It is hoped Dunedin's good air quality record this winter
will be retained even though the city's air exceeded the
National Environmental Standard once.
On Saturday, July 27, the central Dunedin air quality station
recorded 56mcg of airborne pollutants per cubic metres of
Under the national PM10 (very small particle) standard, only
one reading above 50mcg is allowed per year.
Apart from that one high reading, Dunedin's air quality
recordings had been below 50mcg throughout winter.
Environmental information and science director John Threlfall
said at a committee meeting yesterday an investigation into
the cause of the high reading led to the discovery there had
been an equipment failure at a nearby industry's boiler,
which led to a ''stream of pollutants'' leaving a stack
without being filtered.
The company closed the operation until the problem was
As a result of the investigation and with additional evidence
on wind speed and direction, the council was applying to the
Ministry for the Environment for an ''exceptional
If this was granted, it meant the exceedance would not be
included in the total for the year.
''While, with only one failure, we still meet the NES, it
would be nice to have a zero.''
If the request is accepted, it would be the second time since
testing began in Dunedin no exceedances of the national
standard had been recorded.
Under the standard, a site had to comply with the standard
for five years before its considered not a polluted airshed,
It was an area more affected by industrial emissions than
home heating and under World Health Organisation guidelines,
Dunedin had been beneath the ambient standard of 20mcg in
2012 and 2013.