Before I start work in the morning I conduct a scientific survey of air quality in Beijing. That is, I look out the office window. I look west, across the sprawling metropolis of Beijing, towards the distant foothills containing the Great Wall of China.
If I can see those mountains, then I know that the air is clean, that it is one of those rare days when the toxic cloud of pollution which usually envelops the city has been blown away overnight, and that with luck it will be clear for a few hours at least. But usually I can't see as far as the Forbidden City a couple of kilometres away, let alone the mountains.
On most days my scientific glance through the window is sufficient to ascertain that the city is suffering from third- or fourth-degree air pollution. If I am unable to see the Citic Bank building across the courtyard, it has reached the very worst level of five degrees. Beijing last year recorded 265 days when a combination of 20 industrial fumes, nitrogen oxide, ozone, ultraviolet rays, vehicle exhaust and coal smoke formed a thick haze which blocked out the sun.
"My memory of Beijing 20 years ago is of blue skies, brilliant blue skies every day," sighed an elderly neighbour. "Now I just want to spit all the time."
We can both take comfort from the fact that we do not live in Lanzhou in central Gansu province, a petrochemical and oil-producing city locked in a deep valley. With more than 700 total suspended particulates (TSPs) of sulphur dioxide and nitrogen dioxide per cubic litre in its atmosphere, eight times the world permissible amount, Lanzhou frequently disappears from satellite maps.
This means that its citizens, especially children who breathe more quickly, inhale the equivalent of two packets of cigarettes a day, according to Ms Devra Lee Davis, an epidemiologist who led a study of world pollution for the Washington-based World Resources Institute. The survey found that Lanzhou was the most polluted city on the planet, and that altogether nine of the 10 worst polluted cities in the world are located in China.
That report jolted Beijing and gave impetus to an environmental movement which has grown up in China in reaction to the horrific effects of rapid industrial growth.
Apart from the estimated 300,000 deaths every year from air pollution, suspended particles destroy historic stone and bronze sculptures, illegal logging lays waste 5,000 sq km of virgin forest per annum, soil is being washed into the sea in huge quantities, large tracts of land have become desert, acid rain affects 29 per cent of the country and rivers stink from refuse and toxic chemicals.
As China gasps for air, pollution has for the first time appeared at the top of the agenda of the National People's Congress, which began its annual session in Beijing on Friday.
President Jiang Zemin has set the tone for debate some time ago. At a rally in September to mark the struggle to contain the Yangtze river floods last summer he made the frank admission that China had been mistaken in pushing ahead with industrial development regardless of the consequences. From now on there should be "co-ordinated development of the economy and ecological environment," he said.
This is not so easy in a country where one quarter of the global population is trying to exist on 7 per cent of the world's arable land. China gets three-quarters of its energy from coal and the communist government depends on continued economic growth for its very survival. Monitoring the damage is difficult. Beijing does not tolerate non-governmental organisations which could harass the authorities. But an environmental movement is growing.
A start has also been made in the capital to improve the atmosphere. Beijing last week began issuing daily rather than weekly air-quality reports to demonstrate the city's resolve.
One can already see some of the changes on the streets. Roadside food-vendors have begun using gas cylinders instead of braziers which burn low-grade coal. The dangerous little "bread-loaf" taxis which belch smoke have been banned from city-centre streets. Dozens were ceremonially dumped into a furnace at the Capital Iron and Steel Works some weeks ago and smelted down. Petrol is now largely lead-free. Police stop cars and take the registration plates of those who fail emission tests.
The aim is to make Beijing a model city, like Dalian, a coastal metropolis which has banned factories to the outskirts, introduced electric trams and planted millions of trees. Dalian is proof that it is possible to breathe clean air in a Chinese city, and that not everywhere is like Lanzhou or Beijing.