Day 3: Volcanic Eruptions

In accordance to the recent Mount Merapi disaster that have affected many locals and Malaysian students studying in nearby Universities, I would like to share something on Disaster.

Disaster is another main topic that we're going to learn in Block 4.2: Health System and Disaster. Because of the recent Merapi eruptions, I thought I can share something bout Disaster Medicine and Volcanoes Disasters.

First, what criteria defined 'disaster'? Is it the number of victims involved? 

According to definition by WHO, disaster is known as:

1. A serious disruption of the functioning of a community or a society causing widespread human, material, economic or environmental losses which exceed the ability of the affected community or society to cope using its own resources (ISDR). 
2. Situation or event, which overwhelms local capacity, necessitating a request to national or international level for external assistance (CRED). 
3. A term describing an event that can be defined spatially and geographically, but that demands observation to produce evidence. It implies the interaction of an external stressor with a human community and it carries the implicit concept of non-manageability. The term is used in the entire range of risk-reduction activities, but it is possibly the least appropriate for response.

And according to the United Nations Disaster Management Training Programme (UNDMTP), the definition of disaster is:

                "A disaster is a serious disruption of the functioning of a society, causing widespread human, material or environmental losses which exceed the ability of the affected society to cope using only its own resources."

In the mid-1980s, Disaster Medicine evolved from the union of (1) disaster management and (2) emergency medicine.

All disasters follow a cyclical pattern known as the disaster cycle, which describes 4 reactionary stages:

• Preparedness
• Response
• Recovery
• Mitigation/prevention

Ok... Enough with the topics on disaster. I will share this in my future posts dedicated especially to Disaster Medicine.

Right now, I'll share information of volcanic eruptions, in conjunction to Mount Merapi disaster during late October-early November...

Volcanoes

Mount Merapi

Volcanoes are responsible for the formation of much of the Earth’s surface. They are typically hills or mountains that surround a vent leading to reservoirs of molten rock below the Earth’s surface.  There are four primary types of volcanoes:

1. Cinder Cone
2. Composite
3. Shield
4. Lava Dome

There are also levels of volcanic activity intensity that are categorized by a Volcanic Explosivity Index (VEI). This is a composite, semi-quantitative estimate of a volcano’s eruptive power. It includes the quantitative measurements of variables such as the eruption cloud height and amount of ejected tephra. It combines those quantitative values with qualitative eruption observations to place an eruption on a scale from 0 to 8. Each increase in value of one represents a 10-fold increase in eruption intensity. The violence or force of a volcanic eruption determines the characteristic of injuries produced. A volcanic eruption is the ejection of gases and solid material from a vent or hole in the Earth’s surface. 

I quote this from: Sparks et. al., 1997:

              "If one cubic meter of magma containing 5% water is brought from below the surface where it is under extreme pressure to atmospheric pressure as it exits the volcano during eruption, it will expand to 670 m of water vapour, gases, and particulates. This is the primary force behind explosive volcanic eruptions." 

A variety of physical and chemical hazards are associated with volcanic eruptions. Lava is responsible for very few fatalities. The flow is often slow and can be easily avoided. Pyroclastic flows are responsible for the most deaths. A pyroclastic flow is a mass of hot volcanic ash, lava fragments, and gases that erupts from a volcano and moves rapidly down its slope at speeds of up to a few hundred miles per hour, depending on the conditions. Pyroclastic flows can incinerate, burn, and asphyxiate people. They are extremely destructive and fatal to nearly all life in the area through which they travel. The temperatures in a pyroclastic flow may be as high as 600° to 900°C, causing severe, if not fatal, burns.

Another common cause of volcanic eruption–related fatalities is tephra. Tephra includes all of the solid fragments of magma and volcanic rock ejected from a volcano during an eruption.

Tephra fragments:

• Less than 2 mm are termed ash
• 2- to 64-mm fragments are called lapilli
• Fragments larger than 64 mm are often called lava bombs or blocks 

Volcanic gases also pose a potential health threat. Water vapour is the most abundant volcanic gas released, followed by carbon dioxide and sulphur dioxide. Volcanic emissions may also include smaller amounts of hydrogen sulphide, hydrogen, carbon monoxide, hydrogen chloride, hydrogen fluoride, helium, and trace amounts of other gases. The volcanic gases that pose the greatest threat to people, animals, and agriculture are sulphur dioxide, carbon dioxide, and hydrogen fluoride.

1. Sulphur dioxide may produce an irritant effect in the upper and lower airways, on mucosal surfaces, in the eyes, and on the skin. It may also produce acid rain, which may react with zinc in galvanizing on sheet metal roofs and release heavy metals into drinking water and catchments.
2. Hydrogen fluoride also induces an irritant response in the upper and lower respiratory tracts, but it is of greatest risk to livestock secondary to ingestion. Ash becomes impregnated with hydrogen fluoride, and upon ingestion, the fluoride produces fluorosis and death of the animal. Fluorosis is a theoretical risk to a human population post-eruption, but it can be avoided by cleaning ash off of food before ingestion and checking the fluoride levels of local drinking water.
3. Carbon dioxide is the second most common gas released during volcanic activity. Carbon dioxide is odourless, colourless, and heavier than air, thus it will collect in low-lying areas. Breathing air with a carbon dioxide concentration greater than 20% to 30% can rapidly induce unconsciousness and death through asphyxiation.
4. An important consideration is hydrogen sulphide. It is a highly toxic gas that is relatively dense and may collect in depressions and low-lying areas. Hydrogen sulphide gives off a “rotten egg” odour and can cause eye and upper respiratory tract irritation, pulmonary oedema with prolonged exposure, and death through cellular asphyxiation.

