The particles are in our blood, brains and guts – and scientists are only beginning to learn what they do The particles are in our blood, brains and guts – and scientists are only beginning to learn what they do M icroplastics have been found almost everywhere: in blood, placentas, lungs – even the human brain . One study estimated our cerebral organs alone may contain 5g of the stuff, or roughly a teaspoon. If true, plastic isn’t just wrapped around our food or woven into our clothes: it is