New Delhi's pollution levels go from world's worst to even worse

The three-wheeled rickshaw lurched through New Delhi's commuter-clogged streets with an American scientist and several air pollution monitors in the back seat. Car horns blared. A scrappy scooter buzzed by belching black smoke from its tailpipe. One of the monitors spiked.

Joshua Apte has alarming findings for anyone who spends time on or near the roads in this city of 25 million. The numbers are far worse than the ones that have already led the World Health Organisation to rank New Delhi as the world's most polluted city.

Average pollution levels were 50 per cent to 700 per cent higher on the road than urban background readings, including official ambient air pollution measures, according to research by Apte and his partners at the University of California, Berkeley, and the Indian Institute of Technology in New Delhi.

"And you have to keep in mind that the concentrations at urban background sites, where these official monitors are, are already very high," he said.

The point is particularly important for New Delhi residents, about half of whom live within 300 metres of a major road.

"Official air quality monitors tend to be located away from roads, on top of buildings, and that's not where most people spend most of their time," Apte said. "Most people spend a lot of time in traffic in India… one, two, three hours a day."