Pharmaceuticals: a threat to drinking water?

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Recently, considerable interest has developed regarding the presence of pharmaceuticals in the environment, but there has been comparatively little study on the potential of these substances to enter potable supplies. This is surprising because drinking water would provide a direct route into the body for any drugs that might be present. Although many countries employ advanced treatments, such as granular activated carbon, membrane technologies, ozonation and ultraviolet radiation, for treating water intended for human consumption, some compounds have been shown to be unaffected by such processes. Here, we examine the levels of drug substances reported in drinking water around the world. The possible implications of the presence of these compounds are highlighted and assessed, and recommendations are made for further research.

Introduction

During the past three decades, research on the impact of chemical pollution has focused almost exclusively on the conventional ‘priority’ pollutants [i.e. persistent organic pollutants (POPs)] and this has been extensively reviewed recently [1]. Today, these compounds are less relevant for many first world countries because emissions have been substantially reduced through the adoption of appropriate legal measures and the elimination of many of the dominant pollution sources. The focus has consequently switched to compounds present in lower concentrations but which nevertheless might have the ability to cause harm [2]. One of the interesting characteristics of many of the chemicals that might cause this type of pollution is that they do not need to be persistent in the environment to cause negative effects [3]. This is because their high transformation and removal rates can be offset by their continuous introduction into the environment, often through sewage treatment works [4]. This is one reason why there is an increasingly widespread consensus that this kind of contamination might require legislative action sooner rather than later 5, 6.

Section snippets

The problem of pharmaceutical pollution

The issue of pharmaceuticals (and their metabolites) in the environment, notably the aquatic compartment, has been a growth area in environmental chemistry for several years [7]. To date, most of the published literature has addressed the occurrence of drugs in sewage effluent and receiving waters. However, although the risks associated with exposure to drugs are probably most significant with regard to the natural environment, the public's concern is understandably more focused on human

What has been found?

There is currently no regulatory requirement for the monitoring of pharmaceuticals in drinking water. On the basis of the limited dataset (Table 1), human pharmaceuticals have only occasionally been detected in drinking water, with concentrations generally being in the ng l−1 range [18]. Veterinary medicines might also have the potential to enter water sources, even in upland areas, through leaching from fields used to graze stock that are treated with drugs, or disposal of manure from stock so

Potential for human health risks

Research has shown that significant amounts of drugs are released from sewage treatment plants to the environment. Therefore, there is a risk that humans might be exposed to drugs through potable water drawn from contaminated supplies. Although this risk is likely to be relatively minor, the increasing demands on the freshwater supplies of the world will probably lead to greater incidences of indirect and direct water-reuse situations as the spatial and temporal distances between wastewater and

What does the future hold?

Although it is unlikely that a serious problem exists now, it would be prudent to apply the precautionary principle and try to reduce the levels of these compounds in drinking water before any harm is proved. Because it is impractical to assess fully the risks of every medicine and application authorized for use, one approach might be to develop a prioritisation scheme to identify those substances that might pose a risk to human health and therefore warrant further study. This is because a

Acknowledgements

O.A.J. is grateful to the UK Engineering and Physical Sciences Research Council (EPSRC) for the award of a PhD scholarship.

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