Birmingham’s clean air zone (CAZ) has been less effective at reducing the levels of nitrogen dioxide gas (NO2) than was previously thought, new research suggests.
However, new research by scientists at the University of Birmingham has found that it has resulted in ‘modest, but significant’ reductions in NO2 of up to 7.3%.
The researchers used an innovative measuring technique that cuts out the impact on pollution of weather and seasonal effects.
The CAZ also has no detectable impact on the concentrations of fine particles, PM2.5 – the air pollutant with greatest health effects.
Professor Zongbo Shi, a senior author who oversaw the work, said: ‘PM2.5 at monitoring sites in Birmingham still regularly exceed WHO [World Health Organisation] air quality guideline levels, at which health impacts occur with significant health implications, including hundreds of premature deaths every year.
‘More rigorous policy interventions – such as further local measures to reduce wood burning and agricultural emissions and nationally co-ordinated actions to mitigate secondary PM2.5 pollution – are needed to address non-vehicle sources of PM2.5 as quickly as possible.’
A spokesperson for Birmingham City Council said: ‘What is clear from this modelling is that the introduction of the clean air zone led to an overall reduction in the levels of the air pollutant nitrogen dioxide. This modelling also supports our own analysis that the clean air zone has contributed to an overall reduction in the levels of nitrogen dioxide outside of the city centre.
‘However, since the period covered by this modelling, the overall percentage of the most polluting vehicles entering the clean air zone has continued to reduce and we expect there to be further reductions in the levels of nitrogen dioxide.’
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