Volcanoes: The Unseen Air Pollution Culprits

Volcanic eruptions can have a significant impact on air quality, causing a range of environmental and health concerns. When a volcano erupts, it releases a variety of gases and particles into the atmosphere, including lava, small rocks, steam, water vapour, carbon dioxide, sulphur dioxide, hydrogen sulphide, carbon monoxide, hydrogen chloride, and hydrogen fluoride. These gases and particles can travel thousands of kilometres from the eruption site, affecting air quality across broad areas. The health hazards associated with volcanic air pollution include eye, skin, nose, and throat irritation, as well as potential long-term effects, such as silicosis, caused by the inhalation of silica particles found in volcanic ash. Additionally, volcanic gases can contribute to global warming and climate change, with carbon dioxide acting as a greenhouse gas, while sulphur dioxide can lead to global cooling.

Volcanic ash can cause eye, skin, nose and throat irritation

Volcanic eruptions emit a mixture of gases and particles into the air, including ash and sulphur dioxide, which can cause air pollution. Volcanic ash particles can be so fine that they are breathed into the deep lungs, causing respiratory issues. The irritation caused by volcanic ash is not limited to the lungs, however, and can also affect the eyes, skin, nose, and throat.

Volcanic ash can cause eye irritation, with affected individuals feeling as though there are foreign particles in their eyes. In addition to eye irritation, volcanic ash can also cause skin irritation, particularly if the ash is acidic. Symptoms of skin irritation from volcanic ash include reddening and irritation of the skin, as well as secondary infections due to scratching. While skin irritation from volcanic ash is not common, some individuals may experience these symptoms.

The nose and throat can also be irritated by volcanic ash. Coarser particles of ash deposited in the upper airways can cause nasal and throat irritation, as well as a sore throat and coughing. Smaller particles deposited in the thoracic region, including the bronchial tubes and bronchioles, can lead to acute respiratory issues such as asthma and bronchitis.

The most hazardous volcanic eruptions are those that generate fine-grained ash with a high content of free crystalline silica. This mineral can cause silicosis, a chronic lung disease that results in scarring and impaired lung function. While silicosis is primarily an occupational disease associated with occupations such as stone-cutting and construction, volcanic eruptions can mass-produce crystalline silica in lava domes. For example, the Soufrière Hills volcano in Montserrat, West Indies, erupted from 1995 to 2010 and generated ash composed of up to 25% crystalline silica, prompting the UK government to implement controls to minimise population exposure.

Volcanic gases can travel thousands of kilometres and settle as smog

Volcanic gases and fine particles can travel thousands of kilometres, polluting the atmosphere and reducing air quality. These gases can rise up to 10 kilometres (6.2 miles) or more into the air and then blow vast distances from the volcano, affecting air quality across a broad area. This cloud of volcanic gases settles over the land like smog and is known as "vog", short for "volcanic smog".

Vog is created when volcanic gases, including sulphur dioxide (SO2), combine and interact chemically in the atmosphere with oxygen, moisture, dust, and sunlight. This process can take anywhere from minutes to days. Vog is a visible haze composed of gas and a suspended mixture of tiny liquid and solid particles, called aerosol. The aerosol in vog is primarily made up of sulfuric acid and other sulfate compounds, with small amounts of toxic metals, including selenium, mercury, arsenic, and iridium.

SO2 is a poisonous gas that irritates the skin, eyes, nose, throat, and mucous membranes. It can cause respiratory distress, especially during moderate physical activity, as it penetrates deeply into the airway. In the absence of strong winds, SO2 emitted by volcanoes can accumulate in the air, reaching levels that exceed Federal health standards. Vog can induce asthma attacks, especially in adolescents, and impair the upper respiratory tract's ability to remove other potentially harmful particles.

While volcanic gases play a role in air pollution and global warming, their contribution is relatively small compared to human activities. According to the U.S. Geological Survey, volcanoes emit about 200 million tons of carbon dioxide (CO2) annually, while automotive and industrial activities release approximately 24 billion tons of CO2 worldwide. Thus, volcanic gases comprise less than one percent of greenhouse gas emissions compared to human endeavours.

