Pakistan lashed out at India on Monday as the air quality index in Pubjab province hit a record high over the weekend. Tens of thousands — mainly children and elderly people — have fallen sick in Lahore and other areas bordering India over the past month.

Primary schools in Lahore will remain closed for a week because of the pollution, according to a government notification.

The smog crisis in Lahore, similar to the situation in India's capital Delhi, tends to worsen during cooler months due to temperature inversion trapping pollution closer to the ground. Make sense of the latest ESG trends affecting companies and governments with the Reuters Sustainable Switch newsletter. Sign up here.