Residential exposures to pesticides and childhood leukaemia.

Like many chemicals, carcinogenicity of pesticides is poorly characterised in humans, especially in children, so that the present knowledge about childhood leukaemia risk derives primarily from epidemiological studies. Overall, case-control studies published in the last decade have reported positive associations with home use of insecticides, mostly before the child's birth, while findings for herbicides are mixed. Previous studies relied solely on self-reports, therefore lacking information on active ingredients and effects of potential recall bias. Few series to date have examined the influence of children's genetic susceptibility related to transport and metabolism of pesticides. To overcome these limitations, investigators of the Northern California Childhood Leukaemia Study (NCCLS) have undertaken, in collaboration with a multidisciplinary team, a comprehensive assessment of residential pesticide exposure, including: (1) quality control of self-reports; (2) home pesticide inventory and linkage to the Environmental Protection Agency to obtain data on active ingredients; (3) collection and laboratory analyses of approximately 600 home dust samples for over 60 pesticides and (4) geographic information studies using California environmental databases to assess exposure to agricultural pesticides. The NCCLS is also conducting large-scale genotyping to evaluate the role of genes in xenobiotic pathways relevant to the transport and metabolism of pesticides. A better quantification of children's exposures to pesticides at home is critical to the evaluation of childhood leukaemia risk, especially for future gene-environment interaction studies.