Mohammad Akran's memories of the Lahore of his youth as a beautiful, tree-filled, green place are difficult to reconcile with his daily fight with its now notorious smog.

While the market trader grew up in a place which once proudly called itself the city of gardens, nowadays, he can find it difficult to breathe.

Pollution in the capital of Pakistan's Punjab province is bad throughout the year, with one recent ranking saying it has the tenth worst air of any city in the world in 2018 and one of the worst in Asia.

In recent years the menace has spiked in winter as a perfect storm of weather, vehicle emissions, crop burning and industry have conspired to produce a blanket of choking pollution known simply as the smog.

This smog, whose annual arrival is now dreaded like an unwelcome new season, can hang darkly on the historic city of more than 11 million and is especially bad from November to February.