uk air pollution
TRANSCRIPT
UK Air Pollution
This Brochure has been produced by the NationalEnvironmental Technology Centre (Netcen) onbehalf of Defra and the Devolved Administrations.
The quality of the air that we breathe can haveimportant impacts on our health and quality oflife; it’s therefore important to us all.Measuring and understanding air pollutionprovides a sound scientific basis for itsmanagement and control. Considerable effortis therefore devoted in the UK to the system-atic measurement of levels of air pollutionnationwide. This effort started in earnestfollowing the infamous ‘pea-souper’ smogs ofthe 1950s and 60s, but has expandedmassively in scope, coverage and sophistica-tion since then.
Air quality monitoring, and the resultspresented in this brochure, should not be seenas an end in themselves; rather, they offer usthe best way of understanding our pollutionproblems, so they can be tackled effectively atlocal, national and international level.
Monitoring air pollution in the UK has thefollowing broad objectives:
◆ To provide a sound scientific basis forthe development of cost-effective controlpolicies and solutions
◆ To assess how far air quality standardsand objectives are being met
◆ To evaluate potential impacts on popula-tion health and welfare
◆ To provide the public with reliable and up-to-date information on air pollution
◆ To determine the impacts of air pollution onecosystems and our natural environment
This brochure aims to provide a simple guide,written in non-technical language, to what thelatest measurements tell us about air pollutionin the UK. In it, we’ll:
◆ Summarise current UK and Europeanefforts to tackle air pollution
◆ Review where and how air pollution ismeasured
◆ Examine major periods of elevated pollu-tion that have occurred over recent years
◆ Evaluate air pollution impacts on our lives
◆ Investigate how pollution levels varyacross the UK
◆ Assess long-term pollution trends andsee why 2003 proved to be such anexceptional year
◆ Provide details on how you can find out more
about air quality in your neighbourhood
UK Air Pollution
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Air pollution is becoming an increasinglyimportant focus of interest for local, national,European and international policy makers.This has been triggered in part by increasingevidence that air pollution may be stronglyinfluenced by climate change; recent yearshave shown the dramatic impacts of a seriesof unusually hot summers throughout manyparts of Europe. Some of these impactshave, in part, been a consequence ofelevated levels of air pollution.
The European Union and other internationalorganisations are acting to reduce globalpollution. Within the European Community, aseries of air quality Directives over the lastdecade has:
◆ Established Limit Values for key airpollutants and defined overall require-ments for monitoring progress againstthese targets
◆ Defined the monitoring, modelling andair quality management obligations ofMember States
◆ Set targets for pollutant emissions indifferent types of industry as well as inthe transport sector
◆ Confirmed the need to communicateinformation on air quality to the publicat large
Although the lethal smogs in London andother cities caused by coal burning have
now gone for good, air pollution remains aproblem in the UK. Medical evidence showsthat many thousands of people die prema-turely every year because of its effects, andthis process can accelerate during extremeweather conditions. Many more becomeunwell or may require hospital treatment.The young and infirm are often particularlyaffected, as well as people living in deprivedareas. The costs to individuals, families andthe national economy are immense.
Air quality is therefore now one of the UKGovernment’s key headline indicators ofsustainable development. These provide a‘quality of life barometer’ measuring every-day concerns, and are intended to give abroad overview of whether we are achiev-ing a better quality of life for everyone, nowand for generations to come. We’ll be look-ing more closely at the latest air qualityindicator levels in section 6 of this brochure.
The National Air Quality Strategy,published in March 1997 and revised inJanuary 2000, set up a strong frameworkfor tackling air pollution over the comingyears. It established objectives for eightkey air pollutants, based on the bestavailable medical and scientific under-standing of their effects on health. As ourknowledge of these effects has deepened,the objectives have been progressivelyrefined and strengthened. The currentobjectives are shown in Table 1 overleaf.
The UK’s policy for tackling air pollution
The UK’s air quality was dominated for centuries bydomestic and industrial coal burning....
but road transport is now the major source of air pollution in UK cities
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Although its main focus is on protectingthe health of the population at large, theUK’s Air Quality Strategy has also estab-lished corresponding targets for theprotection of vegetation, ecosystemsand the natural environment. Air moni-toring provides a key tool in assessinghow far the health objectives and otherenvironmental targets are being metthroughout the UK.
Central Government and the DevolvedAdministrations in Scotland, Wales andNorthern Ireland are responsible foroverall policy and legislation affectingthe environment, including air quality.However, over the last five years, LocalGovernment has taken an increasinglyimportant role in air quality manage-ment. Authorities are required regularlyto review and assess air quality in theirarea and take decisive action when theobjectives cannot be met.
