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This document has been written as a joint initiative between
IVHHN and the United States Geological Survey (USGS)
and is a sponsored by the Interanational Association of Volcanology
and Chemistry of the Earth's Interior (IAVCEI),
the Cities and Volcanoes Commission (CaV)
and the New Zealand Institute of Geological and Nuclear Sciences
(GNS).
The pamphlet version of this document can be downloaded here as a PDF file or you can download the unformatted pdf version.
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Volcanic ash is composed of fine particles of fragmented
volcanic rock (less than 2 mm diameter). Volcanic ash is often
hot very close to the volcano but is cool when it falls at
greater distances. It is formed during volcanic explosions,
from avalanches of hot rock that flow down the side of volcanoes,
or from red-hot liquid lava spray. Ash varies in appearance
depending upon the type of volcano and the form of the eruption.
Thus, it can range in colour from light grey to black and
can vary in size from being like grit to being as fine as
talcum powder. Airborne ash blocks out sunlight, reducing
visibility and sometimes causes complete darkness during day
light. Eruptions can also generate thunder and lightning from
friction between the fine, airborne particles which can be
localised above the volcano or accompany large ash plumes
as they move downwind.
Large ash deposits can incorporate into existing soils and
become the future topsoil of a volcanic region. The fertility
of the soils around many volcanoes is due to old ash deposits.
This beneficial effect of volcanism outweighs, over time,
the hazards from infrequent eruptions, so fertile volcanic
areas are often densely populated.
Freshly fallen ash particles can have acid coatings which
may cause irritation to the lungs and eyes. This acid coating
is rapidly removed by rain, which may then pollute local water
supplies. Acidic ash can also damage vegetation, leading to
crop failure.
In most eruptions, volcanic ash causes relatively few health
problems, but generates much anxiety. People can be more fearful
of the health hazards of volcanic ash and gases than of the
risk of dying from more major hazards, such as pyroclastic
flows. However, ash falls can affect very wide areas around
volcanoes and may cause major disruption to normal living.
Medical services can expect an increase in the number of
patients with respiratory and eye symptoms during and after
an ash fall event (see IVHHN guidelines on advice to the medical
community).
Effects of ash on health may be divided into several categories:
respiratory effects, eye symptoms, skin irritation and indirect
effects:
In some eruptions, ash particles can be so fine that they
are breathed deep into the lungs. With high exposure, even
healthy individuals will experience chest discomfort with
increased coughing and irritation. Common acute (short-term)
symptoms include:
- Nasal irritation and discharge (runny nose).
- Throat irritation and sore throat, sometimes accompanied
by dry coughing.
- People with pre-existing chest complaints may develop
severe bronchitic symptoms which last some days beyond exposure
to ash (for example, hacking cough, production of sputum,
wheezing, or shortness of breath).
- Airway irritation for people with asthma or bronchitis;
common complaints of people with asthma include shortness
of breath, wheezing and coughing.
- Breathing becomes uncomfortable.
In rare circumstances, long-term exposure to fine volcanic
ash may lead to serious lung diseases. For these diseases
to occur, the ash must be very fine, contain crystalline silica
(for the disease silicosis to occur) and people must be exposed
to the ash in high concentrations over many years. Exposure
to crystalline silica in volcanic ash is typically of short
duration (days to weeks), and studies suggest that the recommended
exposure limits (similar in most countries) can be exceeded
for short periods of time for the general population.
People suffering from asthma or other lung problems such
as bronchitis and emphysema, and severe heart problems are
most at risk.
The fine ash particles irritate the airways and cause them
to contract, making breathing more difficult in people who
already have lung problems. The fine dust also causes the
lining of the airways to produce more secretions which can
cause people to cough and breathe more heavily. Asthma sufferers,
especially children who may be heavily exposed to the ash
when they play, may suffer bouts of coughing, tightness of
the chest and wheezing. Some people who have never knowingly
had asthma before, may experience asthma symptoms following
an ashfall, especially if they go outdoors in the ash and
over-exert themselves.
