Air Quality Strategy Pollutants

Introduction

The original National Air Quality Strategy (NAQS) published in 1997 (DOE 1997) set out a framework of standards and objectives for the air pollutants of most concern (SO2, PM10, NOx, CO, lead, benzene, 1,3-butadiene and tropospheric ozone). The aim of the strategy was to reduce the air pollutant impact on human health by reducing airborne concentrations. Different pollutants have differing timescales associated with human health impacts. Therefore concentrations during episodes (both Winter and Summer) are important for some pollutants, but less so for others.

 

The NAQS identified air quality standards for 8 priority pollutants based on the recommendations of the Expert Panel on Air Quality Standards (EPAQS) or WHO guidance where no EPAQS recommendation existed. EPAQS was set up by the Secretary of State for the Environment in 1991, and is a panel created to “advise, as required, on the establishment and application of air quality standards in the UK… taking account of the best available evidence of the effects of air pollution on human health…”. The NAQS has been subject to periodic review, with consultation documents being published in 1998 and 2000 (DETR 1998a, 2000).

 

The NAQS then evolved into the Air Quality Strategy for England, Scotland, Wales and Northern Ireland (AQS for ESWNI), with the same goals. A second edition of the strategy was published in 2000 (DETR 2000), identifying further revisions and focused on the incorporation of air quality limit values in European Directives, and the impacts of devolution.

 

Following a consultation exercise new objectives for: particles, benzene, carbon monoxide and polycyclic aromatic hydrocarbons were announced for England in August 2002. More details can be found at the Defra website (Defra news release 323/02). The situation for Scotland differs slightly- the Air Quality (Scotland) Amendment Regulations came into force on 12 June 2002. More detailed information can be found on the Scottish Executive website (Scottish Executive News Release SEen057/2002 on www.scotland.gov.uk). For Wales, the consultation paper on the same subject is available from the Welsh assembly web pages (http://www.wales.gov.uk).

In addition to the above, Local Authorities in the UK have a duty, under the 1995 Environment Act: Part IV, to review and assess air quality in their areas.  The Air Quality Regulations 2000 define a staged process of review and assessment on the basis of guidance provided by Defra and the Devolved Administrations.  The first stage primarily involves the collection of existing data on air quality measurements and emission sources for the 8 pollutants of interest in the AQS for ESWNI.  These data are then used to define whether there is likely to be an air quality problem in a specific future year (depending on pollutant).  The second and third stages require the use of increasingly sophisticated monitoring and modelling tools to identify hotspots of pollution and to determine whether or not the relevant air quality objectives will be met in each area.

 

The NAEI is being used as an important source of data for the compilation of appropriate local inventories.  Table 4.1 summarises the total 2000 emissions of the 8 priority pollutants covered by the AQS for ESWNI.

 

 

 

 

Table 4.1  Total UK Emissions of AQS for ESWNI Pollutants

Pollutant

Total 2000 emission (kt)

PM10

171

 

Carbon Monoxide

4167

 

Benzene

16.4

 

1,3 Butadiene

5.7

 

Nitrogen oxides

1512

 

Sulphur dioxide

1156

 

Tropospheric Ozone

NS1

 

Lead

0.50

 

PAH

2.26

 

1 No significant ozone emissions from anthropogenic sources

 

The following sections provide a discussion of the UK emissions for particulate matter, carbon monoxide, benzene and 1,3-butadiene whilst a full discussion of the other pollutants is included in other chapters of this report as indicated in Table 4.2.

 

Table 4.2  Location of Emissions and Discussion of AQS for ESWNI Pollutants

Pollutant

Location

PM10

Chapter 4:   AQS Pollutants

Carbon Monoxide

Chapter 4:   AQS Pollutants

Benzene

Chapter 4:   AQS Pollutants

1,3 Butadiene

Chapter 4:   AQS Pollutants

Nitrogen oxides

Chapter 5:   Acidifying Gases & Ozone Precursors

Sulphur dioxide

Chapter 5:   Acidifying Gases & Ozone Precursors

Tropospheric Ozone

Chapter 5:   Acidifying Gases & Ozone Precursors

Lead

Section 6.3: Heavy Metals

PAH

Section 6.2: Persistent Organic Pollutants

 

 

