Karachi ranked fourth most polluted city of the world on the Air Quality Index (AQI) as winds from Balochistan blowing towards the city.
Karachi was measured to have 187 reading of particulate matter on the air quality index. Dhaka, Bangladesh’s capital city, remained the most polluted city in the world with 340 reading of particulate matter on the AQI. Indian capital Delhi ranked second with 270 reading on the air quality scale.
It is to be mentioned here that AQI as high as 151-200 is considered unhealthy, while an AQI reading between 201 to 300 is more harmful and AQI rate over 300 mark is extremely hazardous.
According to experts, the air becomes heavier in the winter as compared to summer, causing poisonous particles in the atmosphere to move downwards and making the atmosphere polluted. As a result, a layer of polluted particles, including large amounts of carbon and smoke, covers an area.
The smoke produced by factories or by burning coal, garbage, oil or tyres, enters the atmosphere and its impact appears at the onset of the winter and remains till the end of the season, experts said.
The AQI calculation is based on five categories of pollution: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide.
Although southwestern winds blowing from the sea in Karachi may work as a filter for the air, these winds remain mostly suspended during the winter, according to experts.
The winds blowing from the northeast increase concentration of polluted particles, and a healthy atmosphere in such a situation is subject to the rainfall, which washes off polluted particles.
