Pollution (puh-loo-shun):  The introduction of harmful substances or products into the environment

Industrial Pollutants

Industrial pollution occurs across the state every day and is regulated via permits issued by the TN Department of Environment and Conservation. Polluters must disclose the contaminants they are discharging into our waters and keep the levels under certain limits. Third-party oversight over the Tennessee pollution permit process is vital to ensuring water quality.

Agricultural Runoff

Agricultural runoff is an umbrella term for the many different kinds of pollution a farm can produce. These mainly take the forms of sediment, pathogens, excessive nutrients, and pesticides/herbicides, each with their own negative impacts on the environment and human health. Read more.

Heavy Metals

Metals are found naturally in rocks and are released slowly into the environment as rocks erode. Human activities, such as mining or development, speed up the breakdown of rock and the release of metals into soil and water. Aging drinking water infrastructure is also a problem. Heavy metals become toxic to humans and other organisms when exposure reaches a certain threshold. Exposure can cause cancer and nervous/circulatory system impairments. Read more.


Pathogens are disease-causing organisms such as viruses and bacteria that can pose immediate health risks if ingested. These risks are unique to the particular organism that was ingested. In water regulation, E.Coli is used as an indicator species, as its presence strongly suggests the presence of other pathogenic species. Read more.


Sediment becomes a pollutant when construction, land development, stormwater, or agricultural activities disturb the ground and cause runoff. Sedimentation has many negative impacts on water quality: it can reduce oxygen in the water, smother fish eggs, gills, and aquatic insect species, change flow patterns and water temperatures, and transport other pollutants clinging to the individual soil particles, such as pathogens or toxic chemicals. Read more.


PFAS, or Per/Polyfluoroalkyl Substances, are a group of man-made chemicals that have seen extensive use in both the military and manufacturing. Evidence suggests that accumulation of PFAS in the human body can have adverse effects on the immune system, cholesterol levels, and thyroid function, as well as blood pressure in pregnant women. Read more.


The PFAS group of chemicals has been in use in industry since the 1940's due mostly to their nonstick and waterproof coating applications. Now the group contains 3,000 chemicals used extensively  throughout the U.S. economy. The largest source of PFAS pollution in drinking water stems from fire-fighting foam used by military installations, airports, and firefighters, as well as industrial production and manufacturing facilities. 

According to the Environmental Working Group, there are currently 8 known sites of PFAS contamination: The Memphis International Airport, the Naval Support Activity Mid-South in Millington, the Nashville Metropolitan Airport, the Arnold Air Force Base in Coffee County, the McGhee Tyson Airport in Blount County, the Consolidated Utility District of Rutherford in Murfreesboro, Lovell Field in Chattanooga, and the Savannah Valley Utility District in Georgetown.


Heavy Metals

The greatest metals of concern according to TDEC's 2014 305(b) Report are mercury and iron, which contaminate 275 and 243 stream miles, respectively. Mercury can be toxic to humans who come into contact with contaminated water or fish, especially pregnant women and young children. It is advised to follow any current contact or fish consumption advisories posted along impaired water bodies.

Lead and coal ash have made the news recently for creating contamination hot spots. Mandatory testing for lead in water sources in public schools revealed that more than one hundred schools across the state had at least one source of water containing lead above state health standards. Lead enters these public water sources through the deterioration of old lead pipes and the solder holding them together. TCWN is currently working to combat this through our Bringing Tap Back program, aimed at helping to remove pollutants from school drinking water and encouraging kids to drink water over sugar-filled drinks.

The TVA has operated twelve coal fired plant within its lifetime. The residue from burning coal, commonly called coal ash, is stored either onsite or in landfills designed specifically for this purpose. However, the heavy metals present in coal ash commonly make their way into the environment and into public drinking water supplies. Such metals include radium-226, lead, mercury, arsenic, cadmium, chromium, and selenium. Water supplies in and around TVA coal fire plants and coal ash dumpsites test positive for one or more of these metals. 

TCWN currently works to stop the spread of these heavy metals by fighting against the construction of new coal ash dumpsites and advocating for stricter control measures in current coal ash impoundments.



Sediment was the third largest pollutant in Tennessee streams and rivers in 2014, impairing roughly 6,000 miles.

Many practices can reduce sedimentation in Tennessee. TDEC uses BMP's- measures meant to reduce stormwater runoff and sediment erosion in construction and land development sites. The restoration of riparian zones around bare stream/river banks can help reduce the amount of bank erosion caused by increased flow rates and stormwater runoff. Fencing off cattle from stream banks can also greatly reduce the amount of bank erosion experienced by streams and rivers.


Agricultural Runoff

There are 66,600 farms spread across 10.8 million acres in Tennessee, according to the Tennessee Department of Agriculture. These farms are a major contributor of sediment, nutrient, and pesticide pollution in surface waters. In 2014, excessive nutrients comprised 12% of the pollutants found in surface water samples taken by TDEC for its 2014 305(b) report, while sediment made up 22%. 


Nutrient runoff from farms usually takes the form of misapplied or excessive fertilizers containing phosphorous and nitrogen. These fertilizers may attach to soil particles that erode in subsequent precipitation events or simply wash off from atop the soil and enter into nearby surface waters. Once in the water, the phosphorous and nitrogen found in the fertilizers promote the growth of algae and cyanobacteria on the surface of the water. When the algal blooms die, the decomposing organic material consumes most of the dissolved oxygen in the water, suffocating most other living organisms. This can create dead zones in the water. Even worse, some of these algal blooms can contain cyanobacteria species that produce toxins harmful to humans and other organisms.


In the United States, the two most popular pesticides are Glyphosate (Roundup) and Atrazine. Glyphosate is an herbicide used to killed broad leafed plants and grasses. Its effects on humans are disputed, with many sources such as the EPA stating the herbicide is safe. However, other organizations and government agencies, namely the World Health Organization and the United States Agency for Toxic Substances and Disease Registry report links between glyphosate and cancer- particularly non-Hodgkin lymphomas. 

Atrazine is surrounded by less controversy. According to the Center for Disease Control, Atrazine has been linked to cancers and increased risk of pre-term delivery. Other studies have found evidence to suggest that atrazine is a disrupter of human reproductive hormones. It  has also been shown to turn male frogs into functional females. 



Pathogens are the leading cause of river and stream impairment in Tennessee, making up 26% of the total pollutants catalogued by TDEC in 2014. Over 7,500 stream miles are impaired by pathogens. 122 miles were given contact advisories in June of 2019.

Pathogenic contamination stems mainly from human and animal fecal matter. Animal fecal matter enters surface water  through livestock that have direct access to rivers and streams. Failing septic systems release human fecal matter into both surface and groundwater, contaminating local water supplies. 

The most effective way to stop pathogenic contamination is to prevent contact between fecal matter and water. This requires exclusion fencing on farms, in which livestock are fenced off from streams and creeks. They are instead watered at areas specifically designed to limit fecal contact with water. Current septic systems require routine monitoring and maintenance to avoid failure, and many could benefit from upgrades and lifestyle changes (see here). Future septic systems should be installed at a far distance from local surface or groundwater, if possible. 


Tennessee Clean Water Network © 2020

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