It could be cancer that takes years to develop. Most things like that like asbestos, lead, etc… take a long time to be detected/ figure out how they’re damaging the body. Even once they are, you can’t prove that’s what caused it without scientific testing/ statistics.

Microplastics can act as carriers of other environmental toxins, such as PS, and exposure to high concentrations of PS are detrimental to human lung cells, increasing the risk of chronic obstructive pulmonary disease.