Tiny magnetic particles produced by car engines and brakes can travel into the human brain and may trigger Alzheimer's disease, scientists have warned.
Researchers at Lancaster, Oxford and Manchester Universities discovered microscopic spheres of the mineral magnetite in the brains of 37 people in Manchester and Mexico who had suffered neurodegenerative disease.
The mineral magnetite is known to be toxic and is linked to the production of free radicals which are associated with Alzheimer's Disease.
Although magnetite has previously been found in the brains of people who had died of Alzheimer's disease, it was thought it occurred naturally. However the tiny balls spotted by the scientists had a fused surface suggesting they had been formed during extreme heat, such as in a car engine.
Magnetite - a form of iron oxide - is known to be produced in car engines - particularly diesel engines which can emit up to 22 times more particulates than petrol engines - as well as when brakes are used, both by cars and trains. It can also be produced by open fires and poorly fitted stoves.