A pharmaceutical is a molecule with medicinal properties that is manufactured to treat, diagnose, cure, or prevent disease. Pharmaceutical prescribing is now the most common medical intervention in modern healthcare, with more than 3000 substances currently licensed for human use in the UK and EU. This is in response to growing and aging populations, new technological advances, pharmaceutical availability and also the “pill for every ill” culture, which has become a common theme in today’s modern society.
According to the Scottish NHS, pharmaceutical prescribing rates in Scotland have increased by approx. 40% over the past 15 years, with more than 104 million pharmaceutical items dispensed in 2018-2019. Total medicines costs across hospital and community prescribing are approximately £1.8 billion each year. Over-the-counter sales are also a significant route by which patients may privately attain pharmaceutical drugs, and UK sales reached £2.56 billion in 2017.
As a result of this extensive use, these compounds enter waste streams in large quantities, either following ingestion and excretion, or direct disposal.
After administration, pharmaceutical compounds are metabolised and excreted in urine and faeces. Sometimes the compounds undergo minimal metabolism in the body, and are excreted in an unchanged form. Additional activity, such as washing off topically applied medical creams, and improper disposal by flushing down the sink or toilet, adds to this.
Wastewater from homes, businesses, manufacturers, and hospitals is treated at municipal wastewater treatment plants (WWTPs). However, WWTPs were not designed to remove small organic pollutants (such as pharmaceuticals), and are unable to completely eliminate pharmaceuticals from wastewater. Pharmaceutical removal and behaviour during treatment is not fully understood, and potential degradation during treatment is not well characterised (link). Pharmaceuticals (and their transformation products) therefore have a direct pathway into the environment when final effluent is discharged from the WWTP, where the environmental effects are poorly understood.
Some activity, such as agriculture and aquaculture, may result in untreated waste entering the environment directly. This may introduce pharmaceuticals through diffuse routes, following land-application of biosolids, livestock dosing, or poor waste management.
Pharmaceuticals are biologically active compounds, and can elicit specific responses in organisms even at low concentrations (i.e., the low levels which may occur in the environment). Ecotoxicological effects have been reported in laboratory-based studies and the environment, including:
- Feminisation of male fish (link)
- Reproductive changes in wild bivalves (link)
- Physiological changes in amphibians (link)
- Behavioural changes in fish predator avoidance and migration (link)
- Assistance in the spread of antimicrobial resistance (AMR) in bacteria (link and link)
- Potential contamination of raw water sources (link and link and link)
Pharmaceuticals have been widely detected in water around the world, including surface water and ground water. A recent study by the University of York carried out the most extensive global surveillance of pharmaceutical pollution in the world’s rivers – detecting pharmaceuticals in surface water from 104 countries. A literature review of studies from 1987-2013, identified more than 630 compounds in 71 countries around the world (link). Data on the environmental presence of pharmaceuticals varies by location, with monitoring limited or non-existent in low-income, developing countries.
Data on pharmaceutical pollution varies by geographical region (rural or urban). In the UK, knowledge gaps exist on pharmaceutical presence in the Scottish Highlands and Islands (link). Rural regions, such as the Highlands of Scotland, may face challenges related to wastewater management and environmental pollution, as wastewater is generally treated at small, less advanced WWTPs. These WWTPs may struggle to adequately eliminate pharmaceutical compounds as populations grow, wastewater volumes increase, and pharmaceutical usage continues to rise.
The combined effects of these factors in the face of climate change and unusual weather patterns also adds further uncertainty to the potential risk of pharmaceutical pollution on water quality and environmental health.