Particulate matter (PM) collected during the summer period of 2011 at the urban background of Elms Road Observatory Site (EROS) in Birmingham, United Kingdom was studied and apportioned using the mass closure model. Particulate matter samples were analysed for Cu, Zn, Fe, Ni, Mn, Cl–, NO3–, SO42–, PO43–, C2O42–, Na+, NH4+, K+, Ca2+, OC and EC using the standard procedures. Results showed mean mass concentrations of 5.42 ± 1.7 µg m–3 for PM2.5 and 5.41 ± 0.27 µg m–3 for PM10–2.5. Organic carbon (OC, 26%) formed the major component of PM2.5 followed by sulphate (25%) and ammonium (12%). In the coarse PM fraction, ammonium, chloride and OC constituted 17, 15 and 14%, respectively of mass concentration. Metal concentrations in both PM fractions were less than 2% of the observed mass. The mass closure model applied to apportion PM2.5 and PM10–2.5 chemical species was able to identify four components namely: carbonaceous (45 and 19%, respectively), sea salt (7 and 25%), secondary aerosol (48 and 13%) and minerals (13 and 12%). The mass closure model was unable to explain all the chemical components in the coarse PM category leaving the unidentified mass as 31%. On the other hand, the model overestimated the mass of PM2.5 by 14%. The study showed secondary aerosol and carbonaceous species as the dominating sources of PM pollution in the study area.