Genotyping of CYP1A1, GSTP1, GSTM1, GSTT1, and OGG1 was performed, and CYP1A1 enzyme activity and urinary oxidative damage biomarkers were assessed.<h4>Results</h4>The most robust differences were observed in gastric tissue, where 13 individual POPs and selected chemical classes remained significantly different between cancer and control groups after FDR correction. This evidence concerns the gene GSTP1 and cancer.