[Tobacco and leukemia]

Although some epidemiological studies have published findings supporting the hypothesis that smokers are at a higher risk of developing leukemia, the causal relationship between tobacco and leukemia has not been considered conclusive due to the weak association found, to the lack of a dose-response relationship and to the inconsistencies found throughout the different studies. However, most of these studies were not specifically designed to establish the tobacco-leukemia relationship and therefore their capacity to evaluate this hypothesis is rather limited. This hypothesis could be supported by the fact that tobacco causes cancer in sites which are not in direct contact with tobacco smoke. Likewise, the presence of benzene and radioactive compounds would provide some biologic plausibility to the hypothesis that tobacco could be a cause of leukemia. However, since the etiology of leukemia is not well understood, the small excess risk detected may be confounded by some uncontrolled factor.