If someone introduced microplastics to your house while you had no part in it - so you find yourself eating and breathing little bits of hydrocarbon chemicals which none of your ancestors in natural history have ever ingested. No mites can digest it, no moulds can compost it, nothing has ever lived with it, its just a new mysterious stuff that you and your children are going to be surrounded by, and get in your lungs and blood and live within from now on ... And you feel fine about it until convinced by science that you shouldnt. Against the advertisements and persuasions of a big industry, how long did it take to establish that cigarette smoke was dangerous? Leaded petrol? AGW? Ay but its probably fine! We can only imagine, chick skeletons full of plastic beads, certain species of sea creatures and microbiota due to perish because they mistake plastic for food, ecologicaly distruptively novel microbiota evolving which may capable of digesting the different kinds of plastic and additives which are alien to life - after billions of years, an alien substance everywhere. No probs, no 'credible evidence' of probs. Carry on then.