Stop-smoking interventions often focus on addictive nicotine, but cigarettes also contain more than 100 other additives that could reinforce addiction as well as making smoking harmful, HealthDay News reported Aug. 3.

Cigarettes contain 599 additives, 100 of which are potentially harmful, according to researcher Michael Rabinoff of UCLA. Additives like chocolate and cocoa, for example, make it easier for smoke to penetrate the lungs, while others act as anesthetics that prevent coughing. "They're making people less aware of tobacco [smoke] and making the cigarette more addictive," he said. "There is so much going on with these additives that it's an uncontrolled experiment on billions of people around the planet."

Cigarettes are "highly engineered by the industry to smoke in certain ways and taste in certain ways," said James Pankow, a professor at Oregon Health & Science University.

Because tobacco companies closely guard the ingredients in their products, Rabinoff said it is unclear how many of the additives disclosed in a 1994 list are still being used. But researchers who studied the list found that more than 100 of the ingredients "camouflage environmental [secondhand] tobacco smoke emitted from cigarettes, enhance or maintain nicotine delivery, could increase the addictiveness of cigarettes, and mask symptoms and illnesses associated with smoking behaviors," the study said.

Philip Morris said it discloses the ingredients in its cigarettes to the federal government and that "it is our scientific judgment, based on the best data available, that the ingredients used in our cigarettes do not increase the inherent hazards of smoking."

"The ingredients complement the subjective characteristics of the different tobacco types and provide the distinctive flavors, tastes, and aromas associated with our brands," the company added. "We also use ingredients as processing aids and as humectants to keep the tobacco pliant. The flavor ingredients we use, and the precise way in which we use them, help distinguish our products from those of our competitors. The distinctive taste of our products is an extremely important and valuable part of our competitive strategy."

The research was published online and will appear in the September 2007 issue of the American Journal of Public Health.