A transdisciplinary process-oriented approach to evaluate infant exposure to indoor dust

Abstract Background Infants are uniquely vulnerable to indoor dust exposure due to behaviors such as mouthing (hand- or object-to-mouth), crawling with hands on the floor, and close proximity to floor surfaces where dust accumulates. Dust acts as a reservoir for toxicants, including heavy metals, flame retardants, per- and polyfluoroalkyl substances, plasticizers, microplastics, and antimicrobials, which pose significant risks via ingestion and inhalation. Dust also contains allergens and microorganisms that may adversely impact respiratory health but have also been linked to protective immune effects, including a reduced risk of asthma and allergy development in early childhood. However, current exposure assessments lack a mechanistic understanding of how behavioral, developmental, and environmental factors interact to shape infant-specific dust exposure. Objective To develop a transdisciplinary, process-oriented framework that integrates behavioral analysis, advanced dust characterization, and mechanistic modeling to evaluate infant exposure to indoor dust through ingestion and inhalation pathways. Methods Videos of natural infant activity were collected from urban (New York, NY) and rural/suburban (West Lafayette, IN) homes to quantify mouthing frequency, duration, and other exposure-relevant behaviors across developmental stages. Dust samples were collected using standardized protocols and analyzed for surface concentrations, size distributions, morphological features, and toxicant profiles, focusing on heavy metals. Empirical datasets informed a mechanistic mass balance model to estimate size-resolved dust ingestion and inhalation rates. Results Preliminary findings revealed variability in dust surface concentrations between carpets and smooth flooring, and differences in elemental concentrations between urban and rural/suburban homes. Dust size distributions (volume basis) revealed that nearly half of particles were smaller than 50 μm, with approximately 20% smaller than 20 μm, underscoring the role of finer particles in exposure pathways. Impact This study introduces a transdisciplinary, process-oriented framework to evaluate infant exposure to indoor dust, combining video-based behavioral analysis, advanced dust characterization, and mechanistic mass balance modeling. By linking developmental behaviors, environmental conditions, and dust properties, it will reveal key pathways driving ingestion and inhalation of dust-bound contaminants during infancy. These findings will advance exposure science by enabling more refined risk assessments and informing targeted strategies to protect vulnerable populations during critical stages of development.