Estimating Environmental Exposures to Indoor Contaminants using Residential-Dust Samples
Using data from the Northern California Childhood Leukemia Study (NCCLS) and the Fresno Exposure Study this dissertation shows that concentrations of chemical contaminants in residential-dust samples can be useful surrogates for indoor chemical exposures. This dissertation focuses on dust levels of four chemicals or classes which have been associated with childhood leukemia and/or developmental effects, namely polybrominated diphenyl ethers (PBDEs), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and nicotine (a surrogate for tobacco smoke). Chapter 1 assesses the state of the science of residential-dust measurements, reviews global patterns in residential-dust levels of these chemicals, identifies known determinants of these chemicals' concentrations in residential dust, and estimates relative contributions of residential dust to the overall chemical intake of these chemicals in humans. Chapter 2 describes the analytical methods developed to measure PBDEs, PCBs, and PAHs in residential-dust samples. Chapters 3-6 compare residential-dust concentrations of these chemicals measured in California homes to levels reported in other studies from around the world. Chapters 3-5 also identify questionnaire-based predictors of residential-dust concentrations of nicotine, PAHs, and PCBs (chemicals for which sufficient data were available for statistical analyses). Chapter 7 investigates the variability of residential-dust levels of these chemicals within and between California households. A major finding of this work is the demonstration that current levels of nicotine, PAHs and PCBs represent indoor contamination from the distant past (e.g., over a period of years). This knowledge can be extremely useful to investigators who seek to perform retrospective assessment of exposures in studies of human health effects. The concluding Chapter 8 discusses the benefits and limitations of using residential-dust samples to estimate exposures to chemical contaminants, and presents ideas for future research in this field.