"One reason why plastics are so widely used in society is that they’re supposed to be chemically inert under normal circumstances. The researchers’ experiments, however, indicate that this assumption doesn’t hold true once plastics are broken down into the tiny pieces that can enter our bodies. Specifically, they found that microplastics are capable of spontaneously generating unstable molecules known as free radicals when in the presence of water."
https://gizmodo.com/microplastics-are-chemically-alive-and-probably-up-to-no-good-2000827048