stage 2 report - borough of dartford · this report presents the stage 2 review and assessment of...

Review and Assessment of Air Quality in the Borough of Dartford - Stage 2

Public Consultation

This report has been circulated to all local authorities in Kent, local public libraries, other interested parties and to Members of Dartford Borough Council’s Environment, Housing and Community Services Committee. Any comments or questions should be directed to the following address no later than Friday 28 May 1999;

Duncan Philips Scientific Officer Environmental Strategic Development Directorate of Environment and Leisure Dartford Borough Council Civic Centre Dartford Kent DA1 1DR

Tel: 01322-343250 Fax: 01322-343963

e-mail : [email protected]

All comments received will be given due consideration and taken into account during the preparation of the Stage 3 Review and Assessment.

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Contents

The Borough of Dartford 3

1.0 Executive Summary 4

2.0 Stage 2 Review 6

2.1 Carbon Monoxide 7

2.2 Nitrogen Dioxide 11

2.3 PM10 18

2.4 Sulphur Dioxide 22

3.0 Meteorology and Local Weather Conditions 27

4.0 Atmospheric Emissions Inventory 31

5.0 Local Air Quality Monitoring 35

6.0 Conclusions 38

7.0 Recommendations 38

8.0 Appendices 39

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The Borough of Dartford

Dartford Borough lies 15 miles from Central London in North West Kent between the North Downs and the River Thames. One of the smaller of the Kent districts, it covers an area of about 7630 hectares and has a population approaching 84,000. The Borough is strategically located on two of the principal lines of communication within the South East - the M25 London orbital motorway and the A2, linking London to the Channel ports.

The northern part of the Borough between the A2 and the Thames includes the towns of Dartford and Swanscombe and is substantially built-up. It also includes the major development sites within the Borough, and lies within the Kent Thames-side area of the Thames Gateway. This area has been identified by Government as one of two areas within Thames Gateway with the potential for significant growth. The southern part of the Borough is generally rural in character and comprises a mix of open countryside, covered by Green Belt designation, and a number of villages and dormitory settlements.

Dartford is an important employment centre with major employers such as Glaxo Wellcome, Dartford and Gravesham and Thameslink Health Trusts, the Borough Council and J&E Hall located within the town centre. However, the Borough’s proximity to London and it’s good rail and coach connections mean that many residents commute to work elsewhere.

Several major developments are planned or under construction within the Borough e.g. Ebbsfleet, the Channel Tunnel Rail Link and the new Bluewater Regional Shopping Centre. Also there are an estimated 22,000 new homes and other leisure and commercial projects planned for the Thames gateway area, many of which are within the Borough. It is anticipated that road traffic on major and local roads will increase significantly.

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Review and Assessment of Air Quality in the Borough of Dartford

Stage 2

1.0 Executive Summary

Section 88(2) of the Environment Act 1995 places a statutory obligation upon local authorities to periodically review and assess air quality within the boundary of their jurisdiction. The enactment of the Air Quality Regulations 1997 signified the start of the review process and that this should be completed no later than 22 December 1999. Guidance issued by the Department of the Environment, Transport and the Regions (DETR) advises that the review process should be carried out in a staged approach. The aim of the process is to give consideration to the likelihood of the standards specified in the Air Quality Regulations 1997 being achieved by the objective target date of 31 December 2005.

In considering the individual pollutants, each authority is to be aware that national policies are expected to deliver an improvement in air quality by 2005 and that local control measures should be minimal. However, it is accepted that some pollutants, such as fine particulates, need to be dealt with at both local and regional levels and that measures to control them may be more challenging than some other pollutants such as lead.

This report presents the Stage 2 Review and Assessment of Air Quality in the Borough of Dartford. It contains a variety of data that relates to the four pollutants identified in the Stage 1 Review and Assessment (carbon monoxide, nitrogen dioxide, fine particulates and sulphur dioxide) as being of potential concern by the end of the year 2005. These pollutants have been identified and selected for the possibility of them not achieving the required standards by the end of 2005. Assessments have been made to try to predict the changes in development, road traffic and any other influencing factors. At all times, assessments have been made whilst having regard to the risk of exposure to pollutants over the timescale defined in each individual case. Areas of high residential density, retail centres and schools, for example, are of prime concern. The following drawing shows the locations of all the schools in the Borough and demonstrates that there are very few areas that do not need detailed consideration.

Locations of Schools - an indication of The quality of the air that we breathe is influenced by a range of potential sources of pollution and the manner in which that pollution mixes and disperses is a highly complex science, some aspects of which are still being discovered. In undertaking this Stage 2 Review, consideration has been given to the area surrounding the Borough and potential sources of pollution that might not be immediately apparent. Air movement is multi dimensional and the air that moves across the Borough has been subjected to pollution from other places and is in the process of dispersion at the same time as it receives a pollutant load. This is a continual cycle and one that is very difficult to predict. Meteorology has an important influence on this process and consequently upon the levels of pollutants that are recorded by real-time analysis equipment.

This review has considered the results from many real-time analysers across England and they have been chosen because their siting is comparable to sites that might be found in the Borough. It is not unreasonable to suggest that similar circumstances in one area will produce similar results in another that can be used for a ‘rule of thumb’ approach. No attempt has been made to suggest that the results are definitive, but they can be used reliably as an indicative guide. By using results from sites with

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several years data a greater level of confidence can be given to them and having results for the same pollutant from several sites increases that confidence still further. This is a realistic approach as opposed to using complex computer models. The use of computer models is a complicated issue which needs further consideration before deciding upon the most appropriate models to use.

1.1 Review and Assessment Summary

Stage 1 Stage 2 Stage 3

Benzene

1,3-Butadiene

Carbon Monoxide Carbon Monoxide �Lead

Nitrogen Dioxide Nitrogen Dioxide Nitrogen Dioxide

PM10 � PM10 � PM10

Sulphur Dioxide Sulphur Dioxide �

1.2 Nitrogen Dioxide

The evidence suggests that the nitrogen dioxide levels are likely to fail to meet the required standards for the annual average and also for the hourly average in some parts of the Borough by the objective target date. Therefore, a Stage 3 Review and Assessment using real-time analysing equipment needs to be carried out for this pollutant.

1.3 PM10

The evidence suggests that fine particulate levels are likely to fail to meet the required standards in some parts of the Borough by the objective target date. Therefore, a Stage 3 Review and Assessment using real-time analysing equipment needs to be carried out for this pollutant.

1.4 Sulphur Dioxide and Carbon Monoxide

The evidence suggests that sulphur dioxide and carbon monoxide levels are likely to meet the required standards by the objective target date. No further assessment of these pollutants is therefore required at this stage.

1.5 Proposals to amend the National Air Quality Strategy

During 1999, the NAQS will be reviewed and amendments will be made to bring the Strategy into line with current Government policy. When appropriate, changes which may occur in the NAQS and/or the factors influencing local air quality will be incorporated in the review and assessment process being undertaken.

