This study evaluates effectiveness of 4 additives CaO, Ca(OH)2 + NaHCO3, H2O2, and FeSO4 + H2O2 in thermal degradation of hazardous polycyclic aromatic hydrocarbons (PAHs) in petroleum sludge cake. Residual concentrations of 16 priority PAHs were determined using GC-MS. Total PAH conc. was found as: gas, 3.11 � 10-4 - 4.36 � 10-4 ppmv; particulate, 7.92 � 10-5 - 5.24 � 10-4 mg/m3; and residue, 1.37 � 10-4 - 1.07 � 100 μg/g. Total toxicity equivalence of PAHs relative to that of benzoapyrene (BaP) was found as: gas, 3.11 � 10-7 - 4.41 � 10-7; particulate, 3.87 � 10-7 - 3.85 � 10-5; and residue, 6.17 � 10-7 - 9.65 � 10-3. Ca(OH)2 + NaHCO3 was most suitable due to least emission of high molecular weight PAHs, lower equivalent carcinogenicity of products, and lower concentrations of PAHs in gas, particulate and residue.