Particulate Matter

Introduction

Historically, interest in particulate matter focused mainly on smoke which can cause health problems especially in combination with other pollutants.  The classic example was emissions of smoke and sulphur dioxide leading to the London smogs in the 1950s and early 1960s when several thousand excess deaths were recorded.  Smoke emissions have fallen significantly as a result of the Clean Air Acts eliminating domestic coal combustion in many urban areas.  However, there is increasing interest in the measurement of fine particles, such as those arising from the combustion of diesel fuel in the transport sector, and aerosol concentrations in the atmosphere from other sources which may have harmful effects.  Recent epidemiological evidence is also linking concentrations of particles in the atmosphere with human health effects.  Indeed, current ambient mass concentrations are thought to be sufficient to lead to increased mortality and morbidity (EPAQS, 1995).

 

Particles can vary widely in size and composition.  Particles larger than about 30 mm (a mm is a "micrometre", or one thousandth of a millimetre) fall rapidly under gravity and those larger than about 100 mm fall out of the atmosphere so rapidly they are not usually considered.  At the other end of the size scale are particles less than a tenth of a mm which are so small they do not fall under gravity appreciably, but coagulate to form larger particles that are then removed from the atmosphere.

 

The US PM10  standard was a monitoring standard designed to measure the mass of particles less than 10 mm in size (more strictly, particles that pass through a size selective inlet with a 50% efficiency cut-off at 10 mm aerodynamic diameter).  This corresponds to the International Standards Organisation thoracic convention for classifying those particles likely to be inhaled into the thoracic region of the respiratory tract.  The epidemiological evidence of the effects of particulates shows good correlation in the UK between PM10 concentrations and mortality or morbidity (EPAQS 1995, 2001).  Therefore PM10 has become the generally accepted measure of particulate material in the atmosphere in the UK and in Europe. There is also an increasing interest in the correlation between PM2.5 and health indicators.  PM10 measurements are being made in the UK (Bower et al, 1994, 1995 a & b, 1996, 1997) and their emissions have been included in the NAEI since 1995.

 

For many years the monitoring of particulate levels was based on the measurement of “Black Smoke”.  Levels were estimated using a simple non-gravimetric reflectance method in which air is sampled through a filter and the resulting blackening measured.  The method was calibrated for domestic coal smoke.  When most of the emissions come from coal combustion the blackening should be approximately proportional to the mass concentrations.  In the 50s and 60s, domestic coal combustion was the dominant source of black smoke and hence this method gave an indication of the concentration.  The NAEI estimates of black smoke emissions were extended in 1988 to include emissions from all fuel combustion.  Prior to 1988 only emissions from coal combustion had been estimated and published in the DOE Digest of Environmental Statistics.  However, there have been no recent emission measurements to confirm these factors are still accurate.

 

Smoke from different sources has a different blackening effect and so there is no simple relationship between black smoke and the mass of particulate emissions.  For example, typically diesel emissions have a blackening effect three times greater, mass for mass, than coal emissions, while petrol emissions are effectively an order of magnitude less. Black smoke is a poor indicator of the concentrations of particulates in the atmosphere current interest and the NAQS is focused on PM10 (particulate matter less than 10mm i.e. 10 millionths of a metre) and smaller size fractions (EPAQS, 1995). However, black smoke has been shown to have relationships with health effects and is still used as an indicator.

 

For completeness the following sections present emission estimates and discussion for PM10 , PM2.5 , PM1.0 , PM0.1 and Black Smoke.

 

PM10

Sources of emissions

PM10 in the atmosphere arises from two sources.  The first is the direct emission of particulate matter into the atmosphere from a wide range of sources such as fuel combustion, surface erosion and wind blown dusts and mechanical break-up in, for example, quarrying and construction sites.  These are called ‘primary’ particulates.  The second source is the formation of particulate matter in the atmosphere through the reactions of other pollutants such as sulphur dioxide, nitrogen oxides and ammonia to form solid sulphates and nitrates, as well as organic aerosols formed from the oxidation of VOCs.  These are called ‘secondary’ particulates.  This inventory only considers primary sources. For further information on secondary particulate see the third Quality of Urban Air Review Group report (QUARG, 1996) and the report from the Airborne Particles Expert Group (APEG, 1999)- see http://www.aeat.co.uk/netcen/airqual/reports/quarg/q3intro.html and http://www.defra.gov.uk/environment/airquality/airbornepm/index.htm respectively.

