A study by the Natural Environment Research Council has revealed that European policies aimed at tackling air pollution are having a marked effect on the UK’s atmosphere and environment, but warned that much more needs to be done globally to curtail pollution.

According to the Review of Transboundary Air Pollution (RoTAP), conducted by the Centre for Ecology and Hydrology on behalf of the NERC, sulphur emissions and concentrations have greatly declined, having fallen 90 per cent since their peak in the middle of the last century, acid rain no longer poses the problems it once did and soils and freshwaters are slowly becoming healthier.

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However, although some of the report’s findings are encouraging, the assessment team found that background ozone concentrations have grown by about 15 per cent. Although ground level ozone concentrations have dropped by 30 per cent as a result of controls on chemicals that lead to ozone production in Europe, the researchers said overall ozone levels have risen due to increases in precursor emissions elsewhere in the Northern Hemisphere.

The findings are particularly worrying for farmers and environmentalists, as ozone presents a serious threat to crops and natural vegetation. In January, a team of researchers from the Universities of Leeds and York revealed ozone pollution originating in North America is costing Europe 1.2 million tonnes of wheat annually. This damage is the most significant intercontinental ozone-related impact on any food crop the researchers measured.

In the UK, the wheat yield was cut 7 per cent due to ozone pollution in 2000, researchers from the CEH revealed. Professor Martin Williams, from King's College London, who contributed to RoTAP commented, "A steady growth in background ozone as a consequence of ozone precursor emissions throughout the northern hemisphere have eroded these benefits and as a result ground level ozone remains a threat. Ozone will only be mitigated effectively through hemispheric scale controls, which are now an urgent priority."

The NERC study, which highlights the threat posed by high levels of ozone, is particularly pertinent in that it coincides with the Rio+20 Summit currently being held in Rio de Janeiro, at which world leaders are expected to make commitments to tackling pollution and addressing the issues of climate change and poverty.

No change in nitrogen levels

The NERC review also found little change in nitrogen levels in the atmosphere over the past 20 years. Despite large reductions in emissions of nitric oxide and nitrogen dioxide (NOx), the UK has not benefitted from a reduction because, as with ozone pollution, NOx produced in other global regions may be affecting the UK’s atmosphere and emissions of ammonia, another major contributor to nitrogen deposition have not been reduced. The researchers said the levels of nitrogen in the atmosphere could affect the UK’s biodiversity.

Furthermore, the report revealed that “The amount of metals deposited in the UK from the atmosphere greatly exceeds the amount of metals reported to be emitted from anthropogenic [created by human activity] sources by up to a factor of 10.” The researchers said they do not know where the metal being deposited in the UK is coming from.

Professor David Fowler from the NERC Centre for Ecology & Hydrology chaired the RoTAP Review. He summed up the report’s findings, "We found that the policies to control acidification in the UK have been a considerable success, mainly due to the very large reduction in sulphur emissions from combustion gases. Ecosystems are recovering as a consequence of these controls. However, policies to control eutrophication by nitrogen compounds have been less effective, mainly because emissions of a major contributor to nitrogen deposition - ammonia - have not been significantly reduced, and remain a priority for control measures."

60 scientists and researchers contributed to the review over three years. It forms the most detailed analysis of the UK’s chemical climate since 2001.

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