Coal-Burning And The Criteria Air Pollutant: Pm2.5

Coal has long been a reliable energy source, but it is also a major contributor to air pollution. The combustion of coal releases a range of harmful pollutants, including particulate matter, carbon monoxide, nitrogen oxides, sulfur dioxide, and toxic heavy metals. These pollutants have significant impacts on both human health and the environment. This introduction will discuss the various criteria air pollutants primarily associated with coal-burning and their effects.

Nitrogen dioxide (NO2)

NO2 is a major air pollutant, contributing to particle pollution and the formation of ground-level ozone, or photochemical smog, through chemical reactions with volatile organic compounds (VOCs). It is produced by a variety of sources, including trucks, buses, cars, industrial processes, and coal-fired power plants. In 2020, human-made sources in the US emitted 7.64 million short tons of nitrogen oxides, mainly from burning fuels.

NO2 has been linked to a range of harmful health effects, particularly for those who live near emission sources or suffer from respiratory diseases. Short-term exposure can cause eye, nose, and throat irritation, increased respiratory illness, and trigger asthma. Longer-term exposure can lead to actual changes in the lungs and increase the likelihood of hospital admissions. Scientific evidence also suggests that exposure to NO2 could cause asthma in children.

To reduce NO2 emissions, various measures can be taken. For example, a Low NOx burner can be used during combustion to burn fuel at the right air-fuel ratio, reducing nitrogen oxide emissions. Additionally, selective catalytic or non-catalytic reduction processes can be employed after combustion to further decrease emissions.

Carbon monoxide

The combustion of charcoal, often used as a cooking fuel in some restaurants and households, generates a significant amount of carbon monoxide. Inadequate ventilation in enclosed spaces can lead to carbon monoxide accumulation, posing a severe health risk. Symptoms of acute carbon monoxide poisoning include headache, confusion, dizziness, nausea, and even loss of consciousness at high concentrations.

Burning coal inside homes for heating or cooking also releases carbon monoxide, among other harmful chemicals. The use of unvented stoves and fire pits can lead to high levels of indoor air pollution, increasing the risk of adverse health effects. Installing indoor stoves with chimneys can help reduce indoor carbon monoxide levels.

Coal-burning power plants are another source of carbon monoxide emissions. While outdoor coal combustion may not directly impact indoor environments, the release of carbon monoxide into the atmosphere contributes to overall air pollution levels and can have indirect effects on indoor air quality.

To mitigate the risks associated with carbon monoxide exposure, it is crucial to ensure proper ventilation and avoid burning charcoal or coal in enclosed spaces. Additionally, the use of alternative energy sources and fuels can help reduce carbon monoxide emissions and improve overall air quality.

Sulfur dioxide

Coal-fired power plants are the largest human-caused source of sulfur dioxide emissions. In addition to power plants, smaller sources of SO2 emissions include industrial processes such as metal extraction, natural sources like volcanoes, and vehicles and heavy equipment burning fuel with a high sulfur content.

Due to the harmful effects of sulfur dioxide, regulatory bodies like the U.S. Environmental Protection Agency (EPA) have implemented measures to reduce SO2 emissions. The EPA's Clean Air Transport Rule, for example, aims to significantly reduce SO2 and nitrogen oxide emissions from power plants. Additionally, the EPA works with state and local governments to identify areas with poor air quality and develop plans to reduce SO2 levels. These efforts are crucial in mitigating the adverse health and environmental consequences associated with sulfur dioxide pollution.

Particulate matter

Coal-fired power plants release a mixture of soot, smoke, and tiny particles formed from sulfur dioxide, nitrogen oxides, and ammonia. These particles can accumulate in the respiratory system, leading to adverse health effects, especially for sensitive groups such as the elderly, individuals with cardiopulmonary diseases like asthma, and children. The health risks associated with particulate matter, especially PM10 and PM2.5, are well documented. Short-term exposure can irritate small airways in the lungs, triggering asthma, chronic bronchitis, and respiratory symptoms. Long-term exposure has been linked to respiratory and cardiac mortality, lung cancer, and adverse perinatal outcomes.

To mitigate the impact of particulate matter from coal-burning, power plants have employed technologies such as flue gas desulfurization equipment ("scrubbers") and electrostatic precipitators to remove sulfur dioxide, nitrogen oxides, and particulate matter from emissions. These efforts have led to a significant decrease in coal-related deaths over the years, with a 95% reduction between 1999 and 2020.

Mercury and other heavy metals

Mercury is a dangerous air pollutant that is associated with coal-burning. Coal-fired power plants are the largest source of mercury pollution in the United States, with coal having much higher mercury concentrations than other fossil fuels. Mercury is released into the atmosphere during the combustion process of coal and other fossil fuels.

Once in the atmosphere, mercury can travel both locally and globally, contaminating land, oceans, and streams. It is then converted into methylmercury, a harmful toxic that can accumulate in the food we eat and, eventually, in our bodies. As a result, all fish from U.S. waters have detectable levels of mercury, and consumption advisories are in place in all fifty states.

Mercury exposure is associated with neurological and cardiovascular damage, endocrine disruption, and an increased risk of diabetes. It is also a suspected carcinogen of the lungs and kidneys and has adverse effects on the cardio, nervous, and renal systems.

In addition to mercury, coal also contains other heavy metals, which are metallic chemical elements with high densities that are toxic or poisonous at low concentrations. The specific heavy metals found in coal can vary depending on the coal seam and geographic region. When coal is burned, these heavy metals are released into the smokestack, and with modern air pollution controls, they are captured through filtration systems. However, rain falling on coal and ash piles can leach out heavy metal compounds, contaminating groundwater, lakes, and streams.

To reduce mercury and heavy metal emissions, the EPA has implemented standards such as the Mercury and Air Toxics Standards and proposed revisions to the New Source Review performance standards for fossil-fuel-fired plants. Despite these efforts, stronger safeguards are still needed to protect public health, as many power plants continue to emit large quantities of mercury and other dangerous pollutants.

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