The aim of this study was to identify and quantify sources contributing to particulate matter (PM10) at four urban background sites and an industrial site in North West Europe using a harmonized approach for aerosol sampling, laboratory analyses and statistical data processing. Filter samples collected every 6th day from April 2013 to May 2014 were analysed for metals, monosaccharide anhydrides, elemental and organic carbon, water-soluble ions and oxidative potential. The receptor-oriented model EPA-PMF 5.0.14 was used to carry out a source apportionment using the pooled data of all sites. A solution with 13 factor profiles was found which could be aggregated into eight groups: secondary aerosol; furnace slacks, road wear and construction; sea spray; mineral dust; biomass burning; industrial activities; traffic emissions and brake wear; and residual oil combustion. The largest part of PM10 (40–48%) was explained by nitrate-rich and sulphate-rich secondary aerosol, followed by (aged) sea spray (11–21%). Clear traffic and biomass burning profiles were also found. Conditional probability function plots were used to indicate the likely directions of the sources, while air mass back-trajectories were analysed using the HYSPLIT model. A better understanding of the composition and sources of particulate matter can facilitate the development of health-relevant air quality policies.