Authors Christopher Conolly and Hao Wu
Compilation date 11 October 2017
Customer Environment Agency, Department for Environment, Food and Rural Affairs, Department of Environment Northern Ireland, Welsh Government and Scottish Government
Approved by Christopher Conolly
Copyright Ricardo Energy & Environment
End User License Agreement http://ee.ricardo.com/cms/eula/

Contract reference 23102 Report reference ED62291/PAH2016AR/Issue 1

Executive Summary

This annual report for 2016 for the UK PAH Monitoring and Analysis Network was prepared by Ricardo Energy and Environment for the Environment Agency, the Department for Environment, Food and Rural Affairs, the Department of Environment Northern Ireland, the Welsh Government and the Scottish Government.

In 2016 there were 30 ambient air sampling sites operational in the network in the UK in addition to two deposition samplers. The majority of the sampling locations are urban background however the network also includes urban industrial, rural background and a single site that is urban traffic. Of the rural located samplers there are two sites that are located at Chilbolton Observatory, Hampshire and Auchencorth Moss, Midlothian which are used to support the European Monitoring and Evaluation Programme (EMEP) to Level 2. EMEP is a scientifically based and policy driven programme under the Convention on Long-range Transboundary Air Pollution (CLRTAP) (UNECE, 1979) for international co-operation to solve transboundary air pollution problems.

The UK Polycyclic Aromatic Hydrocarbons (PAH) Monitoring Network comprises non automatic systems to measure PAH in ambient air and deposition. Benzo[a]pyrene (B[a]P) has been identified as a human carcinogen and has been determined to be a suitable ‘marker’ for the PAH mixture in ambient air.

There is an EU Target Value that relate to the annual mean concentration of Benzo[a]pyrene (1 ng/m3). There is also a more stringent UK National Air Quality Objective for B[a]P in ambient air is an annual mean concentration of 0.25 ng/m3 as detailed in the Air Quality Strategy (Defra, 2007).

Key findings for 2016:

  • In 2016 the EC target value for B[a]P (annual mean concentration of 1 ng/m3) was exceeded at three sites:
    • Derry/Londonderry Brandywell
    • Scunthorpe Low Santon
    • Scunthorpe Town
  • In 2016 eleven sites exceeding the UK Air Quality Objective for B[a]P (annual mean concentration of 0.25 ng/m3)
    • Derry/Londonderry Brandywell,
    • Scunthorpe Low Santon
    • Scunthorpe Town
    • Port Talbot Margam
    • Ballymena Ballykeel
    • Royston
    • Kilmakee Leisure Centre
    • South Hiendley
    • Leeds Millshaw
    • Swansea Cwm Level Park
    • Nottingham (however only operation for winter months so not representative of full year)
  • The average data capture of all of the sites that were operational throughout 2016 was 99%

1 Introduction

This report was prepared by the Ricardo Energy and Environment as part of the UK PAH Monitoring and Analysis Network (‘the Network’ or ‘the PAH Network’) contract number 23102 with the Environment Agency for the Department for Environment, Food and Rural Affairs, the Northern Ireland Department of Agriculture, Environment and Rural Affairs (DAERA), the Welsh Government and the Scottish Government.

Ricardo assumed full operation of the Network on the 1st of September 2016 following a transition period from the previous contractor. This annual report presents and discusses data from both the current contract and the data reported by the previous contractors since data was collected by the Digitel DHA-80 samplers originally set up by the team at Ricardo Energy & Environment in the late 2000’s.

This interactive annual report contains:

  • An introduction to polycyclic aromatic hydrocarbons (PAHs)
  • Details of air quality policy relating to PAHs
  • A review of the sources of PAHs in the UK according to the National Atmospheric Emissions Inventory (NAEI)
  • A network overview including equipment and details of the sampling locations and changes in 2016
  • Summary of Analytical Techniques
  • A comparison of annual mean B[a]P concentrations with the EU Target Value and the more stringent UK Air Quality Objective
  • Monthly PAH concentrations in 2016
  • Review of correlation of B[a]P and other PAHs
  • Review of measured Deposition concentrations
  • Review of concentration trend of B[a]P at each of the monitoring sites
  • Review of sites with higher B[a]P Concentrations including those that exceed the EU Target Value for B[a]P

The appendices of this report present data for the monthly deposition concentrations of B[a]P at all Network stations that were operational in 2016 however this information, air concentration data and other monthly concentration data for all other PAHs measured at the sites can be found accessed via the UK-AIR website.

1.1 Polycyclic Aromatic Hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutant compounds they contain two or more benzene rings, they are generally produced through incomplete combustion or pyrolysis and sources include industrial, commercial, vehicular and residential sources. A more detailed discussion of the sources of PAH in the UK is presented in Section 1.3 where trends in the emissions of B[a]P presented.

The International Agency for Research on Cancer (IARC) has determined that B[a]P is carcinogenic to humans (group 1) (WHO, 2010) and is currently considered by IARC as the most carcinogenic PAH. There is epidemiological evidence of an association between urban air pollution and excess risk of lung cancer in those most highly exposed according to the Expert Panel on Air Quality Standards (EPAQS) (Defra, 1999) and it is understood that the mechanism involves reactive metabolites of some PAHs binding to cellular proteins and DNA thus potentially resulting in carcinogenic effects in the human body. It is therefore very important to continue to measure the concentrations of PAH in ambient air in order to monitor potential exposure to PAH and help provide policy makers with the information to help protect the health of the public and the environment.

Table 1 below shows the details of PAH that are required to be measured Fourth Daughter Directive (2004/107/EC) (EC, 2005) in the UK plus benzo[ghi]perylene which was more recently included in the 2014 technical standard CEN/TS 16645:2014 (BSI, 2014). The table also included the IARC classifications and structures of the PAH.


Table 1: PAH structures and IARC Carcinogenic Classification of PAH that should be monitored according to the 4th Daughter Directive (2004/107/EC). IARC Group 1: Carcinogenic to humans, Group 2A: Probably carcinogenic to humans, Group 2B: Possibly carcinogenic to humans, Group 3: Not classifiable as to its carcinogenicity to humans

Compound Structure IARC
Benz[a]anthracene 2B
Benzo[b]fluoranthene 2B
Benzo[j]fluoranthene 2B
Benzo[k]fluoranthene 2B
Benzo[a]pyrene 1
Dibenz[a,h]anthracene 2A
Indeno[1,2,3-cd]pyrene 2B
Benzo[g,h,i]perylene 3

1.2 Air Quality Policy

In the UK there is a national air quality objective for B[a]P in ambient air this is based on an annual mean concentration of 0.25 ng/m3. The Expert Panel on Air Quality Standards (EPAQS) proposed this in 1999 after an assessment to identify human health exposure and the suitability of B[a]P as a marker. The intention of the recommendation was to reduce risk to the population from exposure to PAHs to be so small as to be undetectable. The annual mean objective for PAH using B[a]P as a marker was adopted by the UK in the Air Quality Strategy in 2007. The level of 0.25ng/m3 was to be achieved and maintained below that level by the end of 2010.

