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Environment Act 1995

Calderdale Air Quality Management Area (No 6)

Brighouse Further Assessment Report

www.calderdale.gov.uk

November 2010 (revised May 2011)

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What this report is about

In August 2007 Calderdale declared part of Brighouse as an Air Quality Management Area (AQMA) due to the levels of nitrogen dioxide. In this report we sometimes use the chemical symbol NO2 to stand for this pollutant. This brief guide gives a simple explanation of the contents of the report and some of terms used. It should help explain some of the themes of the report as well as some of the technical terms used.

Justifying the AQMA- Measurement and Modelling of nitrogen dioxide

Section 2 of the report examines why the Council thought the AQMA was necessary. We look at the monitoring results that we had to hand and explain why these lead to the decision. We also present the results of monitoring carried out since the AQMA was declared.

What are the likely levels of nitrogen dioxide in the future? The vast majority of today‟s vehicles burn fossil fuels such as petrol and diesel. Burning fuel in air causes, as a side reaction, some of the nitrogen in the air to combine with oxygen to produce gases called oxides of nitrogen (we use the symbol NOx to stand for these pollutants). Complicated chemical reactions convert some of the NOx to nitrogen dioxide, which is the most significant oxide of nitrogen from a health perspective. European Law requires the UK Government to achieve certain air quality objectives (AQOs). It was originally anticipated that NO2 pollution would fall to acceptable levels by 2010, but this has not happened and work to bring about the reductions has not ceased. Section 4 discusses background levels of NO2, which essentially means the levels that would exist if the local traffic were not there. Other local and distant sources, such as local industrial activity and distant traffic, contribute to this background. Knowing the background levels today allows an assessment of the amount of pollution being caused by the traffic today, and is used to predict the situation to future years. In Section 5 the contributions to nitrogen dioxide levels from different sources are considered, and further monitoring is discussed.

Other Considerations for an Action Plan

This report will be used as the basis for an Air Quality Action Plan (AQAP) setting out measures to try to achieve more acceptable levels of NO2. An AQAP is not just about reducing the pollution itself. Reducing exposure to pollution and avoiding situations that prevent the dispersion of pollution is also important. Section 5 discusses local commuting and recent planning development, and how local and national policy might contribute to better air quality in central Brighouse.

If you have any questions about this report, please do not hesitate to contact Environmental Health Services.

The report has been written by Tommy Moorhouse, Ryan Carroll, Commercial Team

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Glossary of terms and abbreviations used in this report Please note that some of these terms are defined in legislation and guidance. This glossary is intended to give an indication only of the meaning of the terms. AQAP air quality action plan – a formal scheme for reducing the level of

pollution, for example by changing traffic flows AQMA air quality management area – an area known to be subject to levels

of pollution above the AQOs. AQO air quality objective – a level of pollution above which action must be

taken Bias correction the adjustment of diffusion tube data to take account of the tendency

for the tubes to over- or under- estimate the true levels Continuous monitor a device for recording pollution levels every 15 minutes, powered by

mains electricity Diffusion tube a short plastic tube containing a substance that absorbs nitrogen

dioxide and gives an average concentration for the exposure period NOx a collective symbol for all oxides of nitrogen in the air Relevant exposure the people who are likely to be exposed to air pollution above the

AQO

Precautionary Note This report was commenced in 2008. It relies on information and guidance available at that time. Publication was delayed for various reasons until 2010. In late 2009 Calderdale commenced working with Leeds University Institute for Transport Studies, to better understand the issues involved in NO2 generation. One project on the A629 at Halifax (near Stump Cross) measured vehicle NOx emissions as they drove by. In March 2010 final reports were awaited. Early indications are that the age and composition of the vehicle fleet is different to that assumed by this report, and that individual vehicle emissions are largely compliant with Government/ manufacturers requirements. Clearly this affects the projections in this report and impacts upon the credible measures that can be brought about by this Council to reduce NO2 in the AQMA. Full implications will be known in 2011, to be considered as part of a revised AQAP.

