Unhealthy: Chemical foam from industrial effluents float on the River Yamuna in Delhi. Credit:AP To assess the content of the air people breathe as they move around the city, Ms Narain and CSE research director Anumita Roychowdhury convinced a group of prominent Delhiites to carry sophisticated air quality monitoring equipment as they conducted their daily routines. The pollutions levels they recorded shocked the authors of the study - and the participants - as they discovered they were being exposed to up to 12 times the level of killer particles that is deemed safe by the World Health Organisation. With the Delhi winter causing severe temperature inversion conditions during the night - where the cold night air acts as a dome trapping in the warmer city air - the study found that real-time pollution levels soared during the night, peaking in the early morning. One participant in the study was Bhure Lal, chairman of the Environment Pollution Authority, who lives in the heart of the greenest part of the city known as Lutyens Delhi, where he takes his morning power walk along with the rest of the city's elite in the lush Lodhi Gardens.

While the WHO recommended daily standard for exposure to small particles is just 60 micrograms per cubic metre, Mr Lal discovered to his horror that the air he was breathing in the Lodhi Gardens on the morning of November 13 had 1195.83 micrograms of small particles per cubic metre. On the morning of November 23, asthma sufferer Avikal Somvanshi took an air quality monitor to the starting line of the Delhi half-marathon where 32,500 runners had gathered at the famous India Gate for the race. As the starting gun was fired, Mr Somvanshi's air monitor recorded small particle levels as high as 815 micrograms per cubic metre. As he followed the runners around the course, the particle levels rose to as high as 1050 micrograms per cubic metre. "I no longer go for a run in the morning," Ms Narain says. "It is simply not safe." William Bissell, the founder of Fabindia, a national furniture, homewares and clothing franchise, carried an air monitor on his morning walk on November 20 through another green area known as Jahanpanah Park, and recorded small particle levels of 705 micrograms per cubic metre.

For comparison sake, the nearest official Delhi Pollution Control Committee monitoring station suggested there were only 308 micrograms of small particles per cubic metre - still a hazardous level that is more than five times the maximum daily exposure considered safe by the World Health Organisation. With more 1400 new cars on the road each day in Delhi, and the number of cars and trucks doubling over the last decade, Ms Narain says vehicle pollution, especially vehicles burning diesel fuel, are the main reason for the dangerously high levels of small particles. In a list of recommendations to the local authorities, the CSE recommended urgent action to control the pollution including introduction of more stringent vehicle emission standards, tax increases on diesel fuel to encourage motorists to switch to cleaner alternatives, strategies to clear the roads of older cars, and measures to reduce the number of vehicles entering the city each day. At 6am on Friday, Fairfax Media surveyed a number of power walkers at the elite - and heavily - polluted Lodhi Gardens. Among them was Vipul Jhalani, 51, who has taken a morning walk through the Lodhi Gardens every day for the last 15 years.

"The figures must be wrong," Mr Jhalani said. "At least, I hope they're wrong." With a 2012 epidemiological study that surveyed nearly 12,000 children from 36 schools across Delhi finding that every third child has reduced lung function, Mr Jhalani admitted that he was very concerned about the health affects of bad air. But one walker who didn't seem at all surprised by the findings of the CSE study was an unassuming man who introduced himself as Jairam Ramesh. Instead of answering questions, Mr Ramesh starting volunteering solutions. Asked what his occupation was, Mr Ramesh said: "Actually I was environment minister in the former government led by Prime Minister Manmohan Singh."

Still a member of parliament, Mr Ramesh acknowledged that the situation was urgent. "We have to take action. Collectively. Our lives depend on it. We have no other choice."