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2.0 Stage 2 Review and Assessment

This section of the report provides a review and assessment of the levels of carbon monoxide, nitrogen dioxide, PM10 and sulphur dioxide in the Borough. Where possible, monitoring data has been used and this has been combined with a comparative analysis from sites in other Boroughs, long term national statistics and data from the National Atmospheric Emissions Inventory (NAEI). Assessments have been based upon a combination of this data and using a professional judgement to estimate the likelihood of exceedences at the end of 2005. The assessment has been made by comparing data to the National Air Quality Strategy (NAQS) although it should be acknowledged that other standards do exist. Standards are not static and can vary with time as new research evidence is released. For comparative purposes, the following table illustrates the relationship between various standards that exist.

Table 1 - Comparison of Air Quality Standards

Pollutant UK NAQS Existing EC standards or guide values

European Commission Proposal

Health Environment

UNECE Critical Level

Carbon Monoxide

10 ppm as running 8-hour

mean

- - - -

Nitrogen Dioxide

287 mg/m3 as 1 hour mean & 40

mg/m3 as annual mean

50 mg/m3 for 1 year as 50th

%ile of 1 hour means: 135

mg/m3 as 98th %ile

200 mg/m3 as 1 hour mean and

40mg/m3 as annual mean

30 mg/m3 as an annual mean

(for NOx)

95 mg/m3 as 4 hour mean, 30mg/m3 as

annual mean (for NOx)

Particulates (PM10)

50mg/m3 as running 24 hour

mean

- 50mg/m3 as running 24 hour

mean and 30 (20 in 2010)


- -

Particulates (PM2.5)

- - 40mg/m3 as 24 hour mean and

20 mg/m3 as annual mean

- -

Sulphur Dioxide 266 mg/m3 as 15 minute

mean

100 - 150 mg/m3

as 24 hour mean, 40-60


350 mg/m3 as 1 hour mean, 125

mg/m3 as 24 hour mean

20 mg/m3 as annual and as winter mean

10, 15 or 20mg/m3 as

annual and as winter mean

depending on vegetation type

(source : Adapted and extracted from NSCA Vol.28, No.2, March/April 1998)

This review and assessment has utilised data and long term trends from suitable sites in comparable areas in other parts of the UK. These have been specially selected for their similarity to sites and locations within the Borough. A description of the sites and a graphical summary of the results is provided in the appendix to this report.

The sites used for the comparison are;

Bath Roadside Leeds Centre Bristol Centre Bury Roadside Leicester Centre Cardiff Centre Exeter Roadside Leamington Spa London Hillingdon London Bexley London Bloomsbury London Cromwell Road

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Wolverhampton Centre Rochester Thurrock

2.1 Carbon Monoxide Carbon Monoxide is produced from incomplete combustion. Its effect on human health is of most concern where it inhibits oxygen uptake by the lungs. Carbon Monoxide is mainly emitted in the UK by petrol engined motor cars as a result of incomplete combustion. Emissions from power stations are small because efficiency, and therefore complete combustion, is a high priority. The following graphs show the UK emissions.

Chart 1 - 1970 and 1994 UK CO Emissions

(Source : DETR web site)

Chart 2 - 1970 to 1994 UK CO Emissions

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(Source : DETR w eb site)

The NAQS standard is 10 ppm, measured as a running 8-hour mean, and the objective is to achieve this standard by the end of 2005.

2.1.1 Sources

Carbon monoxide is produced by the incomplete combustion of carbon based substances. Complete combustion, in the presence of sufficient oxygen leads to carbon dioxide, whereas incomplete combustion, possibly due to slight oxygen deficiency, leads to carbon monoxide. Human exposure can be from a variety of sources, internally and externally. Internal sources might be from domestic heating appliances and is often related to poor installation or maintenance and combined with inadequate ventilation. Smokers are also exposed to high levels and it has been shown that the amount of carbon monoxide in the blood of a regular smoker is considerably greater than that which can be obtained from breathing air in even a heavily polluted street. The NAQS, however, is concerned with exposure for non-smokers in the external environment and the main source is from vehicle exhausts.

When a vehicle engine is cold or badly tuned, or when the engine is idling or moving slowly, it will depart from its optimal operating condition and produces more carbon monoxide. Thus, it is seen that levels of the gas in ambient air are highest close to busy roads, especially when traffic flow is reduced as in peak rush hours.

2.1.2 Health Effects

Carbon monoxide is both colourless and odourless and life-threatening concentrations can be breathed without giving any warning to the vi ctim. The first sign of severe poisoning is loss of consciousness and further inhalation of high concentrations readily leads to death. These effects are due to the interference of carbon monoxide with the processes whereby oxygen is taken up by the blood and utilised in the cells in the body. It does this by both interfering with the transport of oxygen by red cells in the blood (by the formation of carboxyhaemoglobin, which substantially reduces the ability of red cells to carry oxygen) and also by blocking essential biochemical reactions in cells. In those people who recover from accidental or deliberate poisoning by carbon monoxide, brain damage to a greater or lesser extent due to lack of oxygen is a common consequence.

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The formation of carboxyhaemoglobin in the blood of people exposed to carbon monoxide and the amount present depends on both the level and duration of exposure, as well as on the rate and depth of breathing. Thus, someone exercising and breathing more rapidly and deeply, will have higher levels than someone resting but exposed to the same concentration. Some people are at more risk than others, notably; those with pre-existing heart or lung conditions and pregnant women.

2.1.3 Data Sources and Predictions

There is no monitoring for this pollutant in the Borough. Elsewhere in Kent, it is monitored at two background sites at Luton (near Rochester) and Sevenoaks and also at a number of roadside sites in Canterbury. Results from these sites is presented within the Appendix. Data taken from the NAEI on the internet (www.aeat.co.uk/cgi-bin/pix2osco.pl) identifies that estimated background carbon monoxide concentrations across the Borough are in the 0.2 - 0.4 ppb range. This data compares favourably to the data in the following table that has been extracted from information in the NAQS;

Table 2 - Carbon Monoxide Monitoring Data

Site Year Annual Average Maximum 1-hour

Maximum 8-hour Running Average

Bexley 1994 1995

0.5 0.4

8.4 6.2

4.5 4.7

Leicester 1994 1995

0.6 0.5

8.8 10.1

5.9 7.9

London - Cromwell Road (kerbside)

1990 1991 1992 1993 1994 1995

2.9 3.3 2.8 2.2 1.9 1.8

18.4 18.7 11.0 12.6 10.7 9.7

15.5 13.9 8.7 9.1 10.1 6.7

Stevenage 1990 1991 1992 1993

0.7 0.7 0.6 0.5

6.4 7.4 5.0 6.8

3.5 4.9 3.0 3.0

(Source: National Air Quality Strategy 1997, pages 102 & 103) (Units = ppm)

Within the Appendix to this report, there are many charts which illustrate continuous monitoring at various sites with some dating back to 1992. The following series of charts are from the London Bloomsbury site over a five year period and show daily average and maximum values. This site is not unlike many locations within this Borough and the trends shown can be assumed to be comparable. The NAQS standard of 10 ppm as an 8-hour average can be seen to be easily achieved and indeed is never actually in danger of being breached. The same CO values of approximately 0.5 to 2.5 ppm are seen consistently at most of the sites in the Appendix. On the few occasions when there have been exceedences these may be due to equipment malfunction or exceptional local conditions. The principle remains the same, that CO is seen to be a pollutant that is unlikely to be a problem in achieving the NAQS standards.

