Pharmaceutical residues in 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. The Department of the Environment first commissioned research on the possibility of recycling of pharmaceutical residues via sewage effluent in the early 1970s. Those studies led to the identification of chlorination by-products, rather than pharmaceutical residues, as possible health concerns. That finding prompted a long-term research programme on the health significance and control measures for disinfection by-products.(See seperate note)
More recently concern has been expressed about possible adverse effects of endocrine disrupters which might be recycled via sewage effluent discharges to rivers that are used for drinking water abstraction. Substances such as oestrogens that are constituents of the birth control pill have been implicated as potential endocrine disrupters. The birth control pill is possibly the most widely prescribed drug and therefore the Department has supported an active programme of research to assess the significance of the low concentrations of oestrogens in treated sewage effluent.
This research has included the development of highly sensitive analytical methods for ethynyl oestradiol, which is the main component of the birth control pill. Research has also investigated the effect of conventional water treatment processes on the removal and decomposition of ethynyl oestradiol. The results indicate that this substance can be detected at the nanogramme per litre level (1 in 1 million x 1 million) in river water. However disinfectant systems such as chlorination or ozonisation destroy the substance and physical treatment such as sedimentation or filtration remove it through adsorption mechanisms.
Even if one makes an extreme worst case assumption that, for example, antibiotics are excreted unchanged and recycled via tap water, the theoretical dose would be about one million times less than the pharmacologically active dose. In reality, pharmaceuticals are degraded within the body and are subjected to further biodegradation and removal in sewage treatment and in watercourses. The sophisticated treatment processes such as ozone or activated carbon treatment that have been installed to remove pesticides and other organic substances from source waters, are equally effective at removing minute traces of pharmaceutical residues. For these reasons the Inspectorate is confident that such residues would be non-detectable in tap water.
The Inspectorate has recently received a copy of a German research association report on pharmaceutical residues in drinking water. That report identified the possibility that the heart drug, clofibric acid, was present at barely detectable concentrations in some drinking water sources in Germany. Clofibric acid is an extremely stable compound that is used in high doses. In the UK, the use of clofibric acid has fallen significantly in recent years because of adverse side effects. The Inspectorate is confident that this substance is not detectable in drinking water in the UK.
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Drinking Water Inspectorate,
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Updated 11 July 2001
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