The U.S. Centers for Disease Control and Prevention has come out with a study that says U.S. brands of cigarettes have higher levels of cancer causing chemicals than foreign made ones.

CDC researchers took samples from the mouths of smokers in the United States, the United Kingdom and Australia. Their findings were reported in the June issue of Cancer Epidemiology Biomakers and Prevention.

The results centered around nitrosamines, the major carcinogens in tobacco. And the study was the first ever to compare the cancer causing agent in people from different countries.

"We know that cigarettes from around the world vary in their ingredients and the way they are produced," said Dr. Jim Pirkle, deputy director for science at CDC's National Center for Envirnmental Health, Division of Laboratory Sciences, in a statement. "All of these cigarettes contain harmful levelsof carcinogens, but these finding show that amounts of tobacco-specific nitrosamines differ from country to country, and U.S. brands are the highest in the study."

The researchers said U.S. brands had an "American blend" of tobacco with higher nitrosamine levels. The other countries used "bright" tobacco, lighter in color and clue-cured. If the American makers switched blending and curing practices they could reduce exposure to one type of carcinogen, though not necessarily make the cigarettes safer.

So, does this matter to you? If you smoke, how loyal are you to your brand?

AFP/Getty photo