Every year of smoking causes DNA mutations that make cancer more likely. If you're smoking a pack per day, the DNA in every cell in your lungs acquires about 150 NEW mutations per year. Organs with no direct exposure to tobacco smoke are too affected.

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Every year of smoking causes DNA mutations that make cancer more likely. If you're smoking a pack per day, the DNA in every cell in your lungs acquires about 150 NEW mutations per year. Organs with no direct exposure to tobacco smoke are too affected.