The development of respiratory symptoms from the inhalation
of volcanic ash depends on a number of factors. These include
the concentration of particles in the air, the proportion
of fine particles in the ash, the frequency and duration of
exposure, the presence of crystalline silica and volcanic
gases or aerosols mixed with the ash, and meteorological conditions.
Existing health conditions and the use of respiratory protective
equipment will also influence the symptoms experienced.
Eye irritation is a common health effect as pieces of grit
can cause painful scratches in the front of the eye (corneal
abrasions) and conjunctivitis. Contact lens wearers need to
be especially aware of this problem and leave out their lenses
to prevent corneal abrasion from occurring.
Common symptoms include:
- Eyes feel as though there are foreign particles in them.
- Eyes become painful, itchy or bloodshot.
- Sticky discharge or tearing.
- Corneal abrasions or scratches.
- Acute conjunctivitis or the inflammation of the conjunctival
sac that surrounds the eyeball due to the presence of ash,
which leads to redness, burning of the eyes, and photosensitivity.
While not common, volcanic ash can cause skin irritation
for some people, especially if the ash is acidic. Symptoms
include:
- Irritation and reddening of the skin.
- Secondary infections due to scratching.
As well as the short and long term health risks, indirect
impacts on health of large ash falls must also be considered.
These mainly arise from the secondary consequences of ashfall,
for example:
- Effects on roads. The reduction in visibility from
airborne ash alone may cause accidents, however this danger
is compounded by ash covering roads. Not only are road markings
covered up, but thin layers of either wet or dry ash are
very slippery, reducing traction. Thick deposits of ash
may make roads impassable, cutting off communities from
basic supplies.
- Effects on power. Ashfall can lead to power cuts,
these may have implications for health due to lack of heating
or other infrastructural requirements that depend on electricity.
Wet ash is conductive, so it is essential that safe operating
procedures are stringently followed when cleaning power
supply equipment.
- Effects on water supplies. Contamination of water
supplies or blockages of water supply equipment may occur.
Small, open water supplies such as domestic water tanks
with roof drainage are especially vulnerable to volcanic
ashfall, and even small quantities of ash may cause problems
for potability. While the risk of toxicity is low, the pH
may be reduced or chlorination inhibited.
- Effects on sanitation (waste water disposal etc).
The temporary disablement of municipal sanitation systems
may lead to increased risk of disease in affected areas.
- Risk of roof collapse. 1) Roofs can collapse from
the weight of ash, resulting in injury or death for those
underneath. 2) There is a danger of roof collapse whilst
clearing ash from roofs due to the increased load of a person
on an already overloaded roof. 3) In several eruptions people
have died after falling from their roofs while cleaning
up ash.
- Other serious risks to life in large eruptions include
flooding (from heavy rainfall triggered by large ash clouds),
and the formation of lahars or volcanic mudflows in heavy
rain, when large quantities of ash on slopes can be mobilised
and engulf communities.
- If the ash is coated in hydrofluoric acid, the ash can
be very toxic to grazing animals who eat the ash which has
settled on grass.
- Limit driving. Immediately after an ash fall, even
a light one, driving conditions, visibility and air quality
can be dramatically affected, especially by the re-suspension
of ash by traffic. Rainfall has a sudden but temporary effect
in improving air quality until the ash dries out again.
We recommend that, following an ash fall, you refrain from
driving and stay indoors if possible. If you must drive,
maintain a large distance from the vehicle in front of you
and drive slowly.
- Reduce ash in your home. Keep all doors and windows
closed whenever possible.
- Drinking water. After light ash fall it is usually
safe to drink water contaminated with ash, but it is better
to filter off the ash particles before drinking. However,
ash increases the chlorine requirement in disinfected surface-collected
water which, therefore, can be microbiologically unsafe
to drink. Ash will usually make drinking water unpalatable
before it presents a health risk. The safest way to ensure
your well-being is to stock up on water prior to the event
- collect enough drinking water for at least a week (one
gallon per person per day).
- Home-grown food. Ash-covered vegetables grown in
fields are safe to eat after washing with clean water.
