Natural Pollution: Unseen Sources Revealed

While human activities are the most common cause of air pollution, natural sources such as wind-blown dust, wildfires, and volcanoes can also be significant contributors. These natural sources emit harmful substances into the Earth's atmosphere, including particulates and biological molecules, which can have detrimental effects on humans, animals, plants, and the entire ecosystem. For example, dust from places without vegetation, methane gas emitted by cows and cattle, and radon gas from radioactive decay are all examples of pollution stemming from natural sources. While natural sources of pollution may not always create ongoing air pollution problems, they can sometimes be significant, affecting air quality and causing adverse health impacts.

Wildfires

The smoke from wildfires is a mix of hazardous air pollutants, including particulate matter (PM), NO2, ozone, aromatic hydrocarbons, and lead. PM2.5 from wildfire smoke is of particular concern as it is associated with premature deaths in the general population and can cause and exacerbate diseases of the lungs, heart, brain, nervous system, skin, gut, kidney, eyes, nose, and liver. It has also been linked to cognitive impairment and memory loss.

The risk of wildfires increases in extremely dry conditions, such as droughts, heatwaves, and high winds, which are becoming more frequent due to climate change. As a result, the fire season is starting earlier, ending later, and causing more extreme wildfire events in terms of acres burned, duration, and intensity. These fires can have significant impacts on the environment, property, livestock, and human mortality and morbidity, especially when they occur near populated areas.

The impact of wildfires extends beyond the immediate area affected by the fire. Wildfire emissions can cross borders and even continents, as seen in the 2023 wildfire season in North America, where smoke was transported as far as southern Greenland and Western Europe. The chemical species released during wildfires contribute to the degradation of air quality and are typically co-emitted with greenhouse gases, leading to a vicious cycle of climate change, wildfires, and air pollution that negatively affects human health, ecosystems, and agriculture.

To break this cycle, it is essential to address both air pollution and climate change together. Implementing measures such as early warning systems, containing the release of hazardous materials, and restoring primary care services can help reduce the magnitude of physical and human costs associated with wildfires.

Volcanoes

The conversion of sulphur dioxide to sulphuric acid has the most significant impact on climate change. The aerosols increase the reflection of radiation from the Sun back into space, cooling the Earth's lower atmosphere or troposphere. Several eruptions during the past century have caused a decline in the average temperature at the Earth's surface for up to three years. For example, the 1991 eruption of Mount Pinatubo injected a 20-million-ton sulphur dioxide cloud into the stratosphere, causing a decline in temperature of up to 1.3 degrees Fahrenheit for three years.

Volcanic eruptions can also lead to short-term global cooling due to the presence of sulphur dioxide, ash, and other particles in the air and stratosphere, which reflect solar energy instead of letting it into the Earth's atmosphere. The 1991 eruption of Mount Pinatubo, for instance, cooled the Earth's surface by about 0.5 degrees Celsius a year later. Similarly, the 1815 eruption of Mount Tambora produced enough ash and aerosols to cancel summer in Europe and North America in 1816.

Wind-blown dust

To address the issue of wind-blown dust, various dust control methods are employed in different regions. For example, in Benton County, guidelines and forms for submitting a dust control plan are available, and the Benton Clean Air Agency assists with dust control strategies and plans. Additionally, Reasonably Available Control Methods (RACM) are recommended to minimize dust emissions. These include using water or chemical dust suppressants, minimizing activities during periods of high winds, using covered containers for dusty materials, and vegetating or mulching dusty areas.

Overall, wind-blown dust is a significant contributor to air pollution, particularly in dry and disturbed areas. It can have negative impacts on human health, especially for vulnerable individuals such as young children, older adults, and those with respiratory conditions. To mitigate its effects, dust control measures and regulations are implemented in affected regions.

Radon gas from radioactive decay

Radon is a naturally occurring, radioactive, noble gas that is produced by the radioactive decay of uranium, which is found in all rocks and soils. It is a chemical element with the symbol Rn and atomic number 86. It is a colourless, odourless, and tasteless gas that is not detectable by human senses alone.

Radon is one of the leading causes of lung cancer. It is estimated to cause between 3% to 14% of all lung cancers in a country, depending on the national average radon level and smoking prevalence. The risk of lung cancer increases by about 16% per 100 Bq/m3 increase in long-time average radon concentration. Radon is much more likely to cause lung cancer in people who smoke. Smokers are estimated to be 25 times more at risk from radon than non-smokers.

Radon is released from the ground into the air, where it decays and produces further radioactive particles. These particles are deposited on the cells lining the airways, where they can damage DNA and potentially cause lung cancer. Outdoors, radon quickly dilutes to very low concentrations and is generally not a problem. However, radon concentrations are higher indoors and in areas with minimal ventilation, such as mines, caves, and water treatment facilities.

Radon can enter buildings through cracks in the floors or walls, gaps around pipes or cables, and drains or spaces around cables and pipes. This is particularly common in temperate and cold regions due to the pressure-driven flow of gas, which arises because buildings are normally at a slight underpressure compared to the pressure under the building. Radon levels are usually higher in basements, cellars, and living spaces in contact with the ground.

There are several methods to reduce radon levels in buildings, including increasing under-floor ventilation, installing a radon sump system in the basement, sealing floors and walls, and improving the ventilation of the building. Passive systems of mitigation can reduce indoor radon levels by more than 50%.

Methane gas from animal digestion

Methane gas is a significant contributor to global warming and climate change. It is produced as a by-product of the digestive process of ruminant animals, such as cattle, buffalo, sheep, goats, and camels. This process, known as enteric fermentation, occurs in the rumen, the large fore-stomach of these animals, where microbial fermentation breaks down their feed into digestible products. The methane produced is then exhaled by the animals.

Livestock manure is a major source of methane emissions, particularly when stored in uncovered tanks or lagoons. The lack of oxygen in these storage facilities increases methane emissions. One way to mitigate this is through anaerobic digestion, a process that involves collecting methane from manure stored in closed vessels. The captured methane can be used as a source of energy, comparable to natural gas, for generating heat and electricity.

The advantages of methane capture from animal digestion include the production of a useful end-product and the reduction of odor potential from well-digested livestock waste. However, there are also several disadvantages to consider. Methane digesters are large and expensive, requiring effective insulation, airtight construction, and a source of heat. They also demand a very high level of management, as they can be sensitive to environmental changes, and any biological upset may take months to correct. Additionally, methane is challenging to store and can form an explosive mixture if exposed to air.

Overall, while methane gas from animal digestion contributes to pollution and global warming, it can also be captured and utilized as a valuable energy source.

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