Adhesion and Resuspension of Biological Particulate Matter in Early-Childhood Indoor Microenvironments

Purdue University, West Lafayette IN

Investigators

Abstract

Infants and toddlers spend over 90% of their time indoors and are thus exposed to numerous agents in the indoor environment. House dust is heavily enriched with an incredible diversity of microbes and allergens. Early-life inhalation exposures to the microbial and allergenic content of indoor dust can play a significant role in both the development of, and protection against, asthma and allergic diseases. As infants crawl, play, and learn to walk, they stir-up (resuspend) concentrated clouds of biological particulate matter (bioPM: bacteria, fungi, pollen) from settled dust. The resuspension and adhesion of indoor bioPM remains poorly characterized. New research is needed to uncover the underlying transport mechanisms that govern bioPM exposures during this critical period in human immunological development. The goal of this project is to explicitly elucidate the fundamental mechanisms governing the adhesion, resuspension, and airborne transport of bioPM in early-childhood microenvironments. Exposure will be determined using a novel robot designed to simulate the movement of infants in the indoor environment and exposure to bioPM. This research has the potential to transform our understanding of infant exposure to bioPM at a critical stage in their development. Through a mechanistic framework, this project will make substantial contributions towards a fundamental understanding of the complex adhesion and human-driven resuspension processes that control the emissions, airborne transport, and fate of bioPM from settled dust in indoor environments. The specific objectives are: 1) investigate the adhesive interactions between bioPM and indoor surfaces through atomic force microscopy and explore the impact of bioPM morphology, hydrophobicity, charge, and humidity on adhesion forces; 2) develop a novel robotic platform to simulate infant/toddler movements informed by biometric data collected at the Purdue Miller Child Development Laboratory School (MCDLS) and to investigate aerodynamic, vibrational, and electrostatic bioPM removal forces; and 3) discover how infant/toddler movements resuspend bioPM through chamber experiments with the robot and develop a material balance model to predict bioPM fate and transport. This research will create new knowledge on how bioPM physiochemical properties affect adhesion forces to indoor surfaces. For the first time, bioPM removal mechanisms induced by forms of locomotion unique to infants will be determined. This project will generate extensive empirical data on bioPM adhesion forces and resuspension fractions. The novelty of the research is further exemplified by the integration of accelerometry data collected in a childcare center with infants/toddlers from 6 weeks to 3 years of age into the design of a robot for use in research at the interface of aerosol physics and microbiology. Lastly, the study will make innovative use of a Raspberry Pi-based low-cost particle sensor array to explore spatiotemporal variations in concentrations of resuspended bioPM which will infom the development of a multi-zone material balance model. Undergraduate students will participate in the bioPM experiments, in service learning projects on indoor air quality issues in K-12 schools as part of an interdisciplinary Engineering Projects in Community Service (EPICS) team, and in the development of the Raspberry Pi-based sensors and robot. New graduate course content on bioPM material balance modelling will be created. The project will actively involve Purdue MCDLS teachers, parents, custodial staff, and building facility managers to engage those who interact directly with infants and their indoor environments. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.