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Levels of pollutant benzopyrene exceeding EU limits

Several air monitoring stations around the UK record levels of carcinogen benzo[a]pyrene in excess of European Commission and UK air quality targets during 2011, writes Michael Holder

Levels of the harmful carcinogenic pollutant benzopyrene exceeded both European Commission and UK air quality limits in several areas around the UK in 2011, according to a Defra report released this week (2 January).

Three monitoring stations in the UK reported annual mean concentrations of the benzo[a]pyrene compound, known as BaP, in excess of the Commission’s target value, a decrease from the seven stations reporting an excess during 2010.

Graph taken from the Defra report showing UK benzo[a]pyrene emission levels since 1990

Graph taken from the Defra / NPL report showing UK benzo[a]pyrene emission levels since 1990

Also, 13 monitoring stations recorded levels exceeding the UK air quality objective, although this has also fallen from the 20 stations recording excess levels during the previous year.

BaP is one of a number of polycyclic aromatic hydrocarbon (PAH) emissions, which can be made up of various compounds that can cause cancer, mutations and can effect human development from birth. PAHs are produced via incomplete combustion of carbon containing fuels from industrial, commercial, vehicle and residential sources.

Human carcinogen BaP is the PAH most harmful to human health and is therefore commonly used as an indicator for possible general PAH contamination.

It is specified for monitoring by European Commission Directive on ambient air quality (2004/107/EC), and therefore much of the data collected on PAH refers to this compound in particular. This Directive also sets European target values for concentrations of BaP.

According to the Health Protection Agency (HPA), long-term inhalation of PAHs can cause a decrease in lung function, chest pain and irritation. BaP specifically, meanwhile “…is thought to probably cause lung and skin cancer in humans.”

Target values

The European Commission’s target value for concentrations of BaP is 1.0 nanograms per cubic metre (ng.m-3), while the UK’s air quality objective level is 0.25ng.m-3.

The ‘Annual Report for 2011 on the UK PAH Monitoring and Analysis Network’ was put together by the National Physical Laboratory (NPL) – the UK’s national measurement institute – and published on the Defra website.

Data used in the report was collated from 31 PAH monitoring stations across the UK, including four in Scotland, four in Wales and three in Northern Ireland.

Annual mean B[a]P concentrations exceeded the Commission target value at stations at Scunthorpe Low Santon, Scunthorpe Town (both in England) and Ballymena Ballykeel (Northern Ireland) during 2011.

Scunthorpe Low Santon and Scunthorpe Town station – both  situated inside an Air Quality Management Area set up  by North Lincolnshire council in November 2005 – PAH levels were “unusually high”, according to the report, measuring 3.03 and 1.22 ng.m-3 respectively.

However, it notes that as these two stations are situated very close to a nearby steel works, “any variation in the prevailing wind direction may therefore cause large changes in measured PAH concentrations.”

The above three monitoring stations as well as the following also showed levels of the carcinogen exceeding the UK air quality objective during 2011: Derry Brandwell (NI), Lisburn Dunmurry High School (NI), Royston (England), South Hiendley (England), Port Talbot Margam (Wales), Middlesborough (England), Lynemouth (England), Kinlochleven (Scotland), Swansea Cwm Level Car Park (Wales) and Leeds Millshaw (England).

The report states: “The annual mean BaP concentrations in 2011 show a slight decrease from those measured in 2010, which is likely to be a result  of  decreased residential and commercial heating activity due to the higher annual average temperature in 2011.”

Sources of PAH

In the early 1990s, high levels of PAHs were produced by metal production and agricultural and waste burning.

According to the report, however, the implementation of the Environmental Protection Act 1990 and the closure of a number of metal processing plants have made a significant contribution to the decrease of UK BaP emmissions since 1990.

Also, emissions from agriculture and waste burning were effectively eliminated after 1992 due to the introduction of a ban on burning agricultural stubble (short stalks left in fields). The report shows that estimated emissions of BaP were 20 times lower than they were in 1990, and that residential and commercial emissions now produce the majority of BaP emissions.

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