 

There is currently a programme sponsored by Defra and  the Society of Motor Manufacturers and Traders (SMMT) to measure PM10 emissions from road transport.  This programme has developed measurement techniques and aims to produce improved PM10 emission factors, particulate characterisation and particle size distribution.

 

The main sources of primary PM10 are briefly described below:

·     Road Transport. All road transport emits PM10.  However diesel vehicles emit a greater mass of particulate per vehicle kilometre than petrol-engined vehicles.  Emissions also arise from brake and tyre wear and from the re-entrainment of dust on the road surface.  Emission estimates for the re-entrainment of dust have been made. However this does not fall within the UN/ECE reporting format and consequently has been reported separately.

 

·     Stationary Combustion. Domestic coal combustion has traditionally been the major source of particulate emissions in the UK.  However, the use of coal for domestic combustion has been restricted in the UK by the Clean Air Acts, and as a result other sources are more important nationally. Domestic coal can still be a significant source in some smaller towns and villages, in Northern Ireland and in areas associated with the coal industry.  Other fossil fuels emit PM10, but emissions from gas use are small.  In general, particles emitted from combustion are of a smaller size than from other sources.

 

·     Industrial Processes.  These include the production of metals, cement, lime, coke, and chemicals, bulk handling of dusty materials, construction, mining and quarrying. Emissions from these sources are difficult to quantify due to the contribution of fugitive emissions (i.e. those diffuse emissions which are released directly into the atmosphere from a process rather than being collected in a controlled manner and then vented to atmosphere). Few UK measurements are available for these fugitive releases.  Nonetheless, there have been substantial improvements in the estimation of PM10 emissions from industrial processes in recent years. Usually a substantial fraction of the particles from these sources is larger than 10 mm but the large quantities emitted ensure that the fraction less than 10 mm  is still substantial.

 

PM10 Emission estimates

Emissions of PM10 are shown in Table 4.3 and Figure 4.1.  Emissions of PM10 from the UK have declined since 1970.  This is due mainly to the reduction in coal use.  Domestic emissions have fallen from 222 tonnes (41% of the total emission) in 1970 to 28 tonnes (16%) in 2000.

 

Emission estimates for the resuspension of dust from roads is not included in the standard UN/ECE reporting format (and hence not included in Table 4.3). However for completeness it is given in Table 4.4 below.  Estimates for resuspension are based on the deposition of primary particles form all UK sources (including vehicle tailpipes and from brake and tyre wear) that are returned to the air from the turbulence of passing vehicles.  As such, resuspension to some extent double counts the emissions, but is important in reconciling road side concentration measurements.

 

 

 

Table 4.3  UK Emissions of PM10 by UN/ECE Source Category and Fuel (kt)

 

1970

1980

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2000%

BY UN/ECE CATEGORY1

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Comb. in Energy Prod.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   Public Power

67

76

70

70

66

55

49

38

35

24

25

20

22

13%

   Petroleum Refining Plants

5

5

3

4

4

4

4

4

4

4

4

3

3

1%

   Other Comb. & Trans.

16

2

0

0

0

0

0

0

0

0

0

0

0

0%

Comb. in Comm/Inst/Res

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   Residential Plant

222

102

52

55

51

53

43

33

35

33

33

34

28

41%

   Comm/Pub/Agri Comb.

22

11

8

8

8

7

7

6

6

7

6

5

5

3%

Combustion in Industry

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   Iron & Steel Comb.

8

2

1

1

1

1

1

1

1

1

1

1

1

0%

   Other Ind. Comb.

