Measurement Error and Its Impact on the Estimated Relationship between Dust Lead and Children's Blood Lead

Abstract

Objective.Lead-contaminated house dust is a major contributor to lead intake among urban children, but the reliabilities of various dust lead measurement methods and their impact on the estimated correlations between dust lead and children's blood lead levels are unknown.Methods.Repeated field measurements of lead-contaminated dust from children's homes were taken from 16 housing units using five dust lead measurement methods. Estimates of measurement error were used to obtain reliability ratios for the dust lead measurements, which were then used to correct estimated correlations between lead-contaminated dust and children's blood lead.Results.Reliability varied over methods and surface types (from 0.0 to 0.8), but wipe loading and the BRM vacuum loading methods generally had greater reliability. Technician effects, inadvertent field exposure to lead, contamination of collection equipment, and laboratory instrument error were found to contribute little to total measurement error. Corrected correlations between blood lead and wipe loading measurements were 7 to 104% higher than uncorrected correlations. The multipleR2and partialR2for a wipe composite measurement in a multivariate regression model increased from 0.43 to 0.64 and from 0.053 to 0.26, respectively, after correction for measurement error bias.Conclusions.Variation in lead deposition within small areas and variations in collection inherent to the devices are major contributors to measurement error. Measurement error causes dramatic underestimation of correlation between lead-contaminated house dust and children's blood lead.