Has the Clean Air Act 1993 reached its expiry date? Rick Gould considers the evidence.

On 1 May this year, the UK’s Supreme Court ruled that the Government had not fulfilled the requirements of Article 13 of the Air Quality Directive (AQD) (2008/50/EC), which specifies limits and alert thresholds for ambient-air pollutants, in order to protect human health. The case against the Government, which was brought by the non-governmental organisation ClientEarth, paves the way for fines and enforcement action from the European Commission. This in turn would compel the Government to take firm action to deal with the many towns and cities where ambient air quality exceeds the limit values specified in the AQD, and where air quality is unlikely to improve enough to meet the limits set out in the directive, notably in Air Quality Management Areas. ClientEarth referred to 16 major cities and regions in the UK where air quality breaches legal limits and pointed out that 29,000 people are likely to die prematurely each year as a result of the effects of air pollution.

Meanwhile, the World Health Organization (WHO) has published the first results of the Review of Evidence on Health Aspects of Air Pollution (REVIHAAP project). The WHO is examining up-to-date scientific evidence for the impacts of air pollution on human health, and assessing the EU’s air-quality policies and legislation in the light of such results. The WHO was commissioned by the European Commission to conduct the review, which plans to use the findings to steer future EU air-quality policy and legislation. The WHO pointed out that the majority of people in the EU are exposed to detrimental levels of air pollution — resulting in a significant number of premature deaths and a reduction in the average human lifespan — and has recommended stricter thresholds for pollutants such as PM2.5 and nitrogen dioxide (NO2).

Against this background, the UK Government is considering whether to simplify or even scrap the Clean Air Act 1993 (CAA) as part of its Red Tape Challenge. So the Department for Environment, Food and Rural Affairs (Defra) commissioned AEA Technology (AEAT) to examine the potential impacts on air quality, if the Government repealed or modified this law. In March 2013, the Government published a summary (Assessment of the Effectiveness of Measures under the Clean Air Act 1993, AEA) outlining its progress in reviewing environmental laws under the Red Tape Challenge and the CAA, and stated that its intentions were to “identify which measures are redundant and which can be modernised to help local authorities meet EU air quality targets and help reduce costs for businesses”.

What the Act covers

The CCA was introduced following the lethal smogs of the 1950s, and the latest version of the CAA (which dates back to 1993) addresses significant sources of air pollution that are not covered by other laws, such as the Environmental Permitting Regulations 2010 (EPR) in England and Wales, and the Pollution Prevention and Control (PPC) Regulations of 2012, for Scotland and Northern Ireland. So the CAA deals with localised air pollution from sources such as residential fireplaces and small, non-residential furnaces, especially those that burn coal. According to AEAT, which examined current and projected national emissions from all sources, the activities regulated by the CAA are likely to contribute about 20% of the UK’s emissions of sulphur dioxide (SO2) and PM2.5, and about 15% of the UK’s emissions of NO2. AEAT determined these proportions against the background of the revised, national reduction targets for 2020 set within the revised Gothenburg Protocol, based on the likely premise that there would be no great changes in the proportions of emissions and their sources between now and 2020.

The CAA has led to several provisions to control air pollution, and these measures include: the control of dark smoke; the designation and enforcement of smoke control areas (SCAs); the approval of chimney heights for new, non-residential furnaces; the approval of abatement equipment for non-residential furnaces; and the prohibition of cable burning. The latter happens when people burn insulated cables to recover the increasingly valuable metals such as copper within them. This process of recovery may only take place in a controlled, permitted facility, while burning cables in an uncontrolled way can lead to significant emissions of dark smoke and highly toxic substances.

The CAA provides local authorities with the powers to prosecute people who burn cables. In 2012, for example, Leeds City Council successfully prosecuted three men for cable burning, after alert staff from the Environment Agency spotted and reported this illegal activity while on their way to work.

The potential for change

When examining the potential impacts of either simplifying or repealing the CAA, AEAT considered several different scenarios and various fuels such as gas, coal, petroleum coke and wood, and then compared these scenarios with the results of leaving the CCA in place. AEAT also examined whether other legislation and related measures such as product standards cover the same roles as the CAA, or could be amended to have the same effect as the Act.

AEAT’s analysis predicted that if the CCA were repealed altogether, then this could be expected to lead to an increase in dark smoke, a loss of amenity and an increase in the by-products in incomplete combustion. Specifically, removing the requirements for SCAs would probably result in large increases in domestic emissions of the polynuclear aromatic hydrocarbon benzo(a)pyrene, and respirable particulate matter, ie PM10 and PM2.5. Furthermore, any increases in the burning of petroleum coke would lead to subsequent increases in emissions of nickel, vanadium and sulphur dioxide.

On the other hand, product standards such as those for the performance of residential, multi-fuel stoves could have the same positive impact as smoke control areas. That said, legislation would still be required to ensure that all homes and organisations planning to burn coal or wood used such certified stoves, instead of using open fires.

Under all the scenarios of change examined, there could be more breaches of the limit values for PM10 and the recommended threshold for PM2.5. If the controls on minimum chimney heights for non-residential boilers were removed, then this would probably increase local concentrations of NO2. AEAT considered whether other regulations could replace the requirements for minimum chimney heights, but concluded that requirements applied through current planning laws and building regulations would not have the same effect as the CAA.

The requirement to calculate the effective height of a chimney applies to boiler sizes up to 1MW. However, the predicted increase in negative impacts would occur for relatively small boilers, eg over 200kW for most fuels, and as little as 100kW for biomass boilers. If the CAA were repealed, then there would be a gap in the regulation of chimney heights from boilers up to the 1MW threshold.

In summary

AEAT’s analysis shows that the CAA does play a role in controlling ambient air quality, especially for particulate matter. While other regulations and related measures such as product standards can and do replace some aspects of the CAA, repealing the CAA would mean that the remaining gaps would need to be filled in order to preserve and improve ambient air quality. In conclusion, the report implies that there may be measures in the CAA that are redundant in that they are covered by other measures, or could be covered by such measures. However, the underlying principles and provisions of the CAA are still needed, regardless of how they might be applied in the future.

Last reviewed 4 June 2013