89

44

39

39

41

39

38

35

32

30

27

24

20

11%

Production Processes

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   Processes in Industry

14

12

14

14

14

14

14

13

14

13

13

12

11

7%

   Construction

8

3

4

4

3

3

3

4

4

4

4

4

4

2%

   Quarrying

22

21

29

26

25

25

27

26

23

24

23

21

21

12%

Road Transport

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   Combustion

44

53

59

58

56

54

52

48

45

39

35

32

26

15%

   Brake & Tyre Wear

2

3

4

4

4

4

4

4

5

5

5

5

5

3%

Other Trans/Mach

15

13

13

13

12

12

12

11

12

12

11

11

10

6%

Waste

1

4

3

3

2

2

3

2

2

1

1

1

1

1%

Agri. & Land Use Change

11

12

12

13

12

12

12

12

13

13

14

14

14

8%

By FUEL TYPE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Solid

359

199

138

142

135

124

107

84

80

68

65

60

53

31%

Petroleum

96

87

83

83

80

78

75

69

66

59

53

49

41

24%

Gas

5

6

7

7

7

8

8

8

9

9

10

10

10

6%

Non-Fuel

87

73

86

79

77

77

80

77

74

74

74

69

67

39%

TOTAL

546

365

313

311

299

285

270

238

230

209

201

188

172

100%

1 See Annex 1 for definition of UN/ECE Categories

 

Table 4.4 PM10 Emission Estimates from Resuspension

 

1970

1980

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

 Resuspension from Road Trans

8.2

11.2

16.9

17.0

17.0

17.0

17.4

17.8

18.3

18.7

19.0

19.3

19.4

 

The geographical disaggregation of emissions is shown in Figure 4.2.  There is a clear distinction between the important sources in rural and urban areas.  Indeed, many of the sources do not occur inside towns and cities.  While road transport accounts for only 20% of national emissions, it can account for up to 80% of primary emissions in urban areas such as London (Buckingham et. al., 1997).

 

Emissions from electricity generation have also recently been declining (since 1991) despite a significant growth in the electricity generated between 1970 and 2000.  This is due to the move away from coal to natural gas and nuclear power for electricity generation and to improvements in the performance of electrostatic precipitators at coal-fired power stations.  Also the installation of flue gas desulphurisation at two power stations have reduced particulate emissions further.


 

Figure 4.1 UK Emissions of PM10

 

The one sector which has shown significant relative growth in emissions since 1970 is road transport, with a contribution to the total UK emission rising from 13% in 1970 to 20% in 2000.  In urban areas with little industrial activity, where public power and industrial processes do not make a significant contribution, the contribution of road transport to emissions will be even higher; for example as much as 80% of primary emissions in London.  The main source of road transport emissions is exhaust from diesel engined vehicles.  Emissions from diesel vehicles have been growing due to the growth in heavy duty vehicle traffic and the move towards more diesel cars, (diesel cars have increased from 3% to 12% of the UK vehicle fleet between 1990 and 2000).  Since around 1992, however, emissions from diesel vehicles have been decreasing due to the penetration of new vehicles meeting tighter PM10 emission regulations.

 

Among the non-combustion and non-transport sources, the major emissions are from industrial processes, the most important of which is quarrying whose emission rates have remained fairly constant.  Other industrial processes, including the manufacture of steel, cement, lime, coke, and primary and secondary non-ferrous metals, are collectively important sources of particulate matter although emissions from individual sectors are relatively insignificant.


Figure 4.2, Spatially Disaggregated UK Emissions of PM10

 

Finer particulates: PM2.5, PM1 and PM0.1

Inventories for PM2.5, PM1 and PM0.1 have been estimated from the PM10 inventory and the mass fractions in these size ranges available for different emission sources and fuel types.  A total of 33 different size distributions covering PM2.5 and PM1 emissions from different source sectors were taken from the USEPA (1995) as being applicable to sources in the UK; a fewer number of sectors with size fractions in the PM0.1 range were available from the study by the TNO Institute of Environmental Sciences, Energy Research and Process Innovation in the Netherlands for the Dutch National Institute of Public Health and Environment (RIVM) (TNO, 1997) who produced a particulates emissions inventory for Europe.  In general, combustion processes emit a higher proportion of fine particles (<2.5 µm) than mechanical sources such as quarrying and construction.  Gaseous fuels also tend to emit finer particles than petroleum and solid fuels.

 

Each of the detailed source sectors for which a PM10 emission is estimated (a total of 236 individual sectors and sub-sectors) were allocated an appropriate size distribution and used to calculate emission inventories for PM2.5, PM1 and PM0.1.  The results are shown in Tables 4.5-4.7 in the same format as for the PM10 inventory.