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Calderdale Air Quality Management Area (No 6)

Brighouse Further Assessment Report

Section Title Page

Preface – what this report is about 1

Precautionary note and glossary of terms 3

1 Introduction 4

2 Confirmation of the original assessment of air quality 4

2.1 Review of information available prior to declaration of AQMA 4

2.2 Relevant exposure 7

2.3 Assessment of information available post-declaration 8

2.4 Review of existing AQMA boundary 11

3 Review of Comments made by statutory consultees 11

4 Calculation of the extent of improvement in air quality needed 11

4.1 Background concentration of NO2 11

4.2 Road traffic contribution 12

4.3 Projection to future years 14

4.4 Non-traffic sources of nitrogen dioxide 15

4.5 Local traffic data 15

4.6 Developments affecting the AQMA 17

5 Summary and Conclusions 17

Appendix 1

Monitoring and Quality Control 18

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1. Introduction An Air Quality Management Area (AQMA) covering several major routes and associated residential areas around Brighouse came into effect on 1st August 2007.

The AQMA was designated under Section 83 Environment Act 1995. The annual mean air quality objective (AQO) for Nitrogen Dioxide (NO2) specified in the Air Quality (England)

Regulations 2000 is 40 g/m3. The designation was in part due to a known exceedence of the AQO and in part due to modelled evidence of a likely exceedence of the AQO. Section 84(2) of the Act now requires further assessment of the AQMA. This further Assessment addresses the following issues

Confirmation of the original assessment of air quality (Sections 2.1 and 2.2) Review of the existing AQMA boundary (Section 2.3) Review of Comments made by Statutory Consultees (Section 3) Calculation of the extent of improvement in air quality needed (Section 4) The impact of recent policy developments upon the AQMA (Section 5)

2 Confirmation of the original assessment of air quality Essentially this comprises

a review of the information available leading up to declaration of the AQMA assessment of information available post-declaration

2.1 Review of information available prior to declaration of the AQMA Brighouse is the second largest town in Calderdale, lying to the East of Halifax and skirted by the M62. There are several busy main roads carrying commuter traffic, and a large industrial area. Only two diffusion tubes had been deployed in Brighouse since the initial Stage 1 of LAQM, and the Council was aware of the need to gather more data, leading to the deployment in late 2005 of five diffusion tubes along a major through route. The AQMA covers several major commuter routes through Brighouse and is not straightforward to model. The declaration was based on some limited modelling, together with diffusion tube results. No continuous monitoring data was available for this area at the time of declaration, and Table 1 contains the results for the diffusion tubes. The tube locations are shown on Map 3 below.

Table 1: Diffusion Tube Results (Bias-corrected) 2003-2006 in g/m3

tube Location 2004 2005 2006

WR1 Lamp, Wakefield Road 35 37 51

BH1 Near superstore traffic controls 44* -

BH2 Lamp at Stott‟s Arms, busy road junction 48* -

BH3 Huddersfield Road, Brighouse 46* 51

BH4 Rear of Medical Centre, Lawson Road 44* 48

BH5 Bradford Road, Brighouse 50* - Notes to Table 1: * three months data available for 2005

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The results from WR1 appear strange, but a different co-location study was used to bias correct the tubes prior to 2006 and this may be a factor. When declaring the AQMA the Council took into account Statutory Guidance LAQM.PG(03), which promoted the inclusion of areas of modelled poor air quality within the AQMA but blocks of terraced residential property would not be sub-divided, nor houses from their gardens. An AQMA covering the central road network took effect on 1st August 2007 and the boundary is portrayed in Map 1. The quite limited evidence available pointed to exceedences of the annual mean for nitrogen dioxide, and knowledge of the traffic flows, some determined by observations, was used to determine the likely extent of the AQMA. Results from a diffusion tube CD12,

which had been located in the town centre since 1998, were below 30 gm-3 (in 2005 the

mean at this tube was 22 gm-3) and this guided the Council in excluding this part of town centre from the AQMA. The monitoring had concentrated on the East of the town, but parts of the West were known to suffer from traffic congestion and were therefore included. These areas included Halifax Road close to its junction with Ludenscheid Link, and Bridge End.

