Children living in polluted cities are at increased risk of developing neurodegenerative diseases such as Alzheimer's or Parkinson's, say researchers at the University of Montana.

The team compared 58 serum and cerebrospinal fluid samples from a control group living in a low-pollution city and compared them by age, gender, socioeconomic status and education to 81 children living in Mexico City.

Children in Mexico City were found to exhibit immune dysregulation or high levels of auto-antibodies that worked against their own brain components, damaging the brain over time. This indicates damage to the blood-brain barrier that keeps antigens and neurotoxins away from the brain.

Brain auto-antibodies are found in the brains of people with neuro-inflammatory diseases like multiple sclerosis. Mexico City has registered many MS cases.

A breakdown in the blood-brain barrier allows not only particulate matter from air pollution but also the harmful neurotoxins like carbon and sulphur to enter the brain and cause long-lasting damage.

The paper appeared in the Journal of Alzheimer's Disease.

Polluted outdoor air caused 620,000 premature deaths in India in 2010, up from the 100,000 deaths in 2000 according to Global Burden of Disease 2013.

Air pollution killed 7 million people in 2012, causing one in eight of the total deaths globally, says the World Health Organisation. Respiratory ailments and cardio-vascular diseases are the most common fall-outs of long-term air pollution.