[Traffic-related air pollution at the place of residence and risk of cancer among children].

INTRODUCTION

The hypothesis that exposure to traffic-related air pollution increases the risk of cancer developing during childhood was investigated.

MATERIALS AND METHODS

We enrolled 1,989 children notified to the Danish Cancer Registry with a diagnosis of leukaemia, tumour of the central nervous system (CNS), or malignant lymphoma during 1968-1991, and 5,506 control children selected at random from the entire childhood population. The residential histories of the children were traced from nine months before birth up to the time of diagnosis, as was a similar period for the controls. Information on traffic and the configuration of streets and buildings was collected for each of the 18,440 identified addresses. Concentrations of benzene and nitrogen dioxide (indicators of traffic-related air pollution) were calculated for the relevant residential periods, and combined into exposures to air pollution during pregnancy and childhood, respectively.

RESULTS

The risks of leukaemia, CNS tumours, and all selected cancers combined were not related to exposure to benzene or nitrogen dioxide during either period. The risk of lymphomas increased by 25% (p for trend = 0.06) and 51% (p for trend = 0.05) for a doubling of the concentration of benzene and nitrogen dioxide, respectively, during the pregnancy. The association was restricted to Hodgkin's disease.

DISCUSSION

On the basis of a low potential for selection bias, information bias, and confounding factors, we conclude that traffic-related air pollution at the residence of children is not linked to the risk of leukaemia or CNS tumour, which are the two major types of childhood cancer. The results indicated a possible association between air pollution and the risk of Hodgkin's disease, but the evidence allows of no firm conclusion at present.