Northern China on health alert as smog worsens

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."