Cytotoxic drugs in drinking water: a prediction and risk assessment exercise for the Thames catchment in the United Kingdom

Cytotoxic, also known as antineoplastic, drugs remain an important weapon in the fight against cancer. This study considers the water quality implications for the Thames catchment (UK) arising from the routine discharge of these drugs after use, down the drain and into the river. The review focused on 13 different cytotoxic drugs from the alkylating agent, antimetabolite and anthracycline antibiotic families. The exercise used a GIS-based water quality model which was informed by literature values on consumption, excretion and fate data to predict raw drinking water concentrations at the River Thames abstraction points at Farmoor, near Oxford, and Walton, in West London. To discover what the highest plausible values might be, upper boundary values for consumption, and excretion, together with lower removals values for sewage treatment were used. The raw drinking water cytotoxic drug maximum concentrations at Walton (the higher of the two) under mean and low flow conditions were predicted to respectively be 11 and 20 ng/L respectively from the 5 combined alkylating agents, 2 and 4 ng/L for three combined antimetabolites and 0.05 and 0.10 ng/L for two combined anthracycline antibiotics. If they were to escape into tapwater, the highest predicted concentrations are still a factor of between 25 to 40 below the current recommended daily doses of concern. Whilst the risks may be negligible for healthy adults there may be more concern associated with special sub-group populations such as pregnant women, their fetuses and breast feeding infants due to their developmental vulnerability