Natural Air Pollution: Causes And Concerns

Air pollution is a pressing issue that affects the health of people and the planet. While human activity is a major contributor, natural sources also play a role in polluting the air. Natural air pollution refers to the release of hazardous substances into the atmosphere from non-human-made sources, such as wildfires, volcanic eruptions, and decomposing organic matter. These natural sources can emit harmful gases and particles, contributing to the overall decline in air quality and posing risks to human health and the environment.

Wildfires

During a wildfire, concentrations of particles in the air can increase significantly, to the point that particle pollution is visible to the naked eye. The fine particulate matter (PM2.5) is the main component of wildfire smoke, and it has been linked to various health issues. The association between PM2.5 and heart and lung health effects is well-documented in scientific literature. Larger, more frequent, and intense wildfires contribute to reduced air quality for people living nearby or downwind.

The health effects of wildfire smoke exposure have been studied extensively, and evidence suggests that it has similar health impacts to fine particles from other sources. When air quality deteriorates due to wildfire smoke, it is recommended to stay indoors with windows and doors closed to reduce exposure. Using air conditioning with the recirculate setting turned on can also help prevent outdoor smoke from entering the home. Installing high-efficiency filters and using air cleaners can further reduce indoor particle levels.

Wildfire smoke is a significant contributor to air pollution and has detrimental effects on human health. The fine particulate matter it releases can have severe consequences, especially for those with pre-existing health conditions. Taking precautions, such as staying indoors and using air filtration systems, can help mitigate the impact of wildfire smoke exposure.

Volcanic eruptions

Sulphur dioxide (SO2) is a major pollutant emitted by volcanoes. During volcanic eruptions, large amounts of SO2 are injected into the stratosphere. This gas can cause global cooling by reflecting radiation from the Sun back into space, leading to a decline in the average temperature at the Earth's surface. In 1980, the eruption of Mount St. Helens released approximately 10 million tons of SO2 in just 9 hours, resulting in an international pollution event. The prevailing winds carried the ash cloud across the United States in 3 days and around the world in 15 days.

Carbon dioxide (CO2) is another significant gas released during volcanic eruptions. While it is lighter than other expelled gases, it is heavier than air, allowing it to remain close to the Earth's surface. High concentrations of CO2 can have detrimental effects on the Earth's biosphere and can cause unconsciousness and death in humans and other animal species if inhaled in concentrations above 30%. However, it's important to note that present-day volcanic emissions of CO2 are significantly lower than those caused by human activities.

In addition to SO2 and CO2, volcanic eruptions also release hydrogen fluoride (HF). This highly reactive gas is toxic, especially at high concentrations. HF is absorbed into volcanic ash particulates, increasing its dispersal rate and the likelihood of it settling on the Earth's surface. When HF-laden ash particles come into contact with the biosphere, they can impair various elements within it.

Volcanic ash itself is another pollutant that can have significant impacts on the environment and human health. Ash particles can irritate the airways and, when mixed with sulphuric and other acids, can further enhance their irritant properties. The United States Geological Survey has noted that downwind from volcanic vents, acid rain and air pollution pose persistent health problems during volcanic activity.

Windblown dust

The health effects of windblown dust are significant. Particles with a diameter of 10 microns or less (PM10) can pass through the throat and nose and enter the lungs. High concentrations of PM10 are commonly found downwind of loose or disturbed soils during wind events. These particles can lead to respiratory and cardiovascular disorders, conjunctivitis, skin irritations, and other health issues. Additionally, windblown dust can transport pathogens, toxic substances, and allergens, further exacerbating its impact on human health.

The long-range transport of windblown dust can also affect air quality over large distances. For example, dust generated in the Sahara Desert can travel across the Atlantic Ocean and impact the air quality in the Southeast United States. Similarly, the Saharan Air Layer transports African dust to the Americas, affecting air quality and human health in the Western Hemisphere.

To estimate windblown dust emissions and their impact on air quality, models such as CMAQ (Community Multiscale Air Quality Modeling System) are used. CMAQ takes into account various factors, including wind speed, surface roughness, soil moisture, vegetation coverage, soil type, and air density, to provide a comprehensive understanding of dust generation and its impact on atmospheric conditions and human health.

Radon gas

Radon is a naturally occurring, radioactive gas that is both colourless, odourless, and tasteless. It is produced from the natural radioactive decay of uranium, which is found in all rocks and soils. Radon can also be found in water. Radon escapes from the ground into the air, where it decays and produces further radioactive particles.

Radon is the second leading cause of lung cancer after smoking. When radon is outdoors, it quickly dilutes to very low concentrations and is generally not a problem. However, when radon gets trapped indoors, it may exist in dangerous amounts. Radon can enter buildings through cracks in the floors or at floor-wall junctions, gaps around pipes or cables, small pores in hollow-block walls, cavity walls, or sumps or drains. It can also be released from building materials, such as lightweight concrete with alum shale, phosphogypsum, and Italian tuff.

Radon dissolved in drinking water is released into indoor air. However, epidemiological studies have not confirmed an association between consumption of drinking water containing radon and an increased risk of stomach cancer. Normally, a higher radon dose is received from inhaling radon compared with ingestion. The WHO guidelines for drinking water quality recommend that screening levels for radon in drinking water be set based on the national reference level for radon in the air.

Radon occurs naturally in significant quantities in three different chemical variations or isotopes, but only two of these present a risk. Radon-222, a product of uranium-238 or radium-226 decay, is the most dangerous. It has a long decay rate, so it can accumulate indoors, and it is quite common due to high concentrations of uranium-238 in the ground in some regions. Radon-219 is not considered dangerous.

Volcanic ash

Volcanic eruptions release lava, small rocks, steam, gases, and ash into the atmosphere. Ash is a type of particulate matter air pollution, and it can be spewed into the air and carried for miles downwind of the eruption. This can have serious health implications for humans. As per the World Health Organization (WHO), air pollution is responsible for nearly seven million deaths globally each year.

Particle pollution from volcanic ash can persist in the environment for many days after the eruption has ended and can become airborne again during cleanup operations. This prolongs the period of exposure and increases the potential health risks for those in the vicinity. It is recommended that individuals with sensitive airways, such as those with lung diseases, children, and older adults, avoid cleanup duties if possible. Those engaged in cleanup should wear protective gear, including N-95 masks or respirators, goggles, and protective clothing.

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