When this happens, an Authority mustdeclare an ‘Air Quality ManagementArea’ and introduce an Action Plan –
which may include such measures ascongestion charging, traffic management,planning and financial incentives – totackle problems in the affected areas. ByMarch 2004, 127 local authorities – overa quarter of those in UK – had establishedone or more AQMAs, most of these inurban areas and resulting from trafficemissions of nitrogen dioxide (NO2) orfine particulates (PM10).
Note that Management Areas are notdesignated as a result of high ozone levels,because concentrations of this pollutantare not controlled by local factors.
Through the process of Local Air QualityManagement, tackling air pollution isprogressively focussing more on local‘grass-roots’ concerns, initiatives andactions. If you want to know more, whynot follow the web link to:
www.airquality.co.uk/archive/laqm/laqm.php
to see if an AQMA has been establishedin your neighbourhood?
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UK Air Pollution
Pollutant
Benzene
All authorities 16.25 µg m-3 Running annual mean
Annual mean
Annual mean
Annual mean
1 hour mean
24 hour mean
Annual mean
Annual mean
24 hour mean
1 hour mean
24 hour mean
15 minute mean
Annual mean
Running annual mean
Running annual mean
Maximum dailyrunning 8-hour mean
Running 8-hour mean
31.12.2003
31.12.2010
31.12.2004
31.12.2008
31.12.2005
31.12.2004
31.12.2005
31.12.2004
31.12.2010
31.12.2004
31.12.2004
31.12.2005
31.12.2010
31.12.2010
31.12.2003
31.12.2003
31.12.2003
5.00 µg m-3
3.25 µg m-3
2.25 µg m-3
10.0 mg m-3
10.0 µg m-3
0.5 µg m-3
0.25 µg m-3
200 µg m-3 not to beexceeded more than18 times a year
40 µg m-3
50 µg m-3, 35 times a year
40 µg m-3
50 µg m-3, 7 times a year
18 µg m-3
350 µg m-3, 24 times a year
125 µg m-3, 3 times a year
266 µg m-3, 35 times a year
England & Wales only
Scotland & N. Ireland
1,3-Butadiene
Carbon monoxide
Lead
Nitrogen dioxide
England, Wales & NI only
Scotland only
Particles (PM10) (gravimetric)
Sulphur dioxide
All Authorities
Scotland only
Date to be
achieved byConcentration
Air Quality Objective
Measured as
Table 1. Health–related air quality objectives in regulation, 2003
Low (1-3) Effects are unlikely to be noticed even bythose who are sensitive to air pollution
Sensitive people may notice mild effectsbut these are unlikely to need action
Sensitive people may notice significanteffects and may need to take action
Effects on sensitive people describedfor HIGH pollution,may worsen
Moderate (4-6)
High (7-9)
Very High (10)
For reporting airquality and poten-tial health effectsto the public, thefollowing bandingsystem has beenestablished:
The history of air monitoring in the UK goesback a long way. Primarily in response to theserious urban smogs of the 1950 and 60sblack smoke and sulphur dioxide have beenmonitored on a national scale in the UK since1961. Since that time, the coal-burningemissions responsible for this type of wintersmog have decreased substantially, and roadtransport has now become the most impor-tant source of air pollution in most areas. Inresponse to this historic change, the empha-sis in monitoring has moved progressively topollutants such as ozone, nitrogen dioxideand fine particulate matter (PM10).
The UK’s air monitoring networks haveevolved and grown considerably over thepast 10 years (Fig 3.1). This expansionhas been driven by many factors, includ-ing increasing concern about healthimpacts, government’s desire to informthe public of the quality of our air, theUK’s Air Quality Strategy and a range ofEuropean commitments. There has alsobeen considerable growth in the amountof monitoring undertaken by LocalAuthorities. Many of these sites nowcontribute data to nationally organisedmeasurement programmes funded andsupported by Central Government andthe Devolved Administrations.
There are currently over 1300 national airquality monitoring sites across the UK,organised into several automatic and non-automatic networks with differentobjectives and coverage. 120 of these sites(Fig 3.2) operate automatically, providinghourly information on a range of pollutantsthat is communicated rapidly to the public.The non-automatic sites measure averageconcentrations over a specified samplingperiod (typically a week or month) insteadof instantaneous concentrations, but stillprovide invaluable data for assessing levelsand impacts of pollution across the countryas a whole. The pollutants measured, sitenumbers and areas covered in the UK’snationally coordinated monitoringnetworks are summarised in Table 2.
