Sources Of Criteria Air Pollutants: What And Why?

Criteria air pollutants are harmful to human health, the environment, and property. The Clean Air Act requires the Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards (NAAQS) for six commonly found air pollutants, including particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. These pollutants are found all over the United States and are monitored by the EPA to ensure they meet federal air quality standards. Despite progress in reducing these pollutants, they remain a concern, especially in certain regions, with particle pollution and ground-level ozone being the most widespread health threats.

Motor vehicles

Vehicles release criteria air pollutants, such as carbon monoxide (CO), nitrogen dioxide (NO2), and particulate matter (PM). High levels of CO can be harmful to human health, impacting the central nervous system and even leading to death. NOx emissions from vehicles contribute to environmental issues like acid rain, climate change, and the formation of ground-level ozone. Approximately 55% of human-made NOx emissions originate from motor vehicles. PM, including fine particles like PM 2.5 and ultrafine particles (UFP), can aggravate respiratory and cardiovascular diseases. Children are particularly vulnerable to the high levels of air pollutants emitted by buses, both when they are inside or standing nearby.

The transportation sector is a major contributor to greenhouse gas emissions, with carbon dioxide (CO2) being the most abundant greenhouse gas emitted. Additionally, fluorinated refrigerants used in mobile air conditioners have a high global warming potential, further exacerbating the environmental impact of the transportation industry.

While lead has been removed from U.S. gasoline, addressing health concerns, other pollutants remain a challenge. Regulations, such as the ultra-low sulfur diesel standards, have helped reduce the contribution of certain pollutants like SOx. However, electric vehicles introduce new concerns, as electricity generation is the largest source of SOx. Overall, motor vehicles play a significant role in emitting criteria and toxic air pollutants, posing risks to human health and the environment.

Industrial processes

One significant source of air pollution from industrial processes is factories and manufacturing plants. These facilities often emit dangerous airborne pollutants, such as dust particles, gases, smoke, and toxic chemicals. The burning of fossil fuels and the release of organic compounds, hydrocarbons, and chemicals from factories further contribute to air pollution. Additionally, refineries, mills, mines, and power plants are also responsible for releasing harmful substances, including nitrogen oxides and sulfur dioxide.

Commercial transportation is another critical source of air pollution from industrial processes. Vehicles involved in transporting goods and materials emit pollutants such as nitrogen oxides, sulfur dioxide, carbon monoxide, volatile organic compounds (VOCs), and greenhouse gases like carbon dioxide (CO2) and methane. The inefficient combustion processes of vehicular engines contribute to these emissions.

Petrochemical plants, a specific type of industrial facility, process hydrocarbons derived from crude oil and natural gas into petrochemicals used in everyday products. However, these plants emit several airborne pollutants, including fine particulate matter (PM2.5), sulfur dioxide, nitrogen oxides, VOCs like benzene, toluene, xylene, carbon monoxide, and hazardous air pollutants (HAPs) such as formaldehyde and acetaldehyde, which are extremely harmful to human health.

The impact of industrial air pollution on nearby communities and the environment cannot be overstated. Long-term exposure to these pollutants can cause respiratory and cardiovascular diseases, decreased lung function, increased asthma attacks, and various types of cancer. Additionally, industrial air pollution contributes to environmental degradation, including acid rain, depletion of the stratospheric ozone layer, and climate change, affecting both human health and ecological systems.

While complete elimination of industrial air pollution is challenging, especially with increasing global demand, significant reductions can be achieved through collective and individual efforts. Upgrading industrial processes, improving energy efficiency, implementing control technologies for ambient air pollution, and adopting cleaner and more sustainable practices can help mitigate the problem. Additionally, regulatory measures and enforcement of environmental standards are crucial to controlling emissions and waste from industrial sources.

Commercial businesses

Nitrogen Oxides (NOx): Commercial activities, including industrial processes and the use of fossil fuels, release large amounts of nitrogen oxides into the atmosphere. These colourless and odourless gases are produced when fuel is burned at high temperatures. NOx emissions contribute to the formation of smog and acid rain, which have detrimental effects on both human health and the environment. In urban areas, nitrogen dioxide (NO2) is often observed alongside particle pollution, creating a reddish-brown layer in the air.

Particle Pollution: Commercial businesses can generate fine and coarse particulate matter, which consists of solid and liquid droplets suspended in the air. Fine particles, with diameters of up to 2.5 microns, are released through industrial processes, motor vehicle emissions, and wood burning. These minuscule particles can infiltrate deep into the lungs, posing serious health risks. Coarse particles, ranging from 2.5 to 10 microns in diameter, originate from sources such as wind-blown soil and airborne residue from commercial and industrial operations. While individual coarse particles are invisible, they can collectively form haze, dust, or soot, impacting air quality and human respiratory health.

Carbon Monoxide (CO): Incomplete combustion of fuels, such as gasoline, heating oil, natural gas, wood, and charcoal, results in the production of carbon monoxide. Commercial activities, including the use of industrial boilers and waste incineration, contribute to CO emissions. Motor vehicles, particularly in congested urban areas, are a significant source of carbon monoxide pollution. High concentrations of CO can be hazardous and even fatal, underscoring the importance of effective emission control measures in commercial sectors.

