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Particulate matter (PM) and its constituents are recognized risk factors for the development of respiratory symptoms and illness in children. Most measurements of exposure have relied upon stationary indoor monitors (SIMs), overlooking the role of resuspended PM. To improve exposure characterization to resuspended aerosol PM, a recently developed methodology has been employed. The goal of this study was to characterize the resuspendable fraction of house dust and early childhood exposures to PM and its constituents in the child's home and compare conventional SIM and the Pre-toddler Inhalable Particulate Environmental Robotic (PIPER), an innovative mobile sampler. The study seeks to demonstrate that PIPER provides a more relevant estimate of exposure from inhalable particulate matter through improved correlation with respiratory symptoms in young children. Seventy-five households with children between 3 and 59 months of age were recruited from clinics in central New Jersey. Demographic information, and responses to a health questionnaire based upon that used by the International Study of Allergies and Asthma in Childhood (ISAAC), and household data were collected. Household exposures to inhalable PM (PM100) and endotoxin were determined with simultaneous SIM and mobile (PIPER) sampling. Univariate and multivariate analyses were carried out. History of wheeze ("recent" (<1 year) and "ever"), cough, asthma and eczema was evaluated. Multivariate analysis models included PM100 and endotoxin levels by tertiles of exposure. Risk of asthma for the highest tertile of PM100, as measured by PIPER (odds ratio=4.2; 95% confidence interval 0.7-24.0), was compared with measurements by SIM (odds ratio=0.7; 95% confidence interval 0.2-2.6). Measurements of PM and its constituents with PIPER are more strongly associated with asthma, eczema and wheeze compared with measurements using SIMs. Application of this methodology may provide useful insights into early childhood exposures related to the etiology of childhood illnesses associated with inhalation exposures.