Air pollution is a serious problem in many cities. In the present study, the use of mosses as bioindicators of local air pollution is discussed. The contents of Cu, Fe, Cd and Hg were measured in the mosses Ceratodon purpureus, Syntrichia ruralis, Sciuro-hypnum curtum, Brachythecium rutabulum and Rhytidiadelphus squarrosus, and the Hg content was measured in the soil in both contaminated and less polluted areas of the northern European city of Tallinn. Based on the stationary and street pollution source inventory and air pollution dispersion modelling, the long-term concentrations of fine particles (PM10) and nitrogen oxides (NOx) were estimated. The Fe and Cu levels were significantly greater in areas adjacent to multilane streets than in areas farther away. Higher levels of modelled PM10 and NOx correlated with higher levels of Fe and Cu in mosses and Hg in soil. At higher concentrations of Fe in mosses, the concentrations of Cu and Cd in mosses and Hg in soil were also greater. The correlations between heavy metals provide an opportunity for further studies to identify possible environmental pollution without studying all these metals. Based on this work, the best indicator of air pollution was the content of Cu in mosses, and further studies are recommended to identify environmental pollution. Mosses have proven instrumental in promptly assessing environmental pollution, e.g. identifying suitable sites for new community gardens, a trend observed in urban settings, including Tallinn.