Assessing the release of microplastics from reusable plastic water bottles and their exposure to toddlers

Microplastic ingestion has become a concern due to its potential adverse effects on human health. To further explore routes of microplastic exposure, this study investigated the release of microplastics from reusable plastic water bottles with straws designed for toddlers. The study involved prolonged storage of water bottles and mechanical abrasion, simulating the actions of drawing liquid and biting the straw. The release of microplastics was analyzed via laser direct infrared (LDIR) spectroscopy. The characterization results revealed that polypropylene (PP) is the primary material used in plastic bottles, with a minor blend of polyethylene (PE) and polydimethylsiloxane (PDMS) confirmed as the material for the straw. The LDIR results revealed that PP microparticles measuring 20-50 μm were consistently present in water, whereas no PDMS was detected within the analytical size range and the detection capability of the applied methods. The exposure modeling results suggested that the daily polypropylene intake for toddlers aged 3-6 years old would be 1.2 ng/kg/day after 100 sips of water from a PP reusable water bottle, which might be associated with physical stress to the bottles during the experiments. Our findings highlight that toddlers' ingestion of microplastics is not incidental but may occur routinely through everyday practices, such as drinking water from plastic bottles.