Transactions on Ecology and the Environment vol 15, 1997 WIT Press, ISSN

Transcription

1 Assessment of the first phase of the UK National Air Quality Strategy D.M. Elsom,* J.W.S. Longhursf *Air Quality Management Research Group, Department ofgeography, Oxford Brookes University, dm ac. uk ^Department of Environmental Health and Science, Faculty of Applied Sciences, University of the West of England, Frenchay Campus, Coldharbour Lane, Bristol, BS161QY, United Kingdom Abstract The Environment Act 1995 introduced the National Air Quality Strategy which initiated new statutory duties for local authorities from April For the first time, local authorities have been given the responsibility for reviewing and assessing local air quality with regard to national air quality objectives for eight pollutants. Air Quality Management Areas must be designated where air quality objectives are not met, or may not be met if no precautionary action is taken. For those areas, local authorities are required to draw up an air quality management plan (Action Plan) setting out the necessary transport and planning measures needed to ensure that the air quality objectives will be met by In order to reduce the difficulties facing local authorities in reviewing and assessing local air quality, aspects of the National Air Quality Strategy were piloted by 14 local authority groupings in This paper outlines the work undertaken by these authorities with a view to assessing whether this pilot phase was effective in ensuring that all local authorities were better placed to undertake their new duties frrom April Projects undertaken by First Phase authorities include testing the appropriateness of simple screening questions (stage one of the review and assessment process) intended to prevent many local authorities with no significant air quality problems from having to undertake costly monitoring or modelling work. Other projects include the establishment of an intensive street canyon monitoring site in Greater London in order to develop and validate street canyon models, assessing the confidence with which measurements obtained from simple samplers (e.g. passive diffusion tubes) can be used to indicate whether a location is likely to exceed national air quality objectives,fillingin national data gaps (e.g. PM^ levels in the vicinity of quarries), and testing a wide range of models. Delays in the completion of First Phase projects have meant that detailed guidance was not available to all local authorities in April This may have caused unnecessary time and resources to have been spent by some local authorities uncertain whether they needed to have undertaken the second stage of the review and assessment process or not. Some differences in approaches and inconsistences to the review and assessment process may have developed too.

2 16 Air Pollution Modelling, Monitoring and Management 1 Introduction: the National Air Quality Strategy Following the enactment of the Environment Act 1995, the National Air Quality Strategy was implemented in Great Britain (with its implementation pending in Northern Ireland). For the first time, local authorities have been given the responsibility for reviewing and assessing local air quality with regard to national air quality objectives for eight pollutants. This duty falls to all local authorities in Scotland and Wales and to district councils and unitary authorities in England. These new duties were due to come into force in April 1997 but issuing the legal regulations was delayed until after the May 1997 national elections. However, most local authorities began preliminary work on air quality reviews and assessments on the basis of the strategy document [1] and the general principles issued [2]. The National Air Quality Strategy recognises that it will not be possible to eliminate all potential air quality problems in the most cost effective way by the use of national policy instruments alone. It argues that local authorities can provide a more focused approach to local pollution problems and so are given the statutory obligation to identify areas within their boundaries where national policies and instruments alone appear unlikely to deliver air quality objectives by These areas must be declared Air Quality Management Areas. Local authorities must then formulate an air quality management plan (Action Plan) setting out what transport and planning measures are needed to ensure that the air quality objectives in these areas will be met by A limited range of powers and resources have been provided by central Government for this purpose. 2 Air Quality standards and objectives In March 1997, the Government published its National Air Quality Strategy (following a consultation draft in August 1996). The strategy specifies eight health-based air quality standards together with the air quality objectives which must be met by 2005 (table 1). Air quality standards are not given statutory backing and there is no timescale of attainment attached to them. Instead, the government considers the standards as reference points to be used for setting air quality objectives. These objectives "represent the Government's present judgement of achievable air quality by the year 2005 on the evidence of costs and benefits and technical feasibility" [2]. In other words, even by 2005 there may be areas that have achieved the air quality objectives but exceed the air quality standards. However, in the next few years, the government may be forced to give legal status to the air quality standards as a result of the air quality limit values being specified in the daughter Directives of the EU framework Directive on Ambient Air Quality Assessment and Management (96/62/EC) adopted by the Council of Ministers in September The UK considers that the structures established under the Environment Act 1995 and the National Air Quality Strategy will provide the main means of fulfilling the UK's

