Otago Regional Council (ORC) has found there were 21 breaches of national air quality standards this winter.

This is four more than last year, but fewer than the average 33 of exceedances between 2018 and 2021.

“These winter exceedances are due to a combination of emissions and the environment they are emitted into,” ORC air quality scientist Sarah Harrison said.

“These emissions are mostly from wood burners for home heating. We know this because of the extreme seasonal patterns we see in the data.”

The breaches took place in Alexandra (three), Arrowtown (14), and Mosgiel (four).

“So far this year, June has been the worst month for exceedances due to region-wide cold snaps,” Sarah said.

Air quality is evaluated against National Environmental Standards for Air Quality (NESAQ), which requires ORC to measure particulate matter (PM) emitted into the air with a diameter of 10 micrometres or less (PM10), and its limit for 24-hour PM 10 is 50 micrograms per cubic metre of air.

“Year on year, PM concentrations vary,” Sarah said. “Many of the towns in Otago have the geography and climate that allows pollution to build up, rather than disperse.”

“Low temperatures and windspeeds sometimes cause inversion layers to form, which traps pollution at ground level.”

ORC continually monitors air quality and often conducts further research in other parts of Otago that helps determine where PM hotspots are and how these concentrations could be reduced, Sarah said.

“An increase in air quality studies, monitoring sites, and upgrades of instruments are all part of a move to better monitor the finer PM2.5 and focus on combustion-related sources of particulate matter.”

There are a number of things residents can do to help reduce the levels of PM, including replacing older wood burners, open fires, and multi-fuel burners with ultra-low emission burners, or better yet, looking into alternative heating such as pellet burners or heat pumps, Sarah said.

Find more tips on the ORC’s ‘Burn Dry, Breathe Easy’ webpage.

PHOTO: Steve McArthur