An unseasonal day of high air pollution in Christchurch has authorities scratching their heads to figure out the cause. The Garden City recorded its seventh high air pollution day of the year on Wednesday. Environment Canterbury air quality science team leader Tim Mallett said it was an unusual time of year for high air pollution. A high air pollution day is one that averages 50 or more micrograms of particulate (bits of pollution smaller than 10 millionths of a metre) per cubic metre of air over the whole day. Christchurch's other high air pollution nights this year were June 28, July 1, 7 and 28, and August 7 and 8.

Source: Stuff November 28, 2019 06:11 UTC