 

Figures 4.3-4.5 show trends in emissions of each particle size by source sector.  The results show a comparable decline in emissions of each particle size since 1990, although the PM0.1 size fractions indicate a larger decrease. Between 1990 and 2000, UK emissions of PM10 fell by 40%, whereas emissions of PM2.5 fell by 28%, PM1 by 28% and PM0.1 by 40%. There is a gradual change in the relative source contribution with particle size.  This is illustrated in Figures 4.2 to 4.5 which show the contribution of each sector to PM10, PM2.5, PM1 and PM0.1 emissions from 1990 to 2000.  Road transport becomes an increasingly important sector as the particle size decreases.  In 2000, it accounted for 18% of PM10 emissions, but 43% of PM0.1 emissions.

 

 

Table 4.5 UK emissions of PM2.5 by sector (ktonnes) estimated for the mass fraction of particles below 2.5 µm in each sector in the PM10 inventory

 

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2000%

Comb. in Energy Prod/Trans

41

37

34

37

33

34

35

35

36

39

38

19%

Comb. in Comm/Inst/Resid

94

83

71

70

67

57

55

56

52

53

46

23%

Combustion in Industry

70

61

53

55

50

44

44

43

41

43

33

17%

Production Processes

16

16

17

18

17

16

16

15

16

16

14

7%

Road Transport

40

41

43

44

43

43

45

45

46

47

48

24%

Other Transport

12

13

13

14

12

12

12

12

12

12

11

5%

Waste Treatment & Disposal

1

1

1

1

1

1

1

3

4

5

4

2%

Agriculture/Forestry

4

4

4

4

4

4

4

4

4

4

5

2%

TOTAL

277

255

236

244

227

212

212

213

211

218

198

100%

 


 

Table 4.6 UK Emissions of PM1 by Sector (ktonnes) Estimated for the Mass Fraction of Particles below 1 µm in each Sector in the PM10 Inventory

 

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2000%

Comb. in Energy Prod/Trans

21

19

17

18

16

17

16

17

17

18

17

12%

Comb. in Comm/Inst/Resid

73

64

54

53

51

43

41

42

39

40

34

24%

Combustion in Industry

41

37

34

36

32

29

29

28

27

28

21

15%

Production Processes

8

7

8

8

8

7

8

7

7

8

7

5%

Road Transport

36

37

38

40

39

39

40

40

41

42

42

30%

Other Transport

11

11

12

13

11

11

11

11

11

11

10

7%

Waste Treatment & Disposal

1

1

1

1

1

1

1

3

3

5

3

2%

Agriculture/Forestry

4

4

4

4

4

4

4

4

4

4

5

3%

TOTAL

194

180

168

173

161

150

150

152

150

155

140

100%

 

 

Table 4.7 UK Emissions of PM0.1 by Sector (ktonnes) Estimated for the Mass Fraction of Particles below 0.1 µm in each Sector in the PM10 Inventory

 

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2000%

Comb. in Energy Prod/Trans

6

6

6

5

5

4

4

3

3

3

3

10%

Comb. in Comm/Inst/Resid

3

3

3

3

3

3

3

3

3

3

3

8%

Combustion in Industry

8

8

8

8

8

7

7

6

6

5

5

15%

Production Processes

2

2

2

2

2

1

2

1

1

1

1

4%

Road Transport

25

25

24

24

23

22

20

18

16

15

13

43%

Other Transport

2

2

2

2

2

2

2

2

2

2

2

5%

Waste Treatment & Disposal

0

0

0

0

0

0

0

0

0

0

0

1%

Agriculture/Forestry

4

4

4

4

4

4

4

4

4

5

5

15%

TOTAL

51

51

50

48

47

43

42

38

36

34

31

100%

 

Figure 4.3 UK emissions of PM2.5

 


Figure 4.4 UK emissions of PM1

 

Figure 4.5 UK emissions of PM0.1

 

 

Black Smoke

There has been less interest in the emissions of black smoke across recent years. This is because PM10 has superceded black smoke as an indicator of particulate material in the air. As a result, black smoke emission estimates are presented here in less detail than previous years. The total emissions are included below in Table 4.8

 

Table 4.8  UN/ECE1 Total Emission of Black Smoke (kt)

 

1970

1980

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TOTAL

1087

605

484

490

478

454

414

375

364

329

289

273

246

1 See Annex 1 for definition of UN/ECE Categories

 

 

Carbon monoxide emission estimates

Carbon monoxide arises from incomplete fuel-combustion and is of concern mainly because of its effect on human health and its role in tropospheric ozone formation.  It leads to a decreased uptake of oxygen by the lungs and can lead to a range of symptoms as the concentration increases.

