They should have learned by now. American cigarette smokers should have learned that their toxic, smelly habit is the leading preventable cause of death and sickness in the United States.

That's right. Cancer, heart disease, emphysema and other vicious maladies wouldn't claim as many victims if so many people weren't bent on smoking.

For almost 15 years, it seemed people got the message and the numbers were going the right way. According to the U.S. Centers for Disease Control, smoking among adults had been flat or declining since 1994. But the latest survey, released last week, showed that in 2008 just under 21 percent of American adults said they smoked.

That's a tad up -- not down -- from the year before, when 19.8 said they were smokers.

Call it a blip or a reversal -- either way the direction is bad. This despite all sorts of legislative activity in cities and states (like Pennsylvania) to restrict or ban smoking in the workplace. This despite hard-hitting numbers that show the peril of cigarettes -- they account for almost 440,000 deaths a year and they make smokers two to three times more likely to die from coronary heart disease than nonsmokers.

Then there are the stinky clothes and the yellowed teeth. What more negative reinforcement could you need?

Apparently that's not enough for the one-fifth of the population who refuse to give it up. But give it up one day they will -- and, as with all in life they forfeit, most likely at an earlier age.

Cartoonist Rob Rogers does "Rob's Rough," an early look at his work and his creative process, exclusively at PG+, a members-only web site of the Pittsburgh Post-Gazette. Our introduction to PG+ gives you all the details.