How drugs can contaminate drinking water (graphic)

Drugs on tap: Pharmaceuticals in the water supply

*Water purification is a complex process that involves filtration, ozonation, a second filtation through activated charcoal and, finally, a chorination or disinfection stage.

*Several studies have shown that conventional water purification cannot completely remove some prescription drugs from a contaminated water source.

*Water abstraction from rivers is increasing, due to the rise in demand and increasing population density, especially in the south-east of England.

*In 2004, a study of the 50 most common prescription drugs in Britain showed that the amount of each drug consumed annually varied from 12,000kg to 3,500,000kg.

*Cytotoxic (toxic to cells) drugs used in chemotherapy are potentially dangerous in water supplies because they dissolve easily in water, remain potent in low concentrations and may have an additive effect taken together.

*Chemotherapy prescriptions are increasing by 10 per cent a year. Patients having chemotherapy are often given the drugs in hospital but are then allowed home, where they excrete them into the domestic sewerage system.

*Britons consume 2,700kg of 5-fluorouracil – just one of 50 cytotoxic drugs. By comparison, they consume about 45kg of the active ingredient of the contraceptive pill, which is believed to be responsible for freshwater fish changing sex.

*British water companies have to test for 48 potential contaminants in drinking water. None of them is for a pharmaceutical drug that can be excreted from the body.

*Scientists in Germany have found pharmaceutical drugs in Berlin's water supply and have called for further research into what could be a Europe-wide problem.

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