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Icelandic eruption: Apocalypse now? Part 3


Icelandic eruption: Apocalypse now? Part 3

Volcano eruptions and health effects

Dr. Claus Rink, Geoscientist and
Special correspondent of Pattaya Mail
and Chiang Mai Mail

What is happening in and around

In Thailand, volcanic rocks are distributed in most parts, but only very old volcanoes give us the good feeling of being safe. One old volcanic region is around Chiang Mai (Chiang Mai-Chiang Rai Volcanic Belt consist of basic lavas) and Koh Chang. The Koh Chang-Tak-Chiang Khong Volcanic Belt is the most abundant in exposed volcanic rocks in northern Thailand. A very popular volcano is near Khorat, because a famous cultural point in Isaan is the Khmer temple of Phanom Rung, at the top of an old volcano. For the reader who wants to know more about the geology of Thailand, please check the interesting pages of Geological Survey Division, Department of Mineral Resources (

In the surrounding countries of China, Myanmar and Vietnam we also find some volcanoes, which don’t want to work anymore. The Tengchong volcanic district, located in southern China near the border with Burma (Myanmar), was active during five periods. An unconfirmed explosive eruption took place in 1609, and there are unconfirmed reports of eruptions in the Qing Dynasty (1644-1911). The Tengchong district is the site of active geothermal fields, the largest and highest temperature of which is the Rehai geothermal field. More than 20 hydrothermal eruptions have occurred at the Rehai geothermal field since 1993. In Burma we find the Lower Chindwin and the Singhu Plateau, but we are not well informed about them.

Inside of a crater in the Philippines
with deadly toxic emissions. (Photo by Claus Rink)

But only within 1000 miles of us, we have very dangerous volcanoes in Indonesia and Philippines. Please remember, the actual volcanic eruption in Iceland is 2500 km away from Middle Europe.

The Philippines is situated in the so-called Ring of Fire, an arc of fault lines circling the Pacific Basin that is prone to frequent earthquakes and volcanic eruptions. Mayon’s most violent eruption, in 1814, killed more than 1,200 people and devastated several towns. Its last major eruption was in 1993. Since then, it has remained restless, emitting ash and spewing lava.

Although Indonesia leads the world in both the number and the global proportion of eruptions in each of the last four eruptive characteristics (fatalities, destruction of land, mudflows, and tsunamis), the Philippines show substantially higher figures when each characteristic is considered as a percentage of that same region’s total number of eruptions. Fully 13% of Philippine eruptions have resulted in fatalities, and 22% in damage, with the notable Taal and Mayon volcanoes having particularly high human impact.

Mayon volcano, which rises to 2,462 meters, is the Philippines’ most active volcano. The structurally simple volcano has steep upper slopes averaging 35-40 degrees that are capped by a small summit crater. The historical eruptions of this basaltic-andesitic volcano date back to 1616 and range from strombolian to basaltic plinian, with cyclical activity beginning with basaltic eruptions, followed by longer term andesitic lava flows. The volcano’s last eruption was in 2009.

Dangerous for millions of people

Millions of people are potentially exposed to volcanic gases worldwide, and exposures may differ from those in anthropogenic air pollution. A systematic literature review found few primary studies relating to health hazards of volcanic gases. SO2 and acid aerosols from eruptions and degassing events were associated with respiratory morbidity and mortality but not childhood asthma prevalence or lung function decrements. Accumulations of H2S and CO2 from volcanic and geothermal sources have caused fatalities from asphyxiation. Chronic exposure to H2S in geothermal areas has been associated with increases in nervous system and respiratory diseases. Some impacts were on a large scale, affecting several countries (e.g., Laki fissure eruption in Iceland in 1783-84).

Plate tectonics with the “Ring of fires”.
Thailand is encased by the Indian and Pacific fire ring.

Volcanoes pose a threat to almost half a billion people; today there are approximately 500 active volcanoes on Earth, and every year there are 10 to 40 volcanic eruptions. Volcanic eruptions produce hazardous effects for the environment, climate, and the health of the exposed persons, and are associated with the deterioration of social and economic conditions.

