Yellow alert for air pollution

A yellow alert for heavy air pollution, the third highest in a four-tier system, was issued at 7pm on Tuesday by the city's environmental authorities, warning of an air quality index between 201 and 300 in the next 24 hours.

The main pollutant is PM2.5 particles, and the air was slightly polluted on Tuesday night.

The current wave of pollution is blown by a cold front from the north, and stable weather conditions worsen the situation, the Shanghai Environmental Monitoring Center said. 

Children, the elderly and people with heart or lung disease or any other chronic diseases are encouraged to stay indoors and cease outdoor activities. Others should reduce outdoor activities and avoid opening windows. 

Schools and kindergartens should suspend physical education classes and outdoor activities. 

Petrol, steel, chemical, cement, shipping and printing industries should take measures to cut the discharge of pollutants. 

The air quality is expected to improve on Thursday and Friday, reaching the good level, according to the center.