Some experts say that smokers who can't quit could switch to smokeless tobacco to lower their risk of cancer, but researchers say that the toxin levels in such products vary widely.

The Wall Street Journal reported March 27 that studies show that the levels of cancer-causing nitrosamines ranged from 0.99 micrograms in the Revel brand to 4.8 micrograms in a sample of Copenhagen. Moreover, nitrosamine levels also varied from sample to sample of the same brand.

The findings complicate efforts to cast smokeless tobacco as a safer alternative to smoking. Manufacturers are not required to list nitrosamine levels on smokeless-tobacco packaging, leaving consumers in the dark about the relative danger of each product.

Research suggests, however, that products that come in pouches, such as those sold by Swedish Match, tend to have lower nitrosamine levels.

The study was presented by University of Minnesota researcher Dorothy Hatsukami at the recent scientific conference of the Society for Research on Nicotine and Tobacco.