Nature's Air Pollution: What, Why, And How?

Air pollution is a significant environmental health hazard that affects human health and the planet. It is the fourth-largest risk factor for early death worldwide, causing approximately 7 million premature deaths annually. While most air pollution is caused by human activities such as burning fossil fuels and industrial processes, natural sources also contribute to air pollution. These natural sources include wildfires, volcanic eruptions, windblown sand or dust, and radon gas emissions from the Earth's surface. Additionally, natural processes like increasing temperatures can intensify air pollution by increasing the amount of contaminants released from polluted soil and water into the atmosphere.

Forest fires

Wildfire smoke also contains carbon monoxide, a colorless and odorless gas that is common during the smoldering stages of a fire and in close proximity to the fire. Carbon monoxide reduces oxygen delivery to the body's organs and tissues and can lead to headaches, nausea, dizziness, and even death in high concentrations.

In addition to carbon monoxide, wildfires spread other harmful emissions, including nitrogen oxides and hazardous air pollutants. Wildfire smoke has been linked to Valley fever, a type of fungal infection, and it is believed that other disease-causing microbes may be present in the smoke. The health impact of wildfire smoke becomes more widespread as the smoke spreads across the country, exposing millions of people.

Climate change has contributed to the increase in forest fires by causing higher spring and summer temperatures and earlier spring snow-melt, resulting in drier soils and an increased likelihood of drought and longer wildfire seasons. Once wildfires ignite, hot and dry conditions allow the fire to burn more intensely and for longer.

Volcanic ash

Volcanic eruptions can spew ash, a type of particulate matter air pollution, into the air for miles downwind of the eruption. This ash can be transported by wind for thousands of miles from a volcano, affecting communities that live hundreds of miles away from the eruption. Volcanic ash can be especially harmful to children, older adults, and people with lung diseases such as asthma and chronic obstructive pulmonary disease (COPD), which includes chronic bronchitis and emphyseema. Exposure to volcanic ash can trigger asthma attacks and cause wheezing, coughing, and respiratory irritation in individuals with sensitive airways. Volcanic ash has also been linked to eye and upper airway irritation, as well as minor to major damage to vehicles and buildings, water supply contamination, and disruption to sewage, electrical, and vegetation systems.

The unique characteristics of volcanic ash, which can vary across eruptions and volcanoes, present challenges for conducting health impact assessments (HIAs). The short-term nature of most volcanic eruptions, typically lasting from days to months, makes it difficult to establish long-term cohort studies. The composition of particulate matter from natural sources, such as volcanoes, may also differ significantly from that of urban air pollution, resulting in distinct toxicity profiles. While there is limited data on the health effects of volcanic ash, short-term studies suggest that it poses a probable respiratory hazard.

To address the health risks associated with volcanic ash inhalation, it is recommended to avoid driving in affected areas and to keep windows and vents closed if driving is necessary. Air conditioning should only be used in the "recirculate" setting. Ordinary dust masks are not effective in filtering out the fine particles of volcanic ash, and specialized masks with true HEPA filters or an N-95 rating are recommended for protection. It is important to refrain from outdoor exercise if the air quality forecast is poor, and individuals with lung diseases should consult their physicians before using a mask.

Windblown dust

The health and safety risks associated with windblown dust are significant. The particles, known as aeolian dust, can be transported over long distances, affecting regions far from the source. These particles have been linked to respiratory diseases such as asthma and bronchitis, as well as cardiovascular issues. In addition, windblown dust can carry toxic substances and pathogens, including dustborne bacteria like Salmonella, which can contaminate food crops. The impact of windblown dust on transportation safety is also notable, with reduced visibility leading to hazardous driving conditions and an increased risk of accidents.

Dust storms, a more intense form of windblown dust, can result in high levels of particulate matter in the air, specifically PM10 and PM2.5. While PM10 is more commonly associated with aeolian dust, both types of particles can have detrimental health effects. Saharan dust storms, for instance, have been linked to increased mortality and morbidity in Europe and the Eastern Mediterranean. The negative impacts of windblown dust on health, transportation, and infrastructure can result in substantial economic losses, with dust storms in the Middle East and North Africa (MENA) region causing an estimated loss of 13 billion USD in GDP annually.

