Polycyclic Aromatic Hydrocarbons (PAH)


The measurement of polycyclic aromatic hydrocarbon (PAH) in the Network began in 1991. Currently the network consists of over 30 PAH measurement sites across England, Wales, Scotland and Northern Ireland measuring ambient concentrations of PAH in the UK atmosphere. The network uses a non-automatic technique where PAH are collected on filters which are extracted and then analysed. Details of the site locations can be found on the interactive monitoring networks map.

Network Objectives

The primary objective of the network is to provide PAH concentration information at the sites in the network. The collection of this data enable the assessment of current concentrations of PAH for assessment against the National Air Quality Objective for PAH (annual mean of 0.25 ngm-3 Benzo(a)pyrene (B[a]P) in ambient air) published in the UK Air Quality Strategy and to enable demonstration of the UK's compliance with the Fourth Air Quality Daughter Directive (target value of 1 ngm-3 for the annual mean concentration of B[a]P), the OSPAR convention and the UNECE Convention on Long Range Transboundary Air Pollutants.

What PAH Are Measured in the Network?

The following species are currently measured in the Polycyclic Aromatic Hydrocarbon Network:

PAHs in PM10 5-Methyl Chrysene, Anthanthrene, Benzo(a)Anthracene, Benzo(a)Pyrene, Benzo(b)fluoranthene, Benzo(j)fluoranthene, Benzo(b)naptho(2,1-d)thiophene, Benzo(c)phenanthrene, Benzo(e)pyrene, Benzo(ghi)Perylene, Benzo(k)fluoranthene, Cholanthrene, Chrysene, Coronene, Cyclopenta(cd)pyrene, Dibenzo(a,c)anthracene, Dibenzo (ae) pyrene, Dibenzo(ah)Anthracene, Dibenzo (ah) pyrene, Dibenzo (ai) pyrene, Dibenzo (al) pyrene, Indeno(123-cd)Pyrene, Perylene
PAH in Deposition

1-Methyl naphthalene, 1-Methylanthracene, 1-Methylphenanthrene, 2-Methylanthracene, 2-Methylnaphthalene, 2-Methylphenanthrene, 4H-Cyclopenta[def]phenanthrene, 5-Methyl Chrysene, 9-Methylanthracene, Acenaphthene, Acenaphthylene, Anthanthrene, Anthracene, Benzo(a)Anthracene, Benzo(a)Pyrene, Benzo(b)fluoranthene, Benzo(b)naptho(2,1-d)thiophene, Benzo(c)phenanthrene, Benzo(e)pyrene, Benzo(ghi)Perylene, Benzo(j)fluoranthene, Benzo(k)fluoranthene, Biphenyl, Cholanthrene, Chrysene, Coronene, Cyclopenta(cd)pyrene, Dibenzo (ae) pyrene, Dibenzo (ah) pyrene, Dibenzo (ai) pyrene, Dibenzo (al) pyrene Dibenzo(a,c)anthracene, Dibenzo(ah)Anthracene, Fluoranthene, Fluorene, Indeno(123-cd)Pyrene, Naphthalene, Perylene, Phenanthrene, Pyrene, Retene

Sources of PAH

Polycyclic aromatic hydrocarbons (PAHs) are a group of persistent organic pollutant compounds that contain two or more benzene rings, they are generally produced through incomplete combustion or pyrolysis. The National Atmospheric Emissions Inventory (NAEI) estimates emission of PAH for the UK.

Health Effects of PAH

The International Agency for Research on Cancer (IARC) has determined that B[a]P is carcinogenic to humans and is currently considered by IARC as the most carcinogenic PAH. Details of the assessment of the carcinogenicity of PAHs carried out by IARC can be found online.

How is the network run?

Samplers in the PAH Network

The UK PAH Network began in 1991, measurement techniques used have changed over time. Details are provided below:

Current Measurements

Currently the PAH Network undertakes sampling and analysis of two types of samples these are particulate and deposition samples.

Measurement of Solid Phase PAH

Samples of the PM10 fraction of ambient air on a filter are taken daily at all Network stations using Digitel DHA-80 samplers with automatic filter changers. The solid phase filter samples have a measurement period of 24 hours at a flowrate of approximately 30 m3 per hour. The samples are combined into groups representing calendar months for analysis using gas chromatography–mass spectrometry (GC-MS). The Digitel DHA-80 samplers used throughout the Network are considered to be equivalent to the requirements of the European Standard for sampling PM10 matter (EN 12341:2014) and are considered valid for use with the European Standard method for the measurement of B[a]P in ambient air (EN 15549:2008).

Measurement of PAH in Deposition

The PAH Deposition samples are taken fortnightly at two rural Network stations located at Auchencorth Moss and Chilbolton Observatory (since 2016 and previously at Harwell). Each sample is taken for 14 days using a deposition sampler that meets the requirement of the European Standard for the measurement of the deposition of PAH (EN 15980:2011). The deposition samplers 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 samples collected are extracted and analysed using GC-MS.

Historic Measurements

Between 1991 and 2007 the network used Andersen GPS-1 pesticide samplers with omi-directional heads to sample PAH in ambient air. The network sampler was changed to a Digitel DHA-80 high volume PM10 aerosol sampler (operating with 1 day sampling period) in order to comply with the requirements of the Fourth Air Quality Daughter Directive.

View data for sites in this network

PAH data is available on the Polycyclic Aromatic Hydrocarbon (PAH) Data page.

Annual PAH network reports can be found in the library section of this website.

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