LONG-TERM TRENDS IN BLOOD LEAD LEVELS AMONG CHILDREN IN CHICAGO - RELATIONSHIP TO AIR LEAD LEVELS

Objectives. To evaluate trends in blood lead levels among children in Chicago from 1968 through 1988, and to determine the impact of the cha nges in the Centers for Disease Control and Prevention (CDC) blood lea d level of concern. Methods. We reviewed a systematic sample of blood lead screening records of the Chicago Department of Health Laboratory for high-risk children aged 6 months to 5 years. Median blood lead lev els for each quarter of the years 1974 through 1988 were determined an d regressed against mean air lead levels recorded at air-monitoring st ations in Chicago during the same period. Results. Median blood lead l evels declined from 30 mu g/dL in 1968 to 12 mu g/dL in 1988, and were strongly associated with declining average air lead levels (r = .8, P < .001) from 1974 through 1988. A regression model using log-transfor med data predicted a decline of 0.56 mu g/dL in the median blood lead level with each 0.1 mu g/m(3) decline in the mean air lead level when the air lead level was near 1.0 mu g/m(3); the predicted slope was ste eper at lower air lead levels. Despite the nearly 20-fold reduction in air lead levels, the median blood lead level of 12 mu g/dL in 1988 in dicates substantial continuing lead exposure. The CDC blood lead level of concern was lowered twice from 1968 to 1988, but due to the declin e in blood lead levels, fewer than 30% of the children were above the level of concern throughout most of the study. Conclusion. Although su bstantial lead exposure persists in Chicago, reductions in airborne le ad emissions seem to have contributed to a long-term decline in the me dian blood lead level of high-risk Chicago children.