AIR quality in Stoke-on-Trent is steadily improving – despite greater numbers of cars using the city's roads.

Latest figures show developments such as Tunstall's Northern Bypass have helped cut air pollution in areas previously blighted by traffic.

But local air monitoring tests have flagged up worrying levels of pollution in several growing traffic hotspots.

Figures for 2009 reveal two sites in Basford experienced record levels of nitrogen dioxide pollution.

The readings, in the Basford Bank area, are believed to have been caused by vehicles sitting in traffic jams with their engines idling.

The highest showed an average annual concentration of 85.5 micrograms of nitrogen dioxide per cubic metre, compared to a target of below 40.

However, the report says the levels do not pose a serious health risk to residents, because it is unlikely people would be exposed to the pollution for long periods of time.

Parts of Meir, near to the A50, and busy roads in Burslem and Middleport also saw increased levels of traffic-related pollution last year.

The total number of sites across the city which exceeded the 40 micrograms target was 34, compared to 31 in 2008, when there were six fewer sites being monitored.

But the data shows a marked drop in pollution in St Michael's Road, Tunstall, following the July 2008 opening of the Tunstall Northern Bypass.

One sensor in the street recorded 31.5 micrograms, compared to 42.2 the previous year, while the other measured 33.6, down from 43.9.

Derek Smith, Stoke-on-Trent City Council principal environmental protection officer, said the figures showed new traffic initiatives were making a difference, but he admitted more work was needed to address problem areas.

Mr Smith said: "In Burslem, we have plans for road schemes and a bypass to try to generate more traffic movement to improve the situation."

Councillor Joy Garner, licensing and consumer protection committee vice-chairman, welcomed the improved readings around Tunstall, but said the new bypass had created other congestion problems which need monitoring.

She said: "St Michael's Road is almost devoid of traffic now because of the bypass, but at the top of the road the traffic flow is almost stalled.

"The air there must be getting atrocious."

Lucy Windsor, aged 29, of Etruria Road, close to Basford Bank, said: "The road is busy throughout the day.

"If you are outside you do start to notice the fumes after a while, but it's not something you give much thought to."

Peter Williams, aged 38, of Basford Park Road, off Etruria Road, said: "If they're saying it doesn't pose any health risks then I don't think there's anything to be worried about."