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ppm

ppm

ppm

12/0

1/94

24/0

1/94

05/0

2/94

17/0

2/94

01/0

3/94

13/0

3/94

25/0

3/94

06/0

4/94

18/0

4/94

30/0

4/94

12/0

5/94

24/0

5/94

12/0

1/93

24/0

1/93

05/0

2/93

17/0

2/93

01/0

3/93

13/0

3/93

25/0

3/93

06/0

4/93

18/0

4/93

30/0

4/93

12/0

5/93

24/0

5/93

12/0

1/92

24/0

1/92

05/0

2/92

17/0

2/92

29/0

2/92

12/0

3/92

24/0

3/92

05/0

4/92

17/0

4/92

29/0

4/92

11/0

5/92

23/0

5/92

05/0

6/94

Bloomsbury - CO, 1994

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9

8

7

6

05/0

6/93

04

/06/

92

17/0

6/94

17

/06/

93

16/0

6/92

29/0

6/94

29

/06/

93

28/0

6/92

11/0

7/94

11

/07/

93

23/0

7/94

23

/07/

93

04/0

8/94

04

/08/

93

16/0

8/94

16

/08/

93

Max 5

Ave

4

3

2

1

0


10

9

8

7

6

10/0

7/92

22/0

7/92

03/0

8/92

15/0

8/92

28/0

8/94

09/0

9/94

21/0

9/94

03/1

0/94

15/1

0/94

27/1

0/94

08/1

1/94

20/1

1/94

02/1

2/94

14/1

2/94

26/1

2/94

28/0

8/93

09/0

9/93

21/0

9/93

03/1

0/93

15/1

0/93

27/1

0/93

08/1

1/93

20/1

1/93

02/1

2/93

14/1

2/93

26/1

2/93

27/0

8/92

08/0

9/92

20/0

9/92

02/1

0/92

14/1

0/92

26/1

0/92

07/1

1/92

19/1

1/92

01/1

2/92

13/1

2/92

25/1

2/92



10

9

8

7

4

5

6

Max

Ave

3

2

1

0

Max 5

Ave

4

3

2

1

0

10


10

9

8

7

6

ppm

ppm

Max 5

Ave

4

3

2

1

0

01/0

1/96

13/0

1/96

12

/01/

95

25/0

1/96

24

/01/

95

06/0

2/96

05

/02/

95

18/0

2/96

17

/02/

95

01/0

3/96

01

/03/

95

13/0

3/96

13

/03/

95

25/0

3/96

25

/03/

95

06/0

4/96

06

/04/

95

18/0

4/96

18

/04/

95

30/0

4/96

30

/04/

95

12/0

5/96

12

/05/

95

24/0

5/96

24

/05/

95

05/0

6/96

17/0

6/96

29/0

6/96

11/0

7/96

23/0

7/96

04/0

8/96

16/0

8/96

05/0

6/95

17/0

6/95

29/0

6/95

11/0

7/95

23/0

7/95

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8/95

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8/95

28/0

8/96

28

/08/

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/09/

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9/96

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/09/

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0/96

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/10/

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15/1

0/96

15

/10/

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0/96

27

/10/

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1/96

08

/11/

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1/96

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/11/

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2/96

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/12/

95

14/1

2/96

14

/12/

95

26/1

2/96

26

/12/

95



10

9

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6

5 Max Ave

4

3

2

1

0

DETR guidance indicates that consideration for this pollutant should identify roads that have high volumes of traffic (> 50,000 vehicles/day) and those that have a combination of high volumes with very slow speed (> 25,000 vehicles/day and where traffic travels at mean speeds < 10 km/hr). Using data from the Kent County Council Highways transport model, the following roads have been identified as having a current or projected average daily traffic flows greater than 50,000 • M25 • Watling Street • A2 • Princes Road • Thames Road / University Way However, the model did not identify any roads within the Borough with current or projected annual average daily traffic flows greater than 25,000 and where traffic travels at mean speeds < 10 km/hr for prolonged periods. 2.1.4 Assessment

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The NAQS suggests that national emissions of carbon monoxide will reduce by 32% in 2000, 48% in 2005 and by 54% in 2010 when compared with 1995 levels. Data from numerous comparable towns illustrated in the Appendix and predictions quoted in the NAQS would suggest that the Borough should not be at risk of exceeding the standard. Therefore, it is the conclusion of this Stage 2 Review and Assessment that there is no need to consider carbon monoxide in Stage 3.

2.2 Nitrogen Dioxide

Nitrogen Oxides produce acid gas which affect fish and plant life by increasing environmental acidity. Building erosion can also be attributed to Nitrogen Oxide emissions. Nitrogen Oxides are also one of the ingredients that combine to create photochemical smog's. Fuel combustion is the major source of nitrogen oxides in the UK. The two main sources in the UK are power stations and road transport.

Chart 3 - 1970 and 1994 UK Nitrogen Dioxide Emissions


Chart 4 - 1970 to 1994 UK Nitrogen Dioxide Emissions

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The NAQS standard is expressed in two ways. Firstly as 150 ppb, measured as a 1 hour mean, and the objective is to achieve this standard by the end of 2005. Additionally, it is expressed as 21 ppb, measured as an annual mean, and the objective is to achieve this standard by the end of 2005.

2.2.1 Sources

Nitrogen dioxide is a gas produced by the reaction of nitrogen and oxygen generally in a two stage reaction which initially results in the formation of nitric oxide. Nitric oxide, once emitted into the atmosphere, combines further with oxygen atoms, usually derived from ozone, to form nitrogen dioxide. This means that there tends to be an inverse relationship between ozone and nitrogen dioxide. This process can be clearly seen during air pollution episodes. Nitric oxide emitted from motor vehicles in cities reacts with, and thus removes, ozone and generates nitrogen dioxide. The nitrogen dioxide is then carried downwind and acts as a source, under the influence of sunlight, to produce ozone in rural areas.

The two main sources of emissions of oxides of nitrogen are from road transport and fossil fuelled power stations.


Exposure to nitrogen dioxide can bring about adverse effects on lung function and airway responsiveness. In very high concentrations, such as during industrial accidents and the pollution episode in London in December 1991 when the maximum hourly average concentration was recorded at 423 ppb, nitrogen dioxide can cause very severe and sometimes fatal lung damage. Lower level effects are more uncertain but it is believed that the gas have may both short and long term effects on the respiratory system due to inflammation of the airways. Research is still continuing to identify whether asthmatics are at a greater risk and this aspect is largely unclear at the current time.


