Here's the latest hurrah for the anti-smoking lobby. New research shows, for the first time under real-life conditions, evidence of a cancer-causing substance in non-smokers who work in smoke-filled rooms. That substance, called NNK, was biologically processed and its residues detected in their urine. NNK is the only known lung carcinogen found solely in tobacco smoke and is formed from nicotine. According to Dr Stephen Hecht of the University of Minnesota Cancer Centre, NNK is particularly efficient at inducing adenocarcinoma in animals, a cancer of the lung periphery common in smokers.