Air Quality - Environmental Audit Committee Contents

1 Introduction

Types of pollution

1.  Air quality in the UK has improved over recent decades but improvements are now levelling off and are increasingly costly to achieve. A major air quality problem is being caused by three key pollutants where the UK is failing to meet domestic and European targets: nitrogen oxides (NOX), ozone and particulate matter (PM).

  • Nitrogen oxides (NOX) encompasses two gases—nitrogen oxide (NO) and nitrogen dioxide (NO2). NO reacts with other chemicals in the air to form NO2, which is itself involved in the formation of particulate matter.
  • Ozone is a pollutant in the lower atmosphere. It is not emitted directly from any man-made source but is formed from chemical reactions between various air pollutants, primarily nitrogen oxides and volatile organic compounds.
  • Particulate matter (PM) is made up of tiny particles from a variety of materials, including sulphates, nitrates, ammonia, sodium chloride, carbon, mineral dust, and water. Particulate matter is categorised by particle size, as either smaller than 10 microns in diameter (PM10) or smaller than 2.5 microns (PM2.5).

Sources of pollution

2.  Industry and road transport are the main sources of air pollution, though domestic combustion and agriculture are also to blame. Industry is a major source of emissions of NOX (46%) and PM10 (36%). Road transport contributes to significant emissions of NO2 (30%) and PM10 (18%). Emissions and exposure vary greatly depending on location. Although polluting, the majority of large combustion plants are located away from major urban centres. Road transport contributes far more to the public's exposure to pollutants and is responsible for up to 70% of air pollution in urban areas.


3.  European and national air quality legislation is designed to reduce risks to human health and the environment. National emission ceilings are legally-binding, annual, total emission caps set under the EU National Emission Ceilings Directive. Ceilings for each Member State have been set for NOX emissions. EU limit values are legally-binding, maximum parameters for concentrations of pollutants over specified time periods. These are set by the Air Quality Framework Directive and four daughter directives for pollutants including NO2, PM10, PM2.5. EU target values are set out in the same way as limit values, but are not legally binding. A target value is set for ozone.

4.  The Environment Act 1995 sets national objectives for NO2, ozone, and particulate matter that are the same as, or in some cases more prescriptive, than corresponding EU limit values. Air quality objectives are defined in the latest Air Quality Strategy for England, Scotland, Wales and Northern Ireland, published in July 2007. Environment is a devolved matter and for some pollutants objectives are set by the administrations in Northern Ireland, Scotland and Wales.

Our inquiry

5.  In our inquiry we set out to assess whether the Government was developing an effective strategy for meeting its obligations under the EU air quality directives and whether the strategy would ensure that air pollution was reduced to acceptable levels across the UK. In preparation for its inquiry, the Committee commissioned a briefing on air quality from the National Audit Office to provide an overview of the UK's performance to date in meeting the various targets and limits for each air pollutant.[1] The Committee would like to thank all those who gave evidence.[2] We note with sadness the passing of Dr Ian McCrae who provided a valuable contribution in this field and who appeared before the Committee shortly before he died. We are indebted to Professor Mike Pilling, our Specialist Adviser, for all his invaluable advice.[3]

1   NAO, Air Quality, January 2010 Back

2   A list of all those who gave evidence can be found on pages 25 and 26. Back

3   Professor M J Pilling declared an interest on 2 February 2010, that his son works with the Low Emissions Strategies Partnership, who submitted written evidence to the Committee (Ev 84). Back

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Prepared 22 March 2010