Map 1: AQMA boundary

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2.2 Relevant Exposure The areas in which there is likely to be relevant exposure are indicated on Map 2. These are residential areas close to the town centre and in particular close to the roads carrying significant volumes of traffic. The Council identified those which it considered should be included in the AQMA on the basis of proximity to road traffic sources.

The sites identified on the map are: A: Wakefield Road and Blackburn Buildings (residences) B: Bradford Road residential area C: Elland Road and Halifax Road (residences) D: Bridge End (day nursery, public house) E: Huddersfield Road (upper floor dwellings) Several hundred dwellings in total lie within the AQMA, mainly in A, B and C, representing in the order of a thousand people exposed in the area of exceedence of the annual mean. The Council decided to declare one large area to allow for the fact that any measures identified to reduce the traffic pollution in part of the town would necessarily affect traffic flows in other parts, and that a holistic approach would be beneficial in producing an action plan. The area of the AQMA marked S, between the river and the canal, may be subject to residential development and was therefore included in the initial declaration.

A

B

C

D

E

Map 2: relevant exposure

S

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2.3 Assessment of information available post-declaration Three of the tubes in Table 1above were later relocated to reflect relevant exposure, and additional tubes were deployed in September 2006. The Groundhog mobile continuous monitor was deployed in April 2007, measuring both particulate matter and nitrogen dioxide. This has since been supplemented with a second continuous monitor, Romon 1, in the Southern part of the AQMA. Neither monitor is believed to represent relevant exposure for the annual mean objective. The location of both monitors was a compromise between finding a suitable location in terms of pavement space, power and other practical considerations, and obtaining data that would inform the Council‟s decisions. The tubes deployed since September 2006 are described in Table 2 and shown on Map 3.

Two automatic monitors were deployed in April 2007 (the Groundhog) and October 2008 (Romon 1). The locations are shown on Map 3. The continuous monitoring results are shown in Table 5 below.

Table 3: continuous monitoring results ( gm-3) (data capture %)

Unit Grid ref 2007 2008 2009

Groundhog 414803 422927 33.0 (8 months) 36.6 (93.2) 34.9 (92.7)

Romon 1 414384 422456 - - 46.5 (94.0)

The results from the Groundhog indicate that the town centre pollution levels, carried by the predominantly westerly winds down the main street, are below the objective. This

again supports the exclusion of the town centre itself from the AQMA. Using the openair

package it is possible to get confirmation of the distribution of sources of pollution. Figure 1 below is based on 12 months of data collected in 2008. The Groundhog includes a weather station, and we were able to associate the pollution levels with the wind direction

using the polarplot tool. The shape of the plot is based on the windspeed and

direction, giving an idea of distance from the monitor, and the colours represent pollution levels. Thus the intense reds shown close by to the southeast indicate the emissions from traffic at the Wakefield Road junction. It is clear that the major sources of pollution are the road junctions to the East of the Groundhog‟s location. The diffusion tube results for BN20, which is on the opposite side of the road to the Groundhog, support this interpretation.

Table 2: diffusion tubes deployed since the declaration of the AQMA

Reference Location x y in AQMA

BE1 Lamp, Star PH, Bridge End 414406 422468 y

BE2 Lamp adjacent Nursery, Bridge End 414385 422457 y

BE4 lamp, Masonic hall, Bridge End 414478 422692 y

BH3 Huddersfield Road, Brighouse 414671 422740 y

BN20 lamp 20, Wakefield Road, Brighouse 414842 422968 y

ER1 Drainpipe, Elland Road, Brighouse 414235 422901 y

HXR1 Halifax Road, Brighouse 414218 422957 y

WR1 Wakefield Road, Brighouse 415169 422794 y

WR2 Blackburn Buildings, Wakefield Road 415090 422817 y

WR3 Lamp adj Robin Hood Public House 414915 422886 y

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This figure should be compared with the map of the Groundhog location, Map 3, below. The Groundhog can be thought of as lying in the centre of the picture. At this site the strongest winds are seen to be Southerlies and Westerlies. The local sources of nitrogen dioxide lie to the East, the most prominent being the multiple junctions to the East.