Volcanic gases can cause respiratory distress

Sulphur dioxide (SO2) is a poisonous gas released by volcanoes that can irritate the skin, eyes, nose, throat, and mucous membranes. During moderate physical activity, SO2 penetrates deeply into the airway and can cause respiratory distress in some individuals. In the absence of strong winds, SO2 emissions can accumulate in the air, reaching levels that exceed health standards. This has occurred more than 85 times in Hawaii's Volcanoes National Park due to emissions from the Kilauea Volcano.

Volcanic smog, or "vog," is formed when SO2 and other volcanic gases interact chemically with oxygen, moisture, dust, and sunlight. This smog contains highly acidic aerosols composed primarily of sulfuric acid and other sulfur-related compounds. These aerosols are small enough to be breathed deep into the lungs, irritating the lungs and mucous membranes and affecting their function. Studies indicate that elevated levels of these acidic particles can induce asthma attacks and impede the upper respiratory tract's ability to remove other harmful particles.

In addition to SO2, volcanoes release other harmful gases such as hydrogen sulfide, carbon monoxide, and carbon dioxide. Hydrogen sulfide is a colorless, flammable gas with a strong odour. At higher concentrations, it can cause irritation of the upper respiratory tract and, during prolonged exposure, pulmonary edema. Carbon dioxide typically becomes diluted to low concentrations and is not life-threatening. However, in low-lying areas, it can reach higher concentrations and pose serious risks to humans and animals. Breathing air with more than 3% CO2 can lead to dizziness, headaches, increased heart rate, and difficulty breathing. At concentrations above 15%, carbon dioxide can cause unconsciousness and death.

Volcanic activity can lead to acid rain

Sulphur dioxide is a major contributor to acid rain. During periods of sustained volcanic eruption, large amounts of SO2 are released into the atmosphere. This gas can irritate the skin, eyes, nose, and throat, causing respiratory distress in some individuals. When SO2 combines with water vapour in the air, it forms sulphuric acid. This chemical reaction occurs as the volcanic gases interact with oxygen, moisture, dust, and sunlight. The resulting sulphuric acid droplets are then carried by winds, leading to the occurrence of acid rain.

The formation of "vog", or volcanic smog, is another consequence of volcanic emissions. Vog is created when SO2 and other volcanic gases chemically interact, forming a visible haze composed of gas and aerosol particles. These aerosol particles, primarily made of sulphuric acid and other sulfate compounds, are small enough to penetrate deep into the human lung, posing serious health risks. The presence of vog can induce asthma attacks and impair the upper respiratory tract's ability to remove potentially harmful particles.

In addition to sulphuric acid, volcanic activity also releases toxic metals into the atmosphere. Studies have detected the presence of selenium, mercury, arsenic, and iridium in volcanic air pollution. These toxic metals contribute to the overall air pollution and can have further detrimental effects on both human health and the environment. The release of these toxic substances, along with the formation of acid rain, highlights the significant impact of volcanic activity on air pollution and its potential consequences for ecosystems and human populations.

While volcanic activity can lead to acid rain and air pollution, it is important to note that the overall contribution of volcanic emissions to atmospheric CO2 levels is relatively small compared to human activities. According to the U.S. Geological Survey, volcanic emissions account for less than one percent of annual CO2 emissions, with human automotive and industrial activities being much more significant contributors.

Volcanoes contribute to global warming

Volcanic eruptions release a mixture of gases and particles into the air, including ash, sulphur dioxide, and carbon dioxide. These emissions can spread thousands of kilometres beyond the eruption site, affecting air quality across a broad area.

The warming effect of volcanic carbon dioxide emissions is counteracted by the release of sulphur dioxide, which forms a shield in the atmosphere that reflects heat energy away from the Earth, thereby slowing the effects of global warming and climate change. This cooling influence is particularly notable in the case of large eruptions, such as Mount Pinatubo in 1991, which caused a significant dip in global temperatures in the following year.

While the overall impact of volcanoes on modern global climate is considered to be negligible, they can cause short-term temperature fluctuations. For example, the eruption of Mount Pinatubo led to a decrease of almost 0.6°C in average global temperatures over the following 15 months. Similarly, the Bardarbunga eruption in Iceland disrupted global transport and is predicted to have a cooling effect on Central Europe and a warming effect on Northern Europe.

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