The distribution of organometallic compounds in shale oils is somewhat variable, but typical analysis indicate the presence of elemental Cd, V, Hg, Sn, Se, and As. Of these, the relatively high concentrations of arsenic have, in particular, presented problems for the processing and refining of oil shale into final oil products. Typically, approximately 30 ppm of arsenic compounds are present in Paraho retorted (indirect mode) shale oils, with similar [As] ranges being found in shale oils obtained via other above-ground or in situ processing methods.