Pollution: Lahore and Delhi choke as annual smog rolls in

As the smog descended over Lahore, people began to feel the familiar symptoms. First came the scratchy throat and burning eyes, then the dizziness, tightness in the chest and the dry racking cough.

- Shah Meer Baloch, Lahore Hannah Ellis-Petersen, Delhi

"It's become a physical ordeal just to go outdoors," said Jawaria, 28, a master's student in the Pakistani city.

In recent days, the air quality in Lahore, home to more than 14 million people, dropped to the worst levels on Earth, with pollution levels up to 15 times higher than is deemed healthy and the city enveloped in a thick brown smoke. On the air quality index, "healthy" is 50; last week Lahore's air quality soared above 700.

Over the border in India, the capital, Delhi, was also shrouded in the annual thick toxic smog that marks the unwelcome beginning of "pollution season", affecting more than 25 million people, with air quality remaining in the "very poor" category.