Air quality data from the UK automaticnetworks, together with twice-daily pollu-tion forecasts, are widely disseminated bya range of electronic and web-basedmedia; these include a free telephoneservice, TV, and Teletext, as well as glob-ally via the World Wide Web. Informationon UK air quality is also frequentlyexchanged with other countries in Europe,to enable us to track pollution being trans-ported over long distances.
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When and how air pollution is measured
Pollutant Major sources Site numbers Areas covered
Road transport & industry
Sunlight & heat, acting on road transport & industrial emissions
Road transport, industry, construction, soil & naturalsources
Industry & fuel combustion
Road transport
Industry, transport, solvent use& some natural sources
Industrial & other processses
Nitrogen dioxide (NO2)
Ozone (O3)
Particles (PM10 & PM2.5)
Sulphur dioxide
Carbon monoxide (CO)
Volatile Organic Compounds(VOCs) & toxic air pollutants(TOMPS, PAHs)
Metals (Pb, Cd, As, Ni & Hg)
106 (Automatic)1288 (Non-automatic)
65 (A)
68 (A)7 (NA, gravimetric)123 (NA, black smoke)
76 (A)123 (NA, net acidity)
79 (A)
5 (A) 35 (NA)
25 (NA)
17
Mostly urban
All of UK - urban & rural areas
Mostly urban
Mostly urban
Urban
Mostly urban
Urban & Industrial
Table 2. Air pollutants monitored in UK national networks
As highlighted in the next section, thislong-range pollution can often haveimportant impacts here in Britain.
The UK’s award-winning air quality website – www.airquality.co.uk –provides user-friendly and comprehen-sive access to information on all airpollutant concentrations and emissions,together with up-to-date bulletins, fore-casts and measurements from all the UKnational monitoring networks. It’stherefore your best one-shop resourcefor reliable information covering allaspects of air quality in this country. Toprovide you with the most up-to-dateinformation on local or regional issues,we list on the back page of this brochurethe key data sources and informationresources on UK air pollution.
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3.2 Map showing coverage ofautomatic and non-auto-matic monitoring stations inthe UK, 2004
UK Air Pollution
An automatic air quality monitoring station in Harwell, Oxfordshire
1974
1976
1978
1980
1982
1984
1986
1988
1990
1992
1994
1996
1998
2000
2002
1972
Year
140
120
100
80
60
40
20
0
Nu
mb
er o
f S
tati
on
s
Number of Automatic Monitoring Stations1972-2004
3.1 Numbers of automatic air monitoring stationshave risen dramatically over the last 10 years
Air pollution levels can vary considerablyfrom day to day, as well as from one part ofthe country to another. In this section, we’lllook at short-term variations over time, andin particular some recent periods when pollu-tion levels were particularly high. These areusually referred to as episodes. In Section 5,we’ll focus more on variations in pollutionlevels from area to area.
Pollution levels vary over time for two mainreasons:
◆ Variations in pollutant emissions
◆ Changes in atmospheric conditions whichallow pollution levels to build up or trans-port pollutants from other areas
All episodes occur because of a combinationof these factors.
There are two main types of pollutionepisode in the UK. Winter smogs typicallyoccur in cold, still and foggy weather; thistraps pollution produced by motor vehicles,space heating and other sources close to theground and allows it to build up over time.City areas - in particular those close to majorroads - are usually worst affected, togetherwith sheltered or low-lying parts of the coun-try. Winter episodes are characterised byelevated levels of nitrogen dioxide (NO2),particles (PM10) and volatile organiccompounds (VOCs) such as benzene. Highsulphur dioxide levels can also occur in someindustrial or coal-burning regions.
By contrast, summer smogs occur in hot,sunny and still weather. Sunlight and hightemperatures accelerate chemical reac-tions in mixtures of air pollutants that areemitted from road vehicles, fuel burningand solvent usage. The pollutants thatcause such an episode can often travel longdistances - sometimes from other parts ofEurope. During this large-scale air move-ment, they react together to produce highlevels of ozone (O3), together with otherpollutants such as nitrogen dioxide andparticles. Unlike the ozone layer in theupper levels of the atmosphere thatprotects us from ultraviolet radiation,ground level ozone produced in this way is
harmful to human health and vegetation,as well as damaging some man-madematerials.
Long-range transport of pollutants fromEurope, or occasionally from North Africa,can on occasions cause another, third typeof pollution episode. This tends to occurduring the summer months, either in isola-tion or in combination with summer smog.Conversely, short-range transport canresult in elevated concentrations ofprimary pollutants close to major emis-sions sources such as power stations orlarge industrial plant.
