Ground based in situ observations of benz_a_anthracene at Westerland (DE0001R) using high_vol_sampler. These measurements are gathered as a part of the following projects EMEP, CAMPAIGN and they are stored in the EBAS database (http://ebas.nilu.no/). Parameters measured are: benz_a_anthracene in aerosol (mass_concentration_of_benz_a_anthracene_in_dry_aerosol_particles_in _air), benz_a_anthracene in air (mass_concentration_of_benz_a_anthracene_in_air), chrysene_triphenylene in aerosol (mass_concentration_of_chrysene_triphenylene_in_dry_aerosol_particles_in _air)