Exposure to a family of carcinogens called arylamines is associated with bladder cancer risk in both smokers and nonsmokers, according to a new study in the October 6 issue of the Journal of the National Cancer Institute. Arylamines are found in cigarette smoke, permanent hair dyes, and other environmental sources.
Cigarette smoking is an established risk factor for bladder cancer and suspected to play a role in at least half of all U.S. bladder cancer cases. Several arylamine compounds are found in cigarette smoke and are believed to be the source of the risk. However, exposure to an arylamine called 4-ABP is a risk factor for bladder cancer among nonsmokers.
To examine the possible relationship between bladder cancer risk and nine other members of the arylamine family, Paul L. Skipper, Ph.D., of the Massachusetts Institute of Technology in Cambridge, Mass., and colleagues conducted a case–control study of about 300 bladder cancer patients and about 300 control subjects. They measured exposure to the compounds by measuring the levels of arylamine–hemoglobin adducts—reaction products that form in red blood cells after exposure to the arylamine compounds.
Levels of all but one of the nine arylamine–hemoglobin adducts were higher in smokers than in nonsmokers, and levels of all nine adducts were higher in the cancer patients than in the control subjects. In addition, higher levels of three individual adducts were associated with bladder cancer risk after adjusting for other potential risk factors, including current cigarette smoking and lifetime smoking history. Higher levels of adducts were also associated with bladder cancer risk in nonsmokers.
These results "implicate exposure to arylamines as the causal factor responsible for most cases of bladder cancer in humans," the authors write. "Tobacco smoke as a source of these carcinogenic arylamines is already well known. Therefore, identifying the non–smoking-related sources of these carcinogenic arylamines should become a high scientific priority."