Breathless Delhi: Delhi is breathing the most polluted air

Delhi’s air is the most toxic in the world due to high concentrations of PM2.5 — particulate matter less than 2.5 micrometres in diameter — that is believed to pose the greatest health risk because it penetrates deeply into lungs.The PM2.5 limit prescribed by WHO is 10 microgrammes per cubic metre, and the Indian limit is 40 microgrammes per cubic metre. PM2.5 are miniscule particles in the air that reduce visibility, cause the air to appear hazy, and affect respiratory tracts.