UPDATED 6.56pm Figures from the World Health Organisation show Timaru has the highest air pollution levels in Oceania.

Last year the city recorded 26 high pollution nights,10 more than Christchurch.

LISTEN ABOVE: David Bedford, Environment Canterbury Commissioner, talks to Larry Williams

But Environment Canterbury air spokesperson Katherine Trought said it's still a sharp decrease on the year before when there were 41 high-pollution nights.

"We're really thrilled with the response the community has had to this better burning message, and it's coming through reduction and the concentrations of air pollution."

WHO compared close to 800 cities in 67 countries for levels of small and fine particulate matter called PM10 and PM2.5.

Guidelines state that levels of 10 and 20 micrograms per cubic metre respectively are considered safe.

But in Timaru the annual mean level of PM2.5 was 15 micrograms per cubic metre, and 28 micrograms per cubic metre fro PM10.

Ms Trought said much of that comes down to domestic fires, which people could be burning better.

"Install better burning devices, better wood burners, because we know more modern wood burners are less polluting and the better people can light their fires and run a really hot fire, the less smoke comes out their chimney."

South Canterbury Medical Officer of Health Daniel Williams said around 40 premature deaths in Timaru can be put down to air pollution every year.

"And that between 25 and 30 thousand people had restricted activity days where because of the health effects of their pollution, they weren't able to do work or their other usual activities."

Invercargill was the next most polluted town, followed by Alexandra. 

Christchurch is the worst of New Zealand's major cities with Wellington and Auckland's air found to be much cleaner.