| Does Urban Sewage Have a Drug Problem? |
| Wednesday, 26 April 2006 | |
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Oliver Jones tackles the problem of contaminated sewage It’s the morning after a night of indulgent festivities, and Jack’s head hurts. Groggily, he stumbles to the medicine cabinet in the bathroom and reaches for the packet of paracetamol he keeps for just such emergencies. After taking two tablets he crawls back to bed. Later he’ll excrete a large proportion of that dose and send it heading for the nearest sewage treatment works. All over the country the previous night’s revellers are following the same ritual. Other people are taking medicines for a variety of reasons including arthritis, epilepsy, high blood pressure, infection—the list seems endless.  Credit: Oliver Jones Most drugs that have been detected so far have been present at nanogram per litre concentrations and occasionally at microgram per litre levels.This is roughly equivalent to a sugar cube dissolved in an Olympic-sized swimming pool.To detect such low concentrations scientists use a combination of gas chromatography and mass spectrometry. Chromatography is used to separate out the target compounds from the variety of other substances often present in environmental samples, whereas mass spectrometry is better for identifying and quantifying relative amounts of pollutants. The signals produced by the instruments can then be compared to those in accepted spectral libraries, allowing unknown substances to be identified. The big question is whether or not low-scale doping of the environment matters, either to humans or to wildlife. Two of the most pressing concerns are the spread of antibiotic resistance in bacterial populations and the feminization of male fish after exposure to endocrine disrupters. Other effects of drugs in the environment have also been observed. For instance, the painkiller ibuprofen prevents the growth of some bacteria, and the antibiotic streptomycin interferes with the growth of some plants, whilst paracetamol has been shown to be quite effective in controlling pest populations of brown tree snakes. While the risks associated with exposure to drugs are probably greatest with regard to the natural environment, the public’s concern is understandably often more focused on human exposure.This is especially important in areas that practise indirect water reuse—where sewage effluent is released to streams and rivers, which are in turn used as a source of raw drinking water for communities living downstream. Drinking water provides a direct route to the human body for any drug compound that may be present. Other pathways such as ingestion (eating crops irrigated with contaminated effluent or grown on soil contaminated with sewage sludge) or bodily interaction (bathing or showering in waters containing effluent) can also put the body in contact with pharmaceuticals. While modern treatment technologies can remove the majority of drugs from water, they are by no means routinely employed. In developing countries water rarely receives any kind of treatment. In addition, some drugs are resistant even to advanced forms of water treatment. For instance, a 2003 study found detectable concentrations of both the antiepileptic drug carbamazepine and the blood lipid regulator gemfibrozil in four out of ten Canadian cities tested. All used modern treatment technologies to treat their drinking water. Although this report was not published in peer-reviewed literature, but rather commissioned by two Canadian news broadcasters (CTV News and The Globe and Mail newspaper), the results make interesting reading. While only three of the 440 analyte-sample combinations gave detectable levels for carbamazepine, and only one gave detectable levels for gemfibrozil, the results show there is a clear possibility for drug compounds to pass through even modern advanced water treatment facilities. This may sound discouraging, but keep in mind that the concentrations in question are very small. In part, the latest findings simply reflect the increasing ability of researchers to spot pollutants in water, so there is no need to stop taking your medication just yet. But next time you reach for a pill, for whatever reason, think about where it could end up—you might be surprised. Oliver Jones is a postdoc in the Department of Biochemistry |
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