LONDON Up to 17 percent of cropland worldwide is contaminated with at least one type of toxic heavy metal, posing health risks to up to 1.4 billion people, scientists have warned. Published in the journal Science, their study is a first-of-its-kind global overview of heavy metal contamination in soils, based on a meta-analysis, an approach drawing on data from many previous studies, of almost 800,000 samples. The team led by environmental specialist Deyi Hou of China's Tsinghua University