The U.S. Center for Disease Control and Prevention says fewer American adults are smoking cigarettes, and those who continue to smoke are consuming fewer cigarettes.

A CDC report says nearly 20 percent of American adults, or 45 million people, smoked in 2010. That means there were three million fewer American smokers last year than in 2005.

But CDC director Dr. Thomas Frieden said the five year decline was slower than the drop during the previous five years. Dr. Frieden said “People who smoke are smoking less, but we can do much better.”

Smoking and exposure to secondhand smoke kill nearly half a million Americans annually. For every smoking-related death, an additional 20 people live with a smoking-relate disease.

The World Health Organization says in 2011 smoking will kill nearly six million people worldwide.

The CDC says that quitting smoking is the best way for smokers to improve their health.