Figure 1: polar plot of NO2 levels at the Groundhog for 2008.

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The results of diffusion tube monitoring since the AQMA was declared are set out in Table 3 below.

Groundhog

Romon 1

Map 3: monitoring points

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Notes to Table 3 a using local bias correction factor of 0.79 b using helpdesk factor of 0.87. The Council adopted the smaller factor on the basis that it was derived using local data.

2.4 Reconsideration of the AQMA boundary As emphasised in Section 4 of [DA06] modelling of the air quality in this area was not considered practicable. The diffusion tubes were located in such a way as to indicate whether the Council‟s expectations based on experience were on the whole correct, and this has proved to be the case. Thus not all the diffusion tubes represent relevant exposure, but the location of relevant exposure is consistent with the AQMA boundary. Although the automatic monitor at the South of the AQMA shows an exceedence of the annual mean objective it does not represent relevant exposure for this objective. The reason for the elevated levels of nitrogen dioxide at Romon 1 is believed to be a congested mini roundabout at the junction of Bridge End and Bramston Street.

3 Review of Comments made by statutory consultees Of the consultees DEFRA has responded in relation to the content of the Council‟s Updating and Screening Assessment 2005 [USA05], Detailed Assessment 2006 [DA06] and Progress Report 2007 [PR07]. Each of these reports contained monitoring data for this AQMA.

4 Calculation of the extent of improvement in air quality needed This section considers

determination of a background concentration of NO2 for Brighouse for 2008 using the updated maps from the LA helpdesk

consideration of possible sources of nitrogen dioxide in Brighouse establishing local traffic data source apportionment and model projections for

future years.

No further modelling of traffic pollution has been undertaken due to the complexity of the traffic flows and the availability of monitoring data.

Table 4: Diffusion Tube Results (Bias and Period -corrected) since 2006 in g/m3

Ref Location Mean 2007

Mean 2008

Mean 2009a

Mean 2009b

BE1 Lamp, Star PH, Bridge End 44 45 40 44

BE2 Lamp adjacent to Nursery, Bridge End 49 49 44 49

BE4 lamp, masonic hall, Bridge 51 53 53 58

BH3 Huddersfield Road, Brighouse 54 53 51 56

BN20 lamp 20, Wakefield Road, Brighouse 59 59 50 55

ER1 drainpipe Elland Road, Brighouse 43 40 36 39

HXR1 Halifax Road, Brighouse 51 52 52 57

WR1 Wakefield Road, Brighouse 56 55 47 52

WR2 Blackburn Buildings, Wakefield Road 46 44 43 48

WR3 Lamp, Robin Hood Public House Wakefield Rd 41 40 36 39

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4.1 Background NO2 concentration The predominant wind direction in Brighouse is westerly with overlying westerly winds. The diffusion tube BE3 was initially considered as a background tube, but it was subject to removal and was abandoned. The Council used the most recent background maps and selected grid reference 414500 422500 being closest to the centre of the AQMA.

4.2 Road traffic contribution The tools available on the helpdesk website were used to apportion the contributions to mean NOx and NO2 concentrations for the base year 2008. The calculations follow boxes 7.1 and 7.2 of TG(09) as updated on the LAQM Helpdesk in October 2010, and are set out in Boxes 1 to 3 below. The background concentrations were obtained from the maps published on the helpdesk website in 2010 and the 2008 concentrations were used.

Box 1: Background calculations gm-3) (Box 7.1 of TG(09))

TB-NO2 TB-NOx RB-NOx LB-NOx = TB-NOx - RB-NOx 28.8

22.7 36.15 7.35 RB-NO2 = TB-NO2 X(RB-NOx/TB-NOx) 4.6

LB-NO2 = TB-NO2 X (LB-NOx/TB-NOx) 18.1

Figure 4: Background concentrations of NO2 at NAEI reference locations

Map 4: Location of Background NO2 Concentration point

414500, 422500

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The source apportionment calculation was carried out according to box 7.1 of TG(09) and the results are set out in Box 2 below. The number of HGVs, buses and light vehicles was found from a survey undertaken on Huddersfield Road in 2008. ADMS-Urban, with the 2008 emission factors, was then run for each component to determine the relative contributions. Cars and light vehicles account for just under 94% of traffic, with buses and HGVs making up the balance but the ADMS-Urban output shows that they contribute only 42% to the total traffic NOx. This is the basis for the results shown in Box 2.

