For the first time on record, the percentage of U.S. adults who smoke cigarettes has fallen below 20 percent, a new report shows.

An estimated 19.8 percent of American adults - 43.4 million individuals - were smokers in 2007. The new data is a percentage point below the 2006 figure and followed three years of modest progress, according to the U.S. Centers for Disease Control and Prevention.

According to Thomas Glynn of the American Cancer Society, cigarette smoking rates were now the lowest since World War I. "We've begun to come full circle on this," he said.

Although "this is good news," the incidence of deaths related to smoking is still on the rise. “Almost one in five adult Americans smoke, and many former smokers are succumbing to their habit again," said Matthew McKenna, MD, MPH, director of the CDC's Office on Smoking and Health.

Not only smoking, but also secondhand smoke, known as environmental tobacco smoke, leads to death. Among the 438,000 people tobacco kills a year, 38,000 are non-smokers who just inhale tobacco smoke from the others. If the governments fail to adopt more aggressive measures to combat the smoking addiction, in the next century tobacco will kill one billion people worldwide.

No less than 215,020 new cases of lung cancer have been reported in the United States this year. According to health officials, 18 people die from lung cancer each hour. Whereas female smokers have a 1 in 16 chance of developing lung cancer, male smokers have a 1 in 13 chance. But men who never smoked are more likely to develop the disease that women who never lighted a cigarette.

Apart from lung and bronchial cancers, smokers are also susceptible of developing cancers of the stomach, larynx, mouth and pharynx, esophagus, pancreas, bladder and kidney.