Despite the irritating presence of chain-smoking “environmental” scientist Grace Augustine in “Avatar,” the number of characters who smoke in a movies is on the decline, according to a new study.

Companies routinely pay thousands of dollars to have their products placed in movies, but Avatar cause particular outrage. Sigourney Weaver’s Grace Augustine is a tough-talking, swear-like-a-sailor scientist who also chews up Marlboros.

As an environmental scientist, no less, you would think Grace would know better. And, that’s what irked critics. The smoking scenes seem pretty gratuitous and suggests that product placement fees may have had an influence.

It also suggested that cigarette smoking would still be common long into the future, despite efforts to curb tobacco use for health reasons.

So score one for tobacco companies on that one.

But, overall, tobacco use on the silver screen peaked in 2005 and has been on the decline ever since, the study found.

Movies released last year showed about half the number of smoking incidents than films four years earlier.

The Centers for Disease Control and Prevention in Atlanta released the study, which looked at tobacco use in popular films from 1991 to 2009.

Last year, about half of the 145 movies in the study didn’t show any smoking at all.

For films aimed at children or teens, the percentage was even higher at 61 percent.

However, slightly more than half of the movies rated PG-13 did show tobacco use.

Earlier this week, actor Michael Douglas, a former heavy smoker, announced that he had throat cancer. Doctors say his prognosis is good.

Copyright 2010 The Associated Press.