More than half of all rivers have been affected by human activities. Over 80% of the world’s wastewater is released into the environment without treatment. Plastic pollution, agricultural runoff and industrial waste are significant problems too – they are killing wildlife, damaging ecosystems and creating hazards for human life.
Here are ten of the world’s most polluted rivers.
10 most polluted rivers
River Salween
The River Salween is Asia’s longest free-flowering river and one of the world’s most polluted rivers. After rising in the Tibetan Plateau, the Salween flows through China and Myanmar, where it briefly acts as the border with Thailand. It is a lifeline for the communities that live on its banks, and a biodiversity hotspot, but the water contains arsenic levels five times the global safety standard. High levels of sulphur, cadmium, copper, lead, mercury and zinc have also been found.
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Industrial waste from neighbouring textile factories and upstream mines has been blamed. Over the last ten years, satellite imagery detected 127 suspected rare earth mineral mines. When they extract elements needed to make smartphones and other electrical goods, toxic byproducts are released. Now many locals have stopped fishing the waters, out of fear for their health.
Matanzas-Riachuelo River
It may only be 64 kilometres long, but the Matanzas-Riachuelo River in Argentina is one of the most polluted rivers in Latin America. For decades, the river has been a dumping ground for cars, boats and unwanted waste. Industrial discharge from tanneries, meat-packing plants and petrochemical factories also feeds into its waters, where it mixes with household sewage.
A 2013 report found that 25% of children living nearby had lead in their bloodstreams, and more were suffering from gastrointestinal and respiratory issues.
Clean up efforts are ongoing. Thousands of tons of solid waste have been removed from the river, and a $1.2 billion project, supported by the World Bank, aims to build the infrastructure needed to rein in pollution. However, opinions on the project’s success are divided, so watch this space.
Yamuna River
The Yamuna River in India is a long, large waterway that merges with the Ganges at Triveni Sangam in Uttar Pradesh, site of the Kumbh Mela festival. Whilst the Ganges is well known for its high pollution levels, the Yamuna is worse.
It is the Yamuna, rather than the Ganges, that flows through Delhi, a city that dumps about 58% of its waste into the river. Now parts of the Yamuna have so little oxygen, they are considered ‘ecologically dead.’ In some places the water is anoxic, alkaline and thick with faeces, generating layers of thick foam that sit on the surface.
A 2015 study found that towns close to the Yamuna have at least four times the permissible level of fluoride in the water. Officials have blamed the millions of gallons of raw sewage that is discharged into the river, which is seeping into the groundwater.
The Ganges
The Ganges is not exactly pristine either. India’s largest river, which receives inflow from the Yamuna, supplies water to an estimated 500 million people – more than any other river in the world. It’s also home to wildlife including otters, freshwater turtles, gharials (small bulbous-nosed crocodiles) and the unique freshwater Ganges river dolphin.
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The river contains untreated human sewage, as well as waste from industrial plants, including tanneries, textile mills, slaughterhouses and distilleries. In Hinduism, the river has a sacred status. Over 70 million Hindus bathe in the Ganges during festive periods to ‘cleanse’ themselves, but this comes with significant health risks. Water from the river has been linked to outbreaks of dysentery, cholera, hepatitis and severe diarrhoea.
River Danube
By and large, European rivers aren’t too bad, but the Danube is a notable exception. The river begins in the Black Forest mountains, then flows for 2,850 kilometres through ten countries, before emptying into the Black Sea.
Every day, it ditches an estimated 4 metric tons of plastic waste into the Black Sea. And whilst water quality has improved in the river’s upper regions, elsewhere, contamination from microplastics, agricultural runoff and chemical and pharmaceutical waste remains a significant problem. Action is underway from the International Commission for the Protection of the Danube River, and things are slowly improving.
River Fal
In the United Kingdom, Cornwall’s River Fal gets a dishonourable mention. It was described in 2023 as England’s most polluted river due to the high frequency of sewage discharge it receives. Two years earlier, raw sewage was discharged straight into the river for the best part of a year, after the region’s 100-year old sewage system became overwhelmed.
No river wants the ‘most polluted’ title, however, and stakeholders have pointed out that whilst the Fal may suffer from frequent sewer spills, other rivers receive more volume. Potato. Pot-ar-toe. According to the Rivers Trust, in 2025 water companies discharged untreated sewage into rivers, lakes and seas almost 400,000 times, for over two and a half million hours.
Ohio River
In the United States, the Ohio River is frequently cited as the nation’s most polluted river, based on toxic releases from the industrial sector. It’s not alone, however. According to the Environmental Protection Agency, in 2023, 85 million kilograms of toxic substances were released into US waterways, largely from food, petroleum and chemical manufacturing.
Nitrate compounds, such as ammonia and sodium nitrite, make up 40% of this figure. This is a problem because high nitrate levels can spur the growth of algae, leading to blooms that decrease oxygen levels and suffocate aquatic wildlife. In addition, a 2022 study, which analysed 114 US waterways, found that 83% contained at least one PFA. Also known as ‘forever chemicals’, these substances have been linked to health problems, including some cancers and decreased fertility.
Darling River
Don’t be fooled by the name. In New South Wales, Australia, the Darling River is one of Oceania’s most polluted rivers. Water flow in the broader basin area has been declining for the last 50 years. Initially, this was attributed to water being diverted for agricultural and other purposes, but recently, it has been chalked up to climate change.
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When the river levels fall and the water becomes hot and stagnant, it can trigger the growth of harmful algal blooms. The largest bloom ever recorded, occurred on a 1,000 stretch of the Darling and nearby Barwon Rivers in the early nineties. The conditions can suffocate wildlife. In 2023, 20 to 30 million fish died in the Darling River near Menindee, New South Wales.
Yangtze River
Ninety percent of all of the plastic that flows into the ocean comes from just ten rivers. The Yangtze in China is the worst offender. It carries up to 1.5 million tonnes of plastic into the sea every year. To put that in context, the River Thames in England ejects a meagre (but not insignificant) 18 tonnes in the same timeframe.
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The 6,200 km-long Yangtze is one of the world’s longest and busiest waterways, but plastic pollution, damming and contamination from sewage, agriculture and industrial plants have trounced the water quality. Along with overfishing, this led to the disappearance of the river’s very own Yangtze River dolphin, which was declared functionally extinct in 2006.
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Coatzacoalcos River
The Coatzacoalcos River in southeastern Mexico runs for 325 kilometres from the mountains of Oaxaca to the Gulf of Mexico in Veracruz. It makes the list because of the staggering lack of environmental laws that could help to protect this heavily polluted waterway.
The key culprit is the Mexican oil industry. Petrochemical plants discharge waste into the water, and there have been many spills from pipelines. High levels of heavy metals, such as chromium and lead, have been found in the water, as have ‘forever chemicals,’ such as polychlorinated biphenyls (PCBs). The latter can accumulate in fish and then pass to people when they are eaten.
