Dia Mirza was almost two years into thinking the worst was over when the smog caught up with her son.

Marking Clean Air Day, the actress described a hospital emergency that had nothing to do with his rocky start in life and everything to do with the air outside their door. "We had thought it was all behind us until the pollution got to him," she said. "He was almost 2 years old, and we had to rush him to the hospital, and we discovered that he was unable to breathe. Coughing was his body's way of trying to cope."

That line, "until the pollution got to him," carries weight because of what came before it. Dia's son was born extremely premature, in the sixth month, weighing 820 grams. He spent over two months in the NICU and went through two life-saving surgeries before he ever left the hospital as an infant. Premature airways stay narrow longer, she explained, which is part of why respiratory trouble hits harder and more often. She recalled one stretch where he coughed non-stop for six hours straight. "It was excruciating and unbearable," she said.

The family assumed those early battles were the hard part. Pollution had other plans.

Dia also brought up something smaller but telling: a school sports day held on a high-pollution day. Her son wore a mask onto the playground and then simply stood apart from everyone. "He watched his friends from a distance. He refused to go and meet them and his teachers because he was wearing a mask," she said. "He felt uncomfortable about it, and this was not a small thing."

It's a scene a lot of Indian parents in big cities will recognise, the mask that protects a kid's lungs and isolates them from their own birthday party in the same breath.

Dia widened the frame from there, pointing to numbers she said tie air pollution to 2.1 million deaths in India in 2021, and more than 700,000 deaths worldwide among children under five from pollution-linked causes. But the exposure isn't evenly spread, she argued. Families near highways, landfills, construction sites and power plants get the worst of it. So do the people who work outdoors and can't just go inside when the air turns dangerous, street vendors, traffic police, sanitation workers.

"Clean air should never be a privilege," Dia said, before adding the caveat that her own family has access most don't. "We come from a place of privilege. We are able to protect our children at some level. But there are so many children in our country and in the world who are in street situation and are exposed to all of this all the time with no protection."

Dia has made environmental advocacy a running thread through her public life for years now. Whether this particular set of numbers moves the policy needle is anyone's guess. What's clear is that for her, the issue stopped being abstract the day a toddler couldn't catch his breath.