Air Pollutants: What's Being Released Into Our Atmosphere?

Air pollution is the release of various gases, finely divided solids, or finely dispersed liquid aerosols into the atmosphere at rates that exceed the environment's capacity to dilute or absorb them. These pollutants are detrimental to human health and the planet. The World Health Organization (WHO) reports that nearly seven million deaths annually are attributed to air pollution, with 99% of humans currently breathing air that exceeds the WHO's guideline limits for pollutants. The pollutants released into the air include particle pollution, ground-level ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead. These pollutants are emitted by industrial processes, power plants, residential heating systems, automobiles, and other combustion sources.

Characteristics and Values of Pollutants Released into the Air

Particulate matter

The size of particulate matter is an important factor, as it determines its ability to infiltrate the human body. Larger particles, known as PM10, are inhalable and can irritate the eyes, nose, and throat. They are often a result of dust from roads, farms, dry riverbeds, construction sites, and mines. On the other hand, smaller particles, called PM2.5, pose a greater risk as they can penetrate deeper into the lungs and even enter the bloodstream. PM2.5 is primarily associated with adverse health effects, including premature death, especially in individuals with chronic heart or lung diseases, and reduced lung function development in children.

The sources of particulate matter can be both natural and anthropogenic. Natural sources include volcanoes, fires, dust storms, and aerosolized sea salt. Manmade sources, on the other hand, include combustion in mechanical and industrial processes, vehicle emissions, and tobacco smoke. Indoor activities, such as smoking tobacco, cooking, and burning wood, candles, or incense, can also contribute to particulate matter levels.

The health effects of particulate matter have been recognized for centuries, but it was in the twentieth century that the world truly began to understand the impact of air pollution on human health. Major incidents, such as the 1930 Meuse Valley episode in Belgium and the 1952 London smog, brought the lethality of air pollution to light. Today, the World Health Organization estimates that particulate matter air pollution contributes to approximately 800,000 premature deaths each year, making it the 13th leading cause of mortality worldwide.

Ground-level ozone

The U.S. Environmental Protection Agency (EPA) has designated ground-level ozone as one of six "criteria" air pollutants, which are regulated based on human health and environmental criteria. EPA regulations help states reduce ozone levels in outdoor air, and states are required to draft plans to improve air quality in areas that do not meet the national standards.

The effects of ground-level ozone exposure include respiratory issues, increased school absences, and a potential increase in the risk of premature death from heart or lung disease. It also has negative impacts on vegetation, making it harder for plants to breathe. Research indicates that ground-level ozone exposure may lead to increased doctor and emergency room visits and hospital admissions.

Carbon monoxide

CO is also emitted by other combustion sources, including power plants, wildfires, and incinerators. Additionally, CO can be produced through photochemical reactions in the atmosphere from methane, non-methane hydrocarbons, and other volatile organic compounds. Certain industrial processes, such as metal processing and chemical manufacturing, also release CO into the atmosphere.

Indoor sources of CO include gas stoves, malfunctioning or improperly vented gas appliances (such as water heaters, furnaces, and clothes dryers), space heaters, fireplaces, and tobacco smoke. CO levels tend to be higher indoors, especially during colder months when heating systems are in use and pollution becomes trapped near the ground under a layer of warm air.

The health effects of CO are primarily due to its ability to reduce oxygen delivery to the body's organs and tissues. Exposure to CO can cause chest pain, reduced exercise capacity, and other cardiovascular issues, especially in individuals with heart disease. Even healthy individuals can experience adverse effects from high levels of CO exposure, including vision problems, reduced manual dexterity, and difficulty performing complex tasks.

To mitigate CO pollution, the U.S. EPA sets and reviews standards for CO levels in outdoor air under the Clean Air Act. These standards help state, tribal, and local agencies ensure that CO is maintained at safe levels. Additionally, CO emission reductions are considered a potential strategy to mitigate the effects of global warming, as CO contributes to climate change through the formation of ozone, a potent climate change gas.

Nitrogen oxides

In terms of human health, nitrogen oxides can irritate the airways in the human respiratory system and aggravate respiratory diseases, especially asthma. Prolonged exposure to high levels of nitrogen dioxide can cause chronic lung disease and increase susceptibility to respiratory infections. Nitrogen dioxide can also affect the senses, such as reducing a person's ability to smell. Additionally, high levels of nitrogen dioxide are harmful to vegetation, damaging foliage and reducing crop yields.

To address the issue of nitrogen oxide pollution, the EPA works with state, local, and tribal governments to develop plans and implement rules to reduce emissions and improve air quality.

Greenhouse gases

The most abundant greenhouse gases are water vapour, carbon dioxide, methane, nitrous oxide, and ozone. Water vapour accounts for about half of the greenhouse effect, while carbon dioxide is responsible for around three-quarters of global warming. The primary source of carbon dioxide emissions is the burning of fossil fuels, with additional contributions from agriculture and industry. Methane emissions, which cause most of the remaining global warming, originate from agriculture, fossil fuel production, waste, and other sources.

Human activities, particularly since the Industrial Revolution, have significantly increased the concentration of greenhouse gases in the atmosphere. This has led to an enhanced greenhouse effect, resulting in global warming and climate change. The increased concentration of greenhouse gases has also led to a cooling of the upper atmosphere, as it is much thinner and has fewer gas molecules.

To address the issue of climate change caused by greenhouse gases, efforts should focus on reducing emissions and transitioning to renewable energy sources. Phasing out fossil fuels, such as coal, oil, and gas, and adopting renewable alternatives like solar and wind power, can help mitigate the impact of greenhouse gases on the Earth's atmosphere and climate.

Additionally, certain fluorinated gases, such as hydrofluorocarbons, perfluorocarbons, and sulfur hexafluoride, are synthetic greenhouse gases with high global warming potentials. These gases are emitted from various household, commercial, and industrial applications. While they are present in smaller concentrations, they are extremely effective at trapping heat and contribute significantly to global warming.

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