The journal has published in this issue¹ and in a previous recent issue² two papers with striking evidence relating atmospheric contaminants, and mostly emissions derived from oil based combustion from engine exhausts, with increased risk for children of dying from leukaemia and other cancers. The risk was particularly high for children born in the proximities (up to 1 km) of bus stations, but also hospitals and other industrial resources with oil combustion emissions. The results from the different data and several analyses presented in both papers are firmly consistent with the author’s conclusions: childhood cancers are strongly determined by prenatal or early postnatal exposures to oil based combustion gases, especially from engine exhausts. Two key points arise from such a conclusion. Firstly, how good is evidence supporting this statement? Secondly, is there an additional argument for stricter control of atmospheric emissions?

Results from both papers, although clearly coherent, are based on data and analysis with some limitations, a common occurrence in epidemiological research, the same category of …