Consumer Concerns

Pharmaceutical residues in drinking water

The possibility that residues from medications taken by the general public might be present in drinking water has been the subject of research since the nineteen sixties. More recently, studies across America have shown tiny concentrations of some pharmaceuticals in drinking water supplies.

The Drinking Water Inspectorate has recently funded a desk study to review all relevant robust studies that investigate pharmaceutical concentrations in raw or treated waters and assess their relevance to England and Wales. The study found that removal by drinking water treatment systems was significant for almost all of the pharmaceuticals studied when the treatment process included ozonation and activated carbon This combination, together with the more conventional processes, can result in removal rates of >90% for a wide variety of pharmaceuticals. The study went onto estimate concentrations of pharmaceuticals in treated water at five water treatment works using a number of worst case assumptions. Even in the scenario with the highest estimated concentrations, the report concluded there is no significant risk to health from intake of pharmaceuticals via drinking water.

These findings are consistent with the findings of the European Union’s “Poseidon” research contract, which studied the susceptibility of ED and pharmaceutical residues to water treatment processes. Poseidon identified that residues from a wide range of common pharmaceuticals are found in sewage effluents. Residues have also been detected in rivers downstream of sewage effluent discharges, but almost always at concentrations of less than 1µg/l. The results of studies on the susceptibility of pharmaceutical residues to oxidation and adsorption processes have been reassuring. Ozone treatment is shown to be effective against pharmaceuticals, and many that were insensitive to ozone were removed by activated carbon treatment.

Ozone and carbon treatment are now installed at many water works in England and Wales to remove pesticides. It is apparent that this treatment is effective also against a wide range of other trace organic substances that may be present in source waters.

The DWI funded desk study went on to make a number of recommendations. One of which was that it would be prudent to carry out a small scale survey of pharmaceuticals in drinking water. DWI have planned some further research work to address this recommendation .