Smokers with low blood levels of a molecule called bilirubin are at greater risk of developing lung cancer and dying from it, researchers have found. Among 400,000 people, they found that smokers with the lowest levels of bilirubin had a 69% higher rate of lung cancer and were 76% more likely to die from the disease compared to those with the highest bilirubin levels. Among nonsmokers, differences in bilirubin levels did not affect lung cancer risk. It is not clear whether bilirubin has a protective effect against lung cancer or whether low bilirubin is simply a byproduct of other processes involved in lung cancer development. Either way, low bilirubin levels could identify smokers at high risk of lung cancer who are particularly in need of anti-smoking interventions and cancer screening.