Leukaemia incidence, social class and estuaries: an ecological analysis.

Leukaemia incidence data for 1984-1986 for 22 counties of England and Wales have been collected by a specialist registry. The present study is an ecological analysis in which incidence in electoral wards has been tested for association with two predefined ward characteristics: socio-economic status and proximity to estuaries. Small but statistically significant associations have been observed with relative risks in the range 1.05-1.50. Adjustments have been made in the analysis for variation in the underlying regional incidence and also for statistical artefacts consequent upon the rarity of the condition. The results for socio-economic status confirm those of other recent studies, with increased incidence linked to higher status. The results for estuaries are new although derived from a prior hypothesis.