The world's most polluted capital city

In Northern India, a concoction of seven different fungi could help to thin the smog that pervades the capital city with the worst air pollution in the world

The onset of spring brings relief in more ways than one to Delhi. The air is cool and crisp, and with the milder weather come light showers that make the vegetation more lush. Around April, south-westerly winds sweep through the region, and the blanket of acrid smog that covers the city in the autumn and winter months begins to disperse. But it never really goes away.

For the last 10 years, Shaheen Khokhar has witnessed this annual cycle as a resident of Gurugram, south-west of Delhi in the Northern Indian state of Haryana. Around October, when she drives into the city, the unnaturally grey, seemingly overcast skies creep up without warning. "One minute, there's sunshine, and the next, you're engulfed in this dark, smoky haze," she says. "Every day, we see a deeply distressing, visual reminder of the pollution that we're forced to live with."

The effects of that pollution range from skin and eye irritation to severe neurological, cardiovascular and respiratory diseases, asthma, chronic obstructive pulmonary disease, bronchitis, lung capacity loss, emphysema, cancer, and increased mortality rates. Globally, outdoor air pollution kills around 4.2 million people each year.

The year-round average for PM2.5 pollution in New Delhi was the worst of any capital city in the world by a large margin

In October and November, school children across Northern India, especially in India's capital city of New Delhi (which lies within the National Capital Territory of Delhi) and in the vicinity around Gurugram, have to contend with frequent disruptions. As the pollution worsens, schools shut for around two weeks every year. "Our children have worn masks to school long before the Covid crisis," says Khokhar.

Twenty-one of the world's 30 cities with the worst levels of air pollution are in India, according to data compiled in the 2021 World Air Quality Report. Six Indian cities are in the top 10. New Delhi has the highest exposure to toxic air in the country. People in India had the fifth highest annual recordings of fine particulate matter (PM2.5), a particularly harmful form of air pollution. The year-round average for PM2.5 pollution in New Delhi was the worst of any capital city in the world by a large margin.