Box 2: Calculation of proportions of NO2 attributable to road

sources gm-3)

Contibutions to NO2 concentrations

ref T-NO2 L-NO2 Light vehicles Buses HGV

BE1 45 22.3 9.4 4.3 8.6

BE2 49 26.3 11 5.1 10.2

BE4 53 30.3 12.7 5.9 11.7

BH3 53 30.3 12.7 5.9 11.7

BN20 59 36.3 15.2 7 14

ER1 40 17.3 7.3 3.3 6.7

HXR1 52 29.3 12.3 5.7 11.3

WR1 55 32.3 13.6 6.2 12.5

WR2 44 21.3 8.9 4.1 8.2

WR3 40 17.3 7.3 3.3 6.7

The NO2 to roadside NOx converter (January 2010 update) was used to calculate the NOx equivalents of the diffusion tube results, using the local background NO2 levels calculated in Box 1 above. The converter output is the road NOx equivalent, so the method of Box 7.2 of TG(09) is shortened. Box 2A shows an example of the determination of the road NOx equivalent of a diffusion tube measurement.

Box 2A: calculation of road NOx from diffusion tube measurement

Site ID

Diffusion tube NO2,

g m-3 Background

g m-3

Road NOx, g m-3

NOx NO2

HXR1 52 36.2 94.54

Box 3 shows the calculation of the reduction in emissions required as a percentage of the current (ie 2008) emissions.

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Box 3: Calculation of reduction required (2008)

T-NO2

road NOx

NOx required to give NO2 = 40

reduction

required gm-3) % reduction

BE1 45 66.25 48.9 17.4 26

BE2 49 81.8 48.9 32.9 40

BE4 53 98.99 48.9 50.1 51

BH3 53 98.99 48.9 50.1 51

BN20 59 127.9 48.9 79 62

ER1 40 48.94 48.9 0 0

HXR1 52 94.54 48.9 45.6 48

WR1 55 108.22 48.9 59.3 55

WR2 44 62.61 48.9 13.7 22

WR3 40 48.94 48.9 0 0

Of these results BN20 gives the highest percentage reduction required. However, this tube is not close to any relevant receptor, but sits close to the busy controlled junction visible in Figure 1. BE4 is fixed to a public house that may have residential accommodation. HXR1, WR1 and WR2 are all close to relevant receptors, indicating that these locations require possibly the most focus in developing an action plan. The highlighted row, for HXR1, indicates the worst-case relevant exposure. BE1 and BE2 are close to a mini roundabout at which location there is a day nursery and a public house, possibly with residential occupancy. The continuous monitor Romon 1 is close to BE2 and although no annual mean is available for 2008 the 2009 mean was

46.5 gm-3 with no exceedences of the one-hour objective.

4.3 Projection to future years The method set out in Box 2.1 of TG(09) was used to project the measured nitrogen dioxide concentrations from 2008 to future years. The results for the diffusion tubes considered above are set out in Box 4 below. The highlighted cells show exceedences of the annual mean objective. This box takes no account of the background projections, but should in any case be seen as an indication only of the timescale involved.