 

The UK emissions of carbon monoxide are shown in Figure 4.6 and Table 4.9 disaggregated by source and fuel.  Over the period 1970-2000 emissions decreased by 53% reflecting significant reduction in emissions from road transport, domestic and agricultural sectors.

 

Figure 4.6 Time Series CO Emissions

 

 

 

The spatial disaggregation of CO emissions is shown in Figure 4.7.  The observed pattern of emissions is clearly dominated by road transport emissions.  A large proportion of road transport emissions are from vehicles travelling at slow speeds on urban or minor roads, hence the map shows high emissions in urban conurbations.

 

 


Figure 4.7 Spatially Disaggregated UK Emissions of CO

 

Transport

The most important source of CO is road transport and in particular petrol driven vehicles.  Emissions from road transport fell only slightly between 1970 and 1990 but in recent years have declined more significantly.  This is due primarily to the increased use of catalytic converters and to a lesser extent to fuel switching from petrol cars to diesel cars.  The emissions from off-road sources includes portable generators, fork lift trucks, lawnmowers and cement mixers.  The estimation of emissions from such machinery is very uncertain since it is based on estimates of equipment population and annual usage time.

 

Table 4.9  UK Emissions of Carbon Monoxide by UN/ECE1 Source Category and Fuel (kt)

 

1970

1980

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2000%

BY UN/ECE CATEGORY2

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Comb. in Energy Prod.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   Public Power

117

121

114

113

110

99

106

104

102

71

73

61

60

1%

   Petroleum Refining Plants

8

8

7

7

7

8

7

8

8

8

8

7

6

0%

   Other Comb. & Trans.

45

24

22

22

20

20

20

22

23

23

26

27

28

1%

Comb. in Comm/Inst/Res

 

 

 

 

 

 

 

 

 

 

 

 

 

0%

   Residential Plant

1237

608

345

369

347

369

324

260

268

246

239

244

215

5%

   Comm/Pub/Agri Comb.

46

26

23

23

21

21

20

19

19

19

18

18

18

0%

Combustion in Industry

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   Iron & Steel Comb.

776

221

390

369

382

382

346

352

350

357

343

347

245

6%

   Other Ind. Comb.

217

130

125

120

121

121

123

122

113

115

101

137

136

3%

Production Processes

173

135

178

171

163

163

168

172

177

178

163

142

135

3%

Extr./Distrib. of Fossil Fuels

2

2

7

3

3

2

3

3

3

3

3

1

1

0%

Road Transport

5409

5367

5240

5076

4858

4528

4271

4003

3966

3728

3508

3290

2881

69%

Other Trans/Mach

 

 

 

 

 

 

 

 

 

 

 

 

 

 

   Off-Road Sources

584

512

428

445

453

439

428

407

408

407

407

406

405

10%

   Other3

30

28

32

30

29

28

26

26

26

25

23

22

21

1%

Waste

3

45

31

28

27

27

35

24

25

20

21

17

16

0%

Land Use Change

288

449

266

228

165

4

0

0

0

0

0

0

0

0%

By FUEL TYPE

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Solid

2237

989

877

879

867

870

792

730

727

686

663

651

521

12%

Petroleum

6061

5930

5718

5569

5356

5012

4740

4450

4414

4172

3949

3727

3316

80%

Gas

43

35

40

40

43

49

54

57

61

58

60

66

60

1%

Non-Fuel

593

723

573

514

440

279

292

285

285

285

262

273

270

6%

TOTAL

8934

7677

7208

7002

6707

6210

5877

5522

5487

5201

4934

4718

4167

100%

1 UK emissions reported in IPCC format (Salway, 2001) differ slightly due to the different  source categories used.

2 See Annex 1 for definition of UN/ECE Categories

3 Including railways, shipping, naval vessels, military aircraft

 

Other sources

Other emission sources of CO are small compared with transport and off-road sources.  Combustion-related emissions from the domestic and industrial sectors have decreased by 83% and 51% respectively since 1970 due to the decline in the use of solid fuels in favour of gas and electricity.  The sudden decline in emissions from the agricultural sector reflects the banning of stubble burning in 1993 in England and Wales. Currently energy production accounts for only 1% of UK emissions.

