Health effects of microplastics uncertain, despite their omnipresence Plastic is rife in dust, rice, placentas and tap water, but experts say that it is difficult to determine whether it is harmful to humans By Graham Readfearn / The Guardian As much as the idea might be unpalatable, all of our diets are now likely to include tiny servings of plastic. The places where microplastics and plastic fibers have been found is beginning to read like a supermarket shopping list. Studies have found microplastics — that is, pieces or fibers smaller than 5mm — in foods including tea, salt, seaweed, milk, seafood, honey, sugar, beer, vegetables and soft drinks. Tap water contains plastic. Bottled water contains even more.