We know cigarettes cause cancer, sure. Maybe people didn’t know long ago, but you could always choose whether or not to smoke them. Even when smoking was rampant, there were always those that just didn’t want to, whether or not they could tell its effects.
I can’t choose whether or not to have microplastics in my blood so I try not to worry about whether or not it will affect me.
There are so many things in this world that we can choose that it doesn’t really make sense worrying about what we can’t.