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Is tap water safe to drink?

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Every time you enjoy a cool, clear glass of tap water, you could be drinking a cocktail of other people’s second-hand medications.That is thanks to the fact that today’s pharmaceuticals have been designed to be stable and long-lasting. While that makes their doses reliably consistent, it also means that a substantial amount of the prescribed drugs that people take goes through their bodies and out into waste water. Ultimately a proportion of these drugs pours unaltered through the sewage filtering system and re-enters our domestic supply.


And the amount of medicines now being excreted into the water is stunning. Nearly half of women and men in England now regularly take prescription drugs — with a significant proportion taking at least three prescriptions each, according to official figures (with antidepressants, statins and painkillers among the most commonly prescribed medications). And we’re effectively taking some of what they’re taking, as recent research has found. For example, in May, a study in the journal, Environmental Science and Technology Letters, which analysed the water from 59 small streams in the U.S. for the presence of 108 pharmaceuticals, found the anti-diabetic drug, metformin, in almost all of them.

One river alone contained 45 different prescribed drugs, including the anti-epileptic medication carbamazepine; the muscle relaxant, methocarbamol, and the opioid painkiller tramadol. And when Israeli scientists tested people who had been eating crops irrigated with treated wastewater, they found their urine carried significant levels of the epilepsy drug carbamazepine. Professor Benny Chefetz, an environmental scientist at the Hebrew University of Jerusalem, who conducted the study published in the journal Environmental Science & Technology in March, says that because the levels are 10,000 times lower than from a 400 milligram pill, they should not instantly affect healthy adults.

But he told reporters, ‘We don’t know what will happen with small children exposed to low levels of pharmaceuticals for a generation.’

Another concern is that these drugs — even in minuscule amounts — might have a long-term effect on adults, too.

‘We don’t know what it means if you have a lifelong uptake of drugs at very low concentrations,’ says one of the world’s leading experts, Dr Klaus Kuemmerer, professor of sustainable chemistry at Germany’s University of Luneberg.

John Sumpter, professor of ecotoxicology at Brunel University London, adds that while the risks of pharmaceuticals for humans are unknown and possibly minuscule: ‘in general you don’t want strongly psychoactive drugs such as antidepressants in the environment. 

'When they get into the water system they retain their powerful biological activity.’

The European Commission is currently finalising new rules on pharmaceuticals in the environment and has already tightened water-purity legislation so that medicines can either be restricted or placed on danger ‘watch lists’. Professor Sumpter believes that pharmaceutical companies are quietly working to change their drugs to meet the challenge. 


‘Once chemicals get put on danger lists, it is almost impossible to get them off. The pharmaceutical companies understand that and should be taking notice.’

 The best way forward, he believes, is for drug companies to reformulate their medicines so that they degrade into harmless substances after people have excreted them. Professor Kuemmerer has already shown that this can be achieved. He worked with a commonly used drug called propranolol — prescribed to treat high blood pressure and to prevent heart problems. The drug slows down the activity of the heart by interrupting messages sent to it by the nervous system. It is chemically very stable, so does not break down easily, and has frequently been found in waste water, where it can poison fish. Professor Kuemmerer has discovered that, by making a small change in the chemical’s structure, the drug will break down far more easily in water yet still retain its full medicinal powers in the human body. 


He argues that a similar approach could be used to re-design other classes of drugs. Meanwhile drug companies are looking at reducing the impact their manufacturing has on the environment.  UK-based global drug giant GlaxoSmithKline (GSK) has announced a range of initiatives including one that invovles setting up two centres — one in Nottingham, the other in Sao Paulo, Brazil —where scientists at are exploring ways of producing drugs using fewer damaging substances such as heavy metals —which are often used as catalysts to speed up chemical reactions.

 Mike Murray, Head of Quality and Environmental Standards at the Association of British Pharmaceutica Industries (ABPI) says that drug companies are actively engaged in designing greener processes for the manufacture of pharmaceutical products.

 ‘The UK pharmaceutical industry continues to engage with the regulators to address the issue of potential environmental risks of pharmaceutical residues in the environment.’

 The amount of medicines now being excreted into the water is stunning. Nearly half of women and men in England now regularly take prescription drugs

Is tap water safe to drink?