An 80% metabolic conversion of the Tamiflu® pro-drug (oseltamivir phosphate, OP) to its metabolite oseltamivir carboxylate (OC) and a high excretion rate combined with poor removal at sewage treatment works (STWs) means that potentially high STW OC emissions may occur in receiving waters. A risk assessment approach undertaken within the River Lee catchment in North East London indicates that predicted environmental concentrations for surface waters (PECsw) are likely to be in the general range of 40–80 μg L−1 during a pandemic sitaution within urban catchments having low dilution capacities. This implies low risk exposure levels which confirms previous studies, but there are considerable uncertainties associated with the methodology as well as risks that might result from persistent, long term chronic exposure to low-level water and sediment concentrations which might be mobilised under subsequent extreme flow conditions.

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