There is different health implications connected to microplastics like infertility and cardiovascular diseases, although the connections are not quite understood yet. The amount of microplastics in the human body is very alarming though. A study with brain samples found 0.5w% of plastics, which corresponds to roughly 6g of plastic in a brain. That's a credit card's worth of plastic.

This article should give some overview over different findings and implications:

https://www.theguardian.com/environment/article/2024/aug/21/microplastics-brain-pollution-health