Coal Plants: Air Pollution's Dark Clouds

Coal-fired power plants are a major source of air pollution, releasing large quantities of harmful substances into the atmosphere. These pollutants include carbon dioxide, mercury, lead, sulfur dioxide, nitrogen oxides, particulate matter, and other toxic heavy metals. The release of these substances has been linked to a range of environmental and public health issues, including asthma, cancer, heart and lung ailments, neurological problems, acid rain, and global warming. While efforts have been made to reduce emissions, such as the development of carbon capture and storage technologies, the impact of coal plants on air pollution remains a serious concern, contributing to greater mortality than previously thought.

Mercury emissions

Mercury is a toxic heavy metal that is present in trace amounts in coal. When coal is burned, the mercury enters the environment and human bodies, impacting intellectual development and causing damage to the nervous, digestive, and immune systems. Coal plants are responsible for 42% of US mercury emissions, with coal-fired power plants being the largest source of mercury pollution in the United States. In 2017, these plants emitted approximately 8,800 pounds of mercury, and the highest-emitting plants were concentrated in North Dakota and Texas, with other large polluters in Appalachia and the Midwest.

Coal-fired power plants contribute to approximately one-third of all mercury emissions attributable to human activity. The combustion of coal releases mercury into the atmosphere, and coal has higher mercury concentrations than other fossil fuels, resulting in larger quantities of mercury pollution from coal-fired power plants. The release of mercury from coal combustion is a significant environmental concern, as it persists in the environment and can accumulate in the food chain, leading to bioaccumulation and biomagnification.

To address mercury emissions from coal plants, the EPA has proposed regulating hazardous air pollution from power plants under the Clean Air Act. This proposal is expected to greatly improve public health by reducing the risks associated with mercury exposure, such as premature mortality, cancer, and developmental delays in children. The EPA has also found that the cost of implementing the Mercury and Air Toxics Standards has been lower than initially projected, and pollution controls installed at regulated power plants are more effective and less expensive than originally anticipated.

Carbon dioxide

When coal is burned, it reacts with oxygen in the air to produce carbon dioxide. This carbon dioxide, when released into the atmosphere, acts as a heat-trapping gas, warming the Earth beyond normal limits. This warming contributes to global warming and climate change, which carry a host of consequences, including disrupted weather patterns, more frequent and severe droughts, flooding, severe storms, species loss, and the extended range of infectious diseases.

The health impacts of carbon dioxide emissions from coal plants are significant. Carbon dioxide is a major contributor to air pollution, which has been linked to asthma, lung ailments, and other respiratory issues. A study by Dr. Lucas Henneman and colleagues found a strong association between air pollution from coal power plants and increased mortality, with a 1.12% increase in mortality for every 1 μg/m3 increase in coal PM2.5. The study estimated that between 1999 and 2020, 460,000 deaths could have been prevented in the absence of emissions from coal power plants.

While carbon capture and storage technologies (CCS) are emerging as a potential solution to reduce CO2 emissions from coal plants, their effectiveness at the scale needed to address climate change remains unproven, and they do not address other harmful pollutants produced during coal combustion.

Sulfur dioxide

Coal-fired power plants are the largest human-caused source of sulfur dioxide, a pollutant gas that contributes to the production of acid rain and causes significant health problems. Coal naturally contains sulfur, and when coal is burned, the sulfur combines with oxygen to form sulfur oxides. Although natural processes like volcanic eruptions, biological decomposition, and forest fires also produce sulfur dioxide, emissions caused by human activity far exceed natural production in developed countries.

The U.S. Environmental Protection Agency (EPA) estimates that more than 65%, or over 13 million tons per year, of SO2 production in the U.S. is attributable to human activity. In 2014, US coal power plants emitted more than 3.1 million tons of SO2.

To reduce the amount of sulfur emitted by coal-fired power plants, some electric power plants use flue gas desulfurization equipment, also known as scrubbers, to clean sulfur from the smoke before it leaves their smokestacks. In addition, the coal industry and the U.S. government have cooperated to develop technologies that can remove impurities from coal and make coal more energy efficient, reducing the amount of coal burned per unit of useful energy produced.

Nitrogen oxides

NOx emissions from coal plants contribute to the formation of smog, which is created through a chemical reaction between NOx, sunlight, and volatile organic compounds (VOCs) in the atmosphere. This smog, or ground-level ozone, is an invisible gas made up of three oxygen atoms (O3) that irritates the lungs, exacerbates asthma, and increases susceptibility to chronic respiratory diseases like pneumonia and influenza. The presence of NOx in the atmosphere can also lead to the formation of acidic particulates, which can penetrate human lungs and be inhaled deep into the respiratory system, causing further irritation and respiratory issues.

The health impacts of NOx are not limited to the respiratory system. Studies have shown a correlation between high NO2 concentrations in cities and increased death rates, suggesting that nitrogen oxides may also contribute to cardiovascular issues. Research indicates that nitrogen oxides, along with other pollutants, are associated with hospital admissions for potentially fatal cardiac rhythm disturbances.

Coal-fired power plants are a major source of NOx emissions, and their impact on air quality and public health is significant. In 2014, US coal power plants emitted more than 1.5 million tons of NOx into the atmosphere. To mitigate these emissions, various technologies and regulations have been implemented. Power plants use flue gas treatment technologies, such as selective catalytic reduction (SCR) and selective non-catalytic reduction (SNCR), to reduce NOx emissions. Additionally, regulations like the Clean Air Act in the United States aim to reduce pollutants released into the air, including NOx, by setting emission limits and enforcing them through agencies like the Environmental Protection Agency (EPA).

Particulate matter

Coal-fired power plants are a major source of fine particulate matter (PM2.5) air pollution. Exposure to PM2.5 is associated with an increased risk of mortality. Research has shown that for every 1 μg/m3 increase in coal PM2.5, the mortality rate increases by 1.12%. This is a significant finding, as it indicates that coal PM2.5 emissions are more than twice as deadly as previously believed when compared to general PM2.5 exposure from all air pollution sources.

To address the issue of particulate matter from coal-fired power plants, various control strategies have been implemented. These include the use of electrostatic precipitators, baghouses, and scrubbers (flue gas desulfurization equipment) to remove particulates and heavy metals from the smoke before it exits the smokestacks. Additionally, the deployment of carbon capture and storage technologies (CCS) could enable coal plants to capture and store CO2, preventing its release into the atmosphere. However, the technology is still expensive and unproven on a large scale.

Frequently asked questions