Air quality data collected by the Otago Regional Council for the winter months May through to August reveal a lower number of high-pollution days, while separate pollution data showed complaints numbers declined 12.3%, to 170 incidents recorded this winter.
Council compliance manager Tami Sargeant said the most common air complaints related to smoky chimneys and outdoor burning/fires.
The council’s pollution hotline recorded 170 air complaints between May and August, compared with 194 complaints for the same period a year ago — a 12.3 % decline.
"Compliance action has included sending out educational letters to alleged offenders in relation to domestic chimney and outdoor burning complaints, as well as issuing one abatement notice and six infringement notices for alleged breaches of the air plan," she said.
The abatement notice and one of the six infringements was in relation to air discharge consent non-compliance, while the other five infringements were related to outdoor burning/ fires.
Complaint numbers lodged with the ORC were much higher than the number of incidents as some incidents prompted multiple calls, she said.
Council air quality scientist Sarah Harrison has been looking at the number of high-pollution days, when there were exceedances of the national environmental standards for air quality for particulate matter (PM10), emitted by solid-fuel burners for home heating.
"This winter had fewer exceedances than last year, but temperature trends over recent years have been warmer winters than average," she said.
It was difficult to infer pollution trends winter on winter as the number of exceedances could vary depending on how harsh a winter was, and how often calm weather conditions occurred, allowing pollution to accumulate.
Otago has several towns, including Alexandra, Arrowtown, Clyde, Cromwell and Milton, where air quality is considered degraded during winter and the council is required to monitor and improve air quality where necessary.
Ms Harrison said the main pollutant of concern in Otago was particulate matter, a product of combustion, produced by emissions from solid fuel burners during winter.
PM10 is any solid or liquid particle with a diameter of less than 10 micrometres and PM2.5 is particulate matter of less than 2.5 micrometres.
Short-term and long-term exposure to particulate matter can contribute to health dangers.
Ms Harrison said there was no PM10 data for Milton, Cromwell or Clyde this year, because the ORC was switching monitoring to PM2.5.
New instruments had been installed in Arrowtown, Clyde, Cromwell and Milton that monitored PM2.5 and the data was still being analysed.
"It is important we understand how the new instruments relate to the existing ones, so that we can provide accurate data and, ideally, be able to infer long-term trends," she said.
Collecting PM2.5 data was a more direct way of measuring emissions from combustion sources, Ms Harrison said.
Particulate matter from combustion sources is very fine, and falls into the PM2.5 category, whereas PM10 has other sources such as dust, pollen and sea salt.
National environmental standards had proposed introducing a limit of PM2.5, so it was good to be collecting data in preparation for this, she said.
Pollution
Number of times PM10 levels have been exceeded.
Winter 2022 Winter 2021
Alexandra 4 3
Arrowtown 10 23
Dunedin 0 1
Mosgiel 1 4
Staff Reporter
