Many people use drugs including paracetamol on a regular basis to treat headaches. But only part of each drug is taken into the bloodstream, while the rest is released into the wastewater through our urine when we go to the toilet.

Paracetamol is an ingredient in the tablet. Most of the paracetamol is absorbed into the blood. Around 5% of the paracetamol is immediately excreted in urine in its original form.

Over around 24 hours, up to 95% of one dose of paracetamol – including the amount that was previously absorbed into the blood stream – is excreted in urine, after being degraded in the liver.

Mainly as a result of this physical process, paracetamol is increasingly being detected in rivers around the world. In the UK, maximum concentrations around 1 microgram per litre have been measured in the River Thames and in different estuaries. Similar levels were found in rivers and lakes of other European countries, including Serbia and Spain.

In the Nairobi river in Kenya, paracetamol concentrations have reached up to 16 micrograms per litre, which is high enough to cause cellular damage in water organisms such as clams. In Asian surface waters, high paracetamol levels have been reported as well.

And even though 81% of wastewater in the EU is collected and treated in municipal wastewater treatment plants, these facilities are not yet equipped to deal with micropollutants such as paracetamol. The prefix “micro” refers to the concentrations these substances can reach in the environment, and these are typically comparable to the size of a sugar cube in an Olympic swimming........

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