5-Fluorouracil and Its Prodrug Capecitabine: Occurrence, Fate and Effects in the Environment

In this chapter, we examine the available literature on the cycling and effects of 5-flourouracil (5-FU) and capecitabine (CAP) residues in the aqueous environment. The aim is to understand better their environmental occurrence, fate and potential toxic effects. Physicochemical properties of 5-FU and CAP suggest that they are more likely to remain in aqueous environment than adsorbed to solid particles. Detectable levels have been reported in hospital effluents (< 122 μg/L) and in municipal wastewaters (< 280 ng/L), but rarely in surface waters (only 5-FU in one study: < 160 ng/L). Among different water treatments available, the most promising for removing 5-FU and CAP are the advanced oxidation processes (AOPs). So far, indirect photolysis has been most widely applied and is capable of almost completely removing both compounds (to < LOD) and in some cases resulting in complete mineralization. However, these treatments have been mostly tested in MilliQ or potable water and their suitability for complex matrices like wastewaters is questionable and biodegradation is still treatment of choice for these matrices. In other studies, a variety of transformation products has been identified adding to the overall environmental burden. Toxicity tests on single parent compounds have shown that they may have effects above the concentrations of environmental relevance. The studies of complex mixtures of parent compounds highlight that the actual ecological risk posed by mixtures of these compounds is difficult to evaluate. Overall, the main finding from this review is that a real need exists for further studies on the chemical and toxicological effects of environmental mixtures of cytotoxic compounds

Single and simultaneous adsorption of three sulfonamides in agricultural soils: Effects of pH and organic matter content

Veterinary antibiotics reaching the environment have become a matter of global concern, since they can cause serious negative impacts on human and ecological health. Therefore, a deep understanding of their behavior and fate once they reach the soil environment is of utmost importance to design and implement appropriate measures that could reduce their potential risks. With this aim, batch-type experiments were carried out to study competitive adsorption and desorption for three sulfonamide antibiotics (sulfadiazine –SDZ-, sulfamethazine –SMT-, and sulfachloropyridazine –SCP-) in six crop soils presenting different characteristics. The results obtained showed that sulfonamides have a low retention in soils, with average adsorption percentages of 40% for SDZ, 44% for SMT and 54% for SCP, and with desorption percentages up to 36% for SDZ and SCP and up to 29% for SMT. The retention of sulfonamides was strongly influenced by the soil organic carbon content (SOC), with higher adsorption and less desorption associated to higher SOC contents. In addition, the hydrophobicity of sulfonamides also had an influence, as higher hydrophobicity resulted in higher affinity for soils, showing the affinity sequences: SDZ ~ SMT bSCP in acid soils, and SDZ ~ SCP bSMT in neutral soils. The results obtained in the ternary systems were very similar to those found in simple systems, indicating the absence of substantial competition for adsorption sites among the three sulfonamides. Despite the low competition among them, these antibiotics have high mobility in soils and, therefore, they imply a significant risk of contamination ofwater bodies, as well as of entering the food chain, generating serious hazards for human and environmental health. Therefore, fertilization of soilswith sulfonamide polluted manures should be controlled, implementing newmeasurements for the pretreatment of manures before their application, thus contributing to a reduction of potential risks.Ministerio de Economía y Competitividad Fondos FEDERS