When the mercury drops, so does A’town’s air quality


Air quality in Arrowtown’s breaching national standards every time the temperature drops below freezing, new data shows.

Otago Regional Council’s monitoring station in the town recorded eight breaches so far this winter, of which six happened within one week when the mercury plummeted.

Air quality rules, set under the National Environmental Standards, allow up to an average of 50 micrograms per cubic metre of airborne particles over a 24-hour period.

On June 19, Arrowtown’s daily average was more than double that, peaking at 314mg in some hours.

Air quality scientist at the National Institute of Water and Atmospheric Research (Niwa), Ian Longley, says that’s “pretty damn high”.

“The figures are as bad as you will measure anywhere in Australasia and certainly higher than anything that gets measured in Auckland, for instance.”

Arrowtown is notorious for poor air quality during winter, when the town’s covered by a cloud of pollution caused by inefficient heating systems, such as outdated wood burners, and burning wet wood and coal.

Last year, the town breached national standards more than 30 times and, in 2017, it breached them 45 times.

This winter, Niwa’s installed 21 air monitors in residents’ homes and 22 in outside spots around the town as part of a project to better understand the pollution problem and people’s heating habits.

The data’s being used to work out whether poor air is the result of people throwing more wood on to the fire or if the smoke blanketing the valley isn’t dispersing because of cold, frigid air.

“It’s one or the other, or it’s a mixture of both, so we are spending the winter trying to figure it out because it’s important to understand as they imply different control measures.”