The drug industry is heading for confrontation with green campaigners over a European Parliament proposal to clean up rivers, streams, and drinking water supplies contaminated by synthetic hormones from contraceptive pills.

Ecologists say the chemical poses a serious threat to wildlife. Water and drug companies argue that the high cost of the plan is not justified by the risk. One estimate suggests a hormone clean up would raise water purification costs in the UK by £30bn (€37bn; $46bn) over 10 years.

Ethinylestradiol (EE2), the main active ingredient of contraceptive pills, is excreted and washed into sewage systems and rivers and has been found at sites throughout Europe. Even at very low concentrations, it has been shown …