Lahore and Karachi were among the top three most polluted cities in the world on Friday morning due to their “very unhealthy” air quality as Pakistan continues to grapple with smog. The Punjab capital topped the Swiss air quality monitor’s global pollution chart, with an air quality index (AQI) value of 266 at 9:14am, while Karachi’s AQI value was 216, placing it on the third spot. While Punjab has been engulfed by toxic smog for over two months, with Lahore being the mostly worst-hit, Karachi’s air quality has deteriorated over time and crossed the threshold deemed “very unhealthy” for humans for the first time in a month last week. As smog persists in various parts of the country amid the ongoing pollution crisis, the air quality in Karachi deteriorated to “very unhealthy” for the first time in a month. The concentration of toxic PM2.5 pollutants in Karachi’s atmosphere was 27.8 times higher than the World Health Organisation’s (WHO) guidelines value, around 9:20am. Though, the port-city’s stint in the “very unhealthy” category was short lived as it’s AQI improved to 173 by 10:20am. Meanwhile, Bangladesh capital Dhaka ranked as the second-most polluted city in terms of air quality and India’ New Delhi held the fourth spot, with an AQI value of 189, which shows a massive improvement from the unprecedented hike reported last month. Every winter, a mix of low-grade fuel emissions from factories and vehicles, exacerbated by seasonal crop burn-off by farmers, blanket parts of Punjab, trapped by cooler temperatures and slow-moving winds. As cold weather sets in in Karachi as well, the metropolis’ air quality sees gradual decline. The Met Office has predicted night-time temperature to drop as low as 15 degrees Celcius during the ongoing week. Breathing toxic air has catastrophic health consequences, with the WHO warning that strokes, heart disease, lung cancer and respiratory diseases can be triggered by prolonged exposure.