Particulate matter (PM10) is collected on a 24-hour basis with High Volume Sampler (approximately 700 m3 per day). Results are recorded as monthly averages. Among the measured PAHs are:

• Benzo (a) anthracene
• Benzo (k) fluoranthene
• Benzo (a) pyrene
• Indeno_123cd_pyrene
• Dibenzo (ah) anthracene

The filters are kept frozen until analysis. A quarter of a filter is extracted by Accelerated Solvent Extraction (ASE) with a mixture of dichloromethane/ hexane (50:50, v/v).
Before extraction, the filters are spiked with deuterium-labelled PAH. 
Clean up of the extracts is performed on-line in the extraction cell by adding activated silica.

Analysis of the extracts is carried out by gas chromatography-mass spectrometry (GC-MS). Concentrations of individual PAH in samples are corrected for recovery of a deuterium-labelled PAH standard with the closest molecular weight. A total of 18 PAHs are analyzed in the method.