When smoking is added to asbestos exposure, what is the observed effect on mortality risk?

• A. It reduces death rate
• B. It dramatically increases death rate, about 50x greater
• C. There is no effect
• D. It increases death rate by about 2x

Answer: (B)

Two risk factors can interact in a way that multiplies risk rather than simply adding to it. When smoking combines with asbestos exposure, the chance of dying from lung cancer rises far more than either factor alone. In epidemiology, asbestos-exposed smokers show a dramatically higher mortality risk—about fifty times greater for lung cancer than people with neither exposure. This strong synergistic effect comes from smoking introducing additional carcinogens and asbestos-related lung damage creating a more favorable environment for cancer to develop. It’s useful to note this primarily concerns lung cancer mortality; smoking doesn’t similarly amplify mesothelioma risk, which is driven mainly by asbestos exposure.