A new study by an international consortium that includes researchers from Stockholm University looking at the presence of pharmaceuticals in the world’s rivers found concentrations at potentially toxic levels in more than a quarter of the locations studied. The new study, which was published in Proceedings of the National Academy of Sciences, is the first truly global-scale investigation of pharmaceutical contamination in the environment.

“It is well known that pharmaceutical residues end up in lakes and rivers. While the majority of previous studies have monitored active pharmaceutical ingredients in rivers, these studies have often excluded many countries, have measured only a select few pharmaceuticals, and used different analytical methods. This means that it is difficult to make direct comparisons between studies and, hence, assess the scale of pharmaceutical pollution across the globe,” says Anna Sobek, Professor at the Department of Environmental Science and co-author of the study.

Professor Anna Sobek. Photo: Stella Papadopoulou

To address those issues and quantify the scale of the problem from a global perspective, the researchers studied 258 rivers in over half of the world’s countries to measure the presence of 61 pharmaceuticals, such as carbamazepine, metformin and caffeine. Notably, rivers in 36 of these countries having never previously been monitored for pharmaceuticals.

The study included noteworthy rivers such as the Amazon, Mississippi, Thames and the Mekong. More than 1000 water samples were obtained from sites spanning from a Yanomami Village in Venezuela, where modern medicines are not used, to some of the most populated cities on the planet, such as Delhi, London, New York, Lagos and Guangzhou. Areas of political instability such as Baghdad, the Palestinian West Bank and Yaoundé in Cameroon were also included. The climates where samples were obtained varied from high altitude alpine tundra in Colorado and polar regions in Antarctica, to Tunisian deserts.

The water sample analysis, which was performed at the University of York’s Centre of Excellence in Mass Spectrometry, UK, found that:

  • pharmaceutical pollution is contaminating water on every continent
  • strong correlations between the socioeconomic status of a country and higher pollution of pharmaceuticals in its rivers (with lower-middle income nations the most polluted)
  • high levels of pharmaceutical pollution was most positively associated with regions of high median age as well as high local unemployment and poverty rates
  • the most polluted countries and regions of the world are the ones that have been researched the least (namely sub-saharan Africa, South America and parts of southern Asia).
  • the activities most associated with the highest levels of pharmaceutical pollution included rubbish dumping along river banks, inadequate wastewater infrastructure and pharmaceutical manufacturing, and the dumping of the contents of residual septic tanks into rivers.
  • a quarter of the sites contained contaminants (such as sulfamethoxazole, propranolol, ciprofloxacin and loratadine) at potentially harmful concentrations.

The researchers collected water samples from 258 rivers in over half of the world’s countries. Photo: Anna Sobek

”In general, the rivers with the highest level of pharmaceutical pollution were found in low- to medium-income countries where there are no adequate water treatment facilities and where high emissions from the manufacturing of pharmaceuticals are found. Additionally, in over a fifth of the water samples we analysed, at least one contaminant was measured at concentrations that could negatively impact animals and plants in those rivers. Thus, this study shows that pharmaceutical contamination is truly a global problem,” says Sobek.

The researchers hope that by increasing the monitoring of pharmaceuticals in the environment, they can develop strategies to limit the effects potentially caused by the presence of pollutants.

“This study enables us to understand the connection between consumption and waste disposal. Since we clearly show that access to sewage treatment facilities significantly improves water quality, I hope the study will lead to projects that support and expand sewage treatment where it is needed the most. In addition, the findings of this study remind us that  the medicines we buy in pharmacies can have a big impact on the environment of the countries they are manufactured in,” concludes Sobek.

Contact information

Visiting addresses:

Geovetenskapens Hus,
Svante Arrhenius väg 8, Stockholm

Arrheniuslaboratoriet, Svante Arrhenius väg 16, Stockholm (Unit for Toxicological Chemistry)

Mailing address:
Department of Environmental Science
Stockholm University
106 91 Stockholm

Press enquiries should be directed to:

Stella Papadopoulou
Science Communicator
Phone +46 (0)8 674 70 11