A small study of brain autopsies has provided evidence that prolonged exposure to air pollution may raise the risk of developing Alzheimer's disease.

While ambient air pollution is known to affect respiratory and cardiovascular diseases, its effect on neurodegenerative disorders has limited evidence.

The study by researchers from the University of Antwerp in Belgium and the University of Groningen in the Netherlands screened different regions of biobank brains of 4 individuals from Belgium with neuropathologically confirmed Alzheimer's disease for the presence of black carbon particles.

The findings showed a significantly higher number of black carbon particles present in the thalamus (brain's information relay station), the prefrontal cortex (responsible for human cognitive abilities) including the olfactory bulb (a region that helps in the sense of smell), and the hippocampus (that plays a significant role in learning and memory).

In the paper published in JAMA Network Open, the researchers provided "evidence that ambient air pollution particles can translocate to the human brain and accumulate in multiple brain regions involved in cognitive functioning".

They said that the phenomenon may be behind "the onset and development of neurodegenerative disorders but also stressed the need for further studies to confirm their observations. A previous study on predisposed laboratory mice showed that particulate matter in polluted air can drive changes in brain areas and speed up the onset of Alzheimer’s.