Schools were shut across India’s capital on Friday as a noxious grey smog engulfed the megacity and made life a misery for its 30 million inhabitants. Smoke from farmers burning crop stubble, vehicle exhaust and factory emissions combine every winter to blanket Delhi in a choking haze. The public health crisis has persisted for decades and researchers have blamed the smog for hundreds of thousands of premature deaths across India. Levels of the most dangerous PM2.5 particles — so tiny they can enter the bloodstream — were on Friday almost 35 times the daily maximum recommended by the World Health Organization, according to monitoring firm IQAir. “In light of the rising pollution levels, all govt and private primary schools in Delhi will remain closed for the next 2 days,” chief minister Arvind Kejriwal wrote on X, formerly Twitter.