Air pollution episodes in the UK varywidely in terms of the areas they affect,duration and seriousness. Here we exam-ine four episodes, one of each specific typedescribed above.
1. Winter smog episode:December 2001
Historically, the first half of December isparticularly associated with winter smogsin the UK; in fact, many of the most noto-rious coal-burning smogs occurred at thistime of year. The historic London smog of1952, which first galvanised Governmentand public action to tackle air pollution,occurred in the first week of December. Asdiscussed in Section 6, where we examinelong-term pollution trends, these smogs nolonger occur in most of the UK. Howeversimilar episodes – albeit of reduced sever-ity – can still occur in areas such asNorthern Ireland, where coal is still widelyburnt for domestic space heating.
The cold, stable weather that initiates wintersmogs also allows pollutants from motorvehicles and other sources to accumulateover time. As a result, winter smogs can nowbe associated with elevated levels of a widerange of pollutants. A good example ofwinter smog associated with road transportemissions occurred between the 7th and 18th
December 2001. The main pollutantsinvolved were PM10 particles and nitrogendioxide, although sulphur dioxide levels wereelevated throughout the period in Belfast.
7
High pollution episodes
High atmospheric pressure dominated theUK weather patterns during this pollutionevent. This is a characteristic weatherpattern for winter smogs; it is usuallyassociated with low wind speeds, cold,misty or foggy conditions and well-defined atmospheric temperature inver-sion layers which act as a barrier to thedispersion of pollutants, trapping themclose to the ground. As a result, pollutantconcentrations during winter smogs tendto build up slowly over time – the longerthe stable conditions last, the higher thelevels of pollution reached. (Fig 4.1)
During the episode’s peak from the 11th
onwards, this high-pressure system wascentred over Northern Britain (Fig 4.2),resulting in elevated concentrations of arange of pollutants over this part of thecountry, Central Scotland and NorthernIreland. Overnight levels of PM10 reachedthe VERY HIGH band in Glasgow (104and 119 µgm-3) and HIGH in Edinburgh,Manchester and Belfast. These levels wereprimarily attributable to road transportemissions, although local source influences(nearby construction and a ChristmasFayre) also influenced peak PM10 levels inEdinburgh. Domestic heating was animportant factor at Belfast, resulting notjust in elevated PM10 but also sulphurdioxide concentrations in the city.
From the 14th onward, wind directionsshifted to northerly and speeds increased.The resulting improvement in atmosphericdispersion brought the episode to an end.
2. A summer smog episode:August 2003
2003 proved to be a record-breaking yearfor the UK and global climate. It was thesunniest on record for England andScotland, the warmest ever in Scotland,and the second driest year in England andWales since 1766. The highest ever UKtemperature of 38.5˚C was recorded inFaversham, Kent on August 10. Taken over-all, 2003 was the fifth warmest for Britainas a whole since records began in 1659.
The extreme conditions were not justconfined to the UK. 2003 was the thirdwarmest year worldwide since globalrecords began in 1861, and the hottestever over many parts of Europe (Fig 4.3).It is interesting to note that all of theplanet’s ten hottest years have occurredsince 1990, providing solid evidence of aworldwide climate trend.
These extreme weather conditions causedphotochemical ozone production overlarge areas of UK and Europe. 2003 wasnotable both for very early (April) and late
8
UK Air Pollution
Day (December 2001)
Moderate
High
Very High
20
06
S1
07 08 09 10 11 12 13 14 15 16 17 18
No.
of U
K s
ites
in b
and 18
16141210
86420
4.1. Pollution levels build up slowly during wintersmogs (December 2001)
4.2. High-pressure systems like this on 12 Decemberare closely associated with Winter smogepisodes in the UK (Crown Copyright)
(September) summer smogs in the UK.The most exceptional of these was theepisode that occurred during the veryhottest part of the year, the first half ofAugust (Fig 4.4). During the period from1 to 15 August, many rural and urbanmonitoring stations across England andWales recorded hourly ozone levels inthe HIGH (180-360 µgm-3) band; thehighest single hourly measurement was238 µgm-3 at Portsmouth on the 9th,
equalled at London, Brent on the 6th.Moreover, high concentrations wererecorded for 10 consecutive days, anunusually long period for an ozoneepisode. During much of this period, airtransported from continental Europestrongly influenced pollution levels overmuch of the UK (Fig 4.5)
However, despite record-breaking temper-atures, cloudless skies, sunshine and apersistent, stable high pressure system -all conditions closely associated withphotochemical episodes - correspondingpollution levels in August did not break UKrecords. In fact, comparisons with thesimilar ‘heat wave’ summer of 1976showed that maximum hourly ozoneconcentrations in 2003 were approxi-mately 50-60% of those recorded duringthat year. This is consistent with themarked UK and Europe-wide decline inemissions of ‘precursor’ pollutants (nitro-gen oxides and volatile organiccompounds) over that period.
