Karachi's air quality reached dangerously unhealthy levels on Tuesday and was recorded at 244 on the Air Quality Index (AQI).
Today, Karachi was ranked third on the AQI, with India's capital New Delhi taking the second spot and Lahore topping the list for the worst air quality in the world with 257 and 305 AQI readings respectively.
Global scales typically rank good air quality between a 0-50 AQI. An AQI over a 100 is termed dangerous for the more vulnerable groups while an AQI of more than 150 is typically deemed unhealthy and an AQI above 300 is dubbed hazardous.
Experts believe that the winds in winter are much heavier than summer, during which various toxic particles in the air begin to move downwards causing the air to become polluted. According to experts, smoke, coal, garbage, grease, oil and burning tires from industries and small factories are released into the atmosphere throughout the year, the effects of which are noticeable throughout the winter season.
The south-westerly winds of the sea filter the air of Karachi, but in winter most of the sea-winds are interrupted and the northeastern (Balochistan) winds blow in the alternative direction, highlighting the pollution particles.
On Monday night, the port city's air quality was ranked as the fourth worst in the world, with Lahore taking the third spot on the list.
On November 14, the port city woke up to world’s third-worst air quality of 281, better only than Delhi, Lahore.
Poor air quality can have detrimental effects on public health and air pollution has been deemed the greatest environmental health risk currently by the World Health Organisation.