Air Pollutants: What's The Deadliest?

Air pollution is a pressing issue that poses a significant threat to both human health and the planet. According to the World Health Organization (WHO), nearly seven million deaths worldwide each year are attributed to indoor and outdoor air pollution. With 99% of people breathing air that exceeds the recommended limits for pollutants, it is crucial to understand the various types of air pollutants and their impacts. From smog and soot to greenhouse gases and particulate matter, air pollutants have diverse compositions, sources, and effects on human well-being and the environment. Among the range of harmful pollutants, ultrafine particles (UFPs) stand out as one of the most dangerous due to their minuscule size, making them easily inhalable and capable of reaching various organs through the bloodstream. As the awareness of air pollution grows, transitioning to cleaner fuels, improving industrial processes, and adopting renewable energy sources emerge as essential strategies to combat this global challenge.

Particulate matter: Dirt, dust, smoke, and liquid droplets can cause respiratory issues

Particulate matter, or PM, refers to a mixture of solid particles and liquid droplets found in the air. These particles can include dust, dirt, soot, or smoke, and they vary widely in size, shape, and chemical composition. Some particles are large or dark enough to be visible, while others are microscopic and can only be detected with an electron microscope. These particles can be made up of inorganic ions, metallic compounds, elemental carbon, organic compounds, and compounds from the earth's crust.

PM is a common proxy indicator for air pollution and has been shown to have negative health impacts. The World Health Organization estimates that PM air pollution contributes to approximately 800,000 premature deaths each year, making it the 13th leading cause of mortality worldwide. The health effects of PM are complex and vary depending on the specific composition and size of the particles.

PM10 and PM2.5 are two commonly used categories of particulate matter, defined by their diameter. PM10 refers to particles with a diameter of 10 microns or less, which can be inhaled into the lungs and induce adverse health effects, particularly in people with pre-existing respiratory conditions. Short-term exposures to PM10 have been linked to the worsening of respiratory diseases, including asthma and chronic obstructive pulmonary disease (COPD).

PM2.5, on the other hand, refers to fine particulate matter with diameters of 2.5 microns or less. These particles pose the greatest risk to health and are associated with the highest proportion of adverse health effects related to air pollution. Long-term exposure to PM2.5 has been linked to premature death, particularly in individuals with chronic heart or lung diseases, and reduced lung function growth in children.

Particulate matter can come from both natural and anthropogenic sources. Natural sources include volcanoes, fires, dust storms, and aerosolized sea salt. Manmade sources include combustion in mechanical and industrial processes, vehicle emissions, tobacco smoke, and indoor activities such as cooking and burning wood or incense.

Reducing particulate matter pollution is crucial for protecting public health. Various policies and technologies have been implemented to mitigate PM emissions, including clean technologies in industries, improved waste management practices, the promotion of clean household energy solutions, and the development of clean modes of power generation and transportation.

Carbon monoxide: A harmful gas released from burning fossil fuels

Carbon monoxide is a harmful, colourless, odourless, and toxic gas that is released when fossil fuels are burned. It is a significant contributor to air pollution, which the World Health Organization (WHO) considers a public health emergency.

The burning of fossil fuels, such as coal, oil, and gas, is a major source of carbon monoxide emissions. Fossil fuels are formed over millions of years from the burial of photosynthetic organisms. For example, plants on land form coal, while plankton in the oceans primarily form oil and natural gas. When these fossil materials are burned, the carbon stored within them is released back into the atmosphere as carbon dioxide at a significantly faster rate than it took to be buried. This contributes to the greenhouse effect, leading to global warming and climate change.

Carbon monoxide is particularly harmful to human health due to its toxic nature. It is a product of incomplete combustion, often occurring in enclosed or poorly ventilated spaces, such as homes or vehicles. Incomplete combustion happens when there is not enough oxygen for the fuel to burn completely, resulting in the formation of carbon monoxide instead of carbon dioxide. This toxic gas can have severe health consequences, including respiratory illnesses and, in extreme cases, death. According to the WHO, around 2.4 billion people are exposed to dangerous levels of household air pollution, primarily from the use of polluting open fires or inefficient stoves for cooking.

Moreover, carbon monoxide emissions contribute to the formation of smog, particularly during hot weather. Smog is a mixture of smoke and fog, often seen hanging over cities, and is a significant health hazard. It is composed of various pollutants, including carbon monoxide, nitrogen oxides, and particulate matter. Prolonged exposure to smog can lead to respiratory illnesses and aggravate existing respiratory conditions.

To mitigate the harmful effects of carbon monoxide and other air pollutants, a transition to cleaner energy sources and improved energy efficiency is necessary. This includes embracing renewable energy sources, such as solar, wind, and hydropower, and implementing policies that support sustainable land use, cleaner household energy, and energy-efficient housing. By reducing carbon monoxide emissions and other air pollutants, we can improve air quality, protect public health, and contribute to the mitigation of climate change.

Ground-level ozone: One of the most widespread health threats, regulated by the EPA

Ground-level ozone is a major air pollutant and one of the most widespread health threats. It is a colourless gas composed of three oxygen atoms (O3) and is formed by chemical reactions between oxides of nitrogen and volatile organic compounds. This occurs when pollutants emitted by cars, power plants, industrial boilers, refineries, and chemical plants react in the presence of sunlight. Ground-level ozone is distinct from the beneficial stratospheric ozone, which occurs naturally in the upper atmosphere and shields us from harmful ultraviolet radiation.

