aquifer system (northern U.S.), the crystalline rock aquifers of the Piedmont, Blue Ridge, and Valley and Ridge Aquifers (northern U.S.), and the Mississipppi Embayment–Texas Coastal Uplands Aquifer System and Mississippi River Valley Alluvial Aquifer (southeastern U.S.).
In the Southwest basin-fill aquifers, arsenic concentrations in drinking-water wells exceeded the MCL more than twice as frequently as in drinking-water wells nationwide. The source is the volcanic and granitic rocks through which that groundwater moves. [maybe use photo from p. 18] Factors that contribute to elevated concentrations of arsenic in these aquifers include long groundwater residence times, rock type, high pH, arid climate, and irrigation practices.
The USEPA estimated in 2001 that the annual cost to reduce arsenic concentrations to below the MCL would range from $0.86 to $32 per household for customers of large public water systems (more than 10,000 people) to $165 to $327 per household for very small systems (25–500 people). Understanding the factors that affect concentrations of arsenic and other contaminants with geologic sources in groundwater can help water suppliers prioritize areas for new groundwater development and reduce treatment costs.
RELATED USGS RESEARCH
The unique hydrogeologic character of this health hazard makes USGS research crucial for understanding this hazard and helping water-supply and public-health authorities implement strategies to mitigate this risk. The USGS investigates the presence and effect of arsenic in drinking water supplies, monitors the worldwide distribution of arsenic in groundwater, and assesses the impact of arsenic on local stream sediment chemistry.
- Groundwater Quality—Current Conditions and Changes Through Time
- Predicting Groundwater Quality in Unmonitored Areas
ADDITIONAL RESOURCES
- Drinking water requirements for arsenic (U.S. Environmental Protection Agency)
- In Small Doses: Arsenic (Dartmouth University)
- Arsenic (Agency for Toxic Substances and Disease Registry)
- Map of Arsenic concentrations in groundwater of the United States (DATA.GOV)
Drinking Water and Source Water Research
Metals and Other Trace Elements
Public Supply Wells
Domestic (Private) Supply Wells
Groundwater Quality in Principal Aquifers of the Nation, 1991–2010
Groundwater Quality—Current Conditions and Changes Through Time
Predicting Groundwater Quality in Unmonitored Areas
Groundwater Age
Oxidation/Reduction (Redox)
Study to Test a Novel Shallow Well Design that May Provide Contaminant-Free Water Supply to Domestic Well Users in Arsenic-Prone Parts of the United States
Towards Understanding the Impact of Drought on the Arsenic Hazard for the Private Domestic Well Population in the United States
Mapping and Characterizing the Arsenic Hazard in Private Well Water Across the Nation
Stay informed of media alerts and news stories about when and where arsenic is being discovered in water supplies across the country.