A common mineral similar to rust fashioned into a powder of tiny crystals could provide a simple, inexpensive method for removing hazardous levels of arsenic from drinking water, researchers at Rice University in Houston reported last week.

That would help reduce the risk of cancer for tens of millions of impoverished villagers in China and Southeast Asia, where high levels of arsenic occur naturally in many water supplies, the researchers said in telephone interviews. Arsenic contamination is also a threat to water supplies in parts of Latin America, Africa and the US.

The research, reported in the journal Science, is the latest of numerous investigations into the environmental uses of nanotechnology, the manipulation of materials so tiny they are measured in nanometers, or billionths of a metre. At such small scales, common materials often begin to exhibit novel behaviours.

In this case, the researchers made crystals of the rustlike mineral, magnetite. They found that when the crystals were smaller than 40 nanometers wide, they were much more sensitive to low-strength magnetic fields than would have been expected based on the behavior of larger particles.

At 12 nanometers wide, the researchers found, the magnetite particles could bind up to 100 times as much arsenic as the larger iron particles currently used in filters, yet still be extracted from test liquids with inexpensive magnets widely used as computer components.

While the particles’ performance has been tested only in laboratories, the researchers said it seemed likely that removing arsenic could be as simple as pouring a small amount of magnetite powder into a pot of well water and waiting briefly while bound arsenic was pulled to the bottom by a simple magnet.

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