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Nationally and locally, nitrogen dioxide has been widely monitored and of all the pollutants selected in the NAQS it is the one for which the largest body of data is available. Locally, the Borough currently has eight passive diffusion tubes. The locations of all monitoring sites in the Borough are illustrated below;

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Air Quality Monitoring Sites Within The Borough

1 2

3

4 5

6

7

8

9 10

11

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Key to the sites illustrated above

1 Ruskin Grove. NO2 diffusion tube from Jan 1993 to Dec 1997.2 The Terraces. NO2 diffusion tube since Jan 1993.3 Princes Road. NO2 diffusion tube since Jan 1993.4 The Plough, Northfleet. NO2 diffusion tube since Jan 1993.5 Lunn Poly. NO2 diffusion tube since Jan 1993. Benzene diffusion tube since Jan 1998.6 Princes Road. Benzene diffusion tube since Jan 1998. 7 Summerhouse Drive. NO2 diffusion tube since Jan 1998. 8 Ightham Cottages. NO2 diffusion tube from Sept 1997 to Sept 1998. Benzene diffusion

tube since April 1998. SO2 diffusion tube since April 1998. 9. Ightham Cottages. Continuous NO2 analysis. 10 Hope Cottages. NO2 diffusion tube since Oct 1998. 11 Main Road. NO2 diffusion tube since Jan 1998. 12 Axton Chase. NO2 diffusion tube since April 1998. Benzene diffusion tube since April

1998. SO2 diffusion tube since April 1998.

Results for five tubes (plus that of Northfleet which is very close to the Borough boundary) are shown below. The remaining tubes have not yet produced a sufficient volume of data to be included on the graph.

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Annual Average NO2 Diffusion Tube Data

0

5

10

15

20

25

30

ppb

NAQS Lunn Poly Princes Road Terraces Ruskin Grove Ightham Cottages Northfleet

This line represents only one years worth of data and is therefore slightly misleading.

This line stops because the site was discontinued and the tube relocated.

1993 1994 1995 1996 1997 1998

There is currently some debate about the accuracy of the diffusion tubes and research continues to determine their optimum use and this is the reason for the dual tubes by the pedestrian crossing on Lowfield Street in Dartford town centre. One line of thought shown by recent combined continuous monitoring and diffusion tube monitoring, in a study funded by DETR, is that the tubes on a four week cycle may be under-estimating by about 35%. However, a comment in recent DETR guidance suggests, confusingly, that they may be over-estimating by about 10%. The debate about this will be on-going for some time. Taking a ‘worst-case’ scenario it would appear that each of the four tubes included in the National Survey exceed the 21 ppb standard. If no account is taken as to the accuracy issue, the tube on Lowfield Street, outside Lunn Poly, currently exceeds the standard and has done since 1994.

Until the summer of 1998, there had been no data available within the Borough to quantify the hourly average levels of nitrogen dioxide. A continuous chemiluminescent monitor (on loan from the University of Greenwich) was installed in July 1998 in a roadside cabinet near to Ightham Cottages, Bean, which will provide valuable data on the busy junction with the A2. This junction will become an increasingly busy traffic site following the opening of the new Bluewater Regional Shopping Centre in March 1999. Whilst the analyser has only been operational for what is a relatively short period of time, and for some of that time has been off-line due to technical problems, it has already produced some interesting results. The following graphs combining traffic count data from the nearby A2 clearly illustrate the link between nitrogen dioxide and road traffic and the importance of wind direction.

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No.of vehicles (per hou

r) No. of V

ehicles (per hou

r)

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Wed 5th to Tues 11th August 1998 Traffic Flows On The A2 Past The Bean Intersection

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In the graph above, hourly traffic counts over a one week period highlight how consistent the traffic flows are. It would suggest that weekday commuter traffic is very predicable. The morning peak at about 7am takes place very quickly and equally decreases as quickly. The afternoon peak is more subtle and spread over a few hours. The weekend traffic is more sporadic. This is a very interesting observation and one that highlights a snap-shot of human social characteristics. In the following graph, the data from early August was compared with data from May to see whether there was any relationship with schools being on holiday or not. The trend is almost identical and no obvious difference can be observed. It would be interesting to undertake an hourly traffic count study on the local road network as perhaps the trend difference could be more apparent.

Comparison of Traffic flows on the A2

12000

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Wed Thurs Fri Sat Sun Mon Tues


5th - 11th August 1998, Comparison of Wind Direction and NO2 Levels

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North)

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The analyser is monitoring air quality data from the primary source when the wind direction is within this range.

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The graph above illustrates the importance of correctly siting an air quality analyser with respect to the prevailing wind direction. As is discussed later in this report, the prevailing wind direction over the Borough is from the south-west and therefore this should be recognised when siting the analyser. The analyser at Ightham Cottages will pick up nitrogen dioxide from the A2 when the wind is blowing anywhere from within the east to the west range. The graph above demonstrates that when the wind is blowing within this range it registers nitrogen dioxide and as soon as the wind shifts round towards the north it drops off significantly. Then, when the wind moves round again, the analyser starts registering again. This illustrates that the polluted air mass is moving with the wind and that to accurately monitor exposure of the public to the pollution it requires the correct siting of the analyser.

17


Traffic Flows and NO2 Levels 5th - 11th August 1998

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Comparing the traffic flows and nitrogen dioxide levels is more difficult with this example as there is an absence of important and relevant data. The relationship between NO, NO2, O3 and temperature is critical. In the absence of detailed and accurate local ozone and temperature data the trend is difficult to observe. This illustrates the importance of accurate meteorological data in these discussions. In air quality modelling work there can sometimes be a lack of appropriate meteorological data and this can have a major influence on the results obtained and the conclusions derived. Therefore, modelled levels of pollution must be treated with great caution.

Elsewhere within Kent, there are several monitors in comparable locations to sites in the Borough and from time to time some of these have shown that pollution episodes occur. These pollution episodes follow the classic summertime smog scenario and are often associated with ozone and particulate episodes.

DETR guidance suggests that attention is directed at roads where annual average daily traffic flows are greater than 25,000. Data from Kent County Council highways transport model indicates that almost all the main roads in the Borough currently have or are projected to have flows in excess of this figure. Additional to road sources, there are two processes authorised as Part A under Part 1 of the Environmental Protection Act 1990 that are potentially a source of local nitrogen dioxide emission; Littlebrook D power station and the waste incinerator at Glaxo Wellcome.

Data taken from the NAEI on the internet (www.aeat.co.uk/cgi-bin/pix2os2.pl) suggests that estimated background nitrogen dioxide concentrations are in the 21 - 26 ppb region for the higher density town areas to the north of the A2 and in the 17 - 19 ppb for the rural areas to the south of the A2. These figures largely correspond with monitored data previously shown. Emissions of nitrogen dioxide are likely to increase across the Borough as a result of increased traffic growth following completion of anticipated large developments in the area. The M25 currently has daily

18


traffic flows in the order of 135,000 and this peaks to about 175,000. The A2 is slightly less, in the order of 90,000. Following completion of the Bluewater development (expected March/April 1999) the local road network serving that area will see a significant increase in traffic. Large developments in new housing on the Darenth Park hospital site, on the Ingress Abbey/Empire Paper Mills site at Greenhithe and at London Road, Stone, will also contribute to traffic growths. The concern, therefore, is that whilst technological improvements to car engines and fuel may allow for a reduction in emissions per car, this will be over taken by the sheer quantity of additional traffic on the roads. The main areas of concern for nitrogen dioxide emissions are on the following roads; London Road, Greenhithe Lowfield Street Princes Road A2/M25 corridors University Way Bean Road Crossways Boulevard St. Clement’s Way St. Vincent’s Road East Hill Dartford Road/West Hill On the basis of data from the diffusion tube on Lowfield Street (adjacent to Lunn Polly) plus the emissions inventory it is safe to say that the town centre area has been in exceedence of the NAQS annual standard since 1994. Looking at hourly data, any of the sites listed in the Appendix will illustrate that the annual average is more difficult to achieve than the hourly standard. Incidences of exceedence of the hourly standard occur less frequently. The following graphs show three years of daily averages and maximums from the Wolverhampton site and are reasonably typical when compared to other sites as shown in the Appendix and for many sites within this Borough.

