The Effectiveness Environmental Measurements and Biomarkers of Exposure at Minimizing Exposure Misclassification

Abstract

Background: Children's Health after the Storm (CHATS) is a cohort study investigating adverse health effects among children who resided in areas affected by Hurricanes Katrina and Rita in the U.S. A feasibility study is underway. Aim: One study aim is to assess ways to minimize exposure misclassification bias. We hypothesize that personal measurements of environmental exposure have a stronger association with biomarkers of exposure than do indirect exposure measurements. Methods: A substudy of 100 children will assess exposure misclassification. For each child, we are collecting: 1) one-week measurements of personal exposure to particulate matter (PM10), second-hand smoke (SHS), and volatile organic compounds (VOC); 2) one-week residential indoor and outdoor stationary sampling for the same pollutants; and 3) corresponding urinary biomarkers of exposure. We will compare personal exposure data to indoor and outdoor residential data, and environmental SHS and VOC measurements to urinary cotinine and VOC metabolite concentrations. Results: Data from 50 children show that personal exposures to PM10 (mean: 38 mg/m3, GSD = 2.4) exceed the indoor (mean: 25 mg/m3, GSD = 2.4) and outdoor concentrations (mean: 20 mg/m3, GSD = 1.8), with SHS being a key source of the difference. Personal and indoor VOC concentrations are similar (mean: 0.015 mg/L, GSD = 2.1) and are greater than outdoor concentrations (mean: 0.005 mg/L, GSD = 1.9). Additional environmental and biospecimen sample collection and analysis are ongoing and will be presented. Conclusions: Preliminary data suggest that personal measurements are best at minimizing exposure misclassification bias. Strong sources within microenvironments and the child’s proximity to these sources are the most likely causes. The correlation between the personal measurements and the urinary VOC and cotinine biomarkers will confirm this supposition. Our assessment of approaches to minimize exposure misclassification will be fully evaluated to inform the Full Study Phase of CHATS.