Downtown Auckland appears to be serving as a basin for air pollution, including high levels of potentially deadly black carbon.
While air pollution rates have been falling in the city for the past decades, new research indicates this trend has reversed, with black carbon levels three times higher than Canadian cities and twice as high as major North American, European and United Kingdom centres.
The Auckland Council research report found Queen St in central Auckland had the highest levels of black carbons in the country, as well as nitrogen oxide levels that sometimes exceed regional and global guidelines.
Millions of premature deaths around the world have been linked to black carbon, which produces ultra-fine soot particles that can travel deep into lung tissue, into the bloodstream and then to the heart and brain.
According to the report, traffic volumes have been declining in the central city, leading scientists to believe the rise in black carbon levels must be down to other factors - most likely old diesel engines.
The increasing number of tall buildings in Auckland's CBD also reduce air flow, allowing air pollutant concentrations to increase close to the ground.
The report found that pollution emitted further up Queen St might be flowing downtown towards the waterfront.
Heart of the City chief executive Viv Beck hoped the new figures would serve as a catalyst for change.
"I think it's very important that we get under the skin of it very quickly," she said.
Auckland Transport is also introducing more electric buses to its fleet.
Last month, the Ministry for the Environment and Statistics New Zealand released its latest report in the environmental reporting series. That report showed there was an improvement with levels of some pollutants declining, however there were persistent problems such as heat sources.
It found emissions from vehicles were a major contributor of poorer quality air from exhausts, but also through the wearing and abrasion of pavement, tyres and brake pads.