Vast populations drink water with unhealthful levels of arsenic without access to purification technologies. But a cheap, simple answer may lie in polyethylene terephthalate bottles coated in the amino acid cysteine, say researchers. "Our process uses flakes from plastic beverage bottles. When the flakes are coated with cysteine and stirred into arsenic-contaminated water, they work like a magnet -- the cysteine binds up the arsenic. Remove the plastic and you have drinkable water," says Tsanangurayi Tongesayi of Monmouth University.