Last reviewed 12 December 2012

The Clean Air Act (CAA) was first introduced in 1956 in response to the “great smog” of December 1952, which may have killed as many as 12,000 people. It is now under review. Rob Bell reports on the proposed changes.

Updated in 1968 and again in 1993, the CAA regulates a bewildering array of activities relating to smoke, grit, dust, fumes, chimney heights, vehicle fuel content and more. For example, under the Act: “A person who burns insulation from a cable with a view to recovering metal from the cable shall be guilty of an offence unless the burning is part of a process subject to Part I of the M1 Environmental Protection Act 1990 [or] an activity subject to regulations under section 2 of the Pollution Prevention and Control Act 1999.”

Environmental consultancy AEA Technology (AEAT) says: “The CAA was introduced to address air pollution from smogs caused by widespread burning of coal for residential heating and by industry. The CAA covers England, Wales and Scotland with separate legislation for Northern Ireland.

“The legislation targets smoke emissions from chimneys and premises and smoke emissions from residential and non-residential furnaces. Although some activities fall on Defra and the devolved administrations, the key CAA measures are applied and supervised by local authorities and include the control of dark smoke; prohibition of cable burning except at authorised installations; designation and supervision of smoke control areas — control of smoke emission and constraints on the types of appliances and fuels which can be used in such areas; approval of chimney heights for non-residential furnaces; control of grit and dust emissions from non-residential furnaces (up to thresholds in EPR); approval of new non-residential furnaces; and approval of abatement equipment for use on non-residential furnaces.”

In doing so, the CAA plays an important role in minimising emissions of pollutants with a major impact on the UK’s air quality. AEAT says: “The CAA regulates combustion and other activities (including domestic combustion) which provide a significant contribution to the UK’s total emission for many pollutants. Consequently, they are also important contributors to local air quality.”

Act under review

Under the Red Tape Challenge, launched by the Government with the aim of “making regulations simpler and more effective while remaining as strong as ever”, the Act is under review, and it is certainly one of the environmental laws ripe for improvement. According to then Environment Secretary Caroline Spelman, “simpler and smarter environment regulations will provide savings to businesses of more than £1billion over five years and protect the environment”.

Apart from any other issues, the provisions of the CAA — if left in their current form — will undoubtedly create major problems in relation to the Renewable Heat Incentive, which aims to encourage the use of boilers burning wood and other biomass fuels.

In fact, there were reports the CAA was to be scrapped altogether, rumours that were strongly denied by Defra, which published this statement:

“There have been reports in the media that important environmental regulations in legislation such as the… Clean Air Act… could be scrapped as part of the Government’s Red Tape Challenge.

“The truth: Defra is committed to enhancing the natural environment and there are no plans to remove important environmental protections. The Red Tape Challenge is about examining and understanding the impact of regulation on the people, businesses, and communities it affects, to ensure that it is proportionate while delivering the desired outcomes.”

Prior to launching its review, Defra undertook an informal consultation with two groups of local authority environmental health professionals about the value and continued use of the 1993 Act (CAA 93)’s provisions, and what improvements might be made.

The Department was told at a meeting with four officers that the Act was “completely outdated and needed a full overhaul”.

The consultees continued: “All the terminology needed clarifying or modernising; there are problems with enforceability and proportionality; there are too many opt-outs from the dark smoke provisions; it would be better to provide for a warning system rather than a strict offence in relation to dark smoke; it might be possible to achieve some outcomes via the Building Regulations; and certain additional powers were sought.”

However, the officers also felt the growth of biomass burning for electricity and heat generation could give the CAA “a new lease of life”, which meant “now was the time to streamline and focus the legislation, not to scrap most of it”.

Assessing the CAA’s effectiveness

As part of an exercise considering the consequences of repealing or amending the CAA, in particular the impact on air quality and emission ceilings if the Act and associated instruments were to be repealed, Defra commissioned a report — Assessment of the Effectiveness of Measures under the Clean Air Act 1993 — prepared by AEAT.

According to AEAT, PM10/PM2.5 and associated pollutants — particulates from smoke, ie the main target of the CAA — are of growing concern to regulators, both because of greater understanding of their health impacts and their inclusion in revisions to the Convention on Long-Range Transboundary Air Pollution’s Gothenburg Protocol. This protocol saw particulate matter (PM) added to sulphur dioxide (SO2), nitrogen oxides (NOx), volatile organic compounds (VOC) and ammonia (NH3) as a substance with a set national ceiling, which must be met by signatory states.

The Gothenburg Protocol should achieve impressive results for the health of Europe’s ecology and human population once it is fully implemented. The United Nations Economic Commission for Europe (UNECE) states: “It has been estimated that once the protocol is implemented, the area in Europe with excessive levels of acidification will shrink from 93 million hectares in 1990 to 15 million hectares. Land with excessive levels of eutrophication will fall from 165 million hectares in 1990 to 108 million hectares.

“The number of days with excessive ozone levels will be halved. Consequently, it is estimated life-years lost as a result of the chronic effects of ozone exposure will be about 2,300,000 lower in 2010 than in 1990, and there will be approximately 47,500 fewer premature deaths resulting from ozone and particulate matter in the air. The exposure of vegetation to excessive ozone levels will be 44% down on 1990.”

