10 Most Polluted Rivers in the World

6 min read
September 02, 2023

10 Most Polluted Rivers in the World:

A Shocking New Study

The world’s rivers are under assault from many different sources of pollution, but none is more insidious than pharmaceuticals. A new study, published in February 2022, has found that pharmaceutical pollution is rampant in waterways around the globe, and the problem is only getting worse.

The study, conducted by an international team of researchers, analyzed data from over 1,000 sites in 104 countries. The most common drugs identified were antibiotics, anti-inflammatories, and antidepressants.

The study included sampling sites on all 7 continents, in 104 countries, across 258 rivers. It represents the environmental influence of 471.4 million people across 137 geographic regions. This study also included 36 countries that had not previously been monitored for pharmaceutical pollution.

What is Pharmaceutical Pollution and How Does it Harm the Environment?

Pharmaceutical pollution is the contamination of water bodies by pharmaceuticals and personal care products (PPCPs). PPCPs are a wide variety of chemicals that include prescription and over-the-counter drugs, hormones, and cleaning agents. Also included are substances such as caffeine and nicotine. They enter the environment through sewage treatment plants, septic systems, animal feedlots, and agricultural runoff.

While most PPCPs are not considered toxic at low levels, some can have harmful effects on aquatic life and human health. For example, some PPCPs can interfere with the normal hormone function in fish and other animals, resulting in the feminization of male fish, reduced fertility, reproductive failure, and abnormal behavior. In humans, some PPCPs have been linked to cancer, birth defects, and other health problems.

However, there is no data on the effects of a cocktail of pharmaceuticals on aquatic life. We simply cannot predict how this cumulative pollution is affecting or will affect us or the environment long term.

What’s at Stake

One of the greatest concerns regarding pharmaceutical pollution in rivers is the development of antimicrobial-resistant microorganisms due to continued, high-level exposure to antibiotics in the environment. Simply put, diseases that are resistant to antibiotics because they’ve been exposed to them in the environment. This leads to diseases that are harder to treat and people who are sicker, longer. 

Researchers conducting the study determined a level of concentration at which the active pharmaceutical ingredients (APIs) would remain safe for the environment.

One API (ciprofloxacin – an antibiotic) exceeded the safe limit at 64 of the sites that were tested. The highest concentration of an API was found in metronidazole (another antibiotic) at a sampling site in Barisal, Bangladesh. This sampling was over 300 times the safe limit.

Of the 1,052 study sites, 270 had at least one API which exceeded the safe level of concentration in the environment. That’s 25.7% of all river sites sampled. Pharmaceutical pollution is happening worldwide at dangerous levels every day.

What are the most heavily polluted rivers in the world? Here are the top 10 as defined by this study.

The 10 Most Polluted Rivers in The World

*-denotes a river that had never before been tested for APIs

1. The Ravi River in Lahore, Pakistan – A transboundary river of India and Pakistan, the Ravi river is 450 mi long. Pollution in the urban areas of Lahore, Pakistan, is reportedly very high, which is due to poor waste management and drainage systems. Even though some unauthorized discharges into the river have been controlled, the river sediments are severely polluted and have become a secondary source of pollution in the water.

2. *The La Paz River in La Paz, Bolivia – The La Paz is part of the drainage basin of the Amazon. The river is tainted with sewage, and there are suspicions that enteropathogenic bacteria in the water contribute to the high incidence of diarrheal illness in La Paz.

3. *The Akaki River in Addis-Ababa, Ethiopia – The Akaki has, sadly, become the rubbish bin for the city of Addis-Ababa. This puts the rural residents who live in the outskirts of the city at risk, since it is a source of drinking water for them. The value of the river as a vital migratory bird staging ground is also a concern from a conservation standpoint, as it supports approximately 20,000 waterfowl.

4. The Yamuna River in Delhi, India – This river, as the second-largest tributary to the Ganges and India’s longest tributary with a length of 855 miles, provides 70% of Delhi’s water supply. About 57 million people rely on the Yamuna river every day. 96% of its annual flow is used to irrigate crops. 80% of the river’s total pollution occurs along 13.6 miles of its course, just 1.5% of the river’s total length. This is largely due to the fact that only 35% (13 out of 35) of the sewage treatment plants in Delhi comply with the requirements set forth by the Delhi Pollution Control Committee. The four primary reasons for Delhi’s Yamuna pollution are poorly treated water, disposal sites for domestic and municipal waste, soil erosion owing to deforestation in order to cultivate crops, and chemical wash-off (fertilizers, herbicides, and pesticides) and runoff from commercial activity and industrial locations.

