Air Pollution: Beyond The Haze

Air pollution is responsible for an estimated seven million deaths worldwide every year. According to the World Health Organization (WHO), 99% of people currently breathe air that exceeds the recommended guideline limits for pollutants, with those living in low- and middle-income countries suffering the most. Air pollution is caused by various sources, including household activities, industrial processes, and transportation. While particulate matter (PM), carbon monoxide (CO), ozone (O3), nitrogen dioxide (NO2), and sulfur dioxide (SO2) are among the most well-known air pollutants, there are other forms of air pollution that contribute to the degradation of air quality and pose significant health risks.

Particulate matter

PM is classified according to size, with the two major types being PM10 and PM2.5. PM10 refers to coarse inhalable particles that are 10 micrometres or less in diameter. These particles can irritate the eyes, nose, and throat and are often found in dust from roads, farms, dry riverbeds, construction sites, and mines. PM2.5, on the other hand, refers to fine inhalable particles that are 2.5 micrometres or less in diameter. These particles are more dangerous as they can penetrate deep into the lungs and even enter the bloodstream. They are primarily emitted from sources such as construction sites, unpaved roads, fields, smokestacks, and fires.

The health effects of particulate matter are significant. Exposure to PM has been linked to increased risk of cancer, lung and cardiovascular disease, and decreased life expectancy. Long-term exposure to PM2.5, in particular, has been associated with premature death, especially in individuals with chronic heart or lung diseases. It is also the main cause of reduced visibility (haze) in many places, including national parks and urban areas.

In addition to PM10 and PM2.5, there are other types of particulate matter that are of concern. Ultrafine particles, with a diameter of less than or equal to 0.1 micrometres, are not regulated by the EPA but are included in the WHO Global Air Quality Guidelines due to their potential health impacts. Lead fumes, with a size of less than 0.5 micrometres, are another important pollutant found in many diesel fuels. Certain particulates, such as asbestos fibres, are known carcinogens, posing serious risks to human health.

Ground-level ozone

The formation of ground-level ozone is primarily driven by human activities that emit pollutants into the atmosphere. Major sources of these pollutants include motor vehicle exhaust, industrial emissions, power plants, refineries, and chemical plants, and the combustion of fossil fuels. The concentration of ground-level ozone is typically higher during the summer months due to increased heat and sunlight, which facilitate the chemical reactions that produce ozone. However, it can also reach unhealthy levels during the colder months, particularly in urban environments.

Toxic air pollutants

The U.S. Environmental Protection Agency (EPA) has classified 188 pollutants as hazardous. Some of the major sources of outdoor toxic air pollutants include emissions from coal-fired power plants, industries, refineries, and vehicles. Certain industries produce specific toxins, such as ethylene oxide leaks from medical equipment sterilization facilities. Chemical releases from accidents at industrial sites or during hazardous material transport can also release air toxics.

Indoor air quality is also affected by HAPs from tobacco smoke, building materials like asbestos, and consumer products like cleaning supplies and air fresheners. Radon, a radioactive gas that can accumulate in poorly ventilated homes, is another example of an indoor toxic air pollutant. It is the leading cause of lung cancer among non-smokers.

Particulate matter (PM), composed of inhalable particles like sulphate, nitrates, and black carbon, is another form of toxic air pollution. PM can vary in size, with larger particles primarily originating from natural sources like pollen, sea spray, and wind-blown dust, while finer particles are derived from combustion processes in power generation, industries, and vehicles.

The Clean Air Act requires the EPA to regulate hazardous air pollutants from industrial facilities, and efforts are being made to reduce emissions from these sources.

Radon and radioactive pollutants

Radon is a colourless, odourless, and tasteless radioactive gas that is produced by the natural radioactive decay of uranium found in rocks and soils. It can also be found in water sources, such as groundwater in uranium-rich geological areas. Radon escapes from the ground and decays in the air, producing further radioactive particles. While radon quickly dilutes to very low concentrations outdoors, it can accumulate in enclosed spaces such as buildings, mines, and tunnels, where it poses a significant health risk.

Radon is a major source of ionizing radiation to which the general population is exposed. It enters buildings through cracks in the floors, walls, or foundations, gaps around pipes or cables, and drains. Radon levels are typically higher in basements or ground-level floors of homes, particularly in areas with inadequate ventilation. The concentration of radon indoors can vary between countries, buildings, and even within the same building from day to day and hour to hour.

The health risks associated with radon exposure are primarily linked to the inhalation of its decay products. These radioactive particles can attach to aerosol particles or deposit on the cells lining the airways, potentially causing DNA damage and increasing the risk of lung cancer. According to studies, lung cancers attributable to radon can range from 3% to 14%, making it the leading cause of lung cancer among non-smokers.

To mitigate the risks associated with radon, various corrective actions can be taken. These include preventing radon from entering indoor spaces through isolation and air pressure manipulation, as well as improving ventilation rates. Many national building codes now include preventing radon accumulation in newly constructed houses, and the WHO has assembled a radon database to monitor national radon policies and regulations.

In summary, radon is a radioactive gas that poses a significant health risk, particularly in enclosed spaces with inadequate ventilation. Its presence in indoor environments contributes to public exposure to ionizing radiation, and its decay products can lead to lung cancer. Through a combination of prevention, mitigation strategies, and regulatory efforts, the risks associated with radon exposure can be effectively managed.

Fossil fuels and biomass

Biomass, often touted as a "'clean'" energy alternative, also contributes significantly to air pollution. Burning wood, charcoal, and other biological materials releases pollutants similar to those from burning fossil fuels, including particulate matter (PM), nitrogen oxides (NOx), carbon monoxide (CO), and hazardous air pollutants (HAPs). In some cases, biomass burners emit even more pollution than fossil-fuelled facilities, worsening air quality in surrounding communities.

The use of biomass for cooking and heating is prevalent in low-income countries, leading to indoor air pollution. Inefficient burning methods can release harmful pollutants like carbon monoxide and particulate matter. However, modern wood-burning stoves and fuel-efficient cooking stoves can help mitigate these issues and reduce deforestation rates.

While biomass sources capture carbon dioxide (CO2) through photosynthesis, burning biomass releases CO2, a greenhouse gas. Nonetheless, biomass is considered carbon-neutral because the CO2 released during combustion is offset by the CO2 absorbed by the source plants as they grow. Biofuels, derived from biomass, are generally cleaner-burning than petroleum fuels, contributing to a net reduction in CO2 emissions.

Both fossil fuels and biomass contribute to air pollution through the release of various pollutants. The environmental and health impacts of these pollutants are significant, underscoring the importance of exploring cleaner and more sustainable energy alternatives.

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