Their unique study also demonstrated that the amounts of these carcinogens in a smoker's cigarette butts directly correlated with tell-tale compounds in the smoker's urine.
The study, published in the June issue of Cancer Epidemiology, Biomarkers and Prevention, can help researchers trying to trace the harmful effects of smoking.
We know that cigarettes from around the world vary in their ingredients and the way they are produced, said Dr. Jim Pirkle of the U.S. Centers for Disease Control and Prevention, who heads a lab using a mass spectrometer to measure levels of chemicals in people's bodies.
All of these cigarettes contain harmful levels of carcinogens, but these findings show that amounts of tobacco-specific nitrosamines differ from country to country, and U.S. brands are the highest in the study, Pirkle said in a statement.
CDC's David Ashley and colleagues did in-depth tests using 126 smokers in the United States, Canada, Britain and Australia.
Seventeen eligible cigarette brands (between 3 and 5 brands from each country) were selected on the basis of national sales and nicotine yield to identify popular brands with a range of ventilation, the researchers wrote. Ventilation is how much air is mixed in with the smoke from the cigarette as it is inhaled.
The volunteers had their saliva and urine tested and also turned over their used cigarette butts to the researchers.
FIVE MILLION DIE A YEAR
These were all tested for nicotine and for the chemicals 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK for short) and the breakdown product of NNK in the body, called NNAL.
These cancer-causing agents are known as tobacco-specific nitrosamines or TSNAs.
We have shown a direct association between the 24-hour mouth-level exposure of NNK resulting from cigarette smoking and the concentration of its primary metabolite, NNAL, in the urine of smokers, the researchers wrote.
Internal dose concentrations of urinary NNAL are significantly lower in smokers in countries that have lower TSNA levels in cigarettes such as Canada and Australia in contrast to countries that have high levels of these carcinogens in cigarettes, such as the United States.
The popular U.S. cigarette brands studied contained American blend tobacco, known to contain higher TSNA levels than the bright tobacco used in the most popular Australian, Canadian, and British brands.
Australian and Canadian smokers got more nicotine than U.S. and British smokers, but not of TSNAs.
The World Health Organizations says 5 million people die every year from tobacco-related heart attacks, strokes and cancers. Another 430,000 adults die annually from breathing second-hand smoke.
Some of the brands tested included:
* Marlboro, sold by Philip Morris International and Altria Group Inc's Philip Morris USA unit.
* Winfield, manufactured under license by British American Tobacco Australia.
* Silk Cut and Benson & Hedges, produced by Japan Tobacco Inc.
* Players, made by Canada's largest manufacturer, Imperial Tobacco, a division of Imasco Ltd.
* Camels, made by Reynolds American.
* Newports, made by Lorillard Inc.