Other genes in the body produce detoxifying proteins that prepare toxic molecules for quick removal. Again, genetic variation in genes for detoxifying proteins can result in differences from one person to another in the ability to eliminate cancer-causing compounds. On the other hand, some genetic variation may actually produce hyperactive detoxifying gene activity. Then a person who possesses hyperactive detoxifying proteins may have some protection from harmful environmental exposures. Scientists believe, for example, that some persons inherit genes for hyperactive detoxifier proteins in lung tissues. This inheritance may partly explain why some smokers who refuse to give up the habit can still remain free of cancer. (For more information, please see Genetic Variation.)

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