During the August heat wave, severetemperatures and elevated ozone levelswere recorded in many parts of Europe,together with large numbers of reporteddeaths. It’s often difficult to distinguishmortalities caused by heat stroke, dehy-dration and exhaustion from those due to
9
High pollution episodes
Forecast Ozone Concentrations (PPB)and Associated Back Trajectories
10/08/2003 1200
Above 12090 - 12070 - 9050 - 70Below 50
4.4. London’s Canary Wharf during the height of the August smog
4.5. Meteorological analysis showing transport of airfrom Continental Europe to different parts of theUK during the August 2003 summer smog
4.3. NASA analysis of MODIS satellite data showing excess temperatures across Europe during July 2003
air pollution. Very often, multiple factorsare involved. The UK Office for NationalStatistics has reported an additional 2045deaths in England and Wales for periodfrom 4 to 13 August 2003, when comparedagainst the 1998-2002 average mortalityfigures for that time of year. Using previ-ously well-established medical data on theeffects of ozone and PM10 on human-health, it has been estimated that between423 and 769 of the excess deaths wereassociated with elevated concentrations ofthese pollutants. This represents between21 and 38% of the total excess deathsrecorded during this period.
3) An episode involving long-range transport: April 2003
On the 12th April, levels of both ozone andPM10 began to increase at many monitor-ing stations. This rise was associated withunusually warm and sunny weather for thetime of year, combined with air trans-ported from Scandinavia and CentralEurope. From the 14th onwards, however,
winds became stronger and moresoutherly and elevated PM10 levels up tothe VERY HIGH band (118 µgm-3) wererecorded in Northern England. Imagesfrom the US SeaStar satellite, part ofNASA’s Earth Science Enterprise, provide afascinating glimpse of global long-rangetransport of dust and pollution during thisperiod (Fig 4.6). The images show the UKalmost hidden beneath tan-coloured swirlsof Saharan dust and grey haze associatedwith polluted continental air.
As particle levels rose, so did those ofozone, reaching the HIGH band at severallocations. As noted previously, April isunusually early for elevated levels ofozone to be observed in the UK. Long-range transport of air dominated through-out this period, bringing in continentalozone and its precursors, with particlelevels also likely to have been influencedby the large-scale Saharan dust storms.
4) An episode involving short-range transport: May 2003
Short-term elevated levels of primarypollutants can be observed from time totime in the vicinity of major emissionsources such as power stations, refineriesor large industrial plant. Such episodestend to be intermittent, highly localisedand associated with rapidly fluctuatingconcentrations. Well-regulated plant israrely associated with such events; in thecase of sulphur dioxide, for instance,increasingly stringent emission controlsand the move towards lower-sulphur orclean fuels such as natural gas mean thatsuch events are now becoming increasinglyrare. The most recent clearcut example ofsuch a point-source episode for SO2 wasseen in May 2002 in Grangemouth, 300mfrom the nearby large refinery, wheremeasured peak 15-minute averageconcentrations up to 506 µgm-3 wereobserved; these levels were nearly twicethe relevant short-term UK objective forthis pollutant.
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UK Air Pollution
4.6. NASA SeaStar satellite image showing strongtransport of air and dust from the south on 15 April 2003
Levels of air pollutants vary markedlyacross the country. Measurements fromthe national air monitoring networksclearly show that these patterns differfor each pollutant, depending on howthey are formed and where their majorsources are located.
Levels of primary pollutants, thoseemitted directly into the atmosphere,tend to be highest around their sources;these are usually located in urban andindustrial areas. Sulphur dioxideprovides a good example of such apollutant, with domestic or industrialfuel burning being its major sourcesnationwide. As illustrated in the lastsection, the highest sustained levels ofthis pollutant are often found duringwinter in parts of Northern Ireland,where solid fuel is still used extensivelyfor domestic heating.
Measurements from the UK monitoringnetworks can be combined with detailedpollutant emissions data from the UK’sNational Atmospheric EmissionsInventory (NAEI). Together, theseprovide the basis for sophisticatedpollutant models which now enable us toproduce detailed maps (1km resolution)of average or peak pollutant concentra-tions across the country. These mapsenable the UK to fulfil its Europeancommitments to assess nationwidepollution patterns prior to implementingthe European Air Quality Directives.They also provide an extremely power-ful tool for identifying pollutant ‘hot-spots’ and managing UK-wide air qualityproblems in the most direct and cost-efficient manner.
