Regular ground level measurements of particulate sulphate in air taken at Bjørnøya (Bear Island) and Ny Ålesund (Svalbard) are studied. Annual cycles in mean values and variances are observed, both having maxima during winter/spring. The two time-series are transformed into approximately second order stationarity, and the high-pass residuals are used to identify positive and negative anomalies. Days with positive anomalies are frequent during winter/spring and early autumn, however, the autumn anomalies rarely represent pollution episodes. The meteorological analysis selects quasi-stationary, extratropical flow systems on the planetary scale, creating extended meridional exchange of air. Two indices are applied to the 500 hPa flow; a meridional index created by wave numbers 1, 2, 3 and 4, and a zonal index. The agreement between the values of the indices and Arctic ground level air pollution, on the annual as well as the episodic time scale, strongly suggests that the occurrence of quasi-stationary, atmospheric flow systems on the planetary scale is the major cause of long range transport of polluted air to the Arctic.