3 commitments under this directive. Air Pollution Modelling, Monitoring and Management 17 Table 1 UK air quality standards and objectives Pollutant Standard Measuring period 2005 objective Benzene 5ppb running annual mean 5 ppb 1,3 Butadiene 1 ppb running annual mean 1 ppb Carbon monoxide 10 ppm running 8-h mean 10 ppm Lead 0.5 ng/itf annual mean 0.5 jiig/nf Nitrogen dioxide 150 ppb 1-h mean 150 ppb* 21 ppb annual mean 21 ppb* Ozone 50 ppb running 8-h mean 50 ppb, 97th percentile* PM,o 50 jlig/nf running 24-h mean 50 ng/m\ 99th percentile* Sulphur dioxide 100 ppb 15-minute mean 100 ppb, 99.9th percentile* * these objectives should be regarded as provisional The air quality objectives for NO;, O,, PM^ and SO, are described as 'provisional' and may be changed in the future. Although an objective is specified for O,, the government indicates that this is a 'desirable objective' rather than one which must be met by statutory duty by It argues that the responsibility for achieving the O, objective must lie at the national and international levels. In other words, O, will not be a pollutant which, if exceedances of the objective occurs, would trigger a local Air Quality Management Area to be declared. Some changes to air quality standards and objectives were made between issuing the consultation draft and the final version of the strategy. During this period the Expert Panel on Air Quality Standards (EPAQS), the group set up in 1991 to advise the Government on air quality standards, published its report on NO, in December 1996 [3]. It proposed a relaxation of the 1-h standard from 105 ppb to 150 ppb on the basis that the original 105 ppb value had been selected using a 1976 study that claimed to have found health effects from NO, at concentrations as low as 100 ppb yet these results have never been replicated since. The Government accepted the recommendations of EPAQS by adopting the 150 ppb 1-h mean as both the air quality standard and objective. This

4 18 Air Pollution Modelling, Monitoring and Management replaced its draft standard of a 105 ppb 1-h mean and its draft objective of a 105 ppb 1-h mean, measured as the 99.9 percentile. The annual mean air quality standard was increased from 20 ppb to 21 ppb. One other significant change when the final strategy was published was a relaxation of the air quality objective forpm^. The 24-hour running mean air quality objective of 50 [ig/irf would be measured as the 99 percentile rather than the 99.5 percentile suggested in an earlier working draft of the strategy. Such a change to the objective implies a permitted exceedance of four days rather than two days. Air quality standards and objectives for PAHs (the EPAQS report is expected by 1997), ultra-fine particles (e.g. PM^) and metals other than lead may be added later as may ecological standards and objectives. Pressure to include an objective for ultra-fine particles has increased in the light of US proposals in November 1996 for a primary standard for PM^ of 50 jug/m* measured over 24 hours to complement the existing PM^ standard. The introduction of new or revised air quality limit values in the forthcoming EU daughter Directives as well as the results of new research into health-pollution relationships may lead to changes in any of the UK air quality objectives. The planned review of the strategy in 1999 provides the opportunity for additions, strengthening or even relaxation of the standards and objectives. 3 The Review and Assessment Stage Each local authority is required to undertake a review and assessment of air quality within its area. The purpose is to identify areas where national policies to reduce vehicle and industrial emissions are unlikely to result in air quality meeting the government's air quality objectives by The problem of air pollution varies considerably between local authorities. To avoid some local authorities having to undertake costly and time-consuming reviews and assessments when it is likely that national source-based controls will ensure targets are readily met, the Government has adopted a three-stage approach to reviews and assessments [2]. The intention is that the complexity and detail of a review and assessment should be consistent with the risk of the air quality objectives not being achieved by The review and assessment process of deciding whether air quality objectives will be met by 2005 is intended to take into account the effects of national emission reduction measures. Some concern is being expressed about the assumed effectiveness of national measures on which the Government is relying upon to lead to attainment of air quality objectives in most areas. For example, catalytic converters, which became mandatory on all new cars at the beginning of 1993, are expected to reduce traffic emissions. However, although currently around 30% of cars are fitted with catalysts, monitoring is failing to show significant air quality improvement. For example, NC^ levels in Edinburgh increased significantly between 1993 and 1995 [4].