To mitigate the hazards of windblown dust, various control methods are recommended, especially in regions with high erosion potential. These methods include using covered containers for dusty materials, employing dust collection equipment, and implementing soil conservation practices in agricultural areas. By raising awareness about the risks of windblown dust and implementing preventive measures, public health and safety can be better protected.

Overall, windblown dust is a natural contributor to air pollution that can have far-reaching consequences for human health, the environment, and economic activities. Understanding the impacts of windblown dust and taking proactive measures to minimize its effects are crucial for safeguarding public well-being and reducing its harmful consequences.

Radon gas

Radon is a colourless, odourless, and tasteless gas that occurs in nature in three different chemical variations or isotopes. However, only two of these are considered dangerous. Radon-222, a product of Uranium-238 or Radium-226 decay, is the most harmful. It has a long decay rate, allowing it to accumulate indoors, and it is prevalent due to the varying concentrations of Uranium-238 and Radium-226 in the ground and certain building materials. Radon-220, a product of Thorium-232 decay, is the other dangerous isotope, and it often acts with Radon-222 to contribute to radiation exposure for the public. On the other hand, Radon-219 is not considered a threat.

Radon is a naturally occurring radioactive gas that is released from bedrock material and passes through the soil. It is produced in the ground from the breakdown of uranium in rock and soil. Uranium in soil or rock breaks down to form radium, which then turns into radon gas. It then tends to dilute in the air, so outdoors, radon is harmless to human health. Radon escapes from the ground into the air, where it decays and produces further radioactive particles. As we breathe, these particles are deposited on the cells lining the airways, where they can damage DNA and potentially cause lung cancer. Radon is the second leading cause of lung cancer in the United States, after smoking, causing about 21,000 lung cancer deaths each year.

Radon can enter buildings through cracks in the floors, walls, foundation, basement, or crawl spaces, as well as gaps in construction, windows, drains, or spaces around cables and pipes. It can also be found in water, although epidemiological studies have not confirmed a link between drinking water containing radon and an increased risk of stomach cancer. Radon levels are usually higher in basements, cellars, and living spaces in contact with the ground, but considerable concentrations can also be found above the ground floor. The highest levels are found in places like mines, caves, and water treatment facilities. Radon concentrations can vary significantly between adjacent buildings and within a building from day to day and hour to hour.

The World Health Organization (WHO) has developed a radon database to monitor national radon policies and regulations. WHO also provides technical support to its member states and offers guidance and advice on health issues related to radon and its sources.

Wildfires

On the other hand, fine particles are the main pollutant emitted by wildfire smoke, comprising approximately 90% of the total particle mass. These fine particles, with diameters of 2.5 µm or smaller, can easily penetrate homes and buildings, increasing indoor particle concentrations. This is particularly concerning as these particles can be inhaled deeply into the lungs and may even enter the bloodstream. The health effects of fine particle exposure are well documented and include respiratory and cardiovascular issues, as well as potential long-term consequences for children and pregnant women.

The impact of wildfire smoke on air quality and public health is a growing concern, especially with the increasing frequency and intensity of wildfires. During wildfire events, it is recommended that individuals stay indoors with windows and doors closed to reduce exposure to harmful particle pollution. Central-ducted air conditioning systems should be set to "on" to ensure constant air filtration, and high-efficiency filters can be installed to improve indoor air quality. It is also advised to avoid outdoor activities, especially exertive ones, when the Air Quality Index (AQI) reaches unhealthy levels.

The scientific understanding of the health consequences of wildfire smoke exposure is largely derived from research on particle pollution in urban settings. However, the unique characteristics of wildfire smoke, including the presence of ultrafine particles, may require further investigation to fully comprehend its specific health impacts. Nonetheless, the current body of knowledge highlights the significant risks associated with wildfire-induced air pollution, particularly for vulnerable individuals such as those with pre-existing health conditions, children, pregnant women, and individuals of lower socioeconomic status.

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