A map showing average SO2 levelsacross the country, derived in this way, isshown in Fig 5.1. It clearly shows theimpact of power station and industrialemissions in NW England, the ThamesEstuary and Forth Valley, as well asdomestic emissions focussed aroundBelfast in Northern Ireland.
Motor vehicles are now a major source ofair pollution in many large cities. Inparticular, most of the carbon monoxide,nitrogen dioxide, and volatile hydrocar-bons such as benzene and 1,3-butadieneare emitted from traffic, together with asignificant proportion of particles (PM10).Concentrations of all these pollutants aretherefore usually highest in built-upurban areas.
In general, patterns of secondarypollutants such as ground-level ozone -which are formed by chemical reaction inthe atmosphere - are markedly differentfrom those of primary pollutants; theyare characteristically less dependent onemission patterns, and tend to be morestrongly influenced by meteorology andatmospheric chemistry. As a result, they
11
How air pollution varies across the UK
Concentration (ppb)
Below
1 - 2
2 - 4
4 - 6
6 - 8
8 - 10
10 - 12
Above 12
5.1. Background SO2, 2001
also change more from year to year thanthose of primary pollutants. UK-wideconcentrations of two of the most impor-tant secondary pollutants, ozone andnitrogen dioxide are shown in Figures 5.2and 5.3.
As highlighted previously, ground-levelozone is formed by a series of chemicalreactions involving oxygen, oxides ofnitrogen and hydrocarbons - so calledprecursor pollutants. Ultraviolet radia-tion drives these reactions and, as aresult, ozone production rates arehighest in hot, sunny weather. Ozoneformation can take from hours to daysto complete. Consequently, high levelsof ozone can often be formed consider-able distances downwind of the originalpollution sources in UK or Europe.
UK-wide patterns of ground-level ozoneare also influenced by other factors.Concentrations in busy urban areas areoften lower than in the surroundingcountryside. This is because road trans-port emissions react very quickly withozone to remove it from the atmos-phere. Because ozone is very reactive, itis also readily deposited onto theground or adsorbed onto vegetation.These removal processes tend to bemore important in sheltered, lowlandareas than exposed higher altitudes. Asa result, ozone levels are usually higheron elevated ground.
The net result of all these effects, actingtogether is shown in Figure 5.2. Thehighest summer ozone concentrations(here graphed as accumulated totalhours over 80µgm-3 for 2001) are seenin the rural parts of South and SouthEast England; these areas tend to be
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UK Air Pollution
Below 1000
1000 - 2000
2000 - 3000
3000 - 4000
4000 - 5000
5000 - 6000
6000 - 8000
Above 8000
Below 5
5 - 10
10 - 15
15 - 20
20 - 30
30 - 40
40 - 56
Above 56
5.2. Total O3 hours above 80µg m-3
5.3. Background NO2,annual averages(µg/m 3) in 2002
hotter and sunnier than other parts ofthe UK, and are often downwind ofpolluted areas of Northern Europe.Elevated concentrations are also seen inparts of Central/Eastern Scotland, afunction of its altitude. However, thefine detail in these annual ozone mapschanges from year to year, and otheryears have shown evidence of elevatedconcentrations in elevated parts ofWales.
The vast majority of Air QualityManagement Areas (AQMAs) in the UK aredue to current or predicted exceedences ofair quality objectives for nitrogen dioxide(NO2) or PM10 particles. We’ll now exam-ine UK-wide patterns of these pollutantsmore closely.
UK-wide patterns of nitrogen dioxideconcentration shown in Figure 5.3 aremarkedly different from those of ozone orsulphur dioxide. Although some NO2 isemitted directly from vehicles or othersources, most is formed by rapid chemi-cal reaction in the atmosphere.Concentrations of nitrogen dioxide there-fore tend to be highest in urban areaswhere traffic densities are high, such asin London. Although the data mapped inthe figure are background rather thanroadside pollution levels, they clearlyfollow closely the country’s major motor-ways and road network infrastructure.
Particles are not a distinct chemicalspecies like the other pollutants measuredin the automatic networks; rather, theyconsist of material from many sourcesand are usually classified on the basis ofsize and not chemical composition. In theUK automatic networks, particles of aver-age diameter less than 10 microns (whereone micron is a thousandth of a millime-tre) are measured. These fine particlefractions can be inhaled deep into thelungs, and therefore provide a better indi-cation of potential health impacts thancoarser particle size ranges.
