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Plants can be genetically engineered to remove the pollutant arsenic from the soil, according to a study released this week.

The findings could help to combat arsenic poisoning — which causes skin, lung, kidney and liver cancers and damage to the nervous system — especially in countries such as Bangladesh and India, where an estimated 36 million people are at risk through drinking contaminated water.

A team of US-based researchers inserted two genes from the bacterium Escherichia coli that allow the common weed Arabidopsis thaliana to tolerate arsenic, which is usually lethal to plants. As a result, instead of dying from exposure, the genetically modified Arabidopsis is able to take up arsenic from the soil and transport it to its leaves.

"Our data demonstrate the first significant increase in arsenic tolerance," says one of the researchers, Richard Meagher of the University of Georgia, Athens, United States. "This new system is a major step in developing methods of cleaning up the environment using plants."

The researchers say that the plants genetically engineered to remove arsenic in this study — to be published in the November issue of Nature Biotechnology — are ready for use in the field, but that they expect to make significant improvements in the amount of arsenic that can be extracted through future experiments.

"One of the most important aspects of the research is that this new system should be applicable to a wide variety of plant species", Meagher says. Researchers are already working on putting the genes into cottonwood trees, which have a large root system and could be particularly effective in removing arsenic from the soil.

In Bangladesh, West Bengal (India) and some other areas, most drinking water used to be collected from open dug wells and ponds with little or no arsenic. Such water often transmitted diseases such as diarrhoea, dysentery, typhoid, cholera and hepatitis.

Programmes to provide 'safe' drinking water over the past 30 years have helped to control these diseases, but in some areas they have had the side-effect of exposing the population to arsenic.

"It has been a real battle in Bangladesh," says Pat Saunders, a UK-based independent researcher. "I think we need new breakthroughs if we are going to meet people's needs. I would not rule on principle that the solution will be GM, but I would also want to look very closely to see whether it is the right technology to solve the problem."

Arsenic-contaminated water is also a problem in other parts of the world, including Argentina, Australia, Brazil, Chile, Hungary, Mexico, Taiwan, Thailand, the United States and Viet Nam, albeit on a smaller scale than in Bangladesh and India.

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