5 3.1 First stage Air Pollution Modelling, Monitoring and Management 19 Local authorities are issued with a checklist of questions designed to show whether air quality objectives may be expected to be breached. The questions are designed to take into account the likely effects of national emission control measures. Authorities will be asked whether any of the following are present: roads which exceed specified traffic flows or suffer congestion; industrial processes (Part A and B processes) that are likely to emit significant quantities of the key pollutants; other significant emission sources; future developments that are likely to affect air quality significantly. If none of the above significant emission sources exist, the local authority may assume that the likelihood of standards being breached is negligible. If one or more significant sources exist, then the authority must undertake a second stage assessment. Clearly this first stage - primarily a desk study - can be undertaken relatively quickly and inexpensively. This screening stage is intended to identify local authorities with no major industrial sources, only low traffic flows on its roads and no major developments with significant pollution potential planned for the future. For such local authorities, there are no further requirements to be met under the National Air Quality Strategy except to repeat this screening process at least once more before Second stage Where there is a risk that one or more significant emission sources are present or, in the case of future developments, will be present before 2005, maximum concentrations of the key pollutants must be estimated at the: roadside; urban background locations; and at industrial locations. Models to predict such concentrations will be recommended in the Government's guidance notes, based on the validation work undertaken by some local authorities participating in the trial phase of the review and assessment process in These models are intended to be simple, inexpensive but yet reliable. Examples include the Department of Transport's Design Manual for Roads and Bridges (DMRB) model, the Netherlands CAR (Calculation of Pollution from Road Traffic) International model, and AEOLIUS (Assessing the Environment Of Locations In Urban Streets). The latter is a new street canyon model with screen (nomogram or PC-based) and full versions developed by the UK Meteorological Office for calculating kerbside maximum 1-h concentrations of key pollutants. Proxy or surrogate statistics and the results of monitoring elsewhere in similar locations may be employed in this review and assessment stage. Access to the expanding national database of pollution monitoring and emission inventories is intended to help in this respect. The National Environmental Technology

6 20 Air Pollution Modelling, Monitoring and Management Centre are producing 1x1 km grid square maps of the UK giving estimated background concentrations of the key pollutants for both now and the year The database for current NOj concentrations (but based at present on 1994 data) became available on the world wide web in April 1997 (National Air Quality Information Archive, at with others promised to follow soon. If it is predicted that maximum concentrations are likely to approach or exceed air quality targets at any of the specified locations, local authorities must proceed to the more detailed third stage. 3.3 Third stage The third stage assessment is likely to require more sophisticated modelling and monitoring techniques although the Government stresses that tried and tested simple, inexpensive approaches may play a role too. Additional monitoring is likely to be necessary at this stage. If this assessment stage confirms that one or more of the air quality objectives are unlikely to be met in an area by 2005, than that area must be declared an Air Quality Management Area. The Government's view is that its boundaries should be defined in broad terms rather than an attempt be made to delineate accurately a line of poor air quality since spatial and temporal distribution of air quality makes it impracticable to do so. Those local authorities having to undertake the third stage will be involved in a rigorous assessment involving considerable resources (labour time, expenditure for monitoring, compilation of emission inventories, modelling, training of staff and/or the hiring of consultants). The Government intends to allow local authorities some discretion concerning the level of effort and degree of sophistication of the assessment. Such discretion appears to be offered in part to avoid pressures on the Government to provide financial support for expensive monitoring and modelling. 3.4 Timetable for completion of reviews and assessments There is no deadline for completion of the air quality reviews and assessments. However, the government has made it clear that it expects them to be finished within two years, effectively setting a deadline of April the year the strategy will be reviewed. Those local authorities designating an Air Quality Management Area would then have 12 months to produce a more detailed assessment. This is intended to confirm the need for an Air Quality Management Area and to provide the in-depth understanding of the air quality problems that will be needed to formulate an Action Plan. Given the requirement for widespread consultation, local authorities have a further 12 months after completion of the detailed assessment to complete the Action Plan. In other words, the whole process could take up to four years. This leaves a relatively short period for the Action Plan to take effect and for the air quality objectives to be attained by 2005.

