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An introduction to the aims and purpose of the Gas and Aerosol Guidelines
website is given here, as well as further information on international
guideline levels and the units used in the website. A brief review of
safety procedures currently implemented by volcanologists and volcano
observatories is also provided.
Gas and aerosol hazards are associated with all volcanic activity, from
diffuse soil gas emissions to plinian eruptions. The volcanic emissions of most
concern are SO2, HF, sulphate (SO42-), CO2, HCl and
H2S, although, there are
other volcanic volatile species that may have human health implications,
including mercury and other metals. Since 1900, there have been at least 62
serious volcanic-gas related incidents. Of these, the gas-outburst at Lake Nyos
in 1986 was the most disastrous, causing 1746 deaths, >845 injuries and the
evacuation of 4430 people. Other volcanic-gas related incidents have been
responsible for more than 280 deaths and 1120 injuries, and contributed to the
evacuation or ill health of >53,700 people (Witham, in review). Most of these
casualties (149 deaths and 1000 injuries) were caused by a CO2 release during
the eruption of Dieng, Indonesia in 1979. Numerous other incidents of short-term
respiratory distress associated with volcanic emissions probably go unreported.
Little detailed work has been done on the relationship between volcanic air
pollution and health. A review of the medical literature (Hansell and
Oppenheimer, in preparation) revealed only 25 primary epidemiological studies of
varying quality considering the effects of volcanic gases. Individuals requiring more detailed
information on epidemiological studies of the human health effects of the
substances reviewed are referred to the TOXNET database.
Various organisations conduct volcano research. These include volcano
observatories, governmental organisations, national institutes and universities.
Information on the hazards of volcanic emissions is relevant to all these
bodies, as well as to volcano tourists and the people that live and work near
active volcanoes. There is a growing demand, both within the volcanological
community and from the other parties that deal with the impacts of volcanic
activity, for a comprehensive database of information on these hazardous
emissions. We aim to address this need here and present details of the
properties, health impacts, international guidelines for exposure
concentrations, and examples of concentrations and effects in volcanic contexts,
including casualties, for the main hazardous gases and aerosols typically
emitted during volcanic activity.
The international guidelines presented for each substance are generally based
upon urban and industrial pollution studies so are not necessarily strictly
applicable to volcanic emissions, which have a different overall composition.
For example, the guidelines do not account for any "cocktail" effect
that might occur from mixtures of air contaminants. However, as a first order
indication of hazardous levels we believe that they are of considerable value
for the purposes of planning and emergency response in hazardous areas.
Guidelines for both ambient air and occupational exposure are provided. The
purpose of the ambient air guidelines is to provide a basis for protecting
public health from the adverse effects of air pollution and for eliminating or
reducing to a minimum, those air contaminants that are known to be, or are
likely to be, hazardous to human health and well-being (WHO, 1999). These levels
are relevant to monitoring air quality in populated areas surrounding volcanoes
and to protecting tourists. (Although it is necessary to consider that in many
cities anthropogenic pollution levels are already higher than the set guidelines
and that this air pollution alone is considered a major contributor to deaths
and illnesses (e.g. WHO, 1999)). The purpose of occupational exposure levels is
to protect workers in environments where they might be exposed to
higher-than-ambient levels of contaminants, but for shorter work-based
exposures. These levels will be of more relevance to those who manage people
working in volcanic areas, such as national parks and volcano observatories, who
leave the affected area during their off-duty hours.
There is no absolute assurance that levels below the guidelines will not have
damaging effects. In particular, high-risk groups such as children and the
ill can react more sensitively. Equally, if the guidelines are exceeded,
it does not mean that in every case, or immediately, damage will occur.
There will be an increase risk of adverse effects on health, however. We do not claim to provide
an exhaustive review of international guidelines and it is noted that all
guidelines are subject to change over time.
Atmospheric gas abundances can be reported as mixing ratios by volume (units
of ppm and ppb by volume are convenient for volcanic plumes and occasionally %
for very high abundances, e.g. of CO2), or as concentrations (mg m-3 and µg
m-3). Conversion between the two units is possible if the temperature and
pressure at the time of measurement are known. To ensure comparability between
data, approximate conversions to mixing ratios have been made in some cases
using standard pressure and a temperature of 298 K. In these instances, the
original concentrations are also provided in parentheses. All mixing ratios
quoted are by volume.
A safe system of work that includes air monitoring is essential at all
locations where toxic gases may be present. The International Association of
Volcanology and Chemistry of the Earth's Interior (IAVCEI) guidelines recommend
that field volcanologists carry gas-masks at all times, especially when working
in thick fumes or in areas of high gas concentrations (Aramaki et al., 1994).
Volcanologists and volcano observatories have been contacted to determine
what measures, if any, are currently in place to protect against volcanic gases
and aerosols. Procedures used by individuals range from minimal (this can be
strongly influenced by budget constraints) to attendance on annual training
courses and the submission of detailed safety and hazards plans. A wide range of
respirators, gas filters and masks are available, but full-face masks are
preferred, as these have the benefit of protecting the eyes from acidic gases
and particles. The drawbacks of gas masks are that they are cumbersome, hot and
uncomfortable during exertion and when moving over volcanic terrain. Visibility
can also be reduced. Consequently, their use in the field may be initiated only
when an individual feels that gas levels are sufficiently high to cause
discomfort. This threshold will be different for different individuals and may
be above concentrations where damage to health can occur.
It appears that most volcano observatories do not have any guidelines for
volcanic gas and aerosol concentrations and hence no response plans should
levels become hazardous. Procedures for reporting concentrations to relevant
authorities also do not seem well established in many locations. Attitudes of
the authorities in many countries would appear to favour a reactionary approach
rather than a mitigatory one, although there are a number of examples of access
restrictions being implemented based on scientific reports. Any significant
changes to access or procedure based on possible risk would have large
implications on tourism in many areas concerned so there is little impetus for
change unless an incident occurs.
- Aramaki, S., Barberi, F., Casadevall, T. and McNutt, S., 1994. Safety for
Volcanologists. Bulletin of Volcanology, 56(2): 151-154.
- Hansell, A. and Oppenheimer, C., in preparation. Health
hazards from volcanic gases - a systematic literature review.
- WHO, 1999. Guidelines for Air Quality, World Health Organisation,
Geneva.
- Witham, C., in review. Volcanic disasters and incidents:
a new database. Journal of Volcanology and Geothermal Research.
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