KARACHI: Karachi and Lahore have been rated most polluted cities of Pakistan on the Air Quality Index (AQI), ARY News reported on Saturday.
Karachi has been ranked second from the top in the most polluted cities of the world on the air pollution measurement scale.
The port city has been measured to have air pollution of 199 hazardous particulate matter, while Lahore ranked third in the most polluted cities of the planet having 181 particulate matter, according to the air quality index.
It is to be mentioned here that AQI as high as 151-200 is being
considered unhealthy, while an AQI reading between 201 to 300 is more harmful and AQI over 300 mark is dubbed 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 a city.
The smoke produced by factories and by burning coal, garbage, oil or tyres enters the atmosphere and the effects of this appear at the onset of winter and remain till the season’s end, experts said.
Thus, air pollution reaches to extremely dangerous levels in cold weather, severely compromising air quality.
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.
They noted that winds blowing from the northeast increase the concentration of hidden polluted particles, and a healthy atmosphere in such a situation is subject to rainfall, which washes off all polluted particles.
The AQI calculation is based on five categories of pollution: ground-level ozone, particulate matter, carbon monoxide, sulfur dioxide, and nitrogen dioxide.
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