The study published in the Proceedings of the National Academy of Sciences, examined brain tissue from 37 people in Manchester and Mexico, aged between 3 and 92. Abundant particles of magnetite, an iron oxide toxic to the brain, was found in the tissue and abnormal accumulation of these brain metals is a key feature of Alzheimer’s disease. While this raises concerns, the new work is still a long way from proving that the air pollution particles cause or exacerbate Alzheimer’s.