5. The Medjerda River in Tunis, Tunisia – Dams have been built along the 290-mile-long Medjerda and its waters used to irrigate the area’s wheat crops. 

6. *The Ruzizi River, also spelled Rusizi in Bukavu, DRC-Congo – The Ruzizi River runs for 73 miles along the border between Rwanda and the Democratic Republic of Congo (DRC) on the east and west, respectively. It provides hydroelectricity for the Democratic Republic of Congo, Rwanda, and Burundi.

7. *The Hrazdan River in Yerevan, Armenia – Along the Hrazdan’s length, hydroelectric plants have been built and are used for agriculture irrigation. Agricultural, commercial, industrial, and residential development wastewater pollutes the river, in addition to untreated sewage from the town of Yerevan.

8. The Nairobi River in Nairobi, Kenya – Agriculture, slums, and industry all contribute to the pollution of Nairobi’s water. During rainy seasons, rivers on the low-lying riverbanks overflow. As the waters ebb and flow through marshy areas dotted with subsistence farming and human settlements, waste and pollutants collect and are swept further along the stream. The river continues past farms and coffee plantations until finally, it reaches industry: the Nairobi Sewage Company and the Kamiti Tannery Factory cast their waste into the waters as they pass by. As a result of the pollution sources upstream, the waters in the lower stream are brackish and foul. The desperate situation regarding the conservation and preservation of this part of the Nairobi River has yet to be addressed.

9. The San Juan River in San Jose, Costa Rica – The river is home to freshwater bull sharks and a great bounty of biodiversity. People use it for drinking, washing, livestock, laundry, and a host of other daily activities.

10. The Ogun River in Lagos, Nigeria – The river is a source of drinking water and bathing in heavily populated areas. It also drains organic waste from abattoirs (slaughterhouses) that line the river’s route.

The Tip of the Iceberg

This “Top Ten” list is the tip of the iceberg when it comes to our world’s polluted rivers.

The two compounds most commonly found in rivers worldwide in concentrations that exceeded safe limits were sulfamethoxazole and propranolol. Sulfamethoxazole is an antibiotic widely used and recommended by the WHO as a first-choice treatment for urinary tract infections and bronchitis. Propranolol is a beta-blocker, used to treat high blood pressure and migraine headaches.

These two pharmaceuticals were found in unsafe concentrations in rivers on 5 continents: Africa, Asia, Europe, North America, and South America. They found the greatest number of contaminated sites in Africa where 35% of sample sites had levels of sulfamethoxazole beyond safe limits. In Europe, over 10% of sites had unsafe levels of propranolol detected. And in North America, 15% of sample sites had unsafe levels of one or the other.

Out of the study’s 1,052 sites sampled, only 2 were found without pharmaceutical pollution. One in Iceland and one in Venezuela where the tribe of indigenous people do not use modern medicine. Every other site sampled contained some type of pharmaceutical contamination. Even in Antarctica.

How We Can Reduce Pharmaceutical Pollution in Rivers

Pharmaceutical pollution is a tremendous threat to rivers around the world. The problem is not only in those countries where water treatment is unavailable, this study shows us that it exists where we live too.

Run-off from agriculture and livestock farming, industrial waste, and water treatment plants themselves, are all huge contributors to pharmaceutical pollution in rivers everywhere.

The good news is, there are things we can do to help reduce pharmaceutical pollution, starting today!

  • Properly dispose of unwanted or unused drugs: Many pharmacies offer drug take-back programs, or you can bring them to a local hazardous waste facility.
  • Avoid flushing drugs down the toilet: This is one of the main ways that pharmaceuticals end up in our waterways.
  • Use less toxic products when possible: There are many safer options available for cleaning products, pest control, and other products which historically have contained toxic chemicals.
  • Support sustainability initiatives and studies: Look for businesses and organizations that support clean river initiatives and sustainability practices.
  • Spread the word: Talk to your friends and family about the importance of sustainability and river conservation. The more people who are aware of the issue, the bigger the impact we can make.

The United Nations’ Sustainable Development Goals are a perfect example of an initiative we can and should support. Specifically, Goal 6.3: “By 2030, improve water quality by reducing pollution, eliminating dumping and minimizing release of hazardous chemicals and materials, halving the proportion of untreated wastewater and substantially increasing recycling and safe reuse globally.”

By taking some simple steps, by all working together, we can help to reduce pharmaceutical pollution in our rivers and make a real difference for the future health of our waterways.