Comparison of House Dust Lead Exposure Metrics Collected by Vacuum and Wipe Sampling Techniques. J. L. Adgate, P. J. Lioy, G. G. Rhoads, and C. Weisel, UMDNJ, Environmental and Occupational Health Sciences Institute, 681 Frelinghuysen Rd., P. O. Box 1179, Piscataway, New Jersey 08855
Household dust is a major pathway for lead exposure in up to 10 million preschool children. This paper examines the variability in reported household dust lead levels measured in children's primary activity microenvironments using wipe and vacuum sampling techniques. Implications of the observed variability and it's effect on exposure estimation are examined.
As part of the Jersey City Childhood Lead Exposure Assessment and Reduction Study (CLEARS) dust wipe and vacuum samples were collected in preschooler's primary activity microenvironments in more than 150 homes. CLEARS is a controlled clinical trial examining the efficacy of a home cleaning intervention in reducing preschool children's exposure to lead. As part of the study methods were developed to obtain wipe samples that were quantitative for lead concentration as well as lead loading, and vacuum samples that were corrected for variability in collection efficiency under diverse environmental conditions. The wipe and vacuum sample techniques developed for CLEARS allow comparison of dust loading (mg-dust/m2), lead loading (g-Pb/M2), and lead concentration (g-Pb/g dust) metrics from floors, carpets, and other high contact areas where preschools spend their time. Comparison of mean and upper bound concentration data indicate that while the distributions are similar in shape, wipe samples report higher concentrations than vacuum samples. Lead loading on carpets, however, is an order of magnitude higher than on floors. Plotting lead loading versus lead concentration reveals that there is wide variability in lead concentrations over the range of observed lead loadings. Time of year and the clinical trial's cleaning intervention exert consistent but different effects on microenvironmental lead levels.
The collection techniques used in this study allow for quantification of lead loading--a predictor of potential exposure--and lead concentration--an indicator of relative source strength. These data indicate that there is wide variability in lead levels within home environments where preschoolers spend most of their time, and that a variety of intervention techniques may be needed to optimize exposure reduction. The implications for exposure at the median and upper bound end of the distribution are discussed.