A market town has the region's highest levels of dangerous car-related air pollutants, according to a survey.

Air pollution checks at four sites in the region, carried out on behalf of the Chartered Society of Physiotherapy (CSoP), showed that Yarm, near Stocton, was narrowly ahead of Middlesbrough in terms of pollutants released by diesel engines.

While Yarm recorded the highest level of PM10 emissions in the region - 27 micrograms per cubic metres of air (mcg/m3) - it could not compare with the UK's most heavily polluted site, Marylebone Road, in London, with a concentration of 41 mcg/m3.

New CSP analysis of emissions of the highly toxic pollutant PM10 at 61 monitoring points across the UK for the first five months of this year reveal no significant drop in levels of this pollutant since readings were first published at the beginning of the year.

Elsewhere in the North-East, levels of PM10 at Middlesbrough rose by five micrograms to 26 mcg/m3 while the site at Redcar has risen to 24 mcg/m3.

Central Newcastle remained unchanged on 17 mcg/m3. Yarm was also unchanged during this period.

The CSP is calling on car manufacturers to follow the example of Mercedes and fit filters to diesel engines to reduce PM10 emissions.

Respiratory physicians say inhaling PM10 can cause breathing difficulties and there is no safe limit for exposure.

A spokesman for Stockton Borough Council said: "We are committed to regularly reviewing air quality in our area and produce daily bulletins and information on the council's website. The site chosen by the CSoP for Yarm is a roadside site, while the other sites are between 20m and 100m away from roadsides and this will have a significant effect on the readings. There has been a downward trend, year on year."