Worsening air quality in Auckland's central city underlines the need for more pedestrian-only areas, says the city's top health official.

Auckland Regional Public Health Service (ARPHS) Medical Officer Dr David Sinclair said new council research showing rising levels of black carbon in Queen St was concerning. It comes after a decade of falling air pollution levels in the downtown area.

Sinclair said many people did not notice poor air quality but it could have long-term health effects, including respiratory illness, heart attacks, lung cancer, strokes and diabetes. The tall buildings along several busy central streets meant air pollutants were trapped in these "urban canyons", he said.

The regional public health service had long supported changes which would lift air quality in the central city, in particular upgrading diesel fuel, improving emissions from all vehicles and increasing public transport, walking and biking.

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Sinclair noted that pedestrianised areas or shared spaces like High St had better air quality, and the ARPHS backed Auckland Council moves to create more spaces for walking instead of cars. There had been an increase in the number of cities around the world which banned or limited car use in main centres, and this had led to reduced air pollution.

"Making cycling and walking more attractive for Aucklanders is imperative if we are to improve air quality and reduce the risk of chronic disease in our population," Sinclair said.

"Greater patronage on public transport, provided the vehicle fleet is up to scratch, will also reduce air pollution."

Other contributors to rising air pollution in the central city were the low quality fuel used by international ships at Auckland's port, New Zealand's relatively old vehicle fleet, and poor maintenance of diesel vehicles. But a lack of vehicle emissions standards meant it was difficult to improve air quality, Sinclair said.

The council's research found that on Queen St, the major source of the black carbon was higher diesel emissions from older buses, trucks, ferries and ships.

Black carbon emissions were more than three times higher than Canadian cities and twice as high for concentrations in major European, UK and American cities, according to an article published by Auckland Council's research and evaluation unit.

Black carbon, also known as soot, consists of very small ultra-fine carbon particles not much larger than viruses. These can travel deep into lung tissue, into the bloodstream and become deposited in the heart.