SECULAR TREND IN BLOOD LEAD LEVELS IN A COHORT OF MEXICO-CITY CHILDREN

We determined the secular trend in blood lead levels in a cohort of 10 4 children born in Mexico City between 1987 and 1993. We grouped child ren by the calendar year in which they reached 6 mo of age and measure d blood lead levels every 6 mo until they attained 36 mo of age. The o verall geometric mean blood lead level was 9.6 mu g/dl (range = 1.5-59 .5 mu g/dl). A repeated measures analysis of variance revealed a highl y significant linear trend in blood lead level with year (p < .001); t here was a maximum decrease of 7.6 mu g/dl between 1989 and 1993. Ther e was a highly significant quadratic age effect (p < .001); blood lead levels rose between 6 and 18 mo of age and decreased thereafter. Ther e was a marginally significant interaction between age of the child an d year. family use of lead-glazed pottery significantly elevated blood lead levels (p = .028). The downward trend in blood lead levels durin g the time period of study corresponded to the reduction in various so urces of lead exposure.