Not sure about polypropylene, but both nylon and PET are known to shed billions of micro/nano-plastic particles into 95 °C water. https://pubs.acs.org/doi/10.1

Not sure about polypropylene, but both nylon and PET are known to shed billions of micro/nano-plastic particles into 95 °C water. https://pubs.acs.org/doi/10.1021/acs.est.9b02540 https://pubs.acs.org/doi/10.1021/acs.est.9b02540 Note they studied mesh bags. Flat surfaces with less exposed area should have lower emission rates. Still not great. Edit: apparently polypropylene does too. https://www.theguardian.com/environment/2020/oct/19/bottle-fed-babies-swallow-millions-microplastics-day-study https://www.theguardian.com/environment/2020/oct/19/bottle-f...