By Cai Wenjun | 2012-6-12 | NEWSPAPER EDITION
A MYSTERIOUS yellow fog enveloped Wuhan City with a smoky smell yesterday, leading to rumors there had been a major fire, a chemical leak or a factory explosion.
Instead, it was the burning of straw in neighboring provinces that was the major cause of the yellowish, foggy sky in the city in central Hubei Province, according to local government officials who issued an emergency notice to dispel rumors.
In Wuhan, rumors began to spread online yesterday saying many residents felt sick and had started to show symptoms of poisoning.
Hubei authorities said the haze started to cover cities in the province from northwest to southeast starting at about 2am. Wuhan suffered the most serious pollution.
The city's PM10 and PM2.5 readings started to rise quickly at 7am and reached a peak between 2pm and 3pm. PM10 density reached 574 micrograms per cubic meter and PM2.5 density reached 610 micrograms per cubic meter.
PM2.5 are particles 2.5 micrometers or less in diameter.
The nation's maximum allowable daily reading of PM10 is 150 micrograms per cubic meter and, for PM2.5, 75 micrograms per cubic meter.
Wuhan Environmental Protection Bureau said the local meteorological bureau issued a yellow alert at 10:17am yesterday for haze aggravated by little wind and high humidity.
The bureau said that straw burning in the provinces of Anhui and Hebei was the main source of the smog.