Wolverhampton Centre - NO2, 1996

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There are clearly several areas and specific roads within the Borough that are of concern for nitrogen dioxide and these are discussed in greater detail later in this report in the section on air quality monitoring. 2.2.4 Assessment In the light of the evidence obtained above, it is necessary to proceed to a Stage 3 Review and Assessment for nitrogen dioxide. 2.3 PM10

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 210 tonnes (40% of the total emission) to 28 tonnes (11%). Emissions from electricity generation have remained fairly constant despite electricity generation growing by 33% between 1970 and 1994. This is partly due to the recent tendency to switch away from coal but also to the move towards more efficient power stations, burning less coal to produce the same amount of

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electricity and the increasing use of non-fossil-fuelled sources.

Emissions from road transport are steadily growing in line with increasing traffic. In recent years, there has been an increase in the use of diesel powered cars (about 20% of new cars are now diesel powered). While this will lead to higher emissions than those if petrol powered vehicles were used, new regulations are focussing technological improvements to reduce the emissions from diesel vehicles.

In urban areas many of the sources do not occur inside towns and cities but of those that do, road transport accounts for about 80% of primary emissions.

Chart 5 - 1970 to 1994 PM10 Emissions

(Source ; DETR web site)

Chart 6 - 1970 to 1994 UK PM10 Emissions

21



The NAQS standard, which has been set for particulate matter of less than 10 mm in diameter, is 50 mg/m3, measured as a running 24 hour mean, and the objective is to achieve the 99th percentile of this standard by the end of 2005. This means that in any one calendar year the standard should not be exceeded for greater than four 24 hour periods.

2.3.1 Sources

Unlike individual gaseous pollutants, particulate matter in the atmosphere is composed of a wide range of materials and originates from a wide range of sources. Particle composition is divided into primary and secondary categories. Primary particles might be carbon particles from combustion, mineral particles derived from stone abrasion and salt from the sea and are released directly into the air. Secondary particles could be any of these plus chemical reaction of atmospheric gases and water vapour and are formed in the atmosphere into less volatile compounds which condense into particles. Therefore, identifying the nature of particles is complicated. These particles, from whatever source, are all measured as PM10 if they fall within the appropriate size range.

Nationally, the largest source of particulate matter is from fossil fuelled power stations, industrial and quarrying activities and diesel engined vehicles. Particulates have been identified as presenting both a regional and local problem. Episodes of poor air quality related to particulate matter in one town can often be seen to also occur in other towns in the same locality. The following graph shows a ‘snap-shot’ of one week’s worth of hourly data from three sites in November 1997. This data was chosen at random to illustrate the phenomenon. The distance from Greenwich to Folkestone is about 70 miles and Stoke is approximately mid-way between the two. Excepting the slight time delay, the trace of the three data sets (all using TEOM monitors) is very compatible. If the data was analysed at very short time scales it is probable that there would be local variances from traffic sources, but the averaging time used more clearly illustrates the overall atmospheric levels.

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Accurately identifying the source of the particles that cause this to happen is not easy. Other issues, such as meteorology, are also clearly an important factor.

Within the Appendix, the four Kent TEOM sites for 1997 in Chatham, Folkestone, Luton and Stoke are shown on a month by month basis and the trend is clearly apparent. As an example, the month of August 1997 is shown below. This regional aspect of the pollutant makes it very difficult to identify any one single source which can be tackled as a means of reducing the levels. It highlights the importance of a multi-disciplined approach and cross-agency action and communication.

Kent PM10, August 1997

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The size of particle chosen for the standard, 10mm, has been identified as the size most likely to be deposited in the lung. Some research, particularly that originating in the US, suggests that finer particle sizes, possibly PM5, PM2.5 or even PM1, should be chosen. For the purposes of the NAQS, however, only PM10 has been considered. In the 1950’s and 1960’s, the effects of the high levels of airborne particles, in combination with sulphur dioxide, in the notorious smogs were clear. In the last few years, research has demonstrated associations between respiratory and cardio-vascular effects and mortality at much lower levels than in the earlier smog studies. Research is continuing into the long-term effects of exposure to high levels of PM10 and as yet this is an area of uncertainty. It would appear that medical evidence suggests that there is indeed a link between exposure to higher levels of PM10 over a 24 period, or longer, and ill-health.


There is currently no monitoring for PM10 in the Borough. However, there is monitoring at other sites within Kent and there are a good number of sites nationally. The following chart shows a selection of comparable sites to the Borough with the data presented in a manner that is consistent with the NAQS standard and it can be seen that there is a significant improvement required if the standard is to be achieved.

Table 3 - Number of Days Exceeding 50 mg/m3 as a 24 Hour Running Mean Site 1992 1993 1994 1995

Bexley - - 18 33 Bristol - 50 30 27 Edinburgh 6 4 3 18 London Bloomsbury 43 57 39 46 Southampton - - 16 13

(Source: National Air Quality Strategy 1997, pages 155)

Nationally, it is estimated in the NAQS that current levels of PM10 in the UK are such that the standard is exceeded on typically 10% of days in a year. The highest daily means are observed in Belfast where domestic solid fuel heating is widespread.

Data from the NAEI on the internet (www.aeat.co.uk/cgi-bin/pix2ospm.pl) indicates that estimated PM10

background concentrations for the Borough range from 24-26 mg/m3. The National Environmental Technology Centre (NETCEN) suggests that 10mg/m3 should be added to these figures to allow for secondary particles. In the Stage 1 review and assessment a pollutant-specific study of the Part A and Part B authorised processes in the Borough suggests that most could represent a potential primary source of this pollutant.

Making predictions of future PM10 levels is complicated owing the wide range of sources as mentioned above. Joint research carried out by Westminster City Council and King’s College, London, has estimated that emissions from traffic in Oxford Street, London, are at least 50% of the total PM10 count. Analysis of filters at other roadside sites has shown that they include salt spray which has travelled from the coast. It is apparent, therefore, that the composition of the PM10 count may vary both from day to day and location to location. Taking this into consideration, an improvement in overall PM10 levels requires a multi-disciplinary approach and simply tackling diesel vehicle emissions is unlikely to be wholly sufficient. Monitoring data suggests that exceedences of the standard occur relatively regularly and are likely to continue to do so.

2.3.4 Assessment

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Despite there currently being no localised monitoring equipment for PM10 it is considered on the basis of evidence from comparable sites similar to this Borough that it is necessary to proceed to a Stage 3 Review and Assessment for PM10.

