People across much of northern China were warned to stay indoors yesterday to avoid air polllution that, in the Beijing area area at least, was among the worst for a decade.
Thick smog that has blanketed a dozen provinces in the north, cente and east in recent weeks intensified, with environmental advocates describing it as the worst they could recall.
In Beijing, pollution readings by the local environmental watchdog, as well as the US embassy, blew past the upper limit of "hazardous" early yesterday afternoon and stayed there for the rest of the day.
US embassy pollution data published hourly on Twitter showed the level of health-threatening PM2.5 - or particles smaller than 2.5 microns - had reached 886 micrograms per cubic metre at 8pm. Its Air Quality Index, which includes PM2.5 and ozone, had surged past the maximum rating of 500 to 755, or "beyond index".
With no wind forecast to bring more favourable conditions in the next three days, experts said the worst may be yet to come.
"It's so awful that I find it really difficult to breathe," said Zhou Rong , a Greenpeace campaigner in Beijing. "It's the most polluted day I can remember."
The Beijing Municipal Environmental Protection Bureau said its own figures showed PM2.5 levels had exceeded 700 micrograms per cubic metre since early afternoon. That pushed the Air Quality Index to its maximum of 500 for the first time since real-time air pollution updates began on New Year's Day.
Under the mainland's newly revised standards, a level above 200 is considered heavy pollution and unhealthy to those with lung or heart diseases. Readings above 300 are deemed "hazardous for the entire population".
State television and local media warned people to avoid going outdoors as much as possible, quoting forecasts that suggest winds will not arrive to clear the choking smog until Tuesday.
Beijing Children's Hospital said heavy pollution was largely to blame for the number of children being treated for respiratory ailments hitting a five-year high in the past week, with more than 7,000 patients a day.
Exacerbated by heavy fog, pollution in Chengdu , Jinan , Wuhan , Xian , Zhengzhou and many other cities has worsened significantly in recent days. Visibility fell to less than 50 metres in many areas, forcing the closure of dozens of highways and the cancellation of dozens of flights.