An analysis of blood lead data in clinical records by external data on lead pipes and age of household.

This study examined the possibility that lead pipes in the drinking water distribution system were elevating the blood lead levels of children in London, Ontario, Canada. Based on their postal codes, 164 children admitted between 1984 and 1989 to an institution for the behaviorally disordered or developmentally challenged were categorized according to whether they lived in the area of the city known by the local Public Utilities Commission to be serviced by lead pipes. Analysis of covariance was used to obtain confounder-adjusted geometric means in each area. After adjusting for gender, year of lead test (a surrogate for gasoline source), and census tract prevalence of low family income, children in the lead service area (LSA) were found not to have higher blood lead levels (geometric means: LSA = 4.7 micrograms/dl, Non-LSA = 4.8 micrograms/dL; p = 0.839). The average blood lead level declined 60.9% between 1984 and 1989. Using municipal tax assessment data on the age of each child's home, those children living in homes built during or before 1945 (when interior paints were as much as 50% lead by dry weight) had an average blood lead level that was 62.3% higher (p = 0.011) than that of those in homes built since 1975 (when interior paints were limited to no higher than 0.5% lead by dry weight). A clear gradient was observed. This association with age of home remained significant after adjusting for gender, diagnosis, and year of lead test. Variables indicating the amount of industry near the child's residence and the presence of lead service pipes did not enter the model after house-age. In conclusion, no evidence indicated that the lead service pipes were elevating blood lead levels in these London children. The data suggest that with the removal of lead from gasoline, lead-based paint is a significant remaining source of lead exposure. Little data are available on childhood lead exposure from paint in Canada. The present descriptive data suggest that more research into this potential problem in Canada is warranted.