Quote:
Originally Posted by blankall
I disagree on the mechanism. It's more than just random chance. Prolonged exposure to smoke causes damage in the lungs and prevents the lung from healing. Lungs are designed with natural barriers and protection. Over time smoking will break down the lungs ability to protect itself. Yes vehicle combustion may be cleaner, but there's also a question of volume. You're talking about a few grams of tobacco versus many many litres of gasoline. Even if the vehicle is a thousand our a million times more efficient, you are still being exposed to more carcinogens from the vehicles.
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A lot of it does come down to chance rather than overcoming any natural protection from the lung. Cancer happens at a chemical level. There are repair mechanisms in place, but whether they succeed or not is generally not a function of the ability of the lungs to protect themselves being overwhelmed - at least for most of the key carcinogens in cigarette smoke such as benzo(a)pyrene; the mechanism is different for some other carcinogens. Failure to repair a gene affected by a carcinogen really often does come down to chance, often exacerbated by gene mutations affecting these repair processes.
In addition to vehicle combustion being more efficient, the carcinogens emitted are often different, particularly for gasoline-fueled automobiles. Gasoline just doesn't have the high molecular weight organics that produce the nastiest carcinogens. Diesel fuel is a bit of a different story, though it's better now than it used to be.