A review of the world data on the concentrations of thorium activity concentrations in soils, the atmosphere, surface waters, and bottom sediments is presented. It is shown that in the areas with normal radiation background the Th-232 concentrations vary from 5 to 95 Bq/kg in the soil , from 1.0 x 10(-5) to 1.0 x 10(-2) Bq/L in the aquatic environment, from 4 to 100 Bq/kg in bottom sediments of surface waters, from 0.6 x 10(-7) to 1.0 x 10(-4) Bq/L in groundwater, and from 0.1 to 1 x 10(-4) Bq/m(3) in the surface air. The thorium concentrations in those environments can range from one to four orders of magnitude higher in areas with an elevated radiation background and thorium, rare earth, or tin mining areas than in areas with normal radiation background. It is also demonstrated that data on violation in the isotopic equilibrium of the thorium content in various media can be used to assess the pathways of thorium release into the environment. It is noted that the spatial patterns of thorium concentrations are rather close in the soil and bottom sediments and differ from the patterns of thorium distribution in surface waters.
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