Pakistani officials said that the toxic gray smog caused tens of thousands to fall ill in the city of Lahore, forcing authorities to close schools, markets, and parks for 4 days.

This decision came after the country's second-largest city was repeatedly classified as the most polluted city in the world. Doctors advised individuals to wear masks and stay indoors. City residents said many are suffering from coughing and breathing problems.

Salman Kazmi, a doctor at Mayo Hospital in Lahore, where thousands have been taken for treatment, explained, "Wearing masks and staying at home are the easiest solutions to avoid transferring those with respiratory-related diseases, eye infections, and skin diseases to hospitals."

Meanwhile, the concentration of "PM 2.5" (particulate matter 2.5), or fine particles, in the air approached 450, which is considered dangerous.

Experts say that burning crop residues at the beginning of the winter wheat planting season is a major cause of pollution.

Lahore was formerly known as the city of gardens, which were everywhere during the Mughal era in the 16th to 19th centuries. But rapid urbanization and increasing population growth have left little space for greenery in the city.