Mosgiel air pollution exceeded the national limit four times
last month, according to information form the Otago Regional
The council has been monitoring PM10 (particulate matter in
the air smaller than 10 micrometers in diameter) levels
continuously in Mosgiel since 2006. National Environmental
Standards set the air quality threshold at a concentration of
505 micrograms per cubic metre.
The PM10 level in Mosgiel exceeded this threshold four times
last month. One day a year over this threshold is permitted.
ORC engineering, hazards and science director Gavin Palmer
said Mosgiel usually exceeded the standard between four and
nine times per year. The goal was to reduce this to once a
year by 2020.
The high PM10 levels came from emissions from domestic
solid-fuel burners, industry, and occasionally outdoor
burn-offs, he said.
''On June 24 [last Tuesday week], Mosgiel recorded 1085mcg/cu
m, a very high result for the day. Our monitors do take
readings every hour and on that day, PM10 was high (over
505mcg/cu m) every hour from 6am through the end of the day.
This would seem to indicate that there may have been a
burn-off occurring. However, no complaints were received
about the event,'' he said.
Typically, winter had the highest PM10 levels due to
increased emissions from domestic burners.
PM10 concentrations were also highly dependent on the weather
and colder, calmer weather often created conditions that
limited dispersion of smoke.
The council monitored PM10 in nine towns around Otago and
Mosgiel had neither the best nor the worst air quality.
Alexandra, Milton, and Cromwell all had worse air quality in
winter. Mosgiel skies often appeared hazy but this was not
always due to smog.
Occasionally, true ''fogs'' (consisting of harmless water
droplets) covered Mosgiel and much of the Taieri Plain, Mr
Under the Otago regional plan, all newly installed domestic
solid fuel burners within the Mosgiel air zone boundary had
meet emission standardsThe council had been operating the
Clean Heat/Clean Air scheme since 2007, which provided
subsidies for people to upgrade burners and insulate.
- Jonathan Chilton-Towle