Along with magma and steam (H2O), the following gases surface in the environment: carbon dioxide (CO2) and sulphur dioxide (SO2), carbon monoxide (CO), hydrogen sulphide (H2S) carbon sulphide (CS), carbon disulfide (CS2), hydrogen chloride (HCl), hydrogen (H2), methane (CH4), hydrogen fluoride (HF), hydrogen bromide (HBr) and various organic compounds, as well as heavy metals (mercury, lead, gold).

Their unfavourable effects depend on the distance from a volcano, on magma viscosity, and on gas concentrations. The hazards closer to the volcano include pyroclastic flows, flows of mud, gases and steam, earthquakes, blasts of air, and tsunamis. Among the hazards in distant areas are the effects of toxic volcanic ashes and problems of the respiratory system, eyes and skin, as well as psychological effects, injuries, transport and communication problems, waste disposal and water supplies issues, collapse of buildings and power outage.

Further effects are the deterioration of water quality, fewer periods of rain, crop damages, and the destruction of vegetation. During volcanic eruptions and their immediate aftermath, increased respiratory system morbidity has been observed as well as mortality among those affected by volcanic eruptions.

Unfavourable health effects could partly be prevented by timely application of safety measures.

Volcanic gas can be harmful to humans, animals, plants, agricultural crops, and property. Usually, the hazards from volcanic gases are restricted to the areas immediately surrounding volcanic vents and fumaroles and to low spots on the flanks of volcanoes. But these hazards can sometimes persist for long distances downwind from a volcano.

Health hazards

Health hazards can range from minor to life threatening. Exposure to acid gases such as sulfur dioxide, hydrogen sulfide, and hydrochloric acid can damage eyes and mucous membranes along with the respiratory system and, under extreme conditions, can lead to death. The toxicity of carbon monoxide is well known, although it is rarely abundant enough to cause serious problems.

Working around the White Island Volcano and its dangerous gases. (Photo by Claus Rink)

One of the most serious hazards occurs when volcanoes emit large quantities of carbon dioxide. Carbon dioxide is heavier than air and collects in low spots, displacing air in these locations. Hundreds of people have died of carbon dioxide asphyxiation near volcanoes in the past two decades, most of them in Cameroon, Africa, and in Indonesia.

Volcanic gases can also severely damage vegetation. Direct exposure to concentrated volcanic gas or long-term exposure to dilute volcanic gas has a lethal effect on most types of foliage.

Fume clouds from volcanoes also contain water droplets in which acid gases have dissolved. These droplets eventually fall to earth as acid rain. Utility lines, farm equipment, cars, and other metal objects corrode when exposed to volcanic gases or acid rain. Persistent acid rain causes galvanized nails or lead solder in water catchment systems to deteriorate and release heavy metals into drinking water.

Hydrofluoric acid gas emitted from a volcano can attach itself to ash particles. When these particles fall to earth, there can be serious consequences.

Volcanoes spew hot, dangerous gases, ash, lava, and rock that are powerfully destructive. People have died from volcanic blasts.

The most common cause of death from a volcano is suffocation.

Volcanic eruptions can result in additional threats to health, such as floods, mudslides, power outages, drinking water contamination, and wildfires. Health concerns after a volcanic eruption include infectious disease, respiratory illness, burns, injuries from falls, and vehicle accidents related to the slippery, hazy conditions caused by ash. When warnings are heeded, the chances of adverse health effects from a volcanic eruption are very low.

Exposure to ash can be harmful. Infants, elderly people, and people with respiratory conditions such as asthma, emphysema, and other chronic lung diseases may have problems if they breathe in volcanic ash. Ash is gritty, abrasive, sometimes corrosive, and always unpleasant. Small ash particles can abrade (scratch) the front of the eye. Ash particles may contain crystalline silica, a material that causes a respiratory disease called silicosis.

Most gases from a volcano quickly blow away. However, heavy gases such as carbon dioxide and hydrogen sulfide can collect in low-lying areas. The most common volcanic gas is water vapor, followed by carbon dioxide and sulfur dioxide. Sulfur dioxide can cause breathing problems in both healthy people and people with asthma and other respiratory problems. Other volcanic gases include hydrogen chloride, carbon monoxide, and hydrogen fluoride. Amounts of these gases vary widely from one volcanic eruption to the next.

Although gases usually blow away rapidly, it is possible that people who are close to the volcano or who are in the low-lying areas downwind may be exposed to levels that may affect health.

Active region of Merapi, Indonesia.
(Photo by Claus Rink)