7 Air Pollution Modelling, Monitoring and Management 21 For those areas not having to designate an Air Quality Management Area, the Government expects the review and assessment process to be undertaken a second time before The Environment Act 1995 gives the Environment Secretary reserve powers to take action against any local authority that does not comply with the strategy. 4 The trial phase of the National Air Quality Strategy: First Phase areas In order to reduce the difficulties facing local authorities when undertaking their review and assessment of local air quality, aspects of the National Air Quality Strategy were tested and refined by 14 local authority groupings (plus Belfast in Northern Ireland) in These First Phase areas (Aberdeen, Avon, Cambridge, Cornwall, Derbyshire, Glasgow, Greater London, Hampshire, Merseyside, Kibble Valley, South Wales, South Yorkshire, Tyne and Wear, and the West Midlands) comprise 80 local authorities in total, including the Greater London grouping of 33 local authorities. They were chosen to be representative of a range of population sizes and densities, geographical regions, types and complexity of pollution problems, and degrees of experience of local air quality management [5,6]. Funding of 2 million was made available to support the work being undertaken by these areas. However, it was stressed that the funds were not being offered to them to complete their review and assessment of air quality ahead of their statutory responsibilities but instead to: check that initial guidance on reviewing and assessing air quality was suitable for a range of authorities with varying degrees of experience; test the applicability of guidance to areas of differing need, differing complexity and with different sources of pollution; develop best practice on air quality reviews and assessments; and develop further guidance on air quality management [7]. Although the First Phase area trial was announced in February 1996 as being scheduled to last from April 1996 to March 1997, delays in financing (not agreed until June 1996), equipment procurement, planning permission, and clarification of the projects each First Phase area would undertake caused delays such that the pilot phase will not finish until autumn Provisional results and findings for some projects have been reported and incorporated into the guidance notes being developed for issuing to all local authorities. However, it meant that local authorities began implementing the strategy in April 1997 without the benefit of the detailed guidance notes promised. 5 First Phase projects Testing and refining the proposed methodologies of the three stage review and assessment process has meant examining the threshold traffic flows used in the first stage to indicate whether road traffic is likely to be a significant emission source. The defining levels may differ for different pollutants, being lower for

8 22 Air Pollution Modelling, Monitoring and Management than for some other pollutants [8]. Thresholds between 25,000 and 50,000 vehicles per day were originally proposed but work by Cambridge has highlighted that street geometry must be considered when assessing the likely significance of road traffic emissions on air quality. In Cambridge, some wide streets carrying 26,000 vehicles produced no air quality problems whereas canyon-like streets with only 8,000 to 10,000 vehicles experienced NO, (and probably PM^ and benzene) problems. Cambridge has recommended that street geometry be included in the screening question in combination with thresholds of traffic flow and average speed. Simple street geometry-traffic flow charts have now been prepared and are being tested by other First Phase authorities. Many First Phase authorities are undertaking detailed investigations of the levels of pollutants at locations for which the second stage requires estimates of maximum pollution concentrations to be made. Several areas such as Aberdeen and Glasgow are measuring concentrations of traffic-based pollutants at the roadside, especially in congested canyon-type streets. Industrial locations are being monitored by other areas. Avon and South Wales are monitoring VOC, especially benzene and 1,3 butadiene, around industrial complexes. Hampshire is measuring benzene levels in the vicinity of the Fawley refinery and other industrial premises. Little previous work has been undertaken on PM^ levels in areas of mining and quarrying (producing 1 1 per cent of UK PM^ emissions). Consequently, Tyne and Wear have been charged with monitoring PM^ around open cast coal mining, Derbyshire around mineral quarries, and Cornwall (also testing the usefulness of three types of monitor) around a china clay quarry. The confidence with which data obtained from simple and passive monitoring methods rather than automatic monitors can be used to indicate whether an air quality problem is likely to exist is being explored by five of the First Phase areas. In some cases this has meant co-locating instruments. PM^ has received particular attention. The possible use of black smoke measurements obtained from inexpensive 8-port volumetric (bubbler) instruments as a surrogate indicator of PM^ is being examined since local authorities have many years of experience of operating such samplers. First Phase areas are testing assumptions concerning the use of a range of surrogate indicators. For example, Avon (Bristol) is examining the appropriateness of using a simple factor to derive 1,3 butadiene from benzene. Assumptions about the degree of spatial variation of specific pollutants, especially PM^, are being investigated by Avon (Bristol) and West Midlands (Birmingham) by comparing data from various sites. Seven of the First Phase areas have been directed to test and validate modelling techniques so that other local authorities will not have to undertake large expenditure on monitoring. One of Greater London's projects is to establish an air quality monitoring 'super site' in a busy (50,000 vehicles per day) canyon-like street (Marylebone Road), giving highly detailed information about air pollution concentrations, traffic flows and meteorological conditions. This site received approximately one quarter of the total equipment budget allocated to First Phase areas. The primary purpose was to enable the