 

 

 

Benzene

Studies have shown that exposure to benzene gives rise to an increase in the risk of developing leukaemia, and that benzene exerts its effect by damaging the genetic make-up of cells i.e. it is a genotoxic carcinogen. Consequently it is important to understand sources of benzene and their relative strengths, and ensure that emissions do not give rise to unacceptably high concentrations of benzene.

 

Benzene emissions arise predominately from the evaporation and combustion of petroleum products. Emissions of benzene are dominated by the road transport sector, accounting for 47% of the 2000 emission estimate total. As benzene is a constituent of petrol, emissions arise from both evaporative and combustion of petrol. Benzene emissions for 1990 to 2000 are given in Table 4.10 and Figure 4.8 below.

 

Benzene emissions also arise as stack emissions and, more importantly, fugitive emissions from its manufacture and use in the chemical industry.  Benzene is a major chemical intermediate, being used in the manufacture of many important chemicals including those used for the production of foams, fibres, coatings, detergents, solvents and pesticides.

 

Benzene emissions have been steadily decreasing since 1990. These decreases are primarily due to the introduction of cars equipped with catalytic converters since 1991, although emissions from the domestic and industrial sectors are also falling. However, it is the increasing number of cars in the national vehicle fleet that are equipped with catalytic converters which maintains the decreasing total of benzene emissions as the reductions from other source sectors are small by comparison.

 

The most noticeable decrease between 1999 and 2000 arises from the road transport sector. This is because the benzene content of petrol was substantially decreasesd between 1999 and 2000- resulting in a corresponding decrease in emissions.

 

Table 4.10 UK emissions of Benzene by UN/ECE1 Source Category (ktonnes)

 

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2000%

BY UN/ECE CATEGORY1

 

 

 

 

 

 

 

 

 

 

 

 

Comb. in Energy Prod.

 

 

 

 

 

 

 

 

 

 

 

 

   Petroleum Refining Plants

0.00

0.00

0.01

0.01

0.00

0.01

0.01

0.01

0.01

0.01

0.01

0%

   Other Comb. & Trans.

0.29

0.29

0.29

0.29

0.32

0.13

0.15

0.18

0.18

0.20

0.18

1%

Comb. in Comm./Inst/Res

 

 

 

 

 

 

 

 

 

 

 

 

   Residential Plant

4.04

4.20

4.17

4.16

3.62

3.14

3.32

3.16

3.23

3.34

3.00

18%

   Comm/Pub/Agri Comb.

0.11

0.13

0.13

0.12

0.13

0.14

0.15

0.14

0.14

0.15

0.16

1%

Combustion in Industry

 

 

 

 

 

 

 

 

 

 

 

 

   Iron & Steel Comb.

0.31

0.32

0.30

0.30

0.23

0.24

0.24

0.26

0.24

0.23

0.22

1%

   Other Ind. Comb.

0.41

0.39

0.37

0.37

0.53

0.56

0.59

0.60

0.57

0.54

0.60

4%

Production Processes

4.37

4.46

4.67

4.55

4.66

4.59

4.05

3.43

2.26

2.04

1.65

10%

Extr./Distrib. of Fossil Fuels

1.02

1.07

1.12

1.15

1.13

1.08

0.95

0.99

0.96

0.72

0.67

4%

Road Transport

 

 

 

 

 

 

 

 

 

 

 

 

   Combustion

40.07

39.16

37.54

34.64

32.14

29.50

27.30

24.55

22.01

19.69

7.42

45%

   Evaporation

2.41

2.38

2.33

2.17

2.01

1.84

1.72

1.58

1.34

1.22

0.29

2%

Other Trans/Mach

2.44

2.52

2.52

2.44

2.36

2.27

2.31

2.30

2.22

2.19

2.17

13%

Waste

0.10

0.10

0.10

0.09

0.09

0.08

0.08

0.08

0.07

0.07

0.06

0%

Land Use Change

0

0

0

0

0

0

0