Box 4: Projections of annual means to future years gm-3)

ref 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020

BE1 45 41.22 37.4 35.2 33.1 30.9 28.8 26.6 25.1 23.5 22 20.4 18.9

BE2 49 44.884 40.8 38.4 36 33.7 31.3 29 27.3 25.6 24 22.2 20.6

BE4 53 48.548 44.1 41.5 39 36.4 33.9 31.3 29.5 27.7 25.9 24.1 22.3

BH3 53 48.548 44.1 41.5 39 36.4 33.9 31.3 29.5 27.7 25.9 24.1 22.3

BN20 59 54.044 49.1 46.2 43.4 40.5 37.7 34.9 32.9 30.9 28.9 26.8 24.8

ER1 40 36.64 33.3 31.3 29.4 27.5 25.6 23.6 22.3 20.9 19.6 18.2 16.8

HXR1 52 47.632 43.3 40.7 38.2 35.7 33.2 30.7 29 27.2 25.4 23.6 21.8

WR1 55 50.38 45.8 43.1 40.4 37.8 35.1 32.5 30.6 28.8 26.9 25 23.1

WR2 44 40.304 36.6 34.5 32.3 30.2 28.1 26 24.5 23 21.5 20 18.5

WR3 40 36.64 33.3 31.3 29.4 27.5 25.6 23.6 22.3 20.9 19.6 18.2 16.8

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The tubes BN20 and WR1 are not representative of relevant exposure. For the other tubes it can be seen that this method predicts that

at HXR1, BE4 and BH3 the exceedences are likely to occur until 2011 if no other action is taken, but

other locations appear to be likely to meet the annual mean objective by 2010. There are, however, strong indications [AQB11] that primary nitrogen dioxide emissions may not be decreasing in the way this method assumes. Indeed Table 3 shows significant departures from the projections in Box 4. Continued monitoring may help clarify this.

4.4 Non traffic sources of nitrogen dioxide Brighouse hosts a significant amount of industry, most of the larger processes being located to the East at Armytage Road Industrial Estate. There are no large scale combustion activities here, and it is expected that the prevailing wind prevents any significant contribution to the annual mean nitrogen dioxide levels. To the West of the town there is an industrial area at Brookfoot, but no combustion processes or processes expected to produce nitrogen dioxide emissions. A Part A1 permitted installation that used nitric acid in its process ceased to operate in 2009. This was located on the Lowfields Industrial Estate at Elland, approximately 2.5km due West of the AQMA. The same industrial estate is host to several smaller permitted installations including two Part B wood burning appliances and a Part A2 heatset printing process. The contribution to the local background from the latter has been modelled by an independent consultant in connection with the application for an A2 permit. The wood burning installations were described in Section 6 of the USA09, with one being identified for a further assessment for particulates and for nitrogen dioxide. The AQMA itself contains a mixture of retail and residential properties, mostly using gas and electricity. There are no large boilers in the area or within the town centre, and one oil burner. 4.5 Local Traffic data Traffic survey locations are depicted on Figure 5 below. A count carried out in September 2009 on Huddersfield Road estimated the contribution to the two-way flows of vehicles over 1.5 tonnes at 7% to 8%. The Council also referred to the Department for Transport‟s “Transport Statistics Bulletin – Road Traffic Statistics for Great Britain 2005 – Statistics Report SB (06)28” of July 2006. This document would describe the routes around Brighouse as principal urban „A‟ roads, maintainable by the local authority, and offers the following in respect of such roads some 80% of all motor traffic is cars and taxis a typically motor vehicle flow for the Yorkshire and Humberside region would be

between 18700 and 20000 vehicles a day goods vehicle traffic peaks slightly during the autumn period and mid week

(Wednesdays/ Thursdays). Goods vehicle traffic is concentrated between 6am and 5pm, tailing off outside normal working hours

car traffic on urban roads is more evenly distributed throughout the year and rises slowly from Mondays, peaking on Fridays.

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The most recent reported traffic flow data is in the Calderdale Monitoring Report 2009 [CMR09], from which Figure 5 is taken. The Table T1, also taken from [CMR09], shows the weekday flows.

Table T1: weekday traffic flows, Brighouse and Rastrick

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Figure 2: traffic census points around Brighouse

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4.6 Developments affecting the AQMA The development site marked S on Map 2 above is still earmarked for residential development although the precise details are subject to change. The bus station was rebuilt to provide a modern, comfortable waiting space and improved access in 2007.

