As an ordinary person without a science background, I did a bit of research into if microplastics are harmful. I've found 9 articles, and I've summarised my findings in my own words:
Microplastics are ubiquitous, but we don’t know much about their harm. We know they can be carriers of harmful chemicals that remain on the plastic, including carcinogenic chemicals. They can be microscopic and nanoscopic in scale, potentially entering cells on an atomic level. They are easily carried across food chains, persist in our environment, and will never biodegrade and only get smaller and smaller. If large enough, they can be ingested like bigger plastics and cause harm to organisms, in particular to marine life.
If this is correct, I think the problem is not microplastics, but the chemicals on them. As long as microplastics are small enough to not cause any physical damage (suffocation, entanglement, laceration, internal injuries, usually caused by larger plastics), we can let them continue to break into smaller pieces without harm. Do you agree? Do you think there are much more harmful effects yet to be discovered?
NOTE: In the back of my mind, I am thinking about synthetic clothing / textiles. If my suggestion is correct, then synthetic clothing is potentially harmless as long as they are not treated with harmful chemicals – we do no need to worry about the shedding of microplastics.
NOTE: Apologies, I know there are many types of plastics out there. This is something I know little about. Please feel free to say more on this.