Coal ash, also known as coal combustion residuals (CCRs), is the particulate residue that remains from burning coal. Depending on the chemical composition of the coal burned, this residue may contain toxic substances and pose a health risk to workers in coal-fired power plants.
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Background
Coal ash is found in coal-fired power plants. Coal is burned in coal-fired plants to produce electricity. More specifically, the coal is pulverized and then burned to generate energy. The particles that remain after burning coal is called coal ash. The production of coal combustion produces many by-products of coal ash. Some of these by-products are boiler slag, flue gas desulfurization material, bottom ash, fly ash, scrubber residues, cenospheres and fluidized bed combustion ash. Depending on the coal that was burned, the chemical composition found in coal ash can vary. However, most coal ash will contain aluminum oxide (Al2O3), calcium oxide (CaO) and silicon dioxide (SiO2). Regardless of the by-product produced, there are many toxic substances that are present in coal ash that can cause major health problems in humans. Some toxic constituents that are found in coal ash are arsenic, boron, cadmium, chromium, cobalt, copper, lead, mercury, molybdenum, selenium, thallium and uranium.
In the United States, approximately 44.6 percent of electricity is produced from over 450 coal-fired power plants. In 2012, approximately 110 million tons of coal ash was produced from the coal that was burned in the United States. However, more than half of the coal ash produced is dumped into surface impoundments (wet storage) or landfills (dry storage). Specifically, there are approximately 1,070 coal ash waste ponds and about 435 landfill sites located throughout the United States. The major problem of these disposal sites is the toxicity of coal ash escaping and causing harm to humans and the environment. When coal ash waste is not properly controlled, the toxic substances can affect drinking water, food and air.
Occupational health concerns
Coal ash contains many toxic substances that can negatively impact the human body. Employees working in coal-fired power plants or near coal ash waste sites are at major risk of inhaling coal ash dust. Coal ash dust is generally known as particulate matter (particle pollution) and the dust particles can harm the lungs when inhaled. Workers increase their risk of harmful side effects when they inhale the smallest coal ash dust particles. The smaller the coal ash dust particle, the deeper the particle will be inhaled into the lungs. As a result, the toxic particles can inflame the lungs causing severe damage to the body. Furthermore, coal ash dust can enter the body through the nose causing damage to the brain directly. However, regardless of particle entry, the toxicity from coal ash can cause harm to major body parts such as the brain, lungs, heart, liver, kidneys, stomach and intestines. Thus, individuals working near coal ash surface impoundments or landfills are at increased risk for many serious health problems.
Health effects of toxic constituents found in coal ash
Lead: The exposure of lead in coal ash can cause major damage to the nervous system. Lead exposure can lead to kidney disease, hearing impairment, high blood pressure, delays in development, swelling of the brain, hemoglobin damage, and male reproductive problems. Both low levels and high levels of lead exposure can cause harm to the human body.
Cadmium: When coal ash dust is inhaled, high levels of cadmium is absorbed into the body. More specifically, the lungs directly absorb cadmium into the bloodstream. When humans are exposed to cadmium over a long period of time, kidney disease and lung disease can occur. In addition, cadmium exposure can be associated with hypertension. Lastly, chronic exposure of cadmium can cause bone weakness which increases the risk of bone fractures and osteoporosis.
Chromium: The exposure of chromium (IV) in coal ash can cause lung cancer and asthma when inhaled. When coal ash waste pollutes drinking water, chromium (IV) can cause ulcers in the small intestine and stomach when ingested. Lastly, skin ulcers can also occur when the exposure chromium (IV) in coal ash comes in contact with the skin.
Arsenic: When high amounts of arsenic is inhaled or ingested through coal ash waste, diseases such as bladder cancer, skin cancer, kidney cancer and lung cancer can develop. Ultimately, exposure of arsenic over a long period of time can cause mortality. Furthermore, low levels of arsenic exposure can cause irregular heartbeats, nausea, diarrhea, vomiting, peripheral neuropathy and vision impairment.
Mercury: Chronic exposure of mercury from coal ash can cause harm to the nervous system. When mercury is inhaled or ingested various health effects can occur such as vision impairment, seizures, numbness, memory loss and sleeplessness.
Boron: When coal ash dust is inhaled, the exposure of boron can cause discomfort in the throat, nose and eye. Moreover, when coal ash waste is ingested, boron exposure can be associated with kidney, liver, brain, and intestine impairment.
Molybdenum: When molybdenum is inhaled from coal ash dust, discomfort of the nose, throat, skin and eye can occur. As a result, short-term molybdenum exposure can cause an increase of wheezing and coughing. Furthermore, chronic exposure of molybdenum can cause loss of appetite, tiredness, headaches and muscle soreness.
Thallium: The exposure of thallium in coal ash dust can cause peripheral neuropathy when inhaled. Furthermore, when coal ash is ingested, thallium exposure can cause diarrhea and vomiting. In addition, thallium exposure is also associated with heart, liver, lung and kidney complications.
Silica: When silica is inhaled from coal ash dust, fetal lung disease or silicosis can develop. Furthermore, chronic exposure of silica can cause lung cancer. In addition, exposure to silica over a period of time can cause loss of appetite, poor oxygen circulation, breathing complications and fever.
Coal ash reuse
Reuse of coal ash benefits the environment by reducing the production of greenhouse gas and reducing the need to use virgin materials. In addition, when coal ash is recycled, costs related to coal ash disposal sites are avoided. Thus, when coal ash is reused both the environment and economy are benefited.
There are two forms of coal ash recycling- “encapsulated” and “unencapsulated." When coal ash is bound to other materials it is encapsulated. For example, coal ash can be reused in making concrete, bricks and wallboards. On the other hand, unencapsulated use of coal ash is when the ash is not bound to other materials (loose particulate or sludge form). An example of unencapsulated coal ash is distributing the ash on icy roads in the winter.
Even though reusing coal ash minimizes health effects in humans, health problems can still occur when coal ash is recycled. Specifically, workers drilling or cutting encapsulated coal ash increase their risk of inhaling coal ash dust. In addition, when unencapsulated coal ash is scattered on snowy streets in the winter, the loose ash can come in contact with ditches on the side of the road. As a result, the toxins from coal ash can “leach” into the water streams polluting above-ground waterways and eventually contaminating underground water supplies (drinking water). Therefore, both forms of recycled coal ash (encapsulated and unencapsulated) can cause serious health issues in humans.
Coal ash waste regulations
In the United States, the only federal regulation regarding the disposal of coal ash is called “Disposal of Coal Combustion Residuals from Electric Utilities”, which was signed into law on December 19th, 2014. In addition, when coal ash is disposed into surface impoundments and landfills, coal ash is regulated as non-hazardous solid waste under the Resource Conservation and Recovery Act (RCRA). Thus, the requirements of the coal ash disposal law is regulated under subtitle D of the RCRA.
In order for this federal regulation to be effective, there are some major requirements that surface impoundments and landfill facilities must follow. This rule requires facilities to prevent and control coal ash dust from accumulating into the air. As a result, facilities must provide annual plans for coal ash dust control. Furthermore, there are location restrictions where new landfills and surface impoundments can be built. In addition, if regulations of coal ash dust control are not maintained, closure of the facility will occur under the federal law. The law also requires all coal ash waste facilities to create annual groundwater monitoring reports. Lastly, all coal ash waste surface impoundments and landfills must keep a written record of the federal regulations at the facility for five years. Ultimately, this recent federal regulation is trying to eliminate occupational health concerns and environmental health issues regarding coal ash toxicity.