Lahore became the world’s most polluted city on Tuesday as pre-winter smog settled over parts of northern India and adjoining Pakistan, according to air quality data reported by Reuters. Early on Tuesday, the city’s air quality index stood at 447, based on figures from IQAir, a Swiss group that measures air quality from the concentration of toxins in the air.
That reading sits far above the level considered safe. An air quality index of up to 50 is generally treated as good, with little or no health risk, while a reading above 400 falls into the most severe category. Lahore’s fine particulate matter, known as PM2.5, was reported to be 60 times higher than the World Health Organization’s annual exposure guideline, a stark illustration of how thick the haze had become.
Delhi was also badly affected, although its reading was lower on the IQAir scale, at 215. India’s Central Pollution Control Board, which uses a different scale and method, rated the capital’s air quality as very poor, with a reading of 332. Authorities in Delhi responded with curbs on vehicles and construction in an effort to fight the toxic haze over the capital.
Air pollution becomes a severe problem for the region around this time of year, as cooler weather traps smoke and dust close to the ground. Crop burning, vehicle exhaust, construction dust and industrial emissions all contribute, and the onset of winter conditions makes it harder for the pollution to disperse. The result is a familiar seasonal crisis that returns each year across the plains of northern South Asia.
Fireworks during the Hindu festival of Diwali, which falls on 8 November this year, are expected to worsen pollution in India further, adding another source of smoke to air that is already heavily loaded. Health experts routinely warn that such spikes can aggravate breathing problems, particularly for children, older people and those with asthma or heart conditions.
The different readings for Delhi highlight an important point about air quality figures: the Swiss and Indian systems use different scales and methods, so their numbers are not directly comparable. What matters is the direction and the category, and on both measures Delhi’s air was rated as seriously unhealthy on Tuesday, even if Lahore’s reading was higher still.
For residents of Lahore, the ranking is an unwelcome reminder of a recurring challenge. Until weather conditions change or emissions fall, the city is likely to remain near the top of global pollution lists on smoggy winter mornings, with all the health and daily-life disruption that brings.
