Karachi is the fifth most polluted city in the world according to World Health Organization Ambient Air pollution database.
The WHO in his recent 2014 version of the Ambient Air Pollution (AAP) database listed the three cities of Pakistan in the top twenty polluted cities of the world. According to APP database released by WHO, Karachi is at number five, Peshawar is at number six and Rawalpindi is at number seven in the list of most polluted cities in the world.
The APP database consists mainly of urban air quality data of about 1600 cities from 91 countries for the years 2008-2013.
Amazingly, thirteen cities in the list of twenty most polluted cities in the world are from India. Delhi is the reigning king of polluted cities in the world.
The polluted cities according to WHO are ranked after analyzing the presence of harmful gases in their air such as: nitrogen dioxide, carbon monoxide and sulphur dioxide, besides particulate matter 10 and 2.5. Particulate matter (or small airborne particles) is among the most detrimental of these pollutants. Studies link it with increased rates of chronic bronchitis, lung cancer and heart disease.
According to experts: “Particles smaller than 10 micrometers in diameter pose the greatest threat to human health. They can’t only get deep into a person’s lungs but can also enter the blood stream”.
The WHO advises that fine particles of less than 2.5 micrometer in diameter (PM2.5) shouldn’t exceed 10 micrograms per cubic meter.