undoubtedly higher than in many other parts of the world, the country still suffers from the problems of polluted water on an alarming scale. Around 3.5 million Americans get sick each year after coming into contact with contaminated water from swimming, boating or a dozen other ways, with many of the worst sources of pollution being the nation’s rivers¹. Here, we take a look at some of the worst.
Top of the list is clearly the Ohio River, having won the dubious honor of America’s most polluted river seven years in a row, in terms of pollutant discharges². Millions of tons of chemicals are dumped into the river, from a wide range of businesses and industries but nearly three quarters of them come from a single source: AK Steel Corp. More than ninety percent of the pollutants are nitrate compounds, most often found in pesticides, but what these figures hide is the river’s immense diluting power, which reduces the actual environmental impacts of the pollution. This is evidenced by the appearance of fish such as smallmouth bass, which prefer high quality water but it isn’t all good news. High concentrations of mercury have led to fish-consumption warnings for the Ohio while the presence of other chemicals also gives cause for alarm³.
Perhaps the river which is genuinely the most polluted in the US is the mighty Mississippi and although an oil spill in 2014 caused a great deal of concern amongst environmentalists and locals alike, the event was the least of the river’s problems⁴. A report by the Environment American Research and Policy Center in 2012 revealed that 12.7 million tonnes of toxic chemicals were released in a single year, including arsenic, mercury and benzene, much of which is fertilizer runoff. These chemicals can contribute to human health problems such as cancer, reproductive and developmental problems along with a raft of others and the levels found in the Mississippi have led to strident calls for stricter legislation governing their use.
The Holston River in Tennessee is another which suffers terribly from high levels of pollution. The principle threat to the river is the release of a toxic chemical from the Holston Army Ammunition Plant. Recent tests have shown that the plant releases Research Development Explosive (RDX) into the water and which is used in the making of explosives as well as being a known carcinogen⁵. If inhaled or ingested by humans or animals, it can cause seizures and the plant is the only place in the US where it is manufactured. The EPA has established lifetime limits for consumption of the chemical of 2ug/L but samples collected at various sites revealed levels more than twice this value, putting thousands of people who rely on the river for their drinking water at risk.
Also flowing through Tennessee is the Harpeth River, a 125 mile stretch of water that is home to a wide range of freshwater biodiversity, including more than 50 species of fish, many of which are threatened⁶. However, the river passes through the heart of one of the fastest growing cities in the US and which opens it up to threats including nutrient pollution from sewage effluent and stormwater runoff, which can fuel algal blooms which then create highly toxic conditions. Although the impacts on human health aren’t clear, fish in the river have been found with both male and female reproductive organs, while reproduction in mussels is also negatively impacted and which clearly suggests a significant problem⁷.
The New River flows north from Mexico into California but most of it is not natural and is instead formed of agricultural runoff, municipal discharge and industrial dumping, leading it to become known as the most polluted river of its size in the US⁸. Thanks to population growth in towns along its length, discharges into the river from both industrial and municipal sources have increased to the point where there is an overpowering stench emanating from the water which can be smelt from great distances⁹. When the river reaches California it contains a potent mix of chemicals including mercury, arsenic, DDT, and PCBs, along with pathogens that can cause tuberculosis, encephalitis, polio and typhoid. Technicians working on the river wear two sets of protective equipment, thanks to the dead animals, discarded tires and other waste which litter its length, while the large numbers of illegal immigrants who attempt to enter the US from Mexico are also at risk from this toxic nightmare¹⁰.