Unknown exposure to second-hand smoke associated with increased mortality

A new biomarker has identified known and unknown exposure to second-hand smoke and confirmed a strong association to increased mortality in non-smokers, according to a new study. The results provide a more accurate way to gauge second-hand smoke exposure than questionnaires, and present a strong case for more stringent limits on smoking and increased preventive screenings for those more likely to have been exposed to second-hand smoke.