Some solvents and diluents found in epoxy resins have been known to be cancerous. These contaminants have either been removed or are used in tiny, non-harmful amounts from newer epoxy solutions since their discovery of being carcinogenic.  Contaminants that used to be used in epoxy flooring solutions that have been known to be carcinogenic include epichlorohydrin and diamino diphenyl sulfone (DDS). Again, these are no longer used in large quantities with the epoxy systems of today.