Chlorination by-products of anticancer drugs

Abstract

Cytostatic drugs and their metabolites enter the aquatic environment mainly through the excretion of urine and faeces from chemotherapy patients into the public sewer system and can eventually reach tap water if they are not properly eliminated during waste and drinking water treatment processes. Chlorine is globally the most used chemical disinfectant in wastewater treatment plants as well as in the pretreatment of hospital effluents prior to their discharge into the public sewage system, mostly because of its low cost. Since aqueous chlorine is not capable of complete mineralization of many anthropogenic compounds, numerous disinfection by-products may be formed due to oxidation/substitution reactions. Such reactions can happen during wastewater treatment processes and due to the discharge of chlorinated waters (e.g., tap water) or bleach into the sewage system. Very little is also known about their potential transformation into other chemical species, which might be even more toxic than the parent drugs. In recent years, several studies have demonstrated that anticancer drugs can yield a series of by-products when they come in contact with aqueous chlorine. Understanding the chemical fate of these by-products is an important first step to understand their environmental significance. Therefore, the main aim of this chapter is to comprehensively review the existing literature on the reactivity of anticancer drugs in the presence of free chlorine and the formation of their by-products.