Shanghai's density of PM2.5 pollutants jumped this morning to 183.9 micrograms per cubic meter around noon, the Shanghai Environmental Monitoring Center reported.

The city's PM2.5 readings remained below 40 micrograms per cubic meter between yesterday afternoon and 8am this morning, but the foggy weather caused the PM2.5 figure to shoot up afterwards.

Readings collected at two monitoring stations in downtown Hongkou and Yangpu districts exceeded 200 micrograms at noon, the center said. The city currently has ten PM2.5 monitoring stations.

PM2.5 stands for airborne particles smaller than 2.5 micrometers, which mainly come from automobile emissions and smoke from power plants and factories. They are the main cause of urban smog and haze and are harmful to human health.