Air pollution in Delhi is definitely getting close to dangerous levels and the new measure to rein it in will hopefully make the air cleaner. Measurements by local authorities, the World Health Organization and the American embassy all pointed to this sobering fact. Why is air pollution a big deal? According to the World Health Organization, 7 million premature deaths annually are linked to air pollution!
How is air pollution measured? By measuring the amount of tiny airborne pollutants in a given volume of air. Particles less than 10 micrometers in diameter (PM10) pose a health concern because they can be inhaled into and accumulate in the respiratory system. Particles less than 2.5 micrometers in diameter (PM2.5) are referred to as "fine" particles and are believed to pose the greatest health risks. Because of their small size (approximately 1/30th the average width of a human hair), fine particles can get past the body's normal defenses and penetrate deep into the lungs. Sources of fine particles include all types of combustion activities and certain industrial processes.
How do Indian cities fare compared to major cities in the world? Indian cities unfortunately have the highest levels of PM2.5 pollutants- worse than China. Some say actual figures in Chinese cities are vastly under-reported and should be thrice as much but this would still make Indian cities among the worst hit in the world. The chart below shows air pollution (PM2.5) levels across major cities in the world.