Ground-level ozone is harmful to human health, particularly on hot sunny days when it can reach unhealthy levels. People with asthma, children, older adults, and those who are active outdoors are most at risk from breathing air containing ozone. Ozone can cause constriction of the muscles in the airways, trapping air in the alveoli and damaging the airway lining through inflammation. This can lead to increased hospital admissions and even premature death, as seen in studies conducted across the world.

The US Environmental Protection Agency (EPA) has designated ground-level ozone as one of six common air pollutants regulated by the Clean Air Act. The EPA establishes national air quality standards to protect public health and works with states and tribes to improve air quality in areas that do not meet these standards. The Air Quality Index (AQI) is a tool used by the EPA to communicate about outdoor air quality and health, with each category corresponding to a different level of health concern.

To protect public health, the EPA has implemented rules to reduce emissions of pollutants that form ground-level ozone. These include national and regional regulations to help state and local governments meet the Agency's air quality standards. Additionally, the EPA provides educational resources such as the Air Quality Guide for Ozone, which offers detailed information on protecting health when ozone levels are unhealthy.

Ground-level ozone pollution is a serious issue due to its widespread presence and harmful effects on human health. The EPA's efforts to regulate and reduce ground-level ozone through various initiatives and guidelines are crucial steps towards protecting public health and improving air quality.

Nitrogen dioxide: A common air pollutant, particularly from vehicles and industrial facilities

Nitrogen dioxide (NO2) is a gaseous air pollutant composed of nitrogen and oxygen. It is formed when fossil fuels such as coal, oil, methane gas (natural gas), or diesel are burned at high temperatures. NO2 is a major component of traffic-related air pollution and is commonly found in large cities worldwide. The burning of fuels in vehicles, power plants, and industrial facilities are significant sources of NO2 pollution.

NO2 is a harmful pollutant that poses several health risks. Inhalation is the primary route of exposure, and it can cause a range of issues, particularly affecting the lungs. Scientific evidence suggests that exposure to NO2 may cause asthma in children and increase the likelihood of hospital admissions. Additionally, elevated levels of NO2, along with particulate matter and sulfur dioxide, have been associated with adverse health effects.

Road traffic, including vehicles such as cars, trucks, and buses, is the principal outdoor source of nitrogen dioxide. The combustion of fossil fuels in vehicle engines releases NO2 into the atmosphere, contributing to air pollution in urban areas. Traffic control measures, such as emission regulations and congestion pricing, have been implemented in some cities to reduce NO2 emissions from vehicles.

Industrial facilities, including power plants and factories, also contribute significantly to NO2 pollution. The burning of fuels for energy generation and industrial processes releases large amounts of NO2 into the air. In some cases, industrial facilities may release accidental high concentrations of gaseous nitrogen dioxide, which can cause eye irritation upon contact.

While indoor sources of NO2 are generally lower than outdoor sources, certain activities can increase indoor NO2 levels. The use of gas-, wood-, oil-, kerosene-, and coal-burning appliances, such as stoves, ovens, and heaters, can elevate NO2 concentrations indoors, particularly if they are unflued or poorly maintained. Tobacco smoke is another indoor source of NO2.

Nitrogen dioxide pollution is a global issue, with high exposures observed in various regions, including North Africa, the Middle East, high-income countries, and Central and Eastern Europe. However, sustained policy actions and technological advancements have led to a rapid decline in NO2 exposures over time, particularly in high-income countries.

Health impacts: Air pollution causes strokes, heart disease, lung cancer, and respiratory issues

Air pollution is a major public health issue, causing around 6.5 million deaths and 167.3 million disability-adjusted life years (DALYs) in 2015. It is a significant cause of morbidity and mortality, with almost the entire global population (99%) breathing air that exceeds the recommended limits and contains high levels of pollutants.

One of the most concerning health impacts of air pollution is its contribution to strokes. While the relative risk for an individual is small, the widespread exposure to air pollution means that the absolute risk at the population level is significant. Epidemiological studies have found a strong association between air pollution and strokes, with the strength of this association being more pronounced in low and middle-income countries. The underlying biological mechanisms are still a subject of ongoing research, but it is clear that air pollution poses a serious threat to cardiovascular health.

Air pollution also increases the risk of heart disease. Tiny pollution particles in the air, regardless of whether one lives in a densely populated city or a less populated area, can have detrimental effects on the heart. The American Heart Association highlights the growing medical evidence linking air pollution and heart disease, emphasizing that exposure to air pollution can lead to significant cardiovascular problems.

Furthermore, air pollution is linked to an increased risk of lung cancer. Particle pollution, which includes a mix of tiny solid and liquid particles such as acids, organic chemicals, metals, soil, and dust particles, has been identified as a risk factor. These fine particles can penetrate deep into the lungs and are associated with the development of lung cancer. The World Health Organization (WHO) has concluded that particulate matter in the air causes lung cancer, and medical professionals have also attributed cases of lung cancer to air pollution exposure.

In addition to lung cancer, particle pollution has been linked to a range of respiratory issues. These include respiratory symptoms such as cough, phlegm, and wheezing, as well as inflammation of the airways and lungs, bronchial hyperreactivity, acute phase reaction, respiratory infections, and hospitalizations. Particle pollution can also exacerbate asthma symptoms and increase the risk of asthma attacks. It can interfere with the growth and function of the lungs, leading to decreased lung function growth in children and chronic loss of pulmonary function in adults.

Overall, the health impacts of air pollution are far-reaching and pose a significant threat to public health worldwide.

Frequently asked questions