Pollen from genetically engineered plants can travel significant distances and contaminate other crops, according to a report commissioned by the British government and leaked to the public this week. The report asserts that 1 percent of organic plants in any field could become genetically modified hybrids through cross-pollination, and it argues that “acceptable” levels of contamination for organic crops must be agreed upon. Organic farmers are furious. Officials have refused to comment on the report, which is still in draft form.