WASHINGTON — Fewer American adults are smoking, and those who still do are lighting up less, suggests a nationwide survey from the US Centers for Disease Control released on Tuesday.

Using data from 2005 to 2010, researchers with the US government agency reckoned that 19.3 percent of American adults -- or 45.3 million people over the age of 18 -- are smoking cigarettes, down from 20.9 percent in 2005.

"There are three million fewer smokers in America than there were five years ago," said CDC director Tom Frieden, elaborating on the latest Morbidity and Mortality Weekly Report (www.cdc.gov/mmwr).

"People who are continuing to smoke are smoking less -- but we can do much better by continuing to invest in tobacco control programs at all levels."

Among smokers, the proportion of those who consume 30 or more cigarettes a day fell to 8.3 percent from 12.7 percent, although those who smoke nine or less cigarettes a day rose to 21.8 percent from 16.4 percent.

Despite the progress, the CDC's findings -- based on household interviews -- indicated a slower rate of decline in smoking between 2005 and 2010 than in the preceding five-year period.

Smoking and exposure to second-hand smoke is the number-one preventable cause of death and disease in the United States, claiming an estimated 443,000 American lives every year.

Getting Americans to smoke less has been US government policy since the 1960s. Under its Healthy People initiative, the Department of Health wants to bring the national prevalance of smoking to below 12 percent by 2020.

"In many ways, the findings we are releasing today are good news," Tim McAfee, director of the CDC's office on smoking and health, told reporters in a telephone conference call with Frieden.

"It's a slower rate of decline, but we are still moving in the right direction."

Frieden and McAfee attributed the trend to sustained anti-smoking campaigns, including higher excise taxes on cigarettes and an "epidemic spread" of indoor smoking bans that now are in place in half of the 50 states.

"People are cutting back for health benefits, not for pure economic benefits," added McAfee, although the CDC's findings laid bare sharp regional and socio-economic contrasts.

Smoking is most prevalent in West Virginia and Kentucky, for instance, with about one in four adults lighting up in both states. (The rates in Utah and California were 9.1 and 12.1 percent respectively.

It is also more common among men than women (21.5 percent versus 17.3 percent), those between 25 and 64 years of age, and those living under the poverty line (28.9 percent).

Excluded from the research were those under 18 -- a major source of concern for public health authorities, given the danger of youngsters picking up the nicotine habit early in life.

Separately, a study just published by the journal Pediatrics reported that children aged six through 11 with parents who smoke were more likely to miss school than those who did not. They also had more colds and ear infections.

The cost of cigarettes varies widely between states, but typically, a pack of Marlboro goes for about six dollars, according to cigaretteprices.com, a website that compares tobacco prices worldwide.

Last month, four US tobacco companies filed a lawsuit against the US Food and Drug Administration over new rules calling for graphic health warnings on cigarette packing, calling them "unconstitutional."