Sulfur Dioxide (SO2): Commercial activities, especially those involving fossil fuel combustion, are responsible for releasing sulfur dioxide into the atmosphere. Power plants, industrial processes, and the burning of fossil fuels, such as coal, contribute to elevated levels of SO2. Prolonged exposure to sulfur dioxide can have adverse effects on human health, including respiratory issues and increased risk of cardiovascular disease.

Ozone (O3): While ozone in the upper atmosphere is beneficial, ground-level ozone is a harmful pollutant. Commercial businesses, through their emissions of nitrogen oxides and volatile organic compounds (VOCs), contribute to the formation of ground-level ozone. This pollutant can trigger a range of health problems, including respiratory issues, chest pain, coughing, and airway inflammation. Ground-level ozone is a significant concern, especially in urban areas with high population densities.

Lead: Commercial activities, such as manufacturing, construction, and waste incineration, can introduce lead into the air. Lead emissions from commercial sources, including lead-acid battery manufacturing and coal combustion, pose significant health risks. Inhalation or ingestion of lead can lead to adverse health effects, particularly in children, affecting cognitive development and causing behavioural problems.

Residential sources

One of the primary residential sources of criteria air pollutants is the burning of fossil fuels for heating and cooking. Residential wood-burning, often done in fireplaces or wood-burning stoves, releases fine particle pollution and can contribute to increased levels of ground-level ozone. This is especially true in colder regions during the winter months when wood-burning is more frequent and stagnant air patterns prevent the dispersion of pollutants. Older homes may also have oil- or gas-burning furnaces or boilers, which can emit nitrogen dioxide and carbon monoxide if not properly vented or maintained.

Another significant residential contributor is vehicle emissions from garages or driveways, which are considered residential sources. Idling cars, as well as those that are not properly maintained, can emit carbon monoxide, nitrogen dioxide, and particle pollution. Additionally, the use of gasoline-powered tools and equipment, such as lawnmowers, leaf blowers, and snowblowers, can add to carbon monoxide and particle pollution levels in residential areas.

Residential waste burning is another source of criteria air pollutants. When garbage, trash, or debris are burned, they can release a range of toxic substances, including particle pollution, volatile organic compounds, and toxic air contaminants like lead and dioxins. These substances can persist in the environment and have detrimental health effects, especially for children and older adults.

Lastly, certain household products and activities can contribute to indoor air pollution, which can indirectly affect outdoor air quality. For example, the use of cleaning products, paints, and solvents that contain volatile organic compounds (VOCs) can release particle pollution and ground-level ozone. While indoor environments have some protection from outdoor pollutants, poor ventilation or air exchange rates can lead to a buildup of these pollutants, ultimately impacting the outdoor air as well.

It is important to note that the contribution of residential sources to criteria air pollutants can vary depending on geographic location, climate, and the specific practices and behaviors of residents. Additionally, the EPA's efforts to regulate and reduce these pollutants through the Clean Air Act and the development of National Ambient Air Quality Standards (NAAQS) have led to improvements in air quality over the last 30 years. However, continued monitoring and mitigation of residential sources are necessary to ensure the health and safety of communities and the environment.

Fossil fuel combustion

Fossil fuels are a dominant source of criteria air pollutants, which are found all over the United States and can cause harm to human health, the environment, and property. When fossil fuels are burned, they release large amounts of carbon dioxide, a greenhouse gas, into the atmosphere. In 2018, 89% of global CO2 emissions came from fossil fuels and industry.

Coal, one of the three types of fossil fuels, is the dirtiest, responsible for over 0.3 degrees Celsius of the 1-degree increase in global average temperatures. Oil releases a significant amount of carbon when burned—approximately one-third of total carbon emissions. Natural gas, often promoted as a cleaner alternative, is still a fossil fuel and accounts for a fifth of the world's carbon emissions.

The burning of fossil fuels also releases nitrogen oxides into the atmosphere, contributing to smog and acid rain formation. Nitrogen is the most abundant element in the air and is essential to plant and animal life. However, human activities, including the burning of fossil fuels, can upset the natural balance of nitrogen in the environment. Transportation and industry are the primary sources of nitrogen oxide emissions from fossil fuels.

The health impacts of fossil fuel combustion are significant. Exposure to particulate matter from fossil fuels accounted for 21.5% of total deaths in 2012, decreasing to 18% in 2018 due to improved air quality measures in China. In 2018, more than 8 million people died from fossil fuel pollution, with air pollution from burning fossil fuels responsible for about one in five deaths worldwide.

Transitioning from fossil fuels to renewable energy sources is crucial to reducing air pollution and its associated health risks. Leading businesses are taking steps to manage and reduce their greenhouse gas emissions, and improving energy efficiency can help reduce emissions while benefiting corporations' bottom lines.

Frequently asked questions