Highways have been closed and flights grounded as parts of China remain blanketed by smog.
Several cities in China remain blanketed in smog and fog, obscuring visibility to as low as 50 metres in some places.
A car pile-up involving 20 vehicles occurred in Shandong province, northeastern China, after poor visibility combined with sub-zero temperatures and slippery roads caused drivers to lose control.
Hundreds of flights were cancelled and highways closed, and classes at schools were also cancelled.
Citizens donned face masks in an effort to shield themselves from PM2.5 - miniscule particles in the air which can cause damage when inhaled over a long-term.
This week the concentration of dangerous breathable particles in Beijing's air reached levels of about 500. The World Health Organisation’s recommendation for healthy air is 25.
China's National Meteorological Center continued to issue an orange alert for smog, the second highest tier alert, and downgraded an alert for fog from red to yellow at 6 am in parts of central and eastern China, including the capital Beijing.
Soaring energy demand during winter, specifically from burning coal, is being blamed for the haze.
The government has scrambled to to cut emissions and intensify regulations in what it sees as its third year in a war against pollution.
On Thursday, China’s energy agency announced it would invest 2.5 trillion yuan, almost $500 billion dollars, into renewable power generation by 2020 in an effort shift away from dirty coal power towards cleaner fuels.