The EC Air Quality Framework Directive (Directive 96/62/EC) (EC, 1996) set a strategic framework to tackle air quality in a consistent way across Europe by setting limit and target values for air pollutants via a series of Daughter Directives.

B[a]P’s suitability as a marker for the PAH mixture in ambient air by the EC Position Paper (EC, 2001) on PAH led to it being selected as the measure for monitoring in the Fourth Daughter Directive (Directive 2004/107/EC) and the more stringent UK National Air Quality Objective for PAH (annual mean of 0.25 ng/m3 B[a]P in ambient air).

The UK PAH Network is a regulatory air quality monitoring network, it discharges the UK Government’s obligation under the EC Air Quality Fourth Daughter Directive to monitor the concentrations of B[a]P in the PM10 fraction of ambient air (particles which pass through a size-selective inlet with a 50 % efficiency cut-off at 10 μm aerodynamic diameter). The measurements in the UK PAH network are designed to enable the UK to demonstrate compliance with legislation that imposes the target value relating to benzo[a]pyrene in ambient air. The national network of measurement sites in the UK also enables human and environmental exposure to be assessed which enables policy makers to take action to reduce anthropogenic emissions where considered necessary hence reducing human and environmental exposure.

The Fourth Daughter Directive sets a target value for B[a]P and for other pollutants. It set a target value and assessment thresholds for B[a]P these are:

  • Target value (for the total content in the PM10 fraction averaged over a calendar year): 1 ng/m3
  • Upper assessment threshold: 0.6 ng/m3
  • Lower assessment threshold: 0.4 ng/m3

According to the Fourth Daughter Directive measurement are mandatory in zones or agglomerations of the UK where levels are above the lower or upper assessment threshold if exceeded in 3 of the last 5 years. The assessment of measurement requirements for PAH (known as a Monitoring Regime Assessment) is currently undertaken on a minimum 5 yearly basis.

The Fourth Daughter Directive also specifies the data quality objectives for PAH measurements that are outlined in Table 2.

Table 2: Data quality objectives detailed in Annex IV of Fourth Daughter Directive. * Indicative measurements are defined as measurements which are performed at reduced regularity but fulfil the other data quality objectives.
Criterion B[a]P in PM10 Other PAHs in PM10 PAHs in deposition
Expanded uncertainty (fixed and indicative measurements) 50% 50% 70%
Expanded uncertainty (modelling) 60% 60% 60%
Minimum data capture 90% 90% 90%
Minimum time coverage (fixed measurements) 33% NA NA
Minimum time coverage (indicative measurements*) 14% 14% 33%


Measurements of B[a]P in ambient air are covered by the European standard EN 15549 (BSI, 2008), which has been adopted as the European reference method. In order to assess the contribution of B[a]P in ambient air, the Fourth Daughter Directive also requires a number of other PAHs to be monitored at a limited number of measurement stations. The PAH that this must include as a minimum,: benz[a]anthracene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, indeno[1,2,3-cd]pyrene and dibenz[a,h]anthracene.

Measurements of PAH in Deposition are covered by European standard EN 15980 (BSI, 2011) which details the measurement method sampling, sample preparation and analysis for benz[a]anthracene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenz[a,h]anthracene and indeno[1,2,3-cd]pyrene. There is no limit or target value related deposition of PAH in the UK or Europe.

The two sites of located at Chilbolton Observatory, Hampshire and Auchencorth Moss, Midlothian are used to support the European Monitoring and Evaluation Programme (EMEP) to Level 2. EMEP is a scientifically based and policy driven programme under the Convention on Long-range Transboundary Air Pollution (CLRTAP) which was signed by the UK in 1979. The convention aids international co-operation to solve transboundary air pollution problems, provides access to emission, measurement and modelling data and provides information on the effects of air pollution on ecosystems, health, crops and materials.

1.3 Sources of PAHs in the UK

The National Atmospheric Emissions Inventory (NAEI) has estimated the emission of PAH for the UK for many years. The inventory now estimates the emissions of 16 PAH (the US-EPA 16) which includes benzo[a]pyrene. As with all emissions inventories there is some uncertainty in the estimates as the emissions are not based solely on measurements and require some estimation of emission factors and activities being required.

Figure 1 shows UK estimated emissions of benzo[a]pyrene by source sectors. It is apparent from the review of the trend that there has been a significant decrease in the overall emissions of benzo[a]pyrene in the UK since the 1990’s. The total emissions were estimated as 61.7 tonnes in 1990 and by 2015 (the most recent data available at the time of reporting) was 7.5 tonnes representing an 87.8% reduction in anthropogenic emissions.

Figure 1: Estimated UK anthropogenic emissions of B[a]P per sector from 1990 to 2015.

The sources that are thought to dominate the emissions have changed significantly since the early 1990’s. In the early 1990’s the sectors that dominated the emissions were agricultural and production processes. Agriculture & Waste encompassed agricultural stubble burning that was banned in the UK in 1993 by the Crop Residue (Burning) regulations 1993 following environmental concerns relating to the emission. The practice had been employed to improved weed control largely. Production processes contributed a large proportion of the overall emission of B[a]P between the early 1990’s and the early 2000’s these processes were dominated by processes that relating to metal production such as anode baking and aluminium production. Increasingly stringent emissions regulations and the decline of industry has resulted levels of emissions reduced from this sector leaving residential and commercial combustion to dominate the emissions from the late 1990’s and early 2000’s. Residential and commercial combustion continue to dominate emissions with emissions of B[a]P currently making up almost 90% of the estimated emissions of B[a]P in the UK. The residential and commercial combustion sector has also started to increase emissions of B[a]p from an estimated 4.3 tonnes in 2000 to 6.75 tonnes in 2015 which represents a 57% increase. With an increasing trend in the emissions estimates from this spatially distributed sector it is important to understand this source and reduce the uncertainty of the estimates.

Improvements in the calculation of emissions from the domestic wood combustion sector to take into account the age of appliances has been integrated into the NAEI emission estimates shown in this report. Therefore, whilst it is possible to compare emissions between years in the data set they should not be compared with data previously reported.

More information relating to UK Emissions of PAH and other pollutant can be accessed via the NAEI website.

