Application of Aerosol Techniques to Measure Nanoscale Particles Leached from Plastic Infant Feeding Products

STEPHANIE JACOBY, Chun-Ning Mao, James Radney, Akua Asa-Awuku, University of Maryland

     Abstract Number: 26
     Working Group: Chemicals of Emerging Concern in Indoor and Outdoor Aerosol: Sources, Vectors, Reactivity, and Impacts

Abstract
Microplastics (MPs; plastic particles 5 mm - 1 µm) and nanoplastics (NPs; < 1 μm) are emerging pollutants increasingly detected in diverse environments including the atmosphere, aquatic ecosystems, and the human body, posing significant environmental and health risks. Food-contact materials, including plastic infant feeding bottles, have been identified as sources of MPs and NPs, which leach during typical use conditions such as heating. While many studies have investigated MPs release, significant knowledge gaps remain for NPs due to analytical challenges. Traditional spectroscopic and mass-based methods are unable to measure sub-μm particles due to insufficient spatial resolution and mass concentrations below the detection limit. In contrast, aerosol-based techniques effectively measure the size distribution and number density of sub-μm particles, presenting an alternate method to measure NPs via atomization of material leached from macroplastics. Here we present aerosol-based measurements of the size distribution and water-uptake of nanoparticles released from polypropylene baby bottles and polyethylene bottle liners, using a single mobility particle sizer (SMPS) and continuous-flow streamwise thermal-gradient cloud condensation nuclei counter (CCNC). CCNC measurements are used to estimate hygroscopicity, which quantifies the propensity of a particle to absorb water. Importantly, hygroscopicity is strongly influenced by molecular size and can be used to estimate molecular weight of NPs using Flory-Huggins Köhler theory. This approach enables rapid characterization of leached NPs as oligomer or polymer, addressing a challenge in NP research. Oligomers and polymers have the same elemental composition but different chemical and physical properties, affecting their environmental fate and toxicity. By bridging atmospheric aerosol science with materials science, this work provides insight into metrology and techniques for measuring NPs. This approach can be broadly applied to other plastics, supporting a more holistic understanding of consumer products as sources of NPs.