Air pollution in the Chinese capital Beijing has reached levels judged as hazardous to human health.Readings from both official and unofficial monitoring stations suggested that Saturday's pollution has soared past danger levels outlined by the World Health Organization (WHO).
The air tastes of coal dust and car fumes, two of the main sources of pollution, says a BBC correspondent.
WHO guidelines say average concentrations of the tiniest pollution particles - called PM2.5 - should be no more than 25 microgrammes per cubic metre.
Air is unhealthy above 100 microgrammes. At 300, all children and elderly people should remain indoors.
Official Beijing city readings on Saturday suggested pollution levels over 400. Unofficial reading from a monitor at the US embassy recorded 800.