2 The PAH Network

2.1 Network Objectives

The objective of the PAH Network is to determine the ambient concentrations of PAHs in ambient air in the UK through monitoring and chemical analysis, and deliver or aid the delivery the following:

  • A UK assessment of current concentrations of PAHs for assessment against the Fourth Daughter Directive and the UK Air Quality Strategy objectives, and provide measurement input for any future reviews.
  • A Review of the measurements and trends of airborne concentrations of PAHs in representative UK industrial, urban and other areas enabling comparison the rural locations where measurements take place.
  • Provide data and metadata to UK-AIR to enable demonstration of the UK’s compliance with the Fourth Daughter Directive, the OSPAR convention (OSPAR, 2017) and the UNECE Convention on Long Range Transboundary Air Pollutants (UNECE, 1979).
  • To enable a better understanding of sources or potential sources of PAH to potentially enable improvements to the NAEI or identification areas of uncertainty.

2.2 Network Overview

The 30 monitoring stations operating in the UK PAH Network during 2016 are shown in Figure 2. Two monitoring sites where both Digitel particulate samplers and deposition samples are taken are marked with drop marker (Auchencorth Moss and Chilbolton Observatory). Other sites where only Digitel particulate samples are taken are marked with red circles.

Figure 2: Map of UK PAH monitoring stations in 2016.


In 2016 there were 30 ambient air sampling sites operational in the network in the UK in addition to two deposition samplers. The majority of the sampling locations are urban background however the network also includes urban industrial, rural background and a single site that is urban traffic at London Marylebone Road. Of the rural located samplers there are two sites that are located at Chilbolton Observatory, Hampshire and Auchencorth Moss, Midlothian which are used to support the European Monitoring and Evaluation Programme (EMEP).

2.3 Samplers in the PAH Network

The Network requires the sampling and analysis of two types of samples these are particulate and deposition samples.

‘PAH Digitel (solid phase)’ particulate samplers. These samples are in the PM10 fraction of ambient air on a filter and are taken daily at all 30 Network stations using Digitel DHA-80 samplers with automatic filter changers. Each sample is taken for 24 h, and a sample is taken every 24 h, with the sample changeover generally occurring at midnight. The samples are bulked into groups representing calendar months for analysis. The Digitel DHA-80 samplers (see Figure 3) used throughout the Network are considered to be equivalent to the requirements of the European Standard for sampling PM10 matter (EN 12341) (BSI, 2014). The samplers are therefore valid for use with the European Standard method for the measurement of B[a]P in ambient air (EN 15549). The solid phase filter samples have a measurement period of 24 hours at a flowrate of approximately 30 m3/h.

Figure 3: Digitel DHA-80 sampler deployed to measure solid phase PAH in the UK Network.

Figure 3: Digitel DHA-80 sampler deployed to measure solid phase PAH in the UK Network.

‘PAH deposition’ samplers. These Deposition samples are taken fortnightly at two rural Network stations of Auchencorth Moss and Chilbolton Observatory in 2016 and previously at Harwell. Each sample is taken for 14 days using a deposition sampler (Figure 4) that meets the requirement of the European Standard for the measurement of the deposition of PAHs (EN 15980). The deposition samplers itself consist of a glass funnel and a four litre brown glass collection bottle, which are located inside a protective tube in order to minimise photochemical reactions and the degradation of PAHs. The spikes seen on the image have been fitted to the top of the protective tubes to prevent damage and contamination by bird strikes.

Figure 4: Samplers to measure deposition of PAH in the UK Network.

Figure 4: Samplers to measure deposition of PAH in the UK Network.

2.3.1 Sampling Quality Control

To ensure the quality of the sampling procedure there are a number of checks and quality assurance and quality control measures that are undertaken on the data and the filters used in the samplers prior to use. These include the inspection of sampling media prior to use at sampling sites, analysis of field and sample blanks, checking of equipment operation via online systems, review of the measurement data associated with the filters being returned from the sites to ensure they meet the requirement of the EN 15549 standard. In addition to these checks the network is supported by an infrastructure of local site operators who are fully trained and provided with detailed working instructions or site operation.

2.4 Network Activities During 2016

2.4.1 Station Infrastructure and Network Re-organisation

The following network infrastructure changes took place which are not detailed in previous reports covering the time period at the end of 2015 and 2016:

  • Hove PAH sampling ceased 31st December 2015
  • London Crystal Palace Parade PAH sampling ceased 31st December 2015
  • Nottingham Centre PAH sampling began 16th November 2016

2.4.2 Data capture, Station Calibrations, Services and Breakdowns

All Stations were calibrated and serviced in 2016 and checks on flow were undertaken. There were motor failures at a number of site during 2016 but no other major issues affected data capture hence the data. Table 3 below shows the data captures for 2016 excluding Nottingham Centre that was installed in November 2016 which was 100% time coverage but due to the start date in November this represents only 12% of the year.

Table 3: PAH data capture in 2016. * The Chilbolton Observatory was installed on the 11th of January hence slightly reduced data capture.
Site Data capture
Auchencorth Moss 100% (Deposition 100%)
Ballymena Ballykeel 100%
Birmingham Tyburn 98%
Bolsover 100%
Cardiff Lakeside 97%
Chilbolton Observatory* 91% (Deposition 93%)
Derry Brandywell 100%
Edinburgh St Leonards 99%
Glasgow Townhead 100%
Hazelrigg 100%
High Muffles 100%
Kilmakee Leisure Centre 100%
Kinlochleven 96%
Leeds Millshaw 100%
Liverpool Speke 98%
London Brent 98%
London Marylebone Road 100%
Lynemouth 2 100%
Middlesbrough 100%
Newcastle Centre 100%
Newport 100%
Port Talbot Margam 95%
Royston 100%
Salford Eccles 100%
Scunthorpe Low Santon 99%
Scunthorpe Town 100%
South Hiendley 100%
Stoke Ferry 96%
Swansea Cwm Level Park 100%
Station Average 99%

The data capture for those sites operating throughout the majority of 2016 were between 91% and 100% with an average of 99%. This capture is in line with the 2015 data capture and above the 2014 and 2013 data captures which were also an impressive 97% and 96% respectively.

3 Analytical Techniques

The PAH analysed and reported from deposition and particulate samples are shown in Appendix 3 Table A3 along with the typical detection limits. The PAH are consistent with previous years reporting with the exception of Benzo[b+j]fluoranthene and Dibenzo[ah+ac]anthracene which are have been analysed separately as Benzo[b]fluoranthene and Benzo[j]fluoranthene and Dibenzo[ac]anthracene and Dibenzo[ah]anthracene since July 2016 when Ricardo took over the network from the previous contractors. In addition to this Cholanthrene has also been added to the list of PAH that are analysed at this time.