The sources of PM10 particles are diverse.They are produced from motor vehicles,fuel burning, building work, industrial emis-
sions, soil and road dust and quarrying. Asignificant proportion of PM10 particles aresecondary, formed by the reaction of gasesin the air. Particles of ammonium sulphateand nitrate are produced by the samephotochemical reactions that give rise toozone. Like ozone, secondary particles cantherefore be formed considerable distancesfrom the emission sources. This diversity ofPM10 source types and influences is
reflected in the map of average concentra-tions in Figure 5.4, which shows markedlyless variation across the country than forthe other pollutants assessed here.
13
How air pollution varies across the UK
Below 10
10 - 15
15 - 20
20 - 25
25 - 30
30 - 35
35 - 40
Above 40
5.4. Background PM10,
annual averages
(µg/m 3 gravimetric)
in 2002
As highlighted in previous sections, theconcentrations of air pollutants in the atmos-phere can vary over the course of a day, theseasons of a year and from year to year. Inthis section, we focus on long-term trends inthe UK’s Air Quality, and attempt to answerthe perennial question - ‘are things gettingbetter or worse?’ As always, the answer tosuch a straightforward question is notclearcut. It really depends on what pollutantswe’re examining, and over what timescales.
Very reliable indications of long-term trendscan be derived from UK monitoring data. Asnoted previously, large-scale national meas-urements of black smoke and sulphur diox-ide began in the early 1960s. This nationalnetwork, established in response to therecurring serious smogs of that era, wasprobably the earliest air quality measure-ment programme of this scale and sophisti-cation in the world.At its peak, itincluded over 1200measurement sites.The main objectivesof this network wereto assess nationwidelevels of these ingre-dients of coal smog,and to analyse howthese have changedover time; over the40 years of its oper-ation, both of thesenetwork goals havebeen met in full.
In Figure 6.1, we show annual average levelsof both pollutants from the establishment ofthe network to the present day. The pictureshown here is most encouraging. It demon-strates that overall levels of sulphur dioxidehave fallen nearly 10-fold, and smoke levels20-fold. Corresponding measurements fromlater automatic measurements since 1970tell the same story, with urban backgroundSO2 levels now barely distinguishable fromthose in rural areas.
The dramatic decline in atmospheric concen-trations of these pollutants mirrors closelythe fall in national emissions of both pollu-tants. This is because far less coal is used fordomestic and small-scale heating, smoke
control measures have been universallyapplied through a series of Clean Air Acts,and cleaner fuels and fuel-burning technolo-gies have been widely adopted. Overall, thesuccessful regulation and taming of coalburning and its emissions represent aremarkable success story for Air QualityManagement in the UK.
However, this did not mark the end of airpollution problems in the UK. Road transportand industry remain major sources of pollu-tion, with vehicle emissions being the mostimportant factor affecting air pollution in ourcities. The shift from an air pollution climatedominated by coal burning to one mostinfluenced by road transport has occurred incountries world-wide. In many parts ofChina, for instance, we see pollutionclimates in a state of transition, with coalburning and a burgeoning vehicle fleet both
adding to the urbanair quality burden.
Long-term trends ofa wide range of airpollutants can betracked in Britainsince the early1970s; this waswhen automaticmeasurements ofmany other species– including second-ary pollutants andthose producedprimarily by road
transport – commenced in earnest. Evenclearer trends have become apparentsince the massive expansion of the scaleand coverage of national measurementsover recent years.
In Figure 6.2, we graph the UKGovernment’s air quality headline indicatorof sustainable development since 1987;urban and rural trends are shown sepa-rately. This graph shows the averagenumber of days on which levels of any oneof a basket of five pollutants (carbonmonoxide, nitrogen dioxide, ozone, fineparticles and sulphur dioxide) were‘moderate or higher’ according to the AirPollution Information Service bandingslisted earlier in Section 2 of this brochure.
14
UK Air Pollution
1962
300
180
160
140
120
100
80
60
40
20
0
1964
1966
1968
1970
1972
1974
1976
1978
1980
1982
1984
1982
1988
1990
1992
1994
1996
1998
2000
2002
Year Beginning April
Sulphur dioxide concentration, µg m-3
Smoke, µg m-3
Smoke and SO2: Long Term Trends over 40 yearsin Annual Average Levels
Con
cent
ratio
n, µ
g/m
-3
Figure 6.1.
These five pollutants are recognised as themost important for causing short termhealth effects.
