Question: What has the United States set as a limit for arsenic in drinking water?
About the article "Rice", section "Arsenic concerns".

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Rice and rice products contain arsenic, a known poison and Group 1 carcinogen.
There is no safe level of arsenic, but, as of 2012, a limit of 10 parts per billion has been established in the United States for drinking water, twice the level of 5 parts per billion originally proposed by the EPA.
Consumption of one serving of some varieties of rice gives more exposure to arsenic than consumption of 1 liter of water that contains 5 parts per billion arsenic; however, the amount of arsenic in rice varies widely with the greatest concentration in brown rice and rice grown on land formerly used to grow cotton; in the United States, Arkansas, Louisiana, Missouri, and Texas.
The U.S. Food and Drug Administration (FDA) is studying this issue, but has not established a limit.
China has set a limit of 150 ppb for arsenic in rice.
White rice grown in Arkansas, Louisiana, Missouri, and Texas, which account for 76 percent of American-produced rice had higher levels of arsenic than other regions of the world studied, possibly because of past use of arsenic-based pesticides to control cotton weevils.
Rice from Thailand and India contain the least arsenic among rice varieties in one study.
In the United States, since 2006, the maximum concentration in drinking water allowed by the Environmental Protection Agency (EPA) is 10 ppb and the FDA set the same standard in 2005 for bottled water.
The Department of Environmental Protection for New Jersey set a drinking water limit of 5 ppb in 2006.
In 2008, based on its ongoing testing of a wide variety of American foods for toxic chemicals, the U.S. Food and Drug Administration set 23 ppb as the "level of concern" for inorganic arsenic apple and pear juices based on non-carcinogenic effects, and began refusing imports and demanding recalls for domestic products exceeding this level.
In 2011, the national Dr. Oz television show broadcast a program highlighting tests performed by an independent lab hired by the producers.
Though the methodology was disputed (it did not distinguish between organic and inorganic arsenic) the tests showed levels of arsenic up to 36 ppb.
In response, FDA testing of the worst brand from the Oz show showed much lower levels, and its ongoing testing found 95% of apple juice samples were below the level of concern.
Later testing by Consumer Reports showed inorganic arsenic at levels slightly above 10 ppb, with the organization urging parents to reduce consumption.
In July 2013, after taking into account consumption by children, chronic exposure, and carcinogenic effect, the FDA established an "action level" of 10 ppb for apple juice, the same as the drinking water standard.
Concern about arsenic in rice in Bangladesh was raised in 2002, but at the time only Australia had a legal limit for the level found in food (one milligram per kilogram).
The People's Republic of China has a food standard of 150 ppb for arsenic, as of 2011.
Further concern was raised about people who were eating U.S. rice exceeding WHO standards for personal arsenic intake in 2005.
In the United States in 2012, testing by separate groups of researchers at the Children's Environmental Health and Disease Prevention Research Center at Dartmouth College (early in the year, focusing on urinary levels in children) and Consumer Reports (in November) found levels of arsenic in rice which resulted in calls for the FDA to set limits.
The FDA released some testing results in September 2012, and as of July 2013 is still collecting data in support of a new potential regulation.
It has not recommended any changes in consumer behavior.
Consumer Reports recommended that the EPA and FDA eliminate arsenic-containing fertilizer, drugs, and pesticides in food production; that the FDA establish a legal limit for food; that industry change production practices to lower arsenic levels, especially in food for children; and that consumers test home water supplies, eat a varied diet, and cook rice with excess water which is drained off (reducing inorganic arsenic by about one third along with a slight reduction in vitamin content).
A 2014 World Health Organization advisory conference will consider limits of 200–300 ppb for rice. 
United States.
A drinking water standard of 0.05 mg/L (equal to 50 parts per billion, or ppb) arsenic was originally established in the United States by the Public Health Service in 1942.
The Environmental Protection Agency (EPA) studied the pros and cons of lowering the arsenic Maximum Contaminant Level (MCL) for years in the late 1980s and 1990s.
No action was taken until January 2001, when the Clinton administration in its final weeks promulgated a new standard of 0.01 mg/L (10 ppb) to take effect January 2006.
The Bush administration suspended the midnight regulation, but after some months of study, the new EPA administrator Christine Todd Whitman approved the new 10 ppb arsenic standard and its original effective date of January 2006.
Many locations exceed this limit.
Cases of groundwater-caused acute arsenic toxicity, such as those found in Bangladesh, are unknown in the United States where the concern has focused on the role of arsenic as a carcinogen.
The problem of high arsenic concentrations has been subject to greater scrutiny since 2001, when the federal government promulgated a new lower standard for arsenic in drinking water.
Many public water supply systems across the United States obtained their water supply from groundwater that had met the old 50 ppb arsenic standard but exceeded the new 10 ppb MCL.
These utilities searched for either an alternative supply or an inexpensive treatment method to remove the arsenic from their water.
In Arizona, an estimated 35 percent of water-supply wells were put out of compliance by the new regulation; in California, the percentage was 38 percent .
The proper arsenic MCL continues to be debated.
Some have argued that the 10 ppb federal standard is still too high, while others have argued that 10 ppb is needlessly strict.
Individual states are able to establish lower arsenic limits; New Jersey has done so, setting a maximum of 0.005 mg/L for arsenic in drinking water.
A study of private water wells in the Appalachian mountains found that six percent of the wells had arsenic above the U.S. MCL of 0.010 mg/L. 
It has been found that rice is particularly susceptible to accumulation of arsenic from soil.
Rice grown in US has an average 260 ppb of arsenic according to a study, but U.S. arsenic intake remains far below WHO recommended limits.