More information relating to the quality control measures that undertaken are shown in Appendix 3.

4 Results & Discussions

This section presents and discusses the results from the PAH Digitel (solid phase) particulate samplers stations. The discussion focuses on B[a]P as the Fourth Daughter Directive Target Values and UK Air Quality Objective both use B[a]P as the marker for the PAH mixture in ambient air. Some data for other PAHs are also presented however commentary is limited. Data for all PAHs for all stations are made available on the UK-AIR website.

4.1 Comparison of B[a]P annual concentrations against EC target values and UK Air Quality Objective

The annual mean B[a]P concentration measured at all the PAH Digitel (solid phase) particulate samplers are shown in Figure 5.

Figure 5: Comparison of annual B[a]P concentrations at all the monitoring stations against EC and UK target values and UK Air Quality Objective. (It should be noted that the Nottingham Centre site only started from November 2016 so data capture for the full year will obviously be limited).


The data capture results calculated in this analysis is based on the percentage of valid data covering the entire calendar year. The Nottingham Centre site only started monitoring from November 2016, hence the low data capture rate. All other sites running throughout 2016 have a data capture rate over 90% with an average of 99%.

Three sites exceeded the EC target value of 1ng/m3. These were Derry Brandywell, Scunthorpe Low Santon and Scunthorpe Town. One additional site (Port Talbot Margam) exceeded the EC UAT. Four more sites exceeded EC Lower assessment threshold these were Ballymena Ballykeel, Royston, Kilmakee Leisure Centre and Nottingham Centre. However it should be noted that the concentration at Nottingham Centre is only a representation of only 1.5 months of winter average, rather than a representation of the concentration over the whole year.

The more stringent UK Air Quality Objective for PAH (0.25ng/m3 B[a]P) was exceeded at eleven sites:

  • Derry/Londonderry Brandywell
  • Scunthorpe Low Santon
  • Scunthorpe Town
  • Port Talbot Margam
  • Ballymena Ballykeel
  • Royston
  • Kilmakee Leisure Centre
  • South Hiendley
  • Leeds Millshaw
  • Swansea Cwm Level Park
  • Nottingham (1.5 months of winter so not representative of full year)

Whilst some of the above sites have specific emission sources such as steel works (Scunthorpe sites and Port Talbot Margam), other urban may have significant solid fuel use contributing to the air concentrations of PAH such as Derry/Londonderry Bandywell, Ballymena Ballykeel and Kilmakee Leisure Centre. The Royston and South Hiendley sites were positioned to measure concentrations around the Coke works in Royston, this closed in December 2014 however levels continue to be above the UK Air Quality Objective this may be due to solid fuel use in the area or possible re-suspension of previous emissions.

The sites located in Northern Ireland and those around the steel works in Scunthorpe will be discussed in a later section where polar plots are used to present the data.

4.2 B[a]P monthly concentrations

PAH are expected to show seasonality with the higher concentrations observed during the winter months as a result of domestic and industrial combustion processes usually related with heating during the colder months. Industrial sites would generally be expected to show a less seasonality as any seasonality related to such domestic and industrial combustion process for heating would be masked by the more constant emissions from industrial processes. The monthly concentrations of B[a]P for 2016 grouped by the site characteristics types are shown in Figure 6 - 10.

4.2.1 Northern Ireland sites

Figure 6: Monthly average B[a]P concentrations at the Northern Ireland sites and average regional temperatures in 2016.

Monthly variation of B[a]P concentrations in Northern Ireland showed a pronounced seasonal variation with low concentrations in the summer months and higher in winter. The above figure shows that when lower temperatures are observed there is an increase in B[a]P. This supports the understanding that the PAH sites in Northern Ireland are highly influenced by emission from solid fuel usage for domestic heating. The elevation during November is thought likely to be due to bonfires and fireworks on Guy Fawkes Night (November the 5th). In 2016 this effect may have been increased due to the 5th of November falling on a weekend enabling more people to have their own bonfires in the evening or attend local events.

The lower boundary layer depth in the winter months also contributes to the increased concentrations in the winter months. The boundary layer (often called the Atmospheric Boundary Layer) is the layer of atmosphere next to the surface of the earth. Within this layer air is very well mixed. If the boundary decreases in height, as is common in winter months this can increase concentrations within the layer.

4.2.2 GB urban background

Figure 7: Monthly average B[a]P concentrations at urban background sites in GB in 2016.

Similar to the Northern Ireland site the urban background sites in Great Britain also generally exhibited seasonal variability resulting from the anticipated solid fuel usage. Whilst this isn’t as pronounced as the Northern Ireland sites there is still an observed decrease in concentrations during the summer months. The only exception to this is Newport site where elevated concentration was observed in July 2016. However this may have been due to a local emission source. At many urban sites there is also an elevation in concentrations between October and November. This is not only thought to be due to the increase in solid fuel use but also due to Guy Fawkes Night.

4.2.3 GB rural background

Figure 8: Monthly average B[a]P concentrations at rural background sites in GB in 2016.

The rural PAH network sites show much lower concentrations throughout the year than most of the urban and industrial sites. However, there is seasonality observed at the sites. The ‘Guy Fawkes Night effect’ does not appear to be as prominent at the rural locations where PAH are measured. The most rural site in the PAH network is thought to be Auchencorth Moss (red line), it is not thought that this site is influenced significantly by any local sources or by industry and would be the best site to represent the PAH concentration of regional background. The other rural sites whilst considered as rural they have local influences particularly the sites of Chilbolton and Stoke Ferry which both have small villages that could potentially contribute to PAH concentrations particularly during the winter months.

4.2.4 GB industrial

Figure 9: Monthly average B[a]P concentrations at operating industrial sites and those that are now closed in 2016.

These monitoring sites are likely to be influenced by the nearby industrial activities, which are relatively invariant throughout the year. Therefore seasonality is less pronounced. The sites that do have some apparent seasonality are the sites where the local PAH sources have closed. These are Lynemouth, Middlesbrough, South Hiendley and Royston. The sites that are still influenced by industry are Port Talbot Margam, Scunthorpe Town and Scunthorpe Low Santon show limited seasonality as any seasonal sources that may be present such as for domestic heating are masked by the more consistent and dominating industrial emissions at these locations. Industrial sources are more likely to deviate from the usual seasonal patterns seen with PAH concentrations as relatively high concentrations are observed during non-winter months as well as the winter months.

4.2.5 GB urban traffic

Figure 10: Monthly average B[a]P concentrations at the urban traffic site in GB in 2016.


