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Otago Regional Council director of environmental science and information John Threlfall has released results of winter monitoring that show a big improvement for Dunedin.
The city only exceeded the limit of 50mcg per cubic metre of air once, on July 10 (71mcg).
Mr Threlfall said the good results for Dunedin were due to a combination of things.
He said improvements had been made to industrial emissions in the city, solid-fuel burners were being replaced with cleaner heating appliances, the construction of the Forsyth Barr Stadium was complete and there was a relatively frost-free winter.
July was by far the worst month for air quality in Dunedin. On July 10, air pollution peaked at 337mcg between 4am and 5am, contributing to the high reading for that day.
Towns are only allowed to exceed the standard once in a 12-month period to meet National Environmental Standards for air quality.
Mosgiel was not recorded in results this year because its measuring equipment was malfunctioning and the results were not considered reliable enough.
Number of days when air quality did not meet standard:
Dunedin ... 1
Alexandra ... 40
Arrowtown ... 24
Balclutha ... 13
Clyde ... 9
Cromwell ... 30
Lawrence ... 2
Milton ... 38