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The Transport, Fate and Impact of Pharmaceuticals in the Environment in Scotland

The Transport, Fate and Impact of Pharmaceuticals in the Environment in Scotland

water and land

Pharmaceutical pollution in the environment has recently been receiving a lot of attention. Medicines enter wastewater streams and even after treatment, some end up in surface water. Scotland's One Health Breakthrough Partnership aims to reduce pharmaceutical concentrations in the environment. A SEFARI Gateway Specialist Advisory Group was established to support this partnership and has produced a report summarising the results of a literature review and risk assessments. The literature review identified over 60 pharmaceuticals in water environments and 19 in soil environments. Five substances were studied further: ibuprofen, clarithromycin, erythromycin, diclofenac, and 17α-ethinylestradiol. Antibiotics can increase antimicrobial resistance, while non-antibiotic drugs can have mixed effects. Risk assessments showed concentrations in Scottish waters were generally above the ‘no effect’ levels but risk assessments showed that there were no risks to humans.  The report provided a list of recommendations several of which are currently being addressed by Scottish Government-funded research projects.


Work Completed


Pharmaceuticals (medicines) are a key factor in the improvement of human health and wellbeing. However, there is increasing awareness regarding the prevalence of pharmaceuticals within the natural environment due to the use of medicines. About 30-100% of an orally administered dose of a medicine leaves the body unmetabolized along with potentially bioactive metabolites and enters wastewater streams. Levels of pharmaceuticals in wastewater can also be exacerbated by improper disposal of unused medicines down toilets and sinks.  Although wastewater treatment plants can reduce the load of some pharmaceuticals, some still enter surface water following treatment, where they can be transported downstream to the environment.

A major concern of pharmaceutical pollution is its potential to increase antimicrobial resistance (AMR). Exposure to antibiotics can increase resistance in environmental bacteria. The potential exists to pass resistance to clinically relevant microorganisms that cause disease and then become difficult to treat (‘superbugs’). It is important to understand the role and dissemination of AMR in the environment as clearly stated in the UK government’s 5-year National AMR strategy.

In Scotland, a multi-agency alliance was established to understand the issues of pharmaceutical pollution with a key focus to reduce the concentration of pharmaceuticals in the environment. The One Health Breakthrough Partnership (OHBP) consists of representative members from regulators (Scottish Environment Protection Agency), water services (Scottish Water), the health service (NHS Highland) and the Environmental Research Institute at University of the Highlands and Islands, providing leadership towards a non-toxic environment, recognising that the health of humans, animals and the ecosystem are interconnected.

A SEFARI Gateway Specialist Advisory Group was established to support the OHBP to evaluate the potential level of risk of the most prevalent pharmaceuticals found in the Scottish environment as a result of (human) clinical use. Veterinary pharmaceuticals were not considered in this study. A literature review was conducted to determine the occurrence of pharmaceuticals found in both the terrestrial and aquatic environments in Scotland, and for selected pharmaceuticals, review their potential impact on AMR and conduct an environmental risk assessment.


A report summarising the results of the literature review showed that in Scotland, there have been over 60 different pharmaceuticals measured in the aquatic environment (including rivers, streams, inland waters, estuaries and coasts, and wastewater) and 19 measured in the terrestrial environment (sewage sludge and soil). In Scotland and there is currently no information on pharmaceuticals in groundwater. The pharmaceuticals were narrowed down to five for the rest of the study, based on detection frequency (i.e., the number of times the pharmaceutical was detected in the environment), ecotoxicology and how commonly used the pharmaceutical was. These were: ibuprofen (anti-inflammatory), clarithromycin (antibiotic), erythromycin (antibiotic), diclofenac (anti-inflammatory) and 17α-ethinylestradiol (EE2; hormone).

A review on the impact of the five short-listed pharmaceuticals on AMR was conducted. The antibiotics clarithromycin and erythromycin have the potential to increase AMR in the environment. However, various non-antibiotic pharmaceuticals can have different effects on AMR. Some non-antibiotic pharmaceuticals can increase AMR in the environment by, for example, increasing the spread of AMR genes between bacteria. Conversely, some non-antibiotic pharmaceuticals work synergistically with antibiotics, making bacteria more susceptible to the effects of antibiotics.

An environmental risk assessment was completed for the five short-listed pharmaceuticals. Modelling was used to estimate pharmaceutical concentrations in different environmental compartments based on physico-chemical properties and estimates of emissions to the environment, which generally agreed with measured values. Measured concentrations for the five pharmaceuticals in Scottish surface waters (rivers or streams, inland waters) were observed to be above the Predicted No Effect Concentration (PNEC; the predicted concentration below which there are no adverse pharmacological effects), though it should be noted that such studies are biased toward higher risk areas with low dilution. Despite this, the risk assessment showed that surface water for Private Water Supplies or coming into direct dermal contact with surface water during leisure activities are extremely unlikely to pose a risk to human health.


Drawing on the information gathered from this review, we identified key knowledge gaps and produced a list of recommendations for future research. Since the report was produced, several of these recommendations have been taken forward by Scottish Government-funded research projects. One of the recommendations was to address the disparity between research in aquatic vs terrestrial environments, with more research required on terrestrial environments. Since the report, methods to measure antibiotics in soils have been developed in a project exploring the flows of antimicrobial resistance and pathogens through the environment to the food chain. We also proposed more research on the impact of veterinary pharmaceuticals and on the impact of mixtures of pharmaceutical compounds, rather than individual compounds. Both of these are being addressed by a project called ‘Emerging water futures,' aiming to assess future risks to water quality and quantity under a range of scenarios.

Other recommendations in the report included producing a range of risk scenarios, for example, risk of bioaccumulation in fish and risk of exposure to livestock, and subsequent entry in the human food chain; and producing more data to address the assumptions and uncertainties associated with the presented risk assessment  Pharmaceutical pollution is a key research priority shared by both academic and public bodies; bringing such organisations together to discuss research needs and strategic plans will have wider benefits to public health.

Project Partners

  • The James Hutton Institute
  • BioSS
  • The University of Aberdeen 
  • Moredun Research Institute
  • One Health Breakthrough Partnership:
    • Scottish Environment Protection Agency 
    • Scottish Water 
    • NHS Highland 
    • University of the Highlands and Islands