Timaru's air pollution is the worst in Oceania according to the latest urban air quality database.
And it exceeds World Health Organisation (WHO) safety levels on both counts.
The WHO records both small and fine particulate matter (PM10 and PM2.5 respectively), pollutants which pose risks to human health.
Timaru's annual mean levels of small and fine particles are both above the safe air pollution level set by the WHO.
The World Health Organisation recommends a PM10 level of 20 micrograms per cubic metre and PM2.5 of 10 micrograms per cubic metre.
Timaru measured annual mean levels of 28µg/m3 and 15µg/m3 in 2012, ahead of all major cities in New Zealand and Australia.
Invercargill, Gore, Alexandra, Christchurch and Ashuburton also exceeded the recommended level, while Auckland and Wellington fell well below.
But there are signs of improvement in Timaru, while PM2.5 levels remained the same last year, PM10 levels were down to 26µg/m3.
In Christchurch PM10 levels remained the same in 2015 while PM2.5 levels increased to 12µg/m3, taking it above WHO recommended levels.
According to the WHO more than 80 percent of people living in urban areas that monitor air pollution are exposed to air quality levels that exceed WHO limits.
Levels of fine air pollutants were highest in India, while China has improved its air quality since 2011.
The highest mean annual PH10 level was recorded by Onitsha in Nigeria, 594µg/m3 , while Zabol in Iran recorded the highest mean annual PH2.5 level, 217µg/m3.