Climate change and risks 2 min

The first global study to assess the extent of pharmaceutical pollution in rivers

PRESS RELEASE - Although medicines have improved human health and life expectancy, pharmaceutical residues cause pollution and impact the environment and living organisms. For the first time, a large-scale international study led by the University of York (United Kingdom), in which INRAE and more than 80 other research institutes participated, analysed pollution in 258 rivers in over 100 countries across five continents. Their results, published on February 14th in PNAS, show pharmaceutical contamination in all except three of the rivers studied, with levels that are potentially toxic to aquatic life in a quarter of those sites. The most polluted regions are in developing countries where pharmaceutical manufacturers are located or where wastewater treatment is inadequate.

Published on 15 February 2022

illustration The first global study to assess the extent of pharmaceutical pollution in rivers
© Pixabay

When we take medicine, the residues are eliminated in wastewater and can end up in our rivers. Medicines are designed to have a precise action on humans, but they have unknown effects on other living organisms (fish and shellfish, microorganisms, plants, etc.) and can upset their biological functions and life cycles. 

The impact of pharmaceutical pollution is well documented in some areas of the world, such as North America, Western Europe and China, but there has never been a global study to determine the situation at a worldwide level. To address this knowledge gap, the University of York launched a vast study in 2018 in conjunction with 86 other institutes around the world to analyse samples from 258 rivers in 104 countries on five continents, including in 36 countries that had never been studied. The study included major rivers such as the Amazon, the Mississippi and the Mekong, with samples taken from sites in regions where modern medicine is not used (for example, a Yanomami village in Venezuela) as well as in some of the planet’s most populated cities, such as New York and Delhi. The samples were analysed for the presence of 61 common pharmaceuticals, including antibiotics, analgesics, anti-inflammatories, antihistamines, diabetes medicines, antidepressants and stimulants (such as caffeine).

Pharmaceutical contamination found in all rivers

During the study, 1052 samples were taken around the globe according to an identical protocol. One laboratory measured the pharmaceutical concentrations to analyse the degree of contamination in the rivers. The scale of the study offers a global view of this contamination, which was found in all the rivers and on all continents, although at varying concentrations and frequencies. The findings show that the degree of pollution in rivers correlates to the socio-economic conditions of the country: the most contaminated sites are lower-middle income countries and associated with areas with little to no infrastructure to treat domestic or pharmaceutical-industry wastewater. Some of the regions that had never before been studied (South America, sub-Saharan Africa and certain parts of southern Asia) are among those with the highest levels of pharmaceutical pollution. For example, researchers found high concentrations of pharmaceuticals in Pakistan (average concentration of 70.8 µg/L, with a maximum measurement of 189 µg/L) and Bolivia (average of 68.9 µg/L, with a maximum of 297 µg/L). The study also found that a quarter of the sites studied had potentially harmful levels of environmental contaminants, including two antibiotics (sulfamethoxazole and ciprofloxacin), an antihistamine (loratadine) and a drug used to treat hypertension (propranolol).

This study made it possible, for the first time, to have a truly representative overview of pharmaceutical pollution in the world’s rivers, including in countries for which little if any information was previously available. In the future, this approach could be applied to study living organisms or other environments such as soils to develop international pollution-monitoring networks.


John L. Wilkinson et al. Pharmaceutical pollution of the world’s rivers. PNAS February 22, 2022 119 (8) e2113947119;

Study conducted as part of the Global Monitoring of Pharmaceuticals Project

INRAE press office

Scientific contacts

Arnaud Chaumot RiverLy Research Unit – Ecotoxicology Lab

Jeanne Garric RiverLy Research Unit – Ecotoxicology Lab



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