单项选择题

Cigars Instead
Smoking one or two cigars a day doubles the risk of cancers of the lip, tongue, mouth and throat, according to a government study.
Daily cigars also increase the risk of lung cancer and cancer of the esophagus, and increase the risk of cancer of the larynx (voice-box) six-fold, say researchers at the National Cancer Institute in Bethesda, Maryland.
In addition, the report revealed that smoking three or four cigars a day increased the risk of oral cancer to 8.5 times the risk for nonsmokers and the risk of esophageal cancer by four times the risk of nonsmokers.
The health effects of smoking cigars is one of eight sections of the article Cigars. Health Effects and Trends. The researchers report that, compared with a cigarette, a large cigar emits up to 90 times as much carcinogenic tobacco-specific nitrosamines.
"This article provides clear and invaluable information about the disturbing increase in cigar use and the significant public health consequences for the country," said Dr. Richard Klausner, director of the National Cancer Institute, in a statement.
"The data are clear—the harmful substances and carcinogens in cigar smoke, like cigarettes, are associated with the increased risks of several kinds of cancers as well as heart and lung diseases," he added. "In other words, cigars are not safe alternatives to cigarettes and may be addictive."
"To those individuals who may be thinking about smoking cigars, our advice is—don’t. To those currently smoking cigars, quitting is the only way to eliminate completely the cancer, heart and lung disease risks," warned Klausner.
According to a National Cancer Institute press release, there haven’t been any studies on the health effects on nonsmokers at cigar social events, but "...a significant body of evidence clearly demonstrates an increased lung cancer risk from secondhand smoke." In the context of this passage, "secondhand smoke" in the last line means ______.