A recent global study founds that more than a quarter of observed rivers had significant pharmaceutical concentrations.
The study found broad contamination of common pharmaceuticals in many of the world's rivers. More than a quarter of the 1,052 locations included in the study had pharmaceutical concentrations at potentially toxic levels for the environment and human health.
Based on their findings, the authors call for new paradigms of environmental monitoring of different kinds of pollutants, across different environmental media, and under a global, inclusive, and interconnected management.
Professor Kenneth Mei Yee Leung and his postdoctoral fellow Racliffe Weng Seng Lai, of the City University of Hong Kong, participated in this global project with Professor Alistair B.A. Boxall and John L. Wilkinson from the University of York in the United Kingdom. Their findings were recently published in the respected science journal Proceedings of the National Academy of Sciences of the United States of America, entitled "Pharmaceutical Pollution of the World's Rivers".
"We've known for over two decades now that pharmaceuticals make their way into the aquatic environment where they may affect the biology of living organisms,” said Wilkinson. “But one of the largest problems we have faced in tackling this issue is that we have not been very representative when monitoring these contaminants, with almost all of the data focused on a few selected areas in North America, Western Europe and China.”
"This unique global project impressively mobilized 127 scientists and used standardized methods for collecting water samples from 258 rivers around the world and analyzing 61 commonly used pharmaceuticals,” added Leung. “This standardized method allowed a fair global comparison for the first time. We were delighted to play a part in this meaningful project, and contribute to sample collections in Hong Kong and Bhutan, and statistical analyses of the data.”
The previous related studies touched only on the tip of the iceberg, said Leung. He explained that these previous studies employed different analytical methods and monitored different pharmaceuticals. Cumulatively, this has made it difficult to quantify the scale of the problem from a global perspective and leaves a substantial knowledge gap and uncertainty about the actual rate of pharmaceutical pollution around the world.
This study covered all seven continents, 137 countries and regions, and 258 rivers. It included areas with a broad spectrum of anthropogenic activities, ranging from an Amazon Yanomami Village inhabited by only indigenous people, to megacities, such as Delhi, New York, Lagos, Manila, Hong Kong, and Guangzhou.
Importantly, 36 of the sampled countries and regions in the study had not been previously monitored for pharmaceutical contamination. Most of them were in sub-Sahara Africa, South America and parts of southern Asia. Four rivers in these countries were ranked among the top 10 most polluted rivers.
At least one pharmaceutical product out of the 61 evaluated was detected in each of the sampled rivers, except for the two rivers in Iceland and the one in the Amazon's Yanomami Village. This implies that the previous research efforts largely overlooked many areas where there are higher risks from pharmaceuticals to the ecosystem and human health.
Contamination by Multiple Pharmaceuticals
Four chemical compounds — caffeine, nicotine, cotinine and acetaminophen/paracetamol — were readily detected across all seven continents, and an additional 14 pharmaceuticals were detected in all continents except for Antarctica. Many of them also had a high measured concentration in the studied riverine systems. These pharmaceutical contaminants include analgesics, antibiotics, anticonvulsants, antihistamines, antihyperglycemics and stimulants, which are commonly used in our daily life.
High Risk in Lower-Income Regions
Statistical analyses conducted by Leung and Lai identified a strong correlation between the socioeconomic status of a country and the level of pharmaceutical pollution in its rivers. Rivers in lower-middle income countries were found to be the most polluted. High levels of pharmaceutical pollution were most positively associated with regions with a relatively high median age and those with high local unemployment and poverty rates.
Key activities most associated with the severe pharmaceutical pollution included rubbish dumping along riverbanks, inadequate wastewater infrastructure and pharmaceutical manufacturing, and the dumping of contents of residual septic tanks into rivers. Though the analysis was preliminary, it revealed that socioeconomic status and human health may be key predictors of local environmental pollution.
Antimicrobial-Resistant Superbugs
Antibiotics are broadly applied to deal with diseases related to bacterial infection but their release into the environment may perturb the natural bacterial community and affect beneficial bacteria that assist with carbon and nutrient recycling in the ecosystem. Also, when exposed to antibiotics, bacteria can evolve to become resistant to the antibiotics, thus reducing the efficiency of general antibiotic treatments and turning into superbugs.
In Hong Kong, the Kai Tak River and the Lam Tsuen River were ranked as the 20th and 75th rivers most polluted with antibiotics out of 258 rivers in the study. Six different antibiotics out of the 13 monitored were detected in the Kai Tak River and two were found in the Lam Tsuen River. In particular, measured environmental concentrations of the antibiotics ciprofloxacin and clarithromycin in the Kai Tak River exceeded the safety threshold by 1.3 and 5.5 times, respectively, implying a high risk of these two antibiotics to induce antimicrobial resistance.
This study forms part of the Global Monitoring of Pharmaceuticals Project led by the University of York, which is the first global-scale investigation of medicinal contamination in the aquatic environment.
"With 127 collaborators across 86 institutions worldwide, the Global Monitoring of Pharmaceuticals Project is an excellent example of how the global scientific community can come together to tackle large-scale environmental issues." said Wilkinson.
"The study identified rivers with high pharmaceutical contamination and high-risk chemicals. With this information, it is possible to formulate practical and integrative strategies, from legislation to education and pollution control, to minimize the release of these chemicals and create cleaner rivers across the globe," said Leung.
Inspired by this study, a new global project, the Global Estuaries Monitoring (GEM) Program, was recently launched and endorsed as an Ocean Decade Action under the United Nations Decade of Ocean Science for Sustainable Development (2021-2030). The GEM Program, led by Leung, will investigate pollutants in major estuaries around the world, including pharmaceutical residues.
