As winter sets in, Lahore is once again sinking under a blanket of haze. On Friday morning the city topped the list of the world's most polluted cities with an air quality index (AQI) of 410, a level classed as hazardous to health.
According to a global air quality monitoring platform, New Delhi followed with an AQI of 203 and Dakar, Senegal, was third at 196. Lahore was the only Pakistani city among the 20 most polluted, while Karachi, with an AQI of 110, was the only other Pakistani city on the 21-city list.
The platform said PM2.5 concentration in Lahore was 45.2 times the World Health Organization's annual guideline value. These fine particles, 2.5 micrometres or smaller, can enter the bloodstream and even the brain, and long-term exposure can cause serious health problems. Residents were advised to avoid outdoor exercise, keep windows closed, wear masks outside and use air purifiers indoors.
The Punjab government's own air quality monitoring system, based on data from 10 stations across the city, recorded Lahore's AQI at 339 at 11am on Thursday, classifying the air as "very unhealthy". Industrial emissions, vehicle exhaust, crop-stubble burning and stagnant winter air are blamed every year for the smog, which often worsens in the weeks ahead.