The council has also released its Annual Air Quality Report for 2024, highlighting monitoring technology and community engagement in "Otago’s commitment to cleaner air and healthier communities".
Milton was among several towns in Otago where air quality was considered degraded during winter, along with Alexandra, Arrowtown, Clyde, Cromwell and Mosgiel.
The report included data from seven locations monitoring fine air particulate matter (PM) with a diameter of less than 2.5 micrometres (PM2.5), which posed greater health risks to communities.
Otago recorded 28 exceedances of the National Environmental Standards for Air Quality for PM10 during the winter months in 2024, compared with 17 exceedances in winter 2023.
While those areas still faced winter air quality exceedances, the annual report also showed more than 70% of days at monitored sites were classified as "good" under environmental performance indicators.
Long-term exposure to PM2.5 and PM10 contribute to the risks of cardiovascular and respiratory conditions.
The main source of PM in Otago came from home-heating emissions in winter.
"Monitoring smaller sizes of particulate matter (PM2.5) is a significant step forward," the council’s air quality scientist Sarah Harrison said.
"These smaller particles pose greater health risks ... we’re better equipped to inform policy and protect community wellbeing."
Towns including Milton have permanent air quality monitors, but the recent studies have been assisted with the council’s new mobile air quality trailer which can be quickly deployed to environmental events including wildfires or reports to the pollution hotline.
While winter emissions continue to be a challenge where home heating is the main source of particulate matter, Ms Harrison said the seasonal patterns proved the importance of raising awareness about cleaner burning for heat.
