Respiratory health effects of volcanic ash with special reference to Iceland. A review


  • Gunnar Gudmundsson

    Corresponding author
    1. Landspitali University Hospital, Reykjavik, Iceland
    2. Faculty of Medicine, University of Iceland, Reykjavik, Iceland
    Search for more papers by this author

  • Authorship
    Gunnar Gudmundsson wrote and revised the paper.

  • Conflicts of interest
    The authors have stated explicitly that there are no conflicts of interest in connection with this article.

Gunnar Gudmundsson, MD, PhD, Department of Respiratory Medicine, Allergy and Sleep, Landspitali-University Hospital, E-7 Fossvogur, IS-108
Reykjavik, Iceland.
Tel: +354-5436876
Fax: +354-5436568


Background and Aims:  Volcano eruptions occur around the world and can have an impact on health in many ways both locally and on a global scale as a result of airborne dispersion of gases and ash or as impact on climate. In this review, a recent volcanic eruption in Eyjafjallajökull in Iceland is described and its effects on aviation around the globe and on respiratory health in those exposed to the volcanic ash in Iceland. Also, the effects of a large volcano eruption in Iceland in 1789 are described that also had effect on a global scale by causing air pollution.

Methods and Results:  The available studies reviewed here suggest that the acute and chronic health effects of volcanic ash depend on particle size (how much respirable), mineralogical composition (crystalline silica content) and the physico-chemical properties of the surfaces of ash particles. These can vary between volcanoes and even between eruptions, making comparison difficult. Acute respiratory symptoms suggesting asthma and bronchitis have been well described. Exacerbations of pre-existing lung and heart disease are common after inhalation of volcanic ash. Limited information is available on increase in mortality from recent eruptions but historical evidence is well described. No long-term effects on lung function have been found after exposure to volcanic ash. There are concerns for the long-term risks of silicosis from chronic exposure to volcanic ash but no cases have been described.

Conclusion:  Acute respiratory symptoms after exposure to volcanic ash are well described but no long-term effects have been found.

Please cite this paper as: Gudmundsson G. Respiratory health effects of volcanic ash with special reference to Iceland. A review. Clin Respir J 2011; 5: 2–9.


Volcanic eruptions are different from other kinds of natural disaster in that they can result in a wide range of health impacts (1). It has been estimated that over 500 million people worldwide live within a potential exposure range (100 km) of a volcano that has been active within recorded history (2). Many volcanic regions are densely populated and several are close to major cities. Volcanic eruption is also unique in that it can also affect areas hundreds or thousands of kilometres away from the volcano itself, as a result of airborne distribution of ash, or even on a hemispheric to global scale because of impacts on climate and aviation (1, 3–5). This was shown in a recent volcano eruption in Iceland where air traffic was put to halt for several days in large areas of Europe causing major economical impact. The same was also true in 1783 when a volcanic eruption in Iceland had major effects on climate in Europe and in other areas of the world (1, 3, 4). Although eruptions are most often short-lived, ashfall deposits remain in the environment for years up to decades, being redistributed by wind or by human activity (1, 3, 6).

This review focuses on the respiratory effects of ash particles, so other health hazards will not be considered here. Special attention will be given to a recent volcano eruption in Eyjafjallajökull in southern Iceland and previous volcano eruption in Iceland that had effects on global health.

Geology of volcanoes

Volcanic activity can be broadly defined as either effusive (predominantly quiet emission of lavas, e.g. eruption of Kilavez, Hawaii) or explosive (e.g. the eruption of Eyjafjallajökull, Iceland in 2010). Explosive eruptions are basically of two categories, magmatic eruptions where the explosive fragmentation is primarily caused by the expansion of magmatic gases and phreatomagmatic eruptions where fragmentation results from magma–water interaction (7). Volcanoes are most commonly associated