Are cytostatic drugs in surface waters a potential threat?

Cytostatic drugs are pharmaceuticals administered to cancer patients under chemotherapy. Their occurrence in surface waters has been reported worldwide, increasing environmental and human health concerns. This work addresses a question of worldwide interest: are these hazardous pharmaceuticals in surface waters a potential threat? For the first time, this study brings information on the presence of cytostatic drugs in Portuguese rivers. Furthermore, cutting-edge data on the occurrence of two cytostatic drugs is provided; up to the authors' best knowledge, flutamide and mycophenolate mofetil have never been monitored in worldwide surface waters. Nine out of thirteen cytostatic drugs were detected in Portuguese rivers. Despite bicalutamide being the cytostatic most frequently detected, the highest concentration was recorded for cyproterone (19 ± 3 ng/L). Three different scenarios were considered to estimate the risks from the exposure of humans to cytostatic drugs via surface waters. Two scenarios are associated with bathing practices in rivers, particularly in the spring and summer seasons (river beaches): (i) the exposure to cytostatic drugs by dermal contact with contaminated water and (ii) the exposure by accidental ingestion of contaminated water, which is less likely but also occurs. The third exposure scenario is related to (iii) the long-life consumption of drinking water produced from river water capture, under worst-case conditions, i.e. negligible degradation of cytostatic drugs at drinking water treatment plants. It was concluded that the third exposure context to cytostatics could represent a risk to children, if the highest concentration ever reported in the literature for cyclophosphamide in surface waters is considered. Still, attending to the carcinogenicity of some of these compounds (e.g., cyclophosphamide, chlorambucil, etoposide and tamoxifen), health risks might always be expected, regardless of the contamination level. Furthermore, health risks associated with synergic effects and/or long-term exposures cannot be ruled out, even for the remaining cytostatics/exposure contexts.