Alcohol and tobacco, alone or in combination, are associated with an increased risk of various cancers, including those of the upper aero-digestive tract and liver. Both alcohol and tobacco use can increase the risk of cancer of the oral cavity and throat (pharynx, and their combined use has a multiplicative effect on risk. Moreover, those regions of the mouth and pharynx that are more directly exposed to alcohol or tobacco are more likely to be affected by cancer than other regions. A similar effect was found with respect to cancer of the voice box (larynx). For squamous cell carcinoma of the esophagus, alcohol and tobacco also appear to increase risk synergistically. With liver cancer, in contrast, alcohol consumption and tobaacco use appear to be independent risk factors.