India, Jan. 1 -- At Raja Vihar, a small colony in North Delhi, the morning air feels heavy as children walk their way to school through the solid, grey wall of smog. It looks like the wall is made of a thick, clammy substance - the kind that makes your throat itch and your eyes burn within minutes. The haze hangs heavy over cramped houses and narrow lanes where children once played freely. Today, many of them stay indoors, coughing and choking, rubbing their eyes, waiting for relief that never seems to come.

Across Delhi's clumsy, informal settlements, toxic air is no longer a seasonal inconvenience. It has become a daily public health emergency - one that is quietly reshaping childhoods.

When it becomes a struggle to breathe

11-year-o...