2.4 Sulphur Dioxide

Sulphur Dioxide is an acid gas which when deposited, by rain or dry deposition, can increase the acidity of soils and water, affecting aquatic ecosystems. Sulphur Dioxide in the atmosphere also contributes to the erosion of many conventional building materials. The main source of sulphur dioxide in the UK is combustion of sulphur containing fuels such as coal, oil and DERV. 66% of UK emission currently come from power stations.

Chart 7 - 1970 and 1994 UK SO2 Emissions


Chart 8 - 1970 to 1994 UK SO2 Emissions

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(Source : DETR Web site)The NAQS standard is 100 ppb, measured as a 15 minute mean, and the objective is to achieve the 99.9th percentile of this standard by the end of 2005. This means that in any one year there are a maximum of 35 periods of 15 minutes when the standard can be exceeded.

2.4.1 Sources

Sulphur dioxide is a gas at normal ambient temperature and pressure. It dissolves in water to give an acidic solution which is readily oxidised to sulphuric acid. The predominant source of sulphur dioxide is from the combustion of sulphur-containing fuels, primarily coal and heavy oils. As a result of effective enforcement of air quality controls on sulphur emissions and restrictions on the burning of coal for domestic heating, national emissions of sulphur dioxide have decreased by 63% since 1970 and by 52% since 1980. The major source of emissions is from coal fired power stations which is in excess of 60% of the total quantity. Other heavy industry equates for about 20%. Despite the significant reduction in emissions, continued pressure is imposed on the power generation industry and the increasing use of flue-gas desulphurisation (FGD) is reducing emissions still further.

Locally, the Borough has Littlebrook D Power Station, which is currently oil fired. There are other power stations in the Thames Gateway area and further afield at a distance where plume grounding can occur within the Borough. Plume grounding is an effect where the plume reaches ground level before adequate dispersion of the pollutants has taken place. This occurs when unstable weather conditions produce eddies and the plume is brought rapidly down. Early in 1998 a new sulphur dioxide monitoring station was established in Sevenoaks and it has shown that a problem can exist with high sulphur dioxide levels being recorded when the wind blows from the north east Kent direction. There is strong, but unconfirmed, inference that these incidences are related to the power stations along the Thames estuary.

The following map illustrates the locations of all the power generation processes surrounding the Borough. Didcot power station in Oxfordshire is approximately 105km west from the Borough but could still potentially have an influence in adverse meteorological conditions.

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With the prevailing south westerly wind, it can be seen that problems from the power generation industries are likely to be rare and unlikely to be predictable. There are other large industries and Part A and B processes within the surrounding area, and immediately across the River Thames in Thurrock, that could also have an influence and these are included in the discussion later in this report. However, they are also considered to be of a lower level of significance as far as complying with the NAQS standards. The data presented in the Appendix demonstrates that exceedences of the NAQS standards, particularly in neighbouring Bexley, are reducing. Technological improvements and tighter controls on emissions from authorised processes is anticipated to keep SO2 levels within the standards defined in the NAQS.


Exposure to very high concentrations (in excess of 1000 ppb) is known to cause painful irritation of the eyes, nose, mouth and throat, and the acute chemical injury to the linings of the airways may cause serious difficulty in breathing and possibly even death. At lower concentrations, levels more likely to be experienced in ambient outdoor air during pollution incidences, the gas causes an irritant effect by stimulating nerves in the lining of the nose, throat and the lungs airways. This causes a reflex cough, irritation, and the feeling of chest tightness, and may lead to narrowing of the airways. Asthmatics and people who suffer from chronic lung disease are most likely to be affected before other groups of people.


At the current time, long term monitoring for sulphur dioxide has been carried out using the volumetric ‘bubbler’ and the following graph shows the improvement in background levels since 1964.

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microgram

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Additional longer term data is being collected through two diffusion tubes which have been set up at Ightham Cottages and Axton Chase school. This monitoring only started in April 1998 and it is too early to present any results. Data obtained from the NAEI on the internet (www.aeat.co.uk/cgi-bin/pix2osso2.pl) suggest that estimated background sulphur dioxide concentrations are in the order of 5 - 6 ppb. This estimate will be able to be verified later in 1999 after sufficient data has been accumulated.

Whilst this information is of general use, it is not suitable for comparison to the standard which requires 15 minute averaging. Equipment to do this is not currently located in the Borough, but there are suitable analysers located elsewhere in Kent and at other locations nationally. The following chart is extracted from the NAQS and shows the results from some comparable sites to the Borough of the maximum 15 minute average values and the number of times in a calendar year, for 1993-1995, that the 100 ppb standard was exceeded.

Table 4 - Number of Exceedences of the 100 ppb 15 Minute Averages

Maximum 15 minute averages

No. of 15 minute averages > 100 ppb

Site (Units = ppb) 1993 1994 1995 Bexley 481 - 61 164 Bristol 197 14 3 1

Edinburgh 218 50 30 19 London Bloomsbury 306 121 38 63

Southampton 134 - 2 0 (Source: National Air Quality Strategy 1997, page 166)

The data in the table above is slightly misleading as it ends at 1995. Data in the Appendix to this report illustrates that ambient sulphur dioxide levels have improved in recent years and that frequencies of exceedences are reducing significantly. For example, reference to the graphs for the Bexley site on Appendix Page 3 demonstrate this. Improved control of sulphur dioxide emissions from large industries and Part A processes, combined with the effectiveness of local smoke control areas in residential areas, has been largely responsible for a reduction in ambient levels of this pollutant.

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2.4.4 Assessment

The UK Government, under the Second Sulphur Protocol, is committed to reduce emissions of sulphur dioxide from large combustion plant by 50% by 2000, 70% by 2005 and 80% by 2010 when compared to a 1980 base. The enforcement of these obligations falls to the Environment Agency under their jurisdiction as regulators of Part A processes under the Environmental Protection Act 1990. Whilst it is accepted that sulphur dioxide levels are likely to continue falling, it is also apparent that the potential for future exceedences to occur as a result of plume grounding exists from sources outside out the Borough. However, having taken a wider view of potential sources within and around the Borough, and of meteorological factors, it is now considered that the likelihood of sulphur dioxide levels not meeting the NAQS standards is likely to be rare and unpredictable. Therefore, it is the conclusion of this Stage 2 Review and Assessment that there is no need to consider sulphur dioxide in Stage 3.

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3.0 Meteorology and Local Weather Conditions

Air quality is inherently linked with meteorology and the dispersion of atmospheric pollutants is a complex science. Some aspects, especially the source and dispersion of fine particulates, is the subject of continuing research and requires a certain measure of caution. At all times, air quality should be considered to be a three-dimensional subject which has a wide range of influencing factors. It is seen, but often not clearly stated, that periods of poor air quality can be traced back to adverse weather conditions of unusual localised nature. In general terms, linear emissions, from roads, follow a relatively constant trend on a day to day basis whilst point emissions, from industrial processes, are more difficult to predict because of the fluctuations in operating periods. With air quality monitoring, the analysers have to be correctly located so that they are able to detect the pollutants of concern in areas where adverse impacts need to be measured. There are many localised influencing factors that can affect the data, such as proximity of nearby trees and buildings or simply being on the wrong side of a road in terms of the prevailing wind direction.