To supplement this information, we graphseparately in Figure 6.3 the averagenumber of days of pollution at urban sitessince 1993 caused by each individualpollutant.
There is a wealth of information containedin these figures, from which we can extracta number of key conclusions. Firstly, it’sclear that 2003 was an exceptional year asregards both weather conditions and airpollution. Although the headline indicatorhad been showing an overall downwardtrend in UK urban areas since the early1990s, 2003 showed a sharp rise, dueprimarily to an increased number of poorozone days. In urban areas, ozoneaccounted for approximately 70% of theincrease over previous years, with theremainder due to PM10 particles. The
increase in the rural indicator figures wasdue overwhelmingly to ozone.
The main causes of days of moderate orhigher air pollution at urban sites are nowozone and fine particles (PM10). Thenumber of days caused by ozone pollutionhas fluctuated markedly from year to yearin both rural and urban areas. As notedpreviously, the production of ozone isstrongly influenced by the weather; as aresult, the exceptionally hot, sunnysummer in 2003 led to the greatest numberof days of moderate or higher ozone pollu-tion since this modern air quality indicatorseries began in 1987.
Ozone is responsible for the overwhelmingmajority of pollution days in rural areasbut, since 1999, it has also caused moredays of poor air quality in urban areasthan particles or any other pollutants.Between 1993 and 2002, the averagenumber of days of pollution at urban sitescaused by fine particles, solely or incombination with other pollutants, fellfrom an average per site of about 43 daysto 6 days per year, but rose again to 17days in 2003. UK-wide emissions of parti-cles have declined substantially in recentyears, but the number of pollution dayscan still fluctuate from year to year due tovariations in weather conditions and theimpacts of long-range transport.
Sulphur dioxide, which used to make asignificant contribution to the index, hasnow fallen to relatively very low levels.Short-term levels of the other two pollutantsincluded in the index, carbon monoxide andnitrogen dioxide, have very rarely reachedmoderate or higher levels since 1993.However, long-term exposure to nitrogendioxide remains a problem in many parts ofthe UK; this is why it triggers the declarationof Air Quality Management Areas in manyurban areas with high traffic densities.
15
How air pollution has changed over time
45
40
30
25
20
15
10
0
1992 1992 1992 1998 2000 2002
O3
NO2
CO
SO2
PM10
Year
UK Urban Air Pollution Indicators
Num
ber
of d
ays
abov
e th
e st
anda
rds
5
35
0
10
20
30
40
50
60
1987 1989 1991 1993 1995 1997 1999 2001 2003
Year
UK Urban and Rural Air Pollution Indicators; 2003
Rural Average
Urban Average
Num
ber
of D
ays
Abo
ve th
e S
tand
ards
Figure 6.3.
Figure 6.2.
Current and forecast air quality (national & local)
This is rapidly available in a user-friendly form from:
Teletext: page 156
The Air Pollution Information Service:freephone 0800 556677
The UK Air Quality Archive:www.airquality.co.uk
General information on Air Quality
The UK Air Quality Information Archive:www.airquality.co.uk
The National Atmospheric Emissions Inventory:www.naei.org.uk
The Defra air quality information web resource:www.defra.gov.uk/environment/airquality/index.htm
The Scottish Executive Air Quality pages:www.scotland.gov.uk/about/ERADEN/ACEU-AQT/00016215/homepage.aspx
The Welsh Assembly Government Environment link:www.wales.gov.uk/subienvironment/index.htm
The Northern Ireland Environment and Heritage Service website:www.ehsni.gov.uk/environment/environment.shtml
A companion report to this brochure entitled:Air Quality in the UK, 2003 is available from Defra at:
Defra PublicationsAdmail 6000London SW1A 2XXTel: 08459 556000, Fax: 020 8957 5012e-mail: [email protected]
Health Effects of Air Pollution
A concise brochure entitled: Air Pollution, what it means for your healthis available to download from the Defra air quality information web resource listed above or free of charge from Defra publications.
Local Air Quality Issues
For further information on air quality issues in your area, please contact:The Environmental Health Department at your local District Council office.
Further information on Local Air Quality Management may also be found at:www.defra.gov.uk/environment/airquality/laqm.htm andwww.airquality.co.uk/archive/laqm/laqm.php
This brochure has been produced by theNational Environmental Technology Centre (Netcen) on behalf of Defra and the Devolved Administrations
Front cover, inside cover and page 6 images © Jon Bower, Image of TV weather bulletin courtesy the BBC.NASA Satellite images in Section 4 courtesy the Visible Earth Team, Designed & printed by HPL Imaging Centres Ltd.