Air quality data show signs of decline

Long-term improvements in air quality appear to be going into reverse, according to official data.1 Environment Minister Ben Bradshaw says that more needs to be done to secure improvements - but his call looks hollow alongside weaknesses in the revision of the air quality strategy.

The number of days of poor air quality nearly doubled in urban areas during 2006, largely because of increased levels of particulate matter (PM10) and ozone - air pollutants which pose the most significant threat to human health.

Provisional data for 2006 show 41 days of ‘moderate’ or worse air quality in urban areas, up from 22 the year before. In rural areas the number increased from 40 to 57.

Background levels of PM10 in urban areas increased from 22 to 24 micrograms per cubic metre. Although the trend has been decreasing since 1993, it has levelled off in recent years. During 2006, roadside levels also rose from 29 to 35µg/m3 (see figure).

Ozone levels increased from 57 to 61µg/m3 in towns and from 70 to 74µg/m3 in the countryside. Urban background levels have shown an increasing trend since 1993.

Evidence is growing that there is no safe exposure level to particulates, especially ultra-fine particles (PM2.5). Recent research has linked PM2.5 to increased mortality risk - findings given added weight by the rise in popularity of diesel cars. Diesels are more fuel efficient than petrol but emit more particulates (see pp 28-29).

Ozone is generated by nitrogen oxides and volatile organic compounds from transport and industrial sources reacting with sunlight. In hot summers, like 2003 and 2006, ozone can form photochemical smog which can affect breathing. In contrast to other pollutants, ozone levels are predicted to increase over the next decade, in part because of rising background levels in Europe.

The results show the UK is continuing to fail to meet air quality objectives for PM10 and nitrogen dioxide in major urban areas, and has not met the ozone or carbon monoxide objective in some areas. The findings are due to be confirmed in April.

Mr Bradshaw said: "The latest air pollution data show mixed results, in part due to the heatwave that Europe experienced last July, which helped to produce high levels of ozone. Such heatwaves are predicted to become more common because of climate change."

In January, the Royal Society announced a study into the links between ozone and climate change (see p 29 ).

Mr Bradshaw’s vague call for action sits awkwardly alongside proposals to revise the UK air quality strategy. The plans, produced by the Environment Department (DEFRA) last summer, were criticised for lacking ambition by the National Society for Clean Air (ENDS Report 378, pp 44-45 ).

NSCA policy officer Ed Dearnley said: "The new figures indicate that the improvements in air quality we’ve seen since 1993 have bottomed out and may in fact be reversing. With climate change increasingly leading the environmental agenda, we have to remember that air quality is still a significant health issue in many parts of the country, and that policy decisions should be used to produce benefits in both areas."

DEFRA was expected to publish the revised strategy in the new year, but it has been delayed until spring.

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