Marylebone road is the only urban traffic site that measures PAH and is a site that has significant traffic flow. There is a clear seasonality observed at the site and the magnitude of B[a]P measured at Marylebone road is comparable to that measured at other urban background sites in Great Britain. This could indicate that the concentrations of B[a]P at the site may not dominated by traffic even though the site is a traffic site and could indicate that it is as a result of seasonal emissions relating to domestic and other heating emissions.

4.3 Other PAHs Monthly Concentrations

As detailed in earlier in this report the section Fourth Daughter Directive also specifies that six other PAHs should be monitored at a limited number of measurement stations. The PAH the directive refers to are benz[a]anthracene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, indeno[1,2,3-cd]pyrene, and dibenz[a,h]anthracene. The CEN TC264 WG21 developed Technical Specification for the measurement of these PAHs and benzo[ghi]perylene in the particulate phase. The UK PAH Network measures all of the PAH referred to in the Technical Specification at all stations and since Ricardo Energy & Environment took over the network from the previous contractor, these have been analysed and reported separately. The monthly mean concentration of each of these PAHs measured at the sites are shown in the figures below. On a review of the figures on a visual basis only, these PAH appear to follow similar seasonal trends to those of the ‘marker’ B[a]P, which indicates that the assumptions made in using B[a]P as a marker are well founded. In addition to this relatively un-statistical approach of reviewing the suitability of B[a]P as a marker for PAH, a correlation assessment has been conducted for all the PAHs against B[a]P. A visual representation of this is shown in Figure 18.

4.3.1 Benz[a]anthracene

Figure 11: Monthly mean benz[a]anthracene concentrations at the UK PAH sites.

4.3.2 Benzo[b]fluoranthene

Figure 12: Monthly mean benz[a]anthracene concentrations at the UK PAH sites.

4.3.3 Benzo[j]fluoranthene

Figure 13: Monthly mean benzo[j]fluoranthene concentrations at the UK PAH sites.

4.3.4 Benzo[k]fluoranthene

Figure 14: Monthly mean benzo[k]fluoranthene concentrations at the UK PAH sites.

4.3.5 Indeno[1,2,3-cd]pyrene

Figure 15: Monthly mean indeno[1,2,3-cd]pyrene concentrations at the UK PAH sites.

4.3.6 Dibenz[ah]anthracene

Figure 16: Monthly mean dibenz[a,h]anthracene concentrations at the UK PAH sites.

4.3.7 Benzo[ghi]perylene

Figure 17: Monthly mean benzo[ghi]perylene concentrations at the UK PAH sites.

4.4 Review of correlation of B[a]P and other PAHs

Whilst this report concentrates on the measurements of B[a]P which is only one PAH measured in the PAH network it is important to demonstrate that this and the approach of the UK and EU to set objectives and target values for B[a]P is sensible. To investigate if B[a]P can be considered as a ‘marker’ for other PAHs, correlations between B[a]P and other PAHs at each site based on monthly average concentration from all Digitel sampler data available from 2007 to 2016 at each of the sites. This assessment is shown visually in Figure 18. The larger darker red circles indicate high correlation whereas small blue circles indicate a negative correlation of the PAH with B[a]P.

Figure 18: Correlation between monthly average B[a]P and other PAHs concentrations at each monitoring site since the network was established (see Appendix 1 for key to abbreviations).

Figure 18: Correlation between monthly average B[a]P and other PAHs concentrations at each monitoring site since the network was established (see Appendix 1 for key to abbreviations).

Correlations between B[a]P and some other PAHs (from benzo[j]flouranthene to benzo[k]fluoranthene) were consistently high across all monitoring sites. This group of PAH includes the PAH that must be analysed as a minimum within the PAH network according to the Fourth Daughter Directive (benz[a]anthracene, benzo[b]fluoranthene, benzo[j]fluoranthene, benzo[k]fluoranthene, indeno[1,2,3-cd]pyrene, and dibenz[a,h]anthracene). This confirms that over the 10+ years of PAH measurement using the Digitel samplers Benzo[a]pyrene is considered representative of the mixture of the PAH that the Fourth Daughter Directive requires.

At some locations, such as Kilmakee Leisure Centre and Lynemouth 2, B[a]P correlated well with more other PAHs than at others sites. Some PAHs, such as 5-Methyl Chrysene, Dibenz[al]pyrene and dibenzo[ah]pyrene typically have no correlation with B[a]P at most monitoring sites.

4.5 Depositon (‘C’) samples

The measured fortnightly or monthly Benzo[a]pyrene concentrations measured in deposition at the Auchencorth Moss and Chilbolton sites are displayed in Appendix 2. The levels of PAH at these rural sites in the UK are very low and as reported in the previous annual report (NPL, 2016). The levels found are often below or very close to detection limits, which makes any interpretation of the data difficult. Other PAH analysed are also regularly below detection limits. The monitoring conducted at the sites does however enable the UK to meet its obligations under the Forth Daughter Directive. All deposition data is available on the UK-AIR website.

4.7 Trend Assessment at the UK PAH Network sites

To summarise the long-term each at each monitoring site, the slope of the trend for each site was calculated using TheilSen function in the openair R package (Figure 24). A positive slope means that there is an increasing trend of B[a]P annual mean and a negative slope means a decreasing trend. The slope of each site’s B[a]P concentration over time was also calculated with its 95% confidence interval, which indicates the uncertainty of the slope coefficient. If the uncertainty of the slope covers zero, it suggests that no significant trend can be concluded. Figure 24 shows separately the sites that had a significant trend and the sites that did not. It should be noted that sites which have not been installed for very long have not been included due to the limited number of data points, the sites affected are: Kilmakee Leisure Centre, Glasgow Townhead, Nottingham and Chilbolton.

Figure 24: B[a]P concentration trend (ng m^-3^ yr^-1^) from 2008 to 2016.

Figure 24: B[a]P concentration trend (ng m-3 yr-1) from 2008 to 2016.


The trend calculated from many of the monitoring sites did not show a significant decreasing or increasing trend. It was either because there was very little change in the annual concentrations (i.e. a slope was not significantly different from zero) or there were large variations between years but not in a consistent direction (as indicated by the large confidence intervals (red bars) at the two Scunthorpe sites). For all the sites where a significant trend was observed, they generally showed a very small decreasing trend and the sites showing large decreasing trend (South Hiendley, Royston and Ballymena Ballykeel) were associated with larger uncertainties but all appear to have a significant decreasing trend in B[a]P concentrations.

