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.