Otago's latest winter air quality report card shows the region's most polluted towns are still exceeding national standards, although some are showing a steady reduction over time.
All nine monitoring sites recorded at least one day with PM10 (very small particulates) levels above the 50mcg per cubic metre of air standard from January 1 to August 31, the Otago Regional Council's annual air quality report showed.
Of all the regional council-monitored towns, Balclutha had the best air quality, with 95% of winter days in the low pollution category, followed by Dunedin (72%) and Mosgiel (67%).
In Alexandra and Milton, there was good air quality on only a third of all winter days, the council report said.
However, this year Alexandra and Arrowtown, both considered to have among the worst air quality in the region, met the national standard of a steady reduction over time in air pollution levels.
They, along with Dunedin and Milton, had lower maximums this year than last.
Alexandra, Clyde, Cromwell and Milton experienced multiple days with PM10 levels greater than 100mcg per cubic metres, with Cromwell's 14 days the worst.
Cromwell also had the highest daily values and the second highest winter average (48mcg per cubic metre), the same as Alexandra.
Milton had the highest winter average of 49mcg per cubic metre.
Compared with last winter, all sites exceeded the standard more often, except for Balclutha, with half the sites (Balclutha, Clyde, Cromwell and Mosgiel) having higher maximums.
Environmental information and science director John Threlfall told the council's natural resources committee last week the council had been monitoring air long enough to possibly see some trends but there were none.
Arrowtown was showing obvious signs of improvement, with its values dropping but still exceeding the standard, he said.
"There appears to be some change that's not climatic-related."
Weather played a key role in air quality.
This winter's frequent high pressure systems meant clear skies and little wind and as a result colder minimum temperatures, causing high PM10 levels in Central Otago - in particular Cromwell.
Cr Trevor Kempton questioned whether the council could get the region to meet the standards by the deadline of 2013.
Cr Woodhead said progress depended on changing human behaviour and infrastructure, but the council needed to "stick with it".
Where there's smoke
Otago winter 2010
Town Days* Highest value
Alexandra 51 26
Arrowtown 39 101
Balclutha 2 76
Clyde 40 110
Cromwell 43 133
Dunedin 11 62
Lawrence 1 54
Milton 46 119
Mosgiel 8 105
*Number of days levels exceeded national standard(monitored only part winter)(due to forest fire)
