possible influence of radioactive elements, benzene, urethane, and nitrosamines may be contributing factors. All of these chemicals are found in cigarettes and ETS, and they have been shown to be leukemogenic in experimental animals, or in humans.
The findings of increased brain cancer associated with ETS exposure in the Hirayama (1984) study, and possibly in the Preston-Martin et al. (1982) study, are of note. N-nitroso compounds are potent nervous system carcinogens in animals (Magee et al., 1976; Preussman, 1984, 1986).
These recent observations on a possible connection between ETS and various forms of cancer have created much discussion and some confusion. The lack of consistency with other data on tumors among children of smoking mothers and the appearance of tumors that are not clearly smoking-related call for further epidemiologic research. Any new studies in this area will, hopefully, have a very careful, rigorous design, so that more definitive evaluation of this possible health hazard from ETS exposure is possible.
There is no consistent evidence at this time of any increased risk of ETS exposure for cancers other than lung cancer.
Smoking-related cancers other than lung cancer need to be studied with adequate numbers and good exposure data and with consideration of the potential confounding effects from other known risk factors for these cancers.
Some cancers not related to active smoking, especially lymphohematopoietic neoplasms, should be studied in relation to ETS exposure, particularly in childhood. Then the possibility of a etiologic role of inhaled decay products of radon (like bone-seeking lead-210) should be considered.
Austin, H., and P.Cole. Cigarette smoking and leukemia. J. Chronic Dis. 39:417–421, 1986.