EN
Natural occurrence of thiouracil in bovine and swine urine in Poland was investigated. Under the national residue control programme, 537 urine samples were tested. In 77 samples (14.3%) thiouracil was detected above decision limit CCα (0.91 µg L⁻¹), including eight samples over the recommended concentration of 10 µg L⁻¹. Of the bovine urine samples, 95 and 99 percentiles have thiouracil concentration below 4.50 and 14.85 µg L⁻¹, and of porcine samples below 2.35 and 6.80 µg L⁻¹, respectively.