Massive groundwater pumping in Asia may poison millions

IRIN: Millions of people in South and Southeast Asia may be at risk of arsenic poisoning as massive pumping of groundwater pushes tainted water closer to uncontaminated aquifers, scientists warned in a new study published in the journal Nature.

The study, published by experts from Switzerland, the US and Vietnam, examined changing groundwater flow over one decade in Vietnam’s capital, Hanoi.

Hanoi is expanding rapidly, as is water demand. Pumping for municipal water supplies doubled between 2000 and 2010, to around 240 million gallons daily. In the city, water is filtered and treated, but in areas just a few kilometres outside, near the Red River, many households use private untreated wells.

In the past, higher water levels in the aquifer (underground layer of water-bearing rock, sand or silt) meant water from these wells was generally safe. But as more groundwater has been pumped, water from arsenic-rich sediments is increasingly intruding into the previously uncontaminated aquifer.

Arsenic, one of the most common inorganic contaminants found in drinking water worldwide, can be highly toxic to humans. Even in low concentrations arsenic can damage health if ingested over long periods. It is associated with cancer of the skin, lungs, bladder and kidneys.

At some sites in Vietnam investigated for the study, arsenic concentrations were up to 50 times higher than the internationally recommended limit of 10 micrograms of arsenic per litre....

A bridge over the Red River in Hanoi, shot by Luigi Guarino, Wikimedia Commons, under the Creative Commons Attribution 2.0 Generic license

China's arsenic contamination risk is assessed

Rebecca Morelle in the BBC: Nearly 20 million people in China could be exposed to water contaminated with arsenic, a study suggests. Scientists used information about the geology of the country to predict the areas most likely to be affected by the poison.

...Arsenic occurs naturally in the Earth's crust, but if it leaches into groundwater, long-term exposure can cause serious health risks. These include skin problems and cancers of the skin, lungs, bladder and kidney.

Until now, estimating the scale of arsenic contamination in large countries has been difficult. China is thought to have more than 10 million drinking wells, and each needs to be screened to establish whether any toxic compounds are present. This process could take decades.

Instead, researchers from Switzerland and China looked at geological maps of the country. Dr Annette Johnson, from the Swiss Federal Institute of Aquatic Science and Technology (EAWAG) and a co-author of the study, explained: "In the last few years the amount of geospatial information - electronic maps - that's become available is large. You have information such as climate data, land use, and distance to the river or elevation."

Using this information, and by looking at the types of rocks present in the country, and in particular their age, the researchers pinpointed the regions where the toxic element is most likely to be found....

Arsenic from the periodic table, created by Schnee, Wikimedia Commons, under the Creative Commons Attribution-Share Alike 3.0 Unported license

Low-arsenic rice could have major health benefits

Seed Daily via SPX: Millions of people worldwide are regularly exposed to arsenic through drinking water and eating rice grown in soil and water containing high amounts of arsenic. Long-term exposure can lead to the development of different types of cancer as well as serious cardiovascular, neurological, and other health problems.

Scientists have now identified aromatic rice from Bangladesh that has far lower arsenic concentrations than found in non-aromatic rice. The other important benefit is that it contains higher amounts of selenium and zinc. The discovery is reported in Biomedical Spectroscopy and Imaging.

Rice is the staple food of over three billion people. Because the rice plant is highly efficient at absorbing arsenic from soil and water, it is reported to be the highest arsenic-containing cereal. For Bangladeshis, rice is their staple food and they consume on average half a kilogram of rice daily.

A team of scientists led by Dr. Parvez Haris from De Montfort University, Leicester, UK is carrying out research to remove arsenic from water and to identify ways of reducing human exposure to arsenic through diet.

Haris and his team have already demonstrated that exposure to the more toxic inorganic arsenic species is greater in people who eat more rice. In this latest work, published in Biomedical Spectroscopy and Imaging, the De Montfort University team - along with Dr Michael Watts from the British Geological Survey, Keyworth, Nottingham, UK - has identified varieties that are low in arsenic but high in essential trace elements such as selenium and zinc.

Earlier studies showed high concentrations of arsenic in Bangladeshi rice, but the rice samples were mainly from regions where the irrigation water contains higher levels of arsenic....

Child in a deepwater rice field in Bangladesh, shot by the International Rice Research Institute, Wikimedia Commons via Flickr, under the Creative Commons Attribution 2.0 Generic license

Alternate wetting and drying of rice paddies in Bangladesh cuts arsenic contamination

Janet Pelley in Chemical & Engineering News: Rice is the staff of life for millions of Bangladeshis, but it could also damage their health. The well water drawn for irrigating rice in Bangladesh is naturally high in arsenic, a carcinogen with no safe dose. Now a study shows that a simple farming practice promoted to save water could also help cut exposure to arsenic (Environmental Science & Technology (DOI: Environ. Sci. Technol., DOI: 10.1021/es102882q).

Rice usually grows in perpetually flooded fields that provide a reducing and anoxic environment. In such an environment, arsenic becomes bioavailable and gets released from the soil. Plants can then readily take it up. Rice in a typical Asian diet can lead to daily arsenic exposures equivalent to drinking 2 L of water that is at or above the World Health Organization's limit for arsenic of 10 µg/L. Researchers have found that growing rice on dry fields cuts arsenic levels in the grains by 90% but also slashes yields.

A different farming method has been catching on fast in Bangladesh as a way to save water. In it, farmers irrigate their fields and then wait up to 10 days to let their paddies dry out before irrigating again. Stephan Hug, an aquatic geochemist at the Swiss Federal Institute of Aquatic Science and Technology, and colleagues in Switzerland and Bangladesh wondered if intermittent irrigation could also lessen plant exposure to arsenic….

Drying rice in the sun in Bangladesh, shot by Shahnoor Habib Munmun, Wikimedia Commons, under the Creative Commons Attribution 3.0 Unported license