Microplastics Accumulate at Higher Concentrations in the Brain Than in the Liver or Kidneys; Possible Link to Risk of Dementia and Stroke. Analysis suggests that microplastics accumulate in the brain at concentrations more than seven times higher than in the liver or kidneys and may be linked to brain diseases such as dementia and stroke. The microplastic problem should not be viewed merely as environmental pollution, but as a brain issue.