Article in the Telegraph
"Cancer drugs are of particular concern because they dissolve easily in water.
The "cytotoxic" drugs, which are used in chemotherapy, are potentially dangerous because they are hard to break down through traditional water purification methods and remain potent in low concentrations.
About 50 of these drugs are prescribed to patients in Britain and researchers are concerned they could be very dangerous if one or more of the drugs mixed together in the water supplies. The drugs make their way into the water system when people prescribed the treatments use the toilet.
Although drinking water in the UK is monitored, none of the cytotoxic drugs are included in the list of contaminants."