There’s something in the water and Professor Michael Depledge, one of the UK’s leading scientists, has an earthy explanation for how it got there.

The ‘something’ is the broad range of medicines we ‘pass’ via the loo into the environment and, indirectly, into our drinking water — from heart drugs to depression and hormone pills.

‘We are being exposed to a growing number of chemicals, and mixtures of chemicals during our increasingly lengthy lives,’ the former chief scientist at the Environment Agency told Good Health.

‘Low concentrations of highly active pharmaceuticals and pharmaceutical residues are being excreted into sewage works, where one would hope they would be broken down into harmless substances. 

But in fact they are not,’ says Professor Depledge, now chair of environment and human health at Exeter University medical school. 

Some drugs found in water supplies are more worrying ‘because of their potential to affect wildlife or people’, said a report published this year by the Royal Pharmaceutical Society. 

It identified antibiotics, antidepressants, anti-inflammatories and painkillers, beta-blockers, oral contraceptives and hormone replacement therapies as the worst culprits.

Traces of many of these drugs find their way into the sewage system through our urine, but it’s not the only way medicines get into water supplies.

Some have been found downstream from pharmaceutical plants, while drugs such as antibiotics given to farm animals can find their way into lakes and rivers.

Unknown amounts of unused drugs are also disposed of down our loos every day, even though the NHS says they should be returned to pharmacies for safe disposal.

But are the drugs in our water doing us any harm? The worrying answer, says Professor Depledge, is that no one really knows. ‘Most of this debate has been conducted in a sea of ignorance,’ he told Good Health.

However, there are growing fears that while, say, your morning cuppa might not prove fatal, the build-up of chemicals in our bodies could be responsible for many of the health problems that plague us as we grow older.