Reuters: U.S. consumer groups, scientists and food companies are testing substances ranging from breakfast cereal to breast milk for residues of the world's most widely used herbicide on rising concerns over its possible links to disease. The focus is on glyphosate, the active ingredient in Roundup. Testing has increased in the last two years, but scientists say requests spiked after a World Health Organization research unit said last month it was classifying glyphosate as "probably carcinogenic to humans."...