Observations over the electric field strength and the atmospheric electric current density have been carried out in Apatity town of Murmansk Region. It was found that under conditions of dust storms originating from the apatite and nepheline tailing pit the electrostatic field strength and electric current decrease and may change sign. The dust is of erosion origin being produced under conditions of dry summer weather and sufficiently high winds. The regression comparison of the electric field and current records has made it possible to determine the value of the air conductivity and to investigate the contribution of the electric current component being not caused by the conductivity. The obtained values of the air conductivity are close to those observed in midlatitudes. It is shown that the decrease of atmospheric electric field and current and change of their sign can be explained by the volume electric charge of the dust clouds.