Migration patterns of children with cancer in Britain.

OBJECTIVES To investigate the early migration patterns of children who later developed cancer. To test a prior hypothesis that some cancers are initiated by early exposures to toxic atmospheric pollutants from point sources. DESIGN Address changes in children dying from cancer are examined in relation to potentially hazardous sites of several different types. The relative proximities of birth addresses and death addresses to these sites, are compared. The approach is based upon the premise that a local exposure, effective only at an early age, must be preferentially linked with an early address. SETTING AND SUBJECTS Records of 22,458 children dying from leukaemia or other cancer under the age of 16 years in Great Britain between 1953 and 1980: including 9224 who moved house between birth and death. The migration analysis was based upon birth and death addresses, converted first to postcodes and thence to map coordinates. The geographical locations of potentially toxic industrial sites were obtained through direct map searches and from commercial directories. RESULTS Systematic asymmetries were found between measured distances from birth and death addresses to sources emitting volatile organic compounds, or using large scale combustion processes. The children had more often moved away from these hazards than towards them. Many of the sources had already been identified as hazardous using other methods. There was also a birth association with areas of dense habitation; possibly because of unidentified toxic sources contained within them. All forms of cancer were involved although some effluents were associated preferentially with specific types. CONCLUSIONS The main findings of an earlier study, based upon a different and independent method, were confirmed. Proximities to several types of industrial source, around the time of birth, were followed by a raised risk of childhood cancer. Combustion products and volatile organic compounds were especially implicated. Within the 16 year limit of the study, the increased risk did not decay with advancing age. Low atmospheric concentrations of many carcinogenic substances suggest that the mother acts as a cumulative filter and passes them to the fetus across the placenta or in breast milk.