Smoking as a Primary Risk Factor
It has been known for almost 50 years that tobacco use can be linked to cancers of the lung and head and neck. Eighty-five percent of the cases of head and
neck cancer found each year are associated with tobacco use. Long-term smoking
that begins before age 30 also increases the risk for developing colorectal cancer. Smoking contributes to cancer development by causing mutations in genes, impairing lung function, and decreasing the effectiveness of the immune
system. (Refer to the PDQ summary on Lung Cancer Prevention for more
information.)
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