Smoke that comes from the lighted end of a burning tobacco product, such as a cigarette, pipe, or cigar. Sidestream smoke can be a form of secondhand smoke. It contains nicotine and many harmful, cancer-causing chemicals. Inhaling sidestream smoke increases the risk of lung cancer and may increase the risk of other types of cancer. Inhaling it also increases the risk of other health problems, such as heart disease and lung disease.