Close-up Photo of Medicinal Drugs © Pexels (creative commons)

Medicines are essential to the health of humans and domesticated animals. They help us to survive infection, reduce pain and eradicate disease. However, in the last decade, it’s been found that virtually every river across the globe contains some mix of common drugs like ibuprofen, paracetamol, and diclofenac.

Freshwaters support one of the greatest concentrations of biodiversity of all the ecosystems on the planet. They are also some of the most endangered, losing biodiversity faster than any other ecosystem. Only 14% of English rivers have good ecological status and not a single river is free from chemical contamination. Plastic pollution, untreated sewage, agricultural waste, excessive abstraction and climate change are well documented threats and evidenced in the loss of freshwater life.

Pharmaceuticals and invertebrates

In freshwater invertebrates, changes in development, reproduction and behaviour are the most common effects of pharmaceutical pollution. While not always lethal, these changes can lead to shifts in evolution and population structure in ways that are potentially damaging to the species.

Buglife has found that several medicines regularly occur at concentrations greater than current Predicted No Effect Concentrations in our freshwaters. In the case of some drugs, there is evidence that invertebrates are affected at concentrations below these limits. Effects include stress responses, increases, and decreases in reproduction (depending on the chemical), changes in behaviour that could lead to greater predation, and damage to living cells. Some pharmaceuticals can also build up in aquatic invertebrates and other animals in a food chain. This bioaccumulation can result in long term impacts that persist even after successful removal of the contamination, as well as secondary impacts on predators.

Scientists have also found that when medicines break down in the environment, they can produce chemicals that are many times more harmful than the original chemical alone. Diclofenac becomes 6 times more toxic to algae, an important source of food for grazing invertebrates like snails, mayfly, and caddisfly larvae. Meanwhile, when Naproxen, another anti-inflammatory, breaks down it prevents the reproduction of small crustaceans and algae at 4 to 16 times lower concentrations than the original chemical.

Pharmaceuticals of most concern

From our review of current literature and analysis of the Chemical Investigations Programme (CIP2), the main chemicals of concern to invertebrates appear to be:

  • Ibuprofen – Non-steroidal anti-inflammatory medication.  Pervasive and found in all surface waters exceeding safe limits. Recorded to occur at concentrations that impact invertebrates.
  • Carbamazepine – Anti-epileptic medication. Appears to affect invertebrates below the current safety standards at levels that occur in the environment.
  • Fluoxetine – Anti-depressant medication. Occurs in the environment at concentrations that have been observed to alter invertebrate behaviour and reproduction. It is also known to bioaccumulate.
  • Venlafaxine – Anti-depressant medication. Not included in CIP2 sampling but causes stress responses in the freshwater snail, Leptoxis carinata, at concentrations well below the safety standard.
  • Diclofenac – Non-steroidal anti-inflammatory medication. Poorly eliminated through wastewater treatment works, commonly occurs in surface waters above safe limits. Known to bioaccumulate in invertebrates and can impact some avian species.


A pill bottle containing the prescription drug fluoxetine © The Focal Project (Flickr, CC) A pill bottle containing the prescription drug fluoxetine © The Focal Project

What must happen?

Buglife are calling for change to protect freshwater life:

  • Improved evaluation of environmental risks posed by medical drugs must take place. It should include:
    • Retrospective risk assessments for drugs already in use
    • Assessment of breakdown products in the environment
    • Assessments of the effects of mixing chemicals in the environment i.e., the cocktail effect
  • Wastewater treatment facilities must be improved to prevent chemical pollutants from entering the environment;
  • Pharmaceuticals must be considered as part of a circular economy, preventing surplus waste, and reducing incorrect disposal;
  • Prioritise the 12 key asks in the upcoming Chemicals Strategy.
Golitha Falls, Cornwall River © BareFoot Photographer Golitha Falls, Cornwall River © BareFoot Photographer

Urgent action needs to be taken to properly examine the long-term effects of medicines and other chemicals in the environment. The biggest concern with pharmaceuticals is how long they have gone unchecked; we do not know how much damage they are causing. However, it has been shown that adverse effects do increase with time for some drugs, meaning small amounts can cause the same effects over a long period. Some medicines lack assessments altogether and their effects on invertebrates and the wider environment are unknown.

Medical drugs are monitored, but they have little to no enforced environmental regulation. Improved evaluation of environmental risks posed by medicines is needed and should include retrospective risk assessments for drugs already in use. It is also important to conduct environmental assessments of breakdown products, and the effects of mixing chemicals as these are often far greater than those of the individual substances.

As the most manageable source of pollution, wastewater treatment facilities must be improved to prevent chemical pollutants from entering the environment. We also want to see greater examination of other sources of contamination such as septic tanks, sewer overflows, river, and pond sediments, biosolids, landfill run-off, and agricultural run-off.

Alongside preventing pollutants from entering the environment, we must also reduce the number of medical drugs entering our waterways before treatment where possible. In part, this could be achieved through changes in education on usage and disposal of medical drugs, while also improving regulation on those with the worst impact. The opportunity to use scientifically proven alternatives to medicines such as blue-green social prescribing could also help to protect our environment.

Relief © Kent Landerholm (Flickr, CC) Relief © Kent Landerholm

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