Blood lead levels in Toronto children and abatement of lead-contaminated soil and house dust.

South Riverdale in Toronto, Canada, underwent a lead-abatement program. In 1988, lead-contaminated soil was replaced at 970 properties, and in 1989, professional housecleaning for lead removal was conducted in 717 households. The effect of "abatement" on blood lead levels in young children was investigated. Data were analyzed from 12 cross-sectional blood-screening surveys that were conducted during an 8-y period in South Riverdale and in two comparison areas. Responses regarding behavioral, household, lifestyle, neighborhood, and environmental factors, all of which were gleaned from associated questionnaires, were also analyzed. Response rates varied between 32% and 75%. During the years between 1984 and 1992, blood lead decreased in all study areas. There appeared to be a minimal blood lead level of 2-3 micrograms/dl for urban Ontario children who were less than 6 y of age. The significant difference between South Riverdale and the control areas disappeared by 1992. Although abatement activity in South Riverdale was associated with an accelerated decline in blood lead levels, it was difficult to distinguish this from effects of decreased Toronto air lead levels or decreased smelter emissions. Within South Riverdale, abatement appeared to be associated with a slower decline in blood lead levels over time, likely the result of selection bias, soil mixing, or recontamination from the smelter. No difference was observed between the separate effects of housecleaning or soil replacement. The findings could neither strongly support nor refute beneficial effects of abatement.