Historical meteorological data shows that the dominant wind direction across the Borough is from the south- westerly direction. The following series of wind roses illustrates this;

Gatwick London Weather Centre Manston

Thurrock Stoke (Medway towns area)

Wind Rose from Stoke AQ Site N

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Wind Frequency Distribution at Dartford River Crossing -April 1997 to March 1998

This is an important observation. By 0 definition, wind 20blowing from any direction will have the

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dispersing pollutants from that direction. complicated process, but this simple and helps to describe what can happen. 300

acknowledgement of potential pollutant prevailing wind direction can help to possible causes of regular occurrences of 270

Similarly, having an awareness of potential in all directions from the Borough can help occasional episodes of poor air quality. 240

‘long range’ pollutant sources which are 150imported into the area are a myriad of 210

effect of Dispersion is a concept applies

60 An sources from the understand the

90 poor air quality. pollutant sources in identifying

120 Added to these effectively being other potential

180sources of a local nature which will include roads, smaller industrial processes, construction works, combustion plant and many others. These other sources add to the body of air, which will have already started to disperse and dilute the imported air mass. And so, the process continues. The overall air mass is, therefore, made up from a mixture of all of these emission sources.

Pollutants do not all react the same in the atmosphere and the levels that we measure can be affected by a variety of conditions and chemical processes. Generalisations about dispersion of pollutants are difficult, but experience and guidance from the Environment Agency (The Environment Agency and Local Air Quality Management [1998]) suggests that larger industrial processes, such as Part A processes, are unlikely to have an effect in excess of 10km. Using this as a guide, the following map shows the locations of the nearest Part A processes to the Borough. The wind rose illustrations above, confirm that for the majority of the time the Borough is subject to a predominantly south-westerly wind. The closest Part A processes in the south westerly direction are seen to be in excess of 22km from Dartford town centre which is probably too far to be of concern to the Borough under ‘normal’ conditions. There are some other Part A processes to the north-west which could be an influence to this Borough if the air mass moves in from that direction. Power generation processes can have an influence over many times these distances.

On the immediate opposite side of the River Thames from the Borough, in Thurrock, there are a collection of Part B processes which whilst individually may not cause a problem in this Borough do offer the potential for a collective impact to occur should the wind be blowing from the north. Pollutants such particulates and nitrogen oxides are most likely to be a potential problem under these conditions.

Location of Part A Processes Surrounding the Borough

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For the majority of time, the air mass which moves over the Borough is likely to be affected by particulate matter, which has a regional nature, and pollutants originating from road traffic, point sources and numerous others which are in various stages of dispersion. The Borough is less likely to be influenced by ‘long-range’ pollution except in climatic conditions when the wind shifts from the predominantly south-westerly direction. The important observation that needs to be highlighted from this is that, subject to individual case study situations, episodes of short term poor air quality are very likely to be directly related to specific meteorological conditions. This is apparent not only for this Borough, but also for most other areas. The difficulty in predicting the frequency of occurrence of such situations is immense.

In summary, the Borough is affected by air masses that predominately move in from the south west direction, but can also be affected by any air mass from whatever direction. At a local level, there are more specific influences that can affect levels of some pollutants such as proximity of trees, heights and density of buildings, topography and many other attributes of a physical nature. Developments within a ‘cutting’, valley or natural ‘bowl’ will also be subjected to very specific and localised atmospheric conditions usually accompanied by situations with restricted dispersion of pollutants due to restricted air movements. This can be highly significant in winter and summer periods when the weather is either particularly cold or particularly warm.

Location of Part A Processes in the South East

32


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Dartford

The drawing above shows the locations of all the authorised Part A processes in London, Kent, Essex and Sussex. The drawing is interesting as it highlights the density of industry in the London area and parts of Kent.

Location of Part B Processes in the South East

33


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Dartford

The drawing above shows the locations of the authorised Part B processes within London, Kent, Essex and Sussex. Whilst each of these will most likely have only a local influence, it is interesting to observe the sheer number and density across a relatively small geographical area.

In considering air pollution and potential sources on an area, this section has shown that the wider aspects should also be considered. This Stage 2 review has shown that due to the prevailing wind direction, the Borough should not normally be affected too greatly by plume grounding of large industrial processes. When adverse impacts do occur, these will tend to be infrequent, unpredictable and beyond legislative controls of Dartford Borough Council.

34


4.0 Atmospheric Emissions Inventory

The atmospheric emissions inventory data contained within this report is a summary of a combination of data that covers the western part of the Borough up to the M25 produced by the London Research Centre and also the Kent Inventory produced by Kent County Council.

An inventory is not necessarily a record of measured data and it does not take into account factors such as meteorological, topographical or other specific location variances. It uses actual data where it is available and it estimates other data and the results should therefore be used as an indicative guide rather than as a precise science. The inventory is very useful for drawing attention to potential hot spot areas which can later be the focus of more localised monitoring and/or modelling. The data will be very useful during the Stage 3 Review and later as an aid to the preparation of an Air Quality Management Plan.

Obtaining data from air quality measurements is one aspect of study and this can be enhanced by information within an atmospheric emissions inventory. There are a variety of methods of measuring different pollutants in the air, but very little information is available about the sources of these pollutants or of the cumulative impact of several sources. The use of an inventory is one way of obtaining this information and it allows for easy adaptation to predict future changes from development or increases in road traffic etc. More importantly, when it comes to assessing the scope and implications of an Air Quality Management Area and a subsequent Action Plan, a detailed assessment of the sources of pollutants will be invaluable.

The inventory data contained within this report should be considered to be a live tool, not as a completed item or a static project. It offers unlimited scope for enhancement, revision and refinement. As new data becomes available, this can be entered into the inventory and the level of accuracy increases. This is an important aspect to consider. The inventory contains a great deal of estimated data and is not, therefore, a complete scientific record. However, it is a major step in the right direction towards understanding the influences on our air quality.

4.1 Data Compilation

The following text is extracted and adapted from the summary provided at the London Research

Centre web site (www.london-research.gov.uk/emission/webhtm.htm) ;

Data are collected for three types of sources:

• Line sources including roads and railways• Area sources including emissions from agricultural and other land and low intensity emissions from

sources such as building heating systems• Point sources including emissions from industrial plant

Clearly it is impracticable to measure every emission source in a large urban area. The majority of emissions are therefore estimated from other local information such as fuel consumption, vehicle kilometres travelled (VKT), or some other measure of activity relating to the emissions. Emission factors, derived from the results of measurements, are then applied to the activity data in order to estimate the likely emissions:

Activity rate x Emission factor = Emission rate

The most significant source of emissions for urban pollutants is traffic on major roads. Two primary sources of road traffic data are currently in use for preparing urban emission inventories: traffic surveys and transportation models. Information from traffic surveys is attractive because it relates to real traffic on real roads whereas transportation models are a computerised reflection of the actual conditions. However, traffic surveys have the disadvantage that they only provide information relating to the specific

35


survey points, rather than area wide information. On the other hand, transportation models are available for most of the main urban areas and are comprehensive.