4.8 Sites with Higher B[a]P Concentrations

Concentrations of B[a]P at the two Scunthorpe sites and Northern Ireland from 2007 to 2016 were further investigated with respect to other meteorological variables including wind speed/direction and temperature. Bivariate polar plots (Figure 25 - 28) show the variation of B[a]P concentration under different combinations of wind speed (or temperature) and wind direction. Since the meteorological data are hourly average and the B[a]P are monthly average data, monthly B[a]P concentrations were matched to hourly interval using the corresponding concentration for each month. Whilst this is not the ideal method to link the pollution data with meteorological data, this approach enables an assessment using polar plots with a monthly data series.

4.8.1 Scunthorpe

Figure 25: Polar plot of wind speed and direction at two Scunthorpe sites.

The polar plots in Figure 25 show the variation of B[a]P concentration under different combinations of wind speed and wind direction therefore these plots can be used to deduce which direction a potentially dominant sources of B[a]P is located.

Scunthorpe Town site is roughly upwind of the emission sources at the steel works, the blue drop marker represents the approximate location of the coke oven that continue to operate at the site and the red drop marker shows the location of the Dawes Lane coke oven reportedly closed in March 2016. As expected high concentrations are observed at the Scunthorpe Town site when air is coming from the north east wind direction.

The polar plot for Scunthorpe Low Santon reveals high concentration from many directions particularly at high wind speed from many directions. However high concentrations are observed when the wind direction is from the west which is the approximate location of the coke ovens at the steel plant. The slightly anomalous plot with high concentrations from areas which are not considered likely source areas might be due to the method of assigning a constant B[a]P concentration throughout a month over-represented high concentration for a particular wind speed/direction sector. Alternatively it could potentially be due to the site location influencing the airflow between the steel works and the monitoring site. The Scunthorpe Low Santon site is located in a dip between the steel works and Santon and hence there may be local factors influencing the observations. Without more detailed modelling it not possible to provide more insight.

Figure 26: Polar plot of temperature and wind direction at two Scunthorpe sites.

The polar plots shown in Figure 26 show the variation of concentration under different combinations of air temperature and wind direction therefore these plots can be used to deduce whether there is a relationship of a pollutant with temperature and wind direction.

The polar plot showing concentration of B[a]P with temperature and wind direction does not show any significant pattern with respect to the temperature and wind direction at the Scunthorpe sites which would be expected as emissions from an industrial process such as a steel works would not be expected to be temperature dependent. This provides confirmation that the major emission source contributing to the concentrations measured at these site are the coke ovens and not a temperature related source such as combustion for domestic or commercial heating.

4.8.2 Northern Ireland

Figure 27: Polar plot of wind speed and direction at two NI sites.

The polar plots in Figure 27 show the variation of B[a]P concentration under different combinations of wind speed and wind direction therefore these plots can be used to deduce which direction a potential sources of B[a]P is located. Where there is no large industrial sources this can give an indication of the potential locations of smaller sources however due to the monthly averaging of the concentration this can be more uncertain as these smaller sources can be more variable than industrial sources.

The polar plots for Northern Ireland are not as easy to analyse as those of around the steel works in Scunthorpe. Whilst there have been actions taken to reduce solid fuel use in Northern Ireland, there is still substantial solid fuel burning across the country. The three PAH sites in Northern Ireland shown in Figure 27 above enable a review of the potential location of solid fuel use. It should be noted that the polar plots use monthly B[a]P concentrations from 2007 to 2016. Whilst there are likely changes in source areas over the years as a result of any action that takes place locally to reduce particulate matter, sulphur dioxide and subsequently PAH concentrations, the plots show that the areas where sources may dominate for the 2007-2016 period as a whole. It should be noted that this assessment used monthly B[a]P concentrations matched to hourly interval so this adds to the uncertainty of the assessment.

Derry/Londonderry Brandywell’s polar plot appears to indicate that the concentrations of PAH are being measured when the wind direction is coming from the east. This would indicate that urban areas to the east of the sampling site may have higher solid fuel use than that to the west of the sampling site.

The polar assessment at the Ballymena Ballykeel site appears to show a number of potential areas of PAH emissions. These appear to be between the north and the west of the sampling site. The sampling site is to the east of the Ballymena so could indicate that the emissions are from Ballymena or from other areas to the west of Ballymena. The smoke control area information provided by Department of Agriculture, Environment and Rural Affairs (DAERA) shown on the Figure 27 appear to show that some of the areas in central Ballymena may not be covered by smoke control orders. Without better resolution data it is difficult to assess potential source areas further.

The Kilmakee Leisure Centre polar plot appears to clearly show that the higher concentrations occur when the wind direction is from the south west. When the plot is observed alongside with the smoke control areas to the north-east of the site, it appears to indicate that the concentrations observed are lower when wind is blowing from the north-east.

Figure 28: Polar plot of temperature and wind direction at two NI sites.

The polar plots shown in Figure 28 show the variation of concentration under different combinations of air temperature and wind direction therefore these plots can be used to deduce whether there is a relationship of a pollutant with temperature and wind direction. If a plot shows a centrally located hotspot it would generally indicate that concentrations of a pollutant increased with temperature.

In contrast to the patterns observed at the Scunthorpe sites, B[a]P concentrations in the Northern Ireland show an inverse correlation with temperature, indicating that the source of B[a]P measured is due to the combustion of solid fuel for heating.

Figure 29 below shows the mean seasonal contribution to the annual mean based on data from 2007 to 2016. There is a contrast between the Northern Ireland sites and the Industrial sites at Scunthorpe. In Northern Ireland, due to the seasonal dependence of solid fuel use, about 50% of the annual mean B[a]P concentration was contributed by the winter months (Jan, Feb and Dec), whereas the concentrations at the Scunthorpe sites had similar contribution from all seasons.

Figure 29: Mean contribution to the annual mean from the monthly concentrations from 2007 to 2016.

Due to the seasonal dependence of solid fuel use, more than 50% of the annual mean B[a]P concentration was contributed by the winter months (Jan, Feb and Dec) at the Northern Ireland sites. Therefore more stringent smoke control regulation would effectively reduce the bulk the annual mean B[a]P below the target value. However, the annual B[a]P concentrations at the Scunthorpe sites had similar contribution from all seasons. Therefore effective reduction of B[a]P in this area relies on reduction on the emission from the industrial activities.

5 Conclusions

The average data capture of all of the sites that were operational throughout 2016 was 99%. The annual mean Benzo[a]pyrene concentrations observed at the UK networks during 2016 varied greatly between sites. The highest annual mean was observed at the Derry/Londonderry Brandywell site with an annual mean B[a]P concentration of 1.3 ng/m3 and the lowest concentration measured at the Auchencorth Moss site 0.02 ng/m3.