The CAA has an important role in meeting the targets set out in the Gothenburg Protocol that will lead to these positive impacts. The AEAT report says: “The recent revision to the Gothenburg protocol sets national emission ceilings for NOx, SO2, VOC, NH3 and PM2.5. The contribution of small combustion activities to the new 2020 ceilings for SO2, NOx and PM2.5 based on no change to the CAA are about 21, 15 and 20% respectively, which indicates the importance of these activities when considering measures to address the new ceilings.”

Potential changes

AEAT reviewed all the provisions of the CCA in order to identify the key measures available for use and hence potential changes. The changes considered include revocation of measures or changes to provide more focus on air quality, with resulting impacts on public health. Behavioural changes were also identified and their impacts quantified where possible.

The scenarios for potential changes to emission levels from CAA-regulated activities by 2020 were based on removal of smoke control areas (SCAs). AEAT’s researchers also looked into the potential for improved measures such as replacing the Clean Air (Emission of Grit and Dust From Furnaces) Regulations 1971 and national criteria for domestic and non-domestic combustion appliances.

The consultancy found that credible quantifiable scenarios relating to the CAA’s dark smoke and cable burning provisions could not be developed. Its report says: “The impacts from such activity are difficult to quantify as there are no activity data and limited emission factors to develop a reasonable emissions estimate.”

However, if the proposed changes to the CAA saw these provisions removed or weakened, air quality would suffer. AEAT says: “In the absence of CAA controls/supervision, incidents of dark smoke could be expected to increase and this would lead to an increase in loss of amenity, potentially increase emissions of products of incomplete combustion, and/or potentially nuisance situations.”

Grit and dust controls, however, were less significant. The report says: “Changes to reduce the emission limits permitted under the grit and dust regulations had little effect on emissions. However, this may reflect uncertainty in the NAEI [National Atmospheric Emissions Inventory] and activity data for the sector.”

SCAs — central to the CAA, and the main focus of local authorities’ regulatory efforts — are the biggest area of concern. According to the report’s conclusions: “Removal of smoke control area provisions has potential for large increases in UK emissions from domestic solid fuel combustion, including significant impacts on national emissions of benzo(a)pyrene (BaP), PM10 and PM2.5. Uplift in the use of petroleum coke could also increase nickel, vanadium and SO2 emissions.”

AEAT developed three scenarios to investigate the potential impacts on air quality concentrations of PM2.5, PM10, BaP and nitrogen dioxide (NO2) of applying national emission controls on solid fuel appliances to match those controls currently applied in SCAs. These indicated little or no change in NO2 ambient concentrations. However, AEAT’s high PM increase scenario, which included domestic solid fuel use in SCAs switching to wood and additional use of wood in domestic and non-domestic appliances in SCAs, was predicted to lead to exceedences of current and future air quality standards for BaP, PM2.5 and PM10.

A medium PM increase scenario (based on domestic solid fuel in SCAs switching to coal and additional use of wood in non-domestic appliances in SCAs) was predicted to lead to exceedences of current and future air quality standards for BaP and PM10, but only one additional zone for PM2.5.

Finally, no exceedences were predicted for PM10, PM2.5 and NO2 under the changes to the CAA for the third scenario, in which PM emissions were reduced, and there are fewer projected exceedences for BaP.

While there is provision for control of stack height through building regulations, AEAT found that removal of the chimney height provisions in the CAA could have a large impact on local air quality (particularly for NO2) even for comparatively small boilers.

The report says: “Removing the Clean Air Act requirements for approval of stack heights for small boilers (<20 megawatts thermal input) can potentially lead to high local air quality concentrations in excess of the air quality objectives and EU limit values.”

Public consultation

Defra plans a public consultation on changes to the CAA, and it is clear any revision will need to be handled carefully in order to maintain air quality standards without hampering efforts to encourage burning of biomass and the cutting of red tape.

While many local authority environmental health officers would probably happily load the CAA on the truck to the knackers’ yard, it does play an important role in minimising pollution.

What the Clean Air Act 1993 does

CAA93 has 68 sections and five schedules. Parts I–III comprise the main provisions:

Part I prohibits dark smoke emissions from domestic and industrial chimneys. It also prohibits dark smoke from non-chimney sources on industrial or trade premises, eg open bonfires.

Part II sets up a notification and approval system for new non-domestic furnaces to control smoke, grit, and dust emissions and chimney heights. There is provision to make regulations extending some of Part II to control fumes and gases.

Part III contains the smoke control area provisions.

The remaining provisions deal with:

  • making regulations about composition of motor vehicle fuel and sulphur content of fuel oil

  • prohibiting cable burning

  • applicability to vessels and steam engines

  • LAs obtaining information about air pollution

  • emissions from mine waste

  • LA research into air pollution

  • a power to give effect to international agreements

  • the usual sort of ancillary provisions.

There are 13 regulations made under the CAA known still to be extant.

  • Six sets of regulations specifying exemptions/permitted emission periods in relation to the Part I dark smoke provisions.

  • Three sets of regulations amplifying the Part II smoke, grit, dust and chimney height provisions.

  • Two sets of regulations listing authorised fuels and exempt fireplaces for the purposes of Part III (smoke control areas) — these were consolidated from six sets from 6 April 2012 as an initial contribution to the Red Tape Challenge.

  • Two sets of regulations amplifying the provisions enabling local authorities to obtain information about air pollution.

In addition, two sets of regulations are being checked to see whether they are extant — the Clean Air Enactments (Repeals and Modifications) Regulations 1974 and the Motor Fuel (Composition and Content) Regulations 1999. The latter were made using powers under CAA93 and the European Communities Act.