AbstractThe largest commercially exploited oil shale deposit in the world is in northeast Estonia. the accumulation of solid residues by oil shale mines and processing plants has resulted in numerous dumps and ash hills, which are polluting the environment. the groundwater and streams are highly polluted by sulphates, phenols and oil products. a dump hill of radioactive wastes poses a serious threat to the Baltic Sea. Local people suffer from diseases more often than in other regions of Estonia.