In 2016 the EC target value for B[a]P (annual mean concentration of 1 ng/m3) was exceeded at three sites. These were Derry/Londonderry Brandywell, Scunthorpe Low Santon and Scunthorpe Town. The causes of the exceedance of the target value at these sites are thought to be domestic solid fuel use at Derry/Londonderry Brandywell and the steel works at the Scunthorpe sites.

In 2016 11 sites exceeding the UK Air Quality Objective for B[a]P (annual mean concentration of 0.25 ng/m3) these were Derry/Londonderry Brandywell, Scunthorpe Low Santon, Scunthorpe Town, Port Talbot Margam, Ballymena Ballykeel, Royston, Kilmakee Leisure Centre, South Hiendley, Leeds Millshaw, Swansea Cwm Level Park and Nottingham. However Nottingham was only operational for 1.5 months in winter so not representative of full year.

The levels of B[a]P have been seen to be decreasing at sites where industrial sources have ceased operating and also at a number of the urban sites such as Salford Eccles, Newcastle, Liverpool Speke and Leeds that have decreasing tends in concentrations of B[a]P (see Figure 24).

Concentrations measured in the UK monitoring network indicate there is still potential risk to the population from exposure to PAHs as the concentrations measured are above the EU Air Quality Target Value at three sites and above the UK National Air Quality Objective at 11 sites therefore measurements should continue to measure the exposure of the UK population, continue to monitor trends and to provide input to modelling UK PAH concentrations.

References

BSI, 2014. BS EN 12341:2014 Ambient air. Standard gravimetric measurement method for the determination of the PM10 or PM2.5 mass concentration of suspended particulate matter.

BSI, 2011. BS EN 15980:2011 Air quality. Determination of the deposition of benz[a]Anthracene, benzo[b]Fluoranthene, benzo[j]Fluoranthene, benzo[k]Fluoranthene, benzo[a]Pyrene, dibenz[a,h]Anthracene and indeno[1,2,3-cd]Pyrene.

BSI, 2008. Air quality. Standard method for the measurement of the concentration of benzo(a)Pyrene in ambient air. BS EN 15549:2008.

Defra, 2007. The Air Quality Strategy for England, Scotland, Wales and Northern Ireland (Volume 1). URL https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/69336/pb12654-air-quality-strategy-vol1-070712.pdf (accessed 2-June-2017).

EC, 2005. Directive 2004/107/EC of the European Parliament and of the Council of 15 December 2004 relating to arsenic, cadmium, mercury, nickel and polycyclic aromatic hydrocarbons in ambient air. URL http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:32004L0107\&from=EN (accessed 26-July-2017).

EC, 2001. Ambient air pollution by Polycyclic Aromatic Hydrocarbons (PAH). Position Paper. URL http://ec.europa.eu/environment/air/pdf/pp_pah.pdf (accessed 26-July-2017).

EC, 1996. Council Directive 96/62/EC of 27 September 1996 on ambient air quality assessment and management. URL http://eur-lex.europa.eu/legal-content/EN/TXT/PDF/?uri=CELEX:31996L0062\&from=EN (accessed 26-July-2017).

NPL, 2016. Annual report for 2015 on the UK PAH Monitoring and Analysis Network (No. NPL REPORT ENV 10). URL https://uk-air.defra.gov.uk/assets/documents/reports/cat05/1511251258_AQ0636_Defra_PAH_2013_annual_report_final.pdf (accessed 28-July-2017).

OSPAR, 2017. The Convention for the Protection of the Marine Environment of the North-East Atlantic.

UNECE, 1979. 1979 Convention on long-range transboundary air pollution.

WHO, 2010. Some non-heterocyclic polycyclic aromatic hydrocarbons and some related exposures. WHO International Agency for Research on Cancer, Lyon. URL http://monographs.iarc.fr/ENG/Monographs/vol92/mono92.pdf

Appendix 1 PAH Abbreviations

Table A1: Abbreviation of PAHs used in Figure 18.
PAH name Abbreviation
5-Methyl Chrysene 5MeCh_p
Anthanthrene Anthne_p
Benzo[a]Anthracene Beanth_p
Benzo[a]Pyrene Beapyr_p
Benzo[b]fluoranthene Benbfl_p
Benzo[j]fluoranthene Benjfl_p
Benzo[b]naptho[2,1-d]thiophene Bebnap_p
Benzo[c]phenanthrene Becpan_p
Benzo[e]pyrene Beepyr_p
Benzo[ghi]Perylene Beghip_p
Benzo[k]fluoranthene Bekflu_p
Cholanthrene Cholth_p
Chrysene Chryne_p
Coronene Corone_p
Cyclopenta[cd]pyrene Cycdpy_p
Dibenzo[a,c]anthracene Diacan_p
Dibenzo [ae] pyrene Diaepy_p
Dibenzo[ah]Anthracene Diahan_p
Dibenzo [ah] pyrene Diahpy_p
Dibenzo [ai] pyrene Diaipy_p
Dibenzo [al] pyrene Dialpy_p
Indeno[123-cd]Pyrene In123p_p
Perylene Peryne_p

