For a time Beijing looked like a scene from Dickensian London of the Industrial Revolution when pollution blocked out the sun and coal dust was everywhere.

Beijing shrouded in heavy fog [File photo]

On December 4 the capital city was shrouded in a dense smog that seriously disrupted city life. Tens of hundreds of flights were grounded. Road traffic was severely hampered by low visibility. People choked on the heavily polluted air invading their lungs, even though they wore face masks.

It's no longer news that Beijing was smothered by a smog of epic proportions, but this time people's reaction is markedly different.

Many people are now fuming over the government's perceived lack of transparency in releasing meaningful air-quality ratings that truly reflect their impression of the smog's gravity.

Popular outcry and scrutiny has forced the state environmental watchdog to announce that it will add to the air quality monitoring system the so-called PM2.5 particles, or airborne pollutants measuring less than 2.5 microns in diameter.

Currently only particles with a diameter of between 2.5 and 10 microns, or PM10, are reflected in the system that issues daily updates on air quality.

However, fine PM2.5 substances, usually a twentieth as thick as a human hair, are increasingly known as a serious health hazard, and public pressure is building on the Ministry of Environmental Protection (MEP) to publicize PM2.5 readings as soon as possible.

Deadly content

The MEP announcement came as a relief to people who have long inhaled filthy air yet remained unaware of its potentially deadly content.

Seasonal sandstorms besetting much of China help the spread of airborne particles. As sandstorms sweep across the coal-producing areas in northern China, they gather grit as well as soot with a high concentration of toxic heavy metals like lead and arsenic.

The government's belated decision to survey and disclose PM2.5 levels is welcome. But to the public's chagrin, that new particulate measurement standard will not be adopted nationwide until 2016.

This five-year delay is prompting speculation that the government is not taking the PM2.5's public health consequences seriously.

A widely suggested reason for this delay is that if the new gauge is employed, we'll be confronted with frightening PM2.5 readings almost every day.

But that's no reason to procrastinate, according to Zhuang Guoshun, Fudan University professor of environmental science, who has long collected air samples from around China and assessed their content, including PM2.5 components.

In an interview with Shanghai Daily, he said PM2.5 readings in Shanghai average 50 to 80 micrograms per cubic meter a year, while the World Health Organization's PM2.5 levels considered "safe" stand at 35 micrograms per cubic meter.

Following the severe fog on November 13 and 14, the latest to hit Shanghai, the city's PM2.5 levels soared to 190 to 200 microns per cubic meter, almost 5 times the WHO standard.

In fact, although Shanghai has fewer days of "haze" than Beijing, now dubbed rather euphemistically a "misty capital," its PM2.5 readings occasionally exceed those in Beijing, and PM2.5 is the major culprit of haze, said Zhang.

Shanghai cleaned up the skies for the sake of its image during the Expo last year when the city saw consecutive days of blue skies. After the show was over, the air quality quickly deteriorated.

One reason is that construction sites citywide resumed work after the Expo was over. What's more, farmers in the surrounding provinces again burned straw to clear their fields - they had been compensated by Shanghai for not doing so when the Expo was ongoing.

Burning straw and other agricultural waste is one of the main causes of haze apart from industrial emissions and dust storms, Zhang said. But even though Shanghai has closed down many of its polluting factories in recent years, the city's PM2.5 levels are still on the rise.