China has set a standard for arsenic limits in food (150 ppb), as levels in rice exceed those in water.
In the United States, levels of arsenic that are above natural levels, but still well below danger levels set in federal safety standards, have been detected in commercially grown chickens.
The source of the arsenic appears to be the feed additives roxarsone and nitarsone, which are used to increase weight and skin coloring of the poultry. 
Widespread arsenic contamination of groundwater has led to a massive epidemic of arsenic poisoning in Bangladesh and neighboring countries.
It is estimated that approximately 57 million people in the Bengal basin are drinking groundwater with arsenic concentrations elevated above the World Health Organization's standard of 10 parts per billion (ppb).
However, a study of cancer rates in Taiwan suggested that significant increases in cancer mortality appear only at levels above 150 ppb.
The arsenic in the groundwater is of natural origin, and is released from the sediment into the groundwater, owing to the anoxic conditions of the subsurface.
This groundwater began to be used after local and western NGOs and the Bangladeshi government undertook a massive shallow tube well drinking-water program in the late twentieth century.
This program was designed to prevent drinking of bacteria-contaminated surface waters, but failed to test for arsenic in the groundwater.
Many other countries and districts in Southeast Asia, such as Vietnam and Cambodia have geological environments conducive to generation of high-arsenic groundwaters.
was reported in Nakhon Si Thammarat, Thailand in 1987, and the Chao Phraya River is suspected of containing high levels of naturally occurring dissolved arsenic, but has not been a public health problem owing to the use of bottled water.
In the United States, arsenic is most commonly found in the ground waters of the southwest.
Parts of New England, Michigan, Wisconsin, Minnesota and the Dakotas are also known to have significant concentrations of arsenic in ground water.
Increased levels of skin cancer have been associated with arsenic exposure in Wisconsin, even at levels below the 10 part per billion drinking water standard, although this link has not been proven.
According to a recent film funded by the US Superfund, millions of private wells have unknown arsenic levels, and in some areas of the US, over 20% of wells may contain levels that exceed established limits.
Low-level exposure to arsenic at concentrations of 100 parts per billion (i.e., above the 10 parts per billion drinking water standard) compromises the initial immune response to H1N1 or swine flu infection according to NIEHS-supported scientists.
The study, conducted in laboratory mice, suggests that people exposed to arsenic in their drinking water may be at increased risk for more serious illness or death in response to infection from the virus.
Some Canadians are drinking water that contains inorganic arsenic.
Private dug well waters are most at risk for containing inorganic arsenic.
Preliminary well water analyses typically does not test for arsenic.
Researchers at the Geological Survey of Canada have modelled relative variation in natural arsenic hazard potential for the province of New Brunswick.
This study has important implications for potable water and health concerns relating to inorganic arsenic.
Epidemiological evidence from Chile shows a dose-dependent connection between chronic arsenic exposure and various forms of cancer, in particular when other risk factors, such as cigarette smoking, are present.
These effects have been demonstrated to persist below 50 ppb.
Analyzing multiple epidemiological studies on inorganic arsenic exposure suggests a small but measurable risk increase for bladder cancer at 10 ppb.
According to Peter Ravenscroft of the Department of Geography at the University of Cambridge, roughly 80 million people worldwide consume between 10 and 50 ppb arsenic in their drinking water.
If they all consumed exactly 10 ppb arsenic in their drinking water, the previously cited multiple epidemiological study analysis would predict an additional 2,000 cases of bladder cancer alone.
This represents a clear underestimate of the overall impact, since it does not include lung or skin cancer, and explicitly underestimates the exposure.
Those exposed to levels of arsenic above the current WHO standard should weigh the costs and benefits of arsenic remediation.
Early (1973) evaluations of the removal of dissolved arsenic by drinking water treatment processes demonstrated that arsenic is very effectively removed by co-precipitation with either iron or aluminum oxides.
The use of iron as a coagulant, in particular, was found to remove arsenic with efficiencies exceeding 90%.
Several adsorptive media systems have been approved for point-of-service use in a study funded by the United States Environmental Protection Agency (US EPA) and the National Science Foundation (NSF).
A team of European and Indian scientists and engineers have set up six arsenic treatment plants in West Bengal based on in-situ remediation method (SAR Technology).
This technology does not use any chemicals and arsenic is left as an insoluble form (+5 state) in the subterranean zone by recharging aerated water into the aquifer and thus developing an oxidation zone to support arsenic oxidizing micro-organisms.
This process does not produce any waste stream or sludge and is relatively cheap.
Another effective and inexpensive method to remove arsenic from contaminated well water is to sink wells 500 feet or deeper to reach purer waters.
A recent 2011 study funded by the US National Institute of Environmental Health Sciences' Superfund Research Program shows that deep sediments can remove arsenic and take it out of circulation.
Through this process called adsorption in which arsenic sticks to the surfaces of deep sediment particles, arsenic can be naturally removed from well water.
Magnetic separations of arsenic at very low magnetic field gradients have been demonstrated in point-of-use water purification with high-surface-area and monodisperse magnetite (Fe3O4) nanocrystals.
Using the high specific surface area of Fe3O4 nanocrystals the mass of waste associated with arsenic removal from water has been dramatically reduced.
Epidemiological studies have suggested a correlation between chronic consumption of drinking water contaminated with arsenic and the incidence of all leading causes of mortality.
The literature provides reason to believe arsenic exposure is causative in the pathogenesis of diabetes.
Hungarian engineer László Schremmer has recently discovered that by the use of chaff-based filters it is possible to reduce the arsenic content of water to 3 µg/L.
This is especially important in areas where the potable water is provided by filtering the water extracted from the underground aquifer.