Annual Report for 2011 on the UK PAH Monitoring and Analysis Network.

This annual report for 2011 for the UK PAH Monitoring and Analysis Network was prepared by the National Physical Laboratory (NPL) for the Department of Environment, Food and Rural Affairs; the Department of Environment Northern Ireland; the Welsh Government and the Scottish Government. The report contains: - The measured annual (and where applicable, monthly or quarterly) mean concentrations of benzo[a]pyrene (B[a]P) at each Network station, and at each TOMPs Network station. - Selected results from other PAHs at selected Network stations. - A comparison of the B[a]P annual mean concentrations against the target value and assessment thresholds in the EC Fourth Daughter Directive. - A comparison of the performance of Network operation against the relevant data quality objectives in the Fourth Daughter Directive. - An overview of the PAH Network, including a summary of Network operation, a description of notable station maintenance issues and changes to the Network during 2011, and data capture statistics for 2011. - A review of the sources of PAHs in the UK. - A discussion of PAH concentration trends across the Network, and the relationship between PAH emissions and measured concentrations. - A summary of scientific research, international representation and other activities related to the Network. In summary, during 2011: - The EC target value for B[a]P (an annual mean concentration of 1 ng.m-3) was exceeded at three of the 31 stations where PM10 particulate samples were taken. - The EC upper assessment threshold for B[a]P (an annual mean concentration of 0.6 ng.m-3) was exceeded at a total of seven of these 31 stations. - The EC upper lower threshold for B[a]P (an annual mean concentration of 0.4 ng.m-3) was exceeded at the same seven of these 31 stations. - The annual mean B[a]P concentrations in 2011 show a slight decrease from those measured in 2010, which is likely to be an result of decreased residential and commercial heating activity due to the higher annual average temperature in 2011.