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
Thailand?
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 (http://www.dmr.go.th).
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.
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.
Inside of a crater in the Philippines with deadly
toxic
emissions. (Photo by Claus Rink)
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)
