The percentage of American adults who smoke cigarettes has held in a range of 20 to 21 percent since 2005, as the decline in smoking has stalled, according to government figures released Tuesday.
The figures from the Centers for Disease Control showed the number of adult smokers dropped between 2000 and 2005, but the percentage of adult smokers has remained at about 20-21 percent since 2005.
In 2009, nearly 24 percent of men smoked, compared with 18 percent of women. About 31 percent of those living below the poverty line smoked, the government agency said.
"Smoking is still the leading preventable cause of death in this country," said CDC director Thomas Frieden.
"But progress is possible. Strong state laws that protect non-smokers from second-hand smoke, higher cigarette prices, aggressive ad campaigns that show the human impact of smoking and well-funded tobacco control programs decrease the number of adult smokers and save lives."
The CDC said passive or secondhand smoke remains a problem for non-smokers including many children.
It said 54 percent of children between the ages of three and 11 years old were exposed to second-hand smoke, and nearly all children who live with a smoker have measurable levels of toxic chemicals from cigarette smoke.
The figures show prevalence of smoking declines with education. Fewer than six percent of adults with a graduate degree smoke compared to more than 25 percent of adults with no high school diploma.
In 2009, smoking among adults was lowest in Utah, followed by California, which has had a long-running comprehensive tobacco control program and has seen a 40 percent drop in smoking from 1998-2006.
Children whose parents smoke are twice as likely to smoke themselves, but children who grow up in communities with comprehensive smoke-free laws are much less likely to become smokers, according to the CDC.
The CDC said the federal government is intensifying its efforts to reduce tobacco use in order to achieve the tobacco use targets for 2020.
Smoking is considered a leading cause of various types of cancer, heart disease, and lung diseases including emphysema. Exposure to second-hand smoke is a cause of sudden infant death syndrome respiratory symptoms, heart disease and lung cancer in non-smoking adults.