Seasonal influences on childhood lead exposure

We conducted a study to examine seasonal changes in residential dust lead c ontent and its relationship to blood lead in preschool children. We collect ed blood and dust samples (floors, windowsills, and carpets) to assess lead exposure. The geometric mean blood lead concentrations are 10.77 and 7.66 mu g/dL for the defined hot and cold periods, respectively (p < 0.05). Lead loading (milligrams per square meter) is the measure derived from floor an d windowsill wipe samples that is most correlated with blood lead concentra tion, whereas lead concentration (micrograms per gram) is the best variable derived from carpet vacuum samples. The variation of dust lead levels for these three dust variables (floor lead loading, windowsill lead loading, an d carpet lead concentration) are consistent with the variation of blood lea d levels, showing the highest levels in the hottest months of the year, Jun e, July, and August. The regression analysis, including the three represent ative dust variables in the equations to predict blood lead concentration. suggests that the seasonality of blood lead levels in children is related t o the seasonal distributions of dust lead in the home. In addition, the out door activity patterns indicate that children are likely to contact high le aded street dust or soil during longer outdoor play periods in summer. Cons equently, our results show that children appear to receive the highest dust lead exposure indoors and outdoors during the summer, when they have the h ighest blood lead levels. We conclude that at least some of the seasonal va riation in blood lead levels in children is probably due to increased expos ure to lead in dust and soil.