The Committee on the Medical Effects of Air Pollutants (CMEAP) reviewed nearly 70 studies in human populations which have examined the possible link between air pollutants and effects on mental ability and dementia.
It found that the studies show “it is likely” that air pollution can contribute to a decline in mental ability and dementia in older people.
It is already known that air pollution, particularly small particle pollution, can affect the heart and the circulatory system, including circulation to the brain. These effects are linked to a form of dementia caused by damage to the blood vessels in the brain.
Experimental studies suggest that air pollution might also stimulate the immune cells in the brain, which can then damage nerve cells.
It is not clear whether this effect is important at the levels of pollution which occur in the UK today, but it is likely that some very small air pollution particles can enter the brain, and may cause direct damage...