- Protection.Those undertaking clean-up operations
should always wear effective dust masks (see IVHHN Recommended
Masks document). If no approved mask is
available, a fabric mask improvised from cloth will filter
out the larger ash particles which may contribute to throat
and eye irritation. Dampening the fabric with water will
improve its effectiveness. People with chronic bronchitis,
emphysema, and asthma are advised to stay inside and avoid
unnecessary exposure to ash.
- Eye protection.In fine-ash environments, wear goggles
or corrective eyeglasses instead of contact lenses to protect
eyes from irritation.
- Clean up.Lightly water down the ash deposits before
they are removed by shovelling, being careful not to excessively
wet the deposits on roofs, causing excess loading and danger
of collapse. Dry brushing can produce very high exposure
levels and should be avoided. Hosing uses large quantities
of water and may cause water shortages in heavily-populated
areas.
Children face the same hazards from the suspension of ash
as other age groups, but their exposure may be increased because
they are physically smaller and are less likely to adopt reasonable,
prudent, preventive measures to avoid unnecessary exposure
to ash. We recommend you take the following precautions:
- Keep children indoors if possible.
- Children should be advised against strenuous play or running
when ash is in the air, since exertion leads to heavier
breathing, drawing small particles more deeply into the
lungs.
- Communities in heavy ash fall areas may wish to organize
day-care programs to free parents for clean-up tasks.
- If children must be outdoors when ash is present in the
air, they should wear a mask, (preferably one approved by
IVHHN). Many masks, however, are designed to fit adults
rather than children.
- Small children may, at times, swallow ash and evidence
suggests that ingestion of small amounts of ash is not a
hazard to the health of children and adults. If children
must be outdoors when ash is present in the air, they should
wear a mask, (preferably one approved by IVHHN). Many masks,
however, are designed to fit adults rather than children.
- Children should be particularly prevented from playing
in areas where ash is deep on the ground or piled up.
The United States Geological Survey provides information
on effects of ash on health from historical eruptions and
further information on potential chronic diseases caused by
crystalline silica and volcanic ash. http://volcanoes.usgs.gov/ash/health/index.html
- "Resident's guide to the state of the Soufrière Hills
volcano following the scientific assessment of July 1998
and the dangers of volcanic ash with tips for cleaning up
ash". The Emergency Department, St John's, Montserrat, West
Indies. August 1998.
- "Volcanic ashfall. How to be prepared for an ashfall."
USGS, CVO, Vancouver, Washington. November 1999.
- "Ash particles and home clean-up problems; advice from
the University of Idaho." Mt. St. Helens Technical Information
Network. Bulletin 7. Federal Coordinating Network, May 1980.
- "Health criteria for reoccupation of ashfall areas in
Montserrat." Report to the Dept for International Development,
London. Baxter, P. J. and Maynard, R. L., October 1998.
- "The mitigation of ashfall damage to public facilities:
lessons learned from the 1980 eruption of Mount St. Helens."
Washington. Federal Emergency Management Agency, Region
X, Wm. H. Mayer, Regional Director. 1984.
- "Volcanic ash, effects and mitigation strategies." http://volcanoes.usgs.gov/ash/
- "Volcanic Hazards: A Sourcebook on the Effects of Eruptions"
Blong, R. J, Academic Press, Sydney. pp484.1984.
- "Mount St Helens Technical Information Network Bulletin"
14, 1980.
- "Preventive Health Measures in Volcanic Eruptions." Baxter,
PJ. American Journal of Public Health 76 (1986) Supplement:
84-90.
Acknowledgements
This document was written by a panel of IVHHN expert members
chaired by Dr Claire Horwell (University of Cambridge, UK)
and Dr Peter Baxter (University of Cambridge, UK) and by the
United States Geological Survey. IVHHN is grateful to the
Leverhulme Trust, UK, for funding associated meetings.
IVHHN is also grateful to the following people for reviewing
and commenting on the document:
Dr Bob Maynard, Department of Health, UK Government, London,
UK.
Dr Phil Weinstein, School of Population Health, University
of Western Australia.
Steve Brantley, Hawaiian Volcano Observatory, United States
Geological Survey, USA.
Dr David Johnston, Institute of Geological and Nuclear Sciences,
Wellington, New Zealand.
Scott Barnard, Canterbury University, Christchurch, New Zealand.
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