For many of the pollutants of concern, a significant source of emissions is the combustion of fossil fuels. Consequently the collection and analysis of fuel consumption statistics plays an important part in the preparation of emission inventories. However, it is important to consider the differences between consumption and fuel deliveries when making use of the available data. Most of the readily available statistics relate to fuel deliveries which, in many cases, relate closely to consumption. However, in the case of fuels which may be stockpiled, such as coal, there may be significant differences between delivery and consumption. In the case of transport fuels, there may be significant geographical differences between the point of delivery and where the fuel is used. The most striking example is London's Heathrow Airport to which some 3.7 billion litres of aviation fuel are delivered annually. Only a small fraction of this fuel is used within the London area whilst the remainder is used on global journeys.

The following illustration is a computer modelled image generated from the Kent Inventory for industrial emissions of NO2 in Kent in 1997. It is interesting to see that the entire north Kent area has high NO2

levels, including the Dartford area.

Based upon the Ordnance Survey mapping with the permission of the Controller of Her Majesty’s Stationary Office (C) Crown Copyright. Unauthorised reproduction infringes Crown Copyright and may lead to prosecution or civil proceedings. Kent County Council licence No. LA078707. Sept 15, 1998

As indicated in the introduction of this section, the data contained in the results of modelled or inventory work must be used with some caution. The following two illustrations show how errors can occur and how local knowledge can be invaluable. In the following drawings for emissions based upon traffic and industry in Kent, respectively, the eastern part of the Borough of Dartford is shown as having high levels. In reality, this is not necessarily the case.

Charts 9, 10, 11 & 12, below, use a 1km grid and show that, within the limitations of that grid size, the motorway and town centre areas are prime ‘hot spot’ locations for emissions of NOx and PM10. This data needs to be refined and expanded upon within the Stage 3 review.

36


Chart 9-Kent Traffic Emissions

Chart 10 - Kent Industry Emissions

37


Chart 11 - Dartford NO2 Emissions

Chart 12 - Dartford PM10 Emissions

38

These illustrations are extracted from the London Research Centre atmospheric emissions inventory of London which used the M25 as an outer boundary.


39

##


5.0 Local Air Quality Monitoring

There are currently a small number of locations within the Borough that are used for monitoring air quality across a small number of pollutants. Additionally, we receive data from Gravesham Borough Council for results from a site very close to the Borough boundary in Northfleet. These are illustrated on the adjacent drawing and are identified as follows;

Nitrogen Dioxide Lowfield Street (Town Centre) Princes Road The Terraces

'] ']']

']

']

']

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YY

Ightham Cottages, Nr A2 Hope Cottages, Bean Main Road, Sutton-at-Hone Summerhouse Drive Axton Chase School, Longfield

Benzene Lowfield Street (Town Centre) Princes Road Ightham Cottages Axton Chase School

Sulphur Dioxide Civic Centre Ightham Cottages Axton Chase School

Following the detailed appraisal of air quality and taking into consideration future development it is essential to expand the air quality monitoring within the Borough. At the time of preparing this report there is only one continuous analyser in use, that for NO2 located at Ightham Cottages. This Stage 2 review has identified the need for looking at NO2 and PM10 in greater detail at Stage 3 and, in order to do this, an expansion of continuous monitoring analysers is required.

As a minimum, two more new stations are required, plus an additional analyser in the existing cabinet at Ightham Cottages. The provision, and locations, would therefore need to be as follows;

Ightham Cottages NO2 and PM10

Dartford Town Centre NO2 and PM10

London Road NO2 and PM10

40


These locations are illustrated in the following pictures;

This is the existing roadside cabinet near to Ightham Cottages and the A2. It currently contains a nitrogen dioxide analyser and it is recommended in this report that it is also equipped with a PM10

analyser.

It is proposed to site a monitoring station within the Dartford Town Centre area. The precise location has not yet been decided as it will be determined on a number of factors which include; pavement widths, access to electrical and telecommunication services and proximity of obstructions.

41


This is a view of the new roundabout at the junction of London Road and St.Clement’s Way, Greenhithe. It is proposed to site a roadside cabinet on the grass verge.

The existing network of NO2 passive diffusion tubes should remain in place and should ideally be expanded to cover areas of concern for the annual averaging period. A very useful contoured map could be generated with sufficient coverage across the Borough if the expansion of the existing tube network was sufficiently comprehensive. Whilst the tubes are not totally accurate, they do offer valuable information at a modest cost.

The existing network of benzene tubes should be revised on completion of the first year survey in April 1999. Ambient benzene levels are unlikely to be a concern and benzene was excluded from the Stage 2 assessment following the results of Stage 1. It would more prudent to look at specific sources of benzene pollution with a view to having data for the next review and assessment which will need to be carried in the next few years. In this Borough, the most likely cause of public exposure to benzene is at petrol filling stations and it would provide very useful information if the existing network of four tubes were relocated around a busy service station which has residential property nearby. This is a matter for further investigation.

The existing network of sulphur dioxide tubes have not, so far, revealed any useful information and a case for the continuation of the survey after the first year in April 1999 needs to be revi ewed. It might be more appropriate if the survey were discontinued and resources directed elsewhere.

42


6.0 Conclusions

This report has considered the source, health effects, available data and the need for further consideration of four pollutants that have been identified in the Stage 1 Review and Assessment; carbon monoxide, nitrogen dioxide, PM10 and sulphur dioxide. On the basis of the evidence available it is considered that it is unlikely that the standards specified in the Air Quality Regulations 1997 will be exceeded at the end of 2005 for the following pollutants;

• carbon monoxide • sulphur dioxide

Therefore, the following pollutants are believed to offer sufficient doubt to require some more detailed investigation for a Stage 3 Review and Assessment;

• nitrogen dioxide • PM10

7.0 Recommendations

A Stage 3 Review and Assessment of Air Quality within the Borough needs to be carried out for the following pollutants:

• nitrogen dioxide • PM10

To complete the Stage 3 Review and Assessment, it will be necessary to undertake real time monitoring for these pollutants at the sites identified in this report.

The Stage 3 Review and Assessment should utilise detailed monitoring, modelling and comparative data and ultimately give consideration to the necessity for proceeding to declaration of Air Quality Management Areas for those pollutants that might still be considered likely to exceed the standards by the end of 2005. In the event of an Air Quality Management Area being declared it will be necessary to implement an Action Plan which attempts to tackle the problem and bring about an improvement in air quality through a reduction in the levels of the pollutants of concern.

This process will require public consultation and most likely require a multi-disciplined approach, especially for PM10 which have many potential sources and is clearly a regional issue on a scale much bigger than any individual local authority can control.

8.0 Appendices

The following pages of this report contain graphs which illustrate the daily maximum and average levels of pollutants over a number of years for a range of sites. Whilst the graphs are fairly small, they are still capable of showing the trends in relation to the NAQS. The conclusion to proceed to Stage 3 for NO2

and PM10 is adequately confirmed by this comparative data.

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stage 2 report - borough of dartford · this report presents the stage 2 review and assessment of...

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