Appendix 2 PAH Deposition

Table A2: PAH deposition for year 2016.
Station name Start date/time End date/time Measurement (ng/m2/day)
Auchencorth Moss 27/01/2016 11:35 24/02/2016 11:02 <2.2
Auchencorth Moss 24/02/2016 11:02 23/03/2016 10:34 <2.2
Auchencorth Moss 23/03/2016 10:34 20/04/2016 10:25 <1.9
Auchencorth Moss 20/04/2016 10:25 18/05/2016 11:31 <1.9
Auchencorth Moss 18/05/2016 11:31 15/06/2016 09:55 <2.45
Auchencorth Moss 15/06/2016 09:55 13/07/2016 10:00 <2.45
Auchencorth Moss 13/07/2016 10:00 27/07/2016 12:30 <190
Auchencorth Moss 27/07/2016 12:30 10/08/2016 09:45 <190
Auchencorth Moss 10/08/2016 09:45 24/08/2016 11:20 <190
Auchencorth Moss 24/08/2016 11:20 28/09/2016 09:45 <75
Auchencorth Moss 28/09/2016 09:45 12/10/2016 09:45 <190
Auchencorth Moss 12/10/2016 09:45 26/10/2016 10:20 <190
Auchencorth Moss 26/10/2016 10:20 09/11/2016 11:28 <190
Auchencorth Moss 09/11/2016 11:28 23/11/2016 10:04 <190
Auchencorth Moss 23/11/2016 10:04 07/12/2016 10:25 <190
Auchencorth Moss 07/12/2016 10:25 21/12/2016 10:35 <190
Auchencorth Moss 21/12/2016 10:35 04/01/2017 10:35 <190
Chilbolton Observatory 27/01/2016 14:00 03/02/2016 11:00 <9
Chilbolton Observatory 03/02/2016 11:00 02/03/2016 14:30 <2.15
Chilbolton Observatory 02/03/2016 14:30 30/03/2016 12:30 5.7
Chilbolton Observatory 30/03/2016 12:30 27/04/2016 14:05 <1.9
Chilbolton Observatory 27/04/2016 14:05 25/05/2016 14:00 <1.9
Chilbolton Observatory 25/05/2016 14:00 22/06/2016 11:50 <2.45
Chilbolton Observatory 22/06/2016 11:50 20/07/2016 14:00 <2.45
Chilbolton Observatory 20/07/2016 14:00 03/08/2016 10:15 <190
Chilbolton Observatory 03/08/2016 10:15 17/08/2016 11:00 <190
Chilbolton Observatory 17/08/2016 11:00 31/08/2016 10:30 <190
Chilbolton Observatory 31/08/2016 10:30 28/09/2016 10:00 <95
Chilbolton Observatory 28/09/2016 10:00 12/10/2016 12:01 <190
Chilbolton Observatory 12/10/2016 12:01 26/10/2016 10:00 <190
Chilbolton Observatory 26/10/2016 10:00 09/11/2016 11:30 <190
Chilbolton Observatory 09/11/2016 11:30 23/11/2016 11:15 <190
Chilbolton Observatory 23/11/2016 11:15 07/12/2016 10:50 <190
Chilbolton Observatory 07/12/2016 10:50 21/12/2016 12:15 <190
Chilbolton Observatory 21/12/2016 12:15 04/01/2017 11:15 <190

Appendix 3 PAH Analysis

Table A3: PAH analysed in Deposition and particulate samples and their typical detection limits. * During the second part of 2016 these PAH were analysed and reported separately. + Based on typical monthly sample of 30 days for particulate samples and fortnight for deposition.
Deposition samples Particulate samples
PAH Analysed Typical LOD+ ng/m2/day Analysed Typical LOD+ ng/m3
5-Methyl Chrysene Yes 285 Yes 0.0046
9-Methyl anthracene Yes 190 Yes 0.0046
Acenaphthene Yes 190 Yes 0.0046
Benzo(a)Pyrene Yes 190 Yes 0.0046
Benzo(b)fluoranthene Yes 190 Yes 0.0046
Benzo(b)naphtho(2,1-d)thiophene Yes 190 Yes 0.0046
Benzo(c)phenanthrene Yes 190 Yes 0.0046
Benzo(e)pyrene Yes 190 Yes 0.0046
Benzo(ghi)Perylene Yes 190 Yes 0.0046
Benzo(j)fluoranthene Yes 190 Yes 0.0046
Benzo(k)fluoranthene Yes 190 Yes 0.0046
Cholanthrene Yes 190 Yes 0.0046
Chrysene Yes 190 Yes 0.0046
Coronene Yes 190 Yes 0.0046
Cyclopenta(c,d)pyrene Yes 190 Yes 0.0046
Dibenzo(ae)pyrene Yes 190 Yes 0.0046
Dibenzo(ah)pyrene Yes 190 Yes 0.0046
Dibenzo(ai)pyrene Yes 190 Yes 0.0046
Dibenzo(al)pyrene Yes 190 Yes 0.0046
Dibenzo(ac)anthracene* Yes 190 Yes 0.0046
Dibenzo(ah)Anthracene* Yes 190 Yes 0.0046
Indeno(1,2,3-cd)pyrene Yes 190 Yes 0.0046
Perylene Yes 190 Yes 0.0046
2-Methyl naphthalene Yes 190 No -
2-Methyl phenanthrene Yes 190 No -
4.5-Methylene phenanthrene Yes 190 No -
Acenaphthylene Yes 190 No -
Anthanthrene Yes 190 No -
Anthracene Yes 190 No -
Benzo(a)Anthracene Yes 190 No -
Benzo(b+j)fluoranthene* Yes 190 Yes 0.0046
Biphenyl Yes 190 No -
Dibenzo(ah+ac)anthracene* Yes 190 Yes 0.0046
Fluoranthene Yes 190 No -
Fluorene Yes 190 No -
Naphthalene Yes 190 No -
Phenanthrene Yes 285 No -
Pyrene Yes 190 No -
Retene Yes 285 No -

Concept Life Sciences (previously known as Scientific Analysis Laboratories) are the chosen analytical laboratory for the UK PAH network since Ricardo Energy & Environment took on the network from the previous contractors. Concept Life Sciences are a UKAS accredited laboratory for the analysis of PAH in the samples from the PAH network. The procedure used to measure PAH in ambient air sampled on filters and deposition samples is Gas chromatography mass spectrometry (GC/MS). The performance of this method is validated in accordance with internationally recognised procedures and meet the requirement for PAH analysis detailed in the standards for the measurement of PAH in ambient air and deposition (EN15549:2008 and EN15980:2011 respectively). PAH and typical detection limits for the analysis in the PAH network are presented in Table A3 above.

Ambient air, sampled on to glass fibre filters, are bulked into monthly batches with a specific portion extracted in dichloromethane with the use of ultra-sonication. The dichloromethane is then reduced to circa 1 ml prior to analysis by GC/MS in selected ion monitoring mode (SIM).

Deposition samples are initially filtered to separate any particulate content from the aqueous phase. The filters are then extracted in dichloromethane with the use of ultra- sonication, while the aqueous phase is liquid/liquid extracted with dichloromethane. The organic fractions are then combined, reduced to circa 1 ml and analysed by GC/MS in Selected ion monitoring mode (SIM).

In addition to the Performance Expectations of a UKAS accredited analytical laboratory the following analytical quality control measures are undertaken to maintain analytical quality:

  • Multi-point calibration with authentic standards. The calibration fit should be linear, with a typical correlation coefficient of R2 > 0.995
  • Analysis of QC samples within each analytical batch
  • An independent calibration check standard is analysed at the start and end of each batch to confirm the calibration has been prepared correctly and there has been minimal or no drift throughout the run
  • Resolution and peak asymmetry checks are performed
  • Analysis of reagent/method blanks within each analytical batch.
  • Ongoing quality assured by the use of control charts in conjunction with warning and action limits for the QC sample data
  • Participation in external proficiency testing and inter-laboratory schemes such as LGC CONTEST and AQUACHECK for system performance


For further information, please contact:

Name Christopher Conolly
Address Ricardo Energy & Environment, Gemini Building, Harwell, Didcot, OX11 0QR, United Kingdom
Telephone 01235 753375
Email christopher.conolly@ricardo.com