[Personal note: N-95 helps filter 95% of polluted air! Therefore, its the safest mask so far! Though some might complain we look funny with it (eg: look like monkey). =P But look on the bright side, it protect us from those harmful particles in the air... =)]

In addition, lahars are often formed. Lahars are flash floods or mudslides with heavy debris from a volcano. They can cause massive destruction for many miles and leave behind large volumes of sediment. The debris complicates the flooding by making it more destructive and more difficult to clean up during recovery.

Health Effects

There are a variety of health hazards produced by volcanic activity. Some are direct hazards such as the rocks, ash, gases, and heat from an eruption. The larger solid debris can cause ballistic injuries for miles, whereas the gases can cause respiratory damage. Pyroclastic flows and lava flows can cause thermal injuries, whereas the carbon dioxide and debris from an eruption can cause asphyxiation. Other hazards result from secondary events triggered by a volcano; including earthquakes, flooding, landslides, lightning, and even tsunamis.

The volcanic ash or tephra is comprised of very small rock and glass particles. They are hard, abrasive, and acidic. These materials can cause illness and injury through inhalational, mucosal, and direct dermal exposure. The severity of inhalational injuries depends upon the duration of exposure, the dose received, and the physical and chemical characteristics of the tephra. The smaller particles will travel deeper into the lungs and the acidity of the particles will have an immediate irritant effect. The presence of crystalline silica in the particles may pose additional risks. Inhalation of the ash can cause respiratory distress and extended exposures can cause fibrogenic pulmonary effects. These problems are more likely to occur in those with pre-existing conditions like asthma, bronchitis, and emphysema. Particular attention should be given to limiting exposures of infants, the elderly, and those with chronic cardiovascular and respiratory conditions.

Microscopic picture of ash particles

Gas and acidic particles can pose a variety of health risks. Emissions of sulphur dioxide (SO₂), hydrogen chloride (HCl), hydrogen fluoride (HF), hydrogen sulphide (H₂ S), radon, and other gases can occur during eruptions or through daily degassing activities near a volcano. Some chemical risks are unique to specific volcanic scenarios. For example, laze is a hydrochloric acid mist that results from lava meeting sea water. When lava enters sea water, it vaporizes it so quickly that a series of chemical reactions occurs emitting a white plume that consists of hydrochloric acid and seawater. It is called lava haze, or laze.

Top 10 morbidity and mortality effects from volcanic ash:

1. Runny nose and nasal irritation.
2. Dry coughing and throat irritation.
3. Exacerbation of existing respiratory problems (e.g., severe bronchitis or asthmatic symptoms).
4. Exposure to respirable free crystalline silica particles leading to silicosis (scarring of the lungs and impairment of function).
5. Painful, itchy, or bloodshot eyes.
6. Corneal abrasions or scratches.
7. Acute conjunctivitis.
8. Minor skin irritations.
9. Crush injury and trauma from collapsing structures due to the weight of the ash on structures.
10. Traumatic injuries from motor vehicle accidents resulting from poor driving conditions.

Other than health effects, volcanic eruptions caused many other problems.

Following the initial eruption, the falling ash can interrupt a variety of critical infrastructures. The power supplies may be interrupted by ash blocking air intake systems and insulators at power facilities. This can have a serious impact on area residents depending upon home medical equipment and other critical equipment. It can also reduce the effectiveness of public communication during the crisis because many will be without telephones, radios, and televisions. Other infrastructures including the drinking water supply and wastewater treatment can be compromised. Drinking water from open reservoirs can experience heavy ash contamination that is difficult to manage with the existing infrastructure. There is also an excessive demand on the water supply during clean-up that can lead to shortages. The wastewater systems are also vulnerable. Both sewage and storm water systems can become clogged as ash accumulates as a heavy mud in the system. It can also compromise pumping systems and other machinery. The infrastructure damage resulting from volcanic ash can have a substantial impact on morbidity and mortality through the interruption of critical infrastructures such as these.

Transportation may also be disrupted. The ash can obscure road signs and create slick roads. It also creates poor visibility. The ash is sometimes so thick that even brake lights and tail lights are not visible.

More detailed information on the effects of volcanic eruptions can be found in:

http://volcanoes.usgs.gov/ash/index.html

For your additional information as you wish! ^_^

REFERENCES:

1. Disaster Medicine 3rd Edition, Chapter 79: Volcanic Eruption; Elsevier Mosby 2006
2. Disaster and Public Health: Planning and Response, Chapter 12: Volcanoes; Elsevier Mosby 2009
3. http://www.geo.mtu.edu/volcanoes/hazards/primer/pyro.html
4. http://www.who.int/hac/about/definitions/en/