BEIJING (January 12, 2013)--The air in China's notoriously dirty capital was so polluted Saturday that people are being warned to stay indoors and local authorities say it could last into Tuesday.
The Beijing Municipal Environmental Monitoring Center has reported air-quality indexes between 176 and 442 since Friday.
The index indicates the level of airborne PM 2.5 particulates, which are considered the most harmful to health.
The air is considered good when the index is at 50 or less.
A warning scrolled across the monitoring center's website says that the density of PM 2.5 had reached 700 micrograms per cubic meter in many parts of Beijing.
Monitors at the U.S. Embassy recorded an off-the-chart reading of 728. Readings differ in different parts of Beijing.
According to rules issued in December, all outdoor sports activities are to stop and factories have to reduce production if the index exceeds 500.