After days of worsening visibility on the capital's streets, the U.S. Embassy reported early Tuesday morning that the level of pollution was "beyond index." Since Saturday, it has reported hourly pollution levels as hazardous to human health.
The Beijing Municipal Environmental Monitoring Center says pollution across Beijing is severe and expected to persist because there is little wind to disperse pollutants. It advises city residents to stay indoors as much as possible.
According to U.S. Embassy readings, PM2.5 particles among the worst pollutants reached levels more than 18 times what the World Health Organization considers safe.
Beijing experienced another especially bad round of air pollution two weeks ago.