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Previous studies have shown that children's blood lead concentrations tend to increase during hot summer months. In this issue, Lih-Ming Yiin and colleagues from the Environmental and Occupational Health Sciences Institute at Rutgers University and the Robert Wood Johnson Medical School in Piscataway, New Jersey, explore whether some of this elevation can be explained by seasonal increases in the amount of lead in residential house dust [EHP 108:177-182]. Yiin and colleagues compared blood lead concentrations measured in children aged 6-32 months with three residential dust lead variables: concentrations of lead in dust obtained from floors, sills, and carpets; dust loading rates, which describe the amounts of dust typically found in each of these areas; and lead loading rates, described as the product of the dust loading rate and the lead concentration. Blood and dust data were obtained from the Childhood Lead Exposure Assessment and Reduction Study (CLEARS), published in the September 1998 issue of the Journal ofExposure Analysis and Environmental Epidemiology, for which Yiin was an investigator. Samples for CLEARS were collected from families living in Jersey City, New Jersey, over a three-year period from 1992 to 1995. Yiin found that both blood lead and residential dust lead concentrations were highest during warm months, peaking during the summer. Previous analyses performed during CLEARS indicated that nearly two-thirds of the lead in house dust was derived from outdoor sources. In the current study, Yiin attributes the high summertime amounts of leaded house dust to open windows and a greater overall frequency of indoor-outdoor movement. The best (strongest) correlations with elevated blood lead in the hot months were observed for Summertime dust may raise the risk of childhood lead exposure. floor lead loading, sill lead loading, and carpet lead concentrations. However, floor and sill loading data varied insignificantly from season to season, prompting Yiin to suggest that flaking paint chips contaminate floor and sill dust in a nonseasonal manner. In contrast, Yiin's study found that carpet dust and lead loadings were highest in the warm, cool, and cold months, and lowest during the hot months. This might reflect people's tendency to track mud and soil indoors during the winter. Carpet data were not strongly correlated with blood lead in the cold seasons, leading Yiin to suggest that summer lead sources may be more highly concentrated. Previously, researchers suggested that the increased blood lead concentrations observed in summer might result from biosynthesis of …