The question of how to compare levels of pollution is a tricky one. Although it’s easy to talk of sheer amounts of chemicals pumped into waterways, there are other factors to consider, such as number of people or species affected by contaminants, while it is also difficult to quantify precisely the effects of pollutants, and over what scale. However, regardless of definitions of the term ‘most polluted’, there’s no doubt that the rivers on the following list are in need of a serious clean-up.
Widely considered one of the filthiest rivers, the Ganges in India is undeniably unpleasant, unhealthy and a disgrace to its revered stature. Over 400 million people rely on it, using it for drinking water, agriculture and bathing, with millions more pilgrims also coming to bathe and worship[sc:1]. However, because of an ever expanding population, it is so full of toxins that levels are over 3000 times what the World Health Organization considers safe. Industries such as leather production pump chromium and other chemicals into the water but even more disturbing, particularly to Western eyes, is the wholesale dumping of human and animal corpses, including babies, some cremated, others merely abandoned and left to rot[sc:2].
Citarum River in Indonesia supplies 30 million people with water but to rely on it is to put your life at risk. More than 200 textile factories are found along its 186 miles but thanks to demand for growth and consumer goods, little regulation has been applied to industry, leading to the river becoming choked with lead, arsenic, and mercury, creating a deadly cocktail of contaminants[sc:3]. Detritus floats along in a tide of waste, with plastic, packaging and other unsavoury items clogging up waterways and devastating ecosystems. Fishermen have given up catching fish, as they are all dead, instead turning to recycling plastic, but while this entrepreneurial spirit is admirable, the reason behind it is heartbreaking.
China’s environmental problems are well known, but the state of the Yellow River stands as one of the most damning examples of human short-sightedness. Economic expansion is again responsible for much of the problem. For example, the city of Shizuishan, one of the world’s most polluted cities, boasts a veritable forest of chemical and pharmaceutical factories, and which are responsible for the surreal and terrifying sight of blood red waste pumping into the water and turning it a hideous purple[sc:4].
The severity of pollution in the Yamuna River has caused the Times of India to call it ‘beyond redemption’, with the Central Water Commission stating boldly that the water is safe for neither drinking nor agriculture[sc:5]. Biochemical Oxygen Demand (BOD) refers to the amount of oxygen required by living organisms to break down organic material, and once it reaches certain levels, it becomes a pollutant, giving rise to harmful bacteria[sc:6]. In the Yamuna, BOD levels can be as high as 50 times the permissible level, putting millions of lives at risk.
The Mississippi, one of the world’s mightiest rivers, is also one of its dirtiest[sc:7]. Vast stretches exceed recommended levels for mercury, PCBs, sediment, and other contaminants, making it hazardous to swim, fish or use its waters for drinking. Worse still is the vast dead zone in the Gulf of Mexico which has been created by the sheer volumes of fertilizer and raw sewage pollution which flow from the river and which stands as a desolate reminder of our actions[sc:8].
The Sarno River
The Sarno River in Italy might not be one of the world’s best known, but it is on the list of most polluted[sc:9]. Although its upper reaches are virtually pristine, travelling its length reveals waters covered with oily scum and chemical foam. The cause? Mainly mass dumping of untreated agricultural and industrial waste but research also points to illicit drugs such as cocaine and morphine in the water and which pose an entirely new, but as yet undetermined, threat to humans and wildlife[sc:1][sc:0].
The Marilao River runs through the Philippines and suffers greatly from increased pollution loads, causing environmental degradation and numerous human health issues[sc:1[sc:1]. This contamination comes from a variety of sources, notably precious metal refining, lead acid battery recycling, jewellery making and open dumpsites. Problems stem from the fact that the river is used for aquaculture, with the fish bioaccumulating the toxins and passing them up the food chain, with significant risks of heavy metal poisoning.
The Philippines is also home to the Pasig, cutting through the heart of Manila. Problems started after WWII, when thousands flooded into Manila looking for work. Slums and industries sprang up, with untreated sewage released wholesale into the water, along with unregulated discharges from factories and which has now led to the river being biologically dead.
The Tiete River in South America received so much sewage and factory discharges that by the 1990s it was declared dead as well[sc:1][sc:2]. Toxic foam formed on the surface during dry months, giving rise to massive public outcry to improve treatment infrastructure, but even so, several million citizens still lack basic sewage[sc:1][sc:2].
China’s Yangtze River supplies 40% of its freshwater and contributes 40% to its GDP, making it all the more alarming that it is so polluted[sc:1][sc:3]. Almost half of the country’s waste ends up in its waters, amounting to 25 billion tons, causing fisheries to go extinct, severe health problems such as intestinal diseases and thousands of dead pigs to end up its tributaries[sc:1][sc:4].