Car exhaust

A significant part of that increase comes from the growing number of cars on the city's roads. Their exhaust fumes, rich in sulfur dioxide and nitric oxide, form PM2.5 particles after a series of chemical reactions under air pressure.

Beijing shrouded in heavy fog [Bejing News]

And snarled road traffic contributes to emissions of automobile-generated PM2.5, as idling engines consume more fuel and thus discharges more exhaust, said Zhang.

He dismissed the belief that planting trees would reduce PM2.5, as these pollutants move at an altitude of several thousand meters and are extremely small in size. Trees can do little to sequester them from reaching the ground.

Worse, trees release volatile organic compounds (VOC), which after oxidization also develop into PM2.5 particles. So having more greenery will not help lower PM2.5 levels, Zhang said.

What really matters in the fight to control PM2.5 is a change of the mindset that places growth above all else, and this is what the Fudan professor has been calling for all these years.

"Growth should benefit people. When it harms their health, what's the point of growth anyway?" asked Zhang.

Zhang advocates developing public transport over private cars. Although haze and smog are sometimes meterological anomalies and increasingly a regional problem, controlling the local sources of emissions is within a city's ability, he said.

Nevertheless, it is a question whether a city is willing to demonstrate that ability. As a critic of the delayed implementation of the PM2.5 gauges, Zhang argues that China should adopt the same air quality evaluation criteria as the West. We cannot sacrifice people's health just to develop the economy, he said.

There are signs that some regions may lead the nation in having PM2.5 included in air quality ratings. Shanghai, for example, seeks to be among the first areas in adopting a stricter air quality monitoring system before it is introduced nationwide in 2016.

If that quest succeeds, it surely will be something to celebrate - not just about more accurate weather forecasts, but about a government more receptive to people's environmental concerns.

After all, as Zhang says, what we lack is not the equipment and know-how to take PM2.5 figures, but the courage to do so.