9 Air Pollution Modelling, Monitoring and Management 23 development and validation of street canyon models. The project was delayed (it was intended to be operational by the end of January 1997) because of planning difficulties but should commence in June Various modelling packages are being tested and validated by other First Phase areas to help assess which models are best suited to conducting air quality reviews and assessments. Given the importance of traffic emissions in causing air quality problems, particular attention is being given to the use of models in estimating pollution concentrations in congested streets and street canyons. Simple models being tested include the DMRB, CAR International, AEOLIUS, CALINE4 (California Line Source Dispersion Model, version 4) and ADMS (UK Atmospheric Dispersion Modelling System). Delays in establishing the detailed London monitoring site as well as delays in the starting date of model testing projects by other First Phase authorities has meant other local authorities began their review and assessment in April 1997 without the benefit of clear guidance on the most suitable models to use. Some First Phase authorities are assessing the use of micro- and macro-scale emission inventories. Many local authorities do not have detailed emission inventories for their area and will rely on data from the national 10x10 km grid square emission inventories for NO,, CO, SO, and VOC. First Phase authorities are assessing the cost, difficulty and value of constructing more detailed inventories for local hotspots in order to facilitate the prediction process needed for the second and third stages of the review and assessment. Hampshire is undertaking a VOC emissions inventory of part B processes in order to assess the validity of information derived from this methodology against data taken from the national emissions inventory, and to assess its cost effectiveness [7]. 6 Conclusion The pilot phase of testing and refining the three-stage review and assessment required by the National Air Quality Strategy was intended to ensure that all local authorities would be better placed to undertake their own air quality reviews and assessments from April Although the projects are producing some very useful information and insights which are being fed into the guidance notes being prepared for all local authorities, delays in implementing First Phase projects have meant that this guidance was not available in April 1997 as promised. Since the First Phase areas were to establish practical and simple criteria for eliminating areas which are unlikely to have air pollution problems with regard to the national air quality objectives, the delay may have caused unnecessary time and resources to have been spent (including expenditure on modelling and monitoring) by some authorities uncertain whether they should have progressed to the second stage or not. Without the finalised guidance notes, some inconsistencies and different approaches may have developed in early attempts at review and assessment. Some key issues were not considered by the First Phase authorities. For example, very limited attention was given to ozone, except for VOC emissions

10 24 Air Pollution Modelling, Monitoring and Management as precursors of ozone. Gaining experience of the review and assessment process for rural areas seems to have been largely ignored. For those authorities progressing to the third stage and perhaps having to designate an Air Quality Management Area and formulate an Action Plan this trial phase of the national strategy offers only limited advice. Further testing and refining of these practical aspects of the strategy will be needed. One general lesson gained from the experiences of First Phase authorities is that some of the practical issues connected with undertaking the later stages of the review and assessment process, such as gaining planning permission for monitoring sites, can take considerable time. Another lesson concerns the need to involve all relevant local, county and regional groups such as Environmental Health Officers, planners, traffic engineers, medical practitioners, academics and industrialists very early on. Cambridge City Council has emphasised the need for a partnership approach to the review and assessment process even though it is the local authority which has the statutory responsibility to undertake this duty. Indeed, most First Phase authorities have established an Air Quality Forum or similar working group which involves representatives from all groups who have a part to play in air quality management. Key words: air quality management, model validation, air quality standards References 1. Department of the Environment (DoE). The United Kingdom National Air Quality Strategy, The Stationery Office, London, Department of the Environment (DoE). General Principles of Reviewing and Assessing Air Quality, DoE, London, November Expert Panel on Air Quality Standards (EPAQS). Nitrogen Dioxide, Seventh Report, The Stationery Office, London, ENDS Report. Doubts grow over benefits of catalytic converters. ENDS Report 263, December 1996, p Elsom, D.M. and Crabbe, H. Implementing the National Air Quality Strategy in the United Kingdom, Air Pollution IV: Monitoring, Simulation and Control, eds B. Caussade, H. Power & C.A. Brebbia, pp , Computational Mechanics, Southampton, Longhurst, J.W.S. Some theoretical and practical issues associated with the development of local air quality management in Great Britain, Air Pollution IV: Monitoring, Simulation and Control, eds B. Caussade, H. Power & C.A. Brebbia, pp , Computational Mechanics, Southampton, Higgins, A. Hampshire and Isle of Wight Air Quality Management Pilot Area, Paper presented at 21st Investigation of Air Pollution Standing Conference, London, December Coster, S. Overview of the Environment Act 1995, Paper presented at 21st Investigation of Air Pollution Standing Conference, London, December 1996.