Presence of cancerostatic platinum compounds in hospital wastewater and possible elimination by adsorption to activated sludge

Platinum originating from the excreted cancerostatic platinum compounds (CPC) cisplatin, carboplatin and oxaliplatin was monitored over a period of 28 days in the wastewater of the oncologic ward of the Vienna University Hospital. Concentration levels ranging from 4.7 to 145 microg L(-1) were measured by inductively coupled plasma mass spectrometry (ICP-MS). An average ratio of weekly drug emission/drug consumption of 0.27+/-0.12 was assessed. Model studies were carried out for fundamental understanding of CPC interaction with the solid phases present at different stages of the water cycle. Wastewater and activated sludge were spiked with CPC at concentration levels as found in the sewer of the oncologic ward. The platinum concentration remaining in the tested solution was measured after 24 h of incubation. Depending on pH, the three substances exhibited considerably different adsorption rates in wastewater. At pH 7, cisplatin was adsorbed by 88%, whereas only 26% of carboplatin and 54% of oxaliplatin were removed from the aqueous phase. Adsorption by activated sludge was higher, less affected by pH variation and comparable for all investigated CPC (96% for cisplatin, 70% for carboplatin and 74% for oxaliplatin at pH 6.8). In a next step, the dependence of CPC adsorption was tested for wastewater and activated sludge of different sampling sites. Strong variations were found only for wastewater, whereas activated sludge showed more consistent elimination rates (average values: cisplatin 92%, carboplatin 72%, and oxaliplatin 78%). These findings indicate that the major part of the excreted CPC is adsorbed by the solid phase in the water cycle and is thus expected to be removed from the wastewater by sewage treatment plants.