5 Summary and Conclusions The reported data indicates that the decision to declare the AQMA was appropriate, and that the relevant exposure has been properly identified. The additional monitoring undertaken since declaration clearly identifies the „hot spots‟ on Wakefield Road, at Bridge End mini roundabout and at the southern end of Halifax Road. It is too early to determine whether any changes could be made to the AQMA boundary, although removing parts of the area that do not have relevant exposure could be usefully considered. The future year projections indicate that the levels of nitrogen dioxide are set to fall over the next four years, but there is some doubt as to the validity of the predictions given the increase in primary NO2 emissions from the modern fleet. These matters will be more fully explored in the Air Quality Action Plan (AQAP) which will be produced with consideration to the results set out in this report. References [AQB11] Air Quality Bulletin, „Report ends NO2 complacency?‟ April 2011 [CMR09] Calderdale Monitoring Report 2009, Transport Policy Monitoring 2010 [DA06] Detailed Assessment 2006, Calderdale MBC, May 2007 [Openair] Carslaw, D. C. And Ropkins, K (2009) Open-source tools for analysing air

pollution data Institute for Transport Studies, The University of Leeds, 2009 www.openair-project.org

[PR07] Progress Report 2007, Calderdale MBC, 2007 [PR10] Progress Report 2010, Calderdale MBC, 2010 [USA05] Updating and Screening Assessment 2005, Calderdale MBC, 2005

This Assessment is open to public comment until 1 August 2011. Comments should be made to

Head of Service, Environmental Health Services, Calderdale MBC, Northgate House, Northgate, Halifax, HX1 1UN

Environmental Health Services Calderdale Metropolitan Borough Council

www.calderdale.gov.uk/environment/pollution/air-quality/index.html

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Appendix 1: Monitoring and Quality Control The Council uses two different methods to measure nitrogen dioxide levels across the Borough. We use a type of electronic monitor assembled in a robust roadside cabin known as a Romon. The units continuously measure NO2 and the results can be analysed to give hourly means, monthly and annual statistics and so on. We have five continuous monitors across the Borough. We also use „passive diffusion’ tubes which are exposed at monitoring points across the Borough, normally for a month at a time. The tubes are then sent off for analysis to give an average level of nitrogen dioxide for that month. Some tubes are located close to the inlet of a continuous monitor. We derive average nitrogen dioxide concentrations for a whole year from the two different sets of monitor. As the Romon gives more accurate and precise readings than the diffusion tubes we adjust the results from the tubes by comparing them with the results from the Romon. This is called bias correction. If only a part-year of results is available for a tube we adjust those results by comparing them to tubes where a full year of results is available. This is called period correction. Sometimes where no data is available we use computer programs to predict or model levels of pollution. Modelling offers the best estimate of pollution in the absence of monitoring data, but it is subject to several limitations and it cannot replace actual measurement. Equipment The air quality monitoring in Brighouse is carried out using diffusion tubes and two continuous monitors. Diffusion Tubes are supplied and analysed by West Yorkshire Analytical Services. They are prepared using 50% TEA in acetone and are exposed for approximately 1 month. West Yorkshire Analytical services has demonstrated satisfactory performance in the WASP scheme for analysis of NO2 diffusion tubes, January 2008 – January 2009. The laboratory is rated „good‟ on both sets of criteria at www.laqmsupport.org.uk/no2qaqc.php Raw Data and Calculations All raw data received from the laboratory is entered on a spreadsheet and saved to a secure network. Bias correction and other calculations are carried out on copies of the raw data, which is therefore preserved for future analysis. Bias correction is based on continuous monitoring at Romon 4, a roadside continuous monitor located in Sowerby Bridge, approximately 10km from this AQMA at grid reference 414384 422456. The collocation data is included in the national study, and the bias correction factors are derived from that study. More detail about the Council‟s quality assurance and quality control in relation to air quality monitoring is contained in [PR10].

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Environmental Health Services

Northgate House

Northgate

Halifax

HX1 1UN

Telephone: 01422 392373

Fax: 01422 392399

Email: environmental.health @calderdale.gov.uk

If you would like this information in another format or language, please contact: Halifax (01422) 392373

Halifax (01422) 392373