After Neeno Kaur received chemotherapy and a bone marrow transplant to treat her leukemia, doctors advised her to stay out of New Delhi during the winter months to protect her lungs.

The Indian capital has some of the worst quality air in the world, and almost never dips below the level that scientists consider hazardous to human health. 

During Diwali, when residents routinely flout a ban on firecrackers, the smog is almost unbearable.

Ms Kaur’s solution, with her husband of 49 years, Peter Satwant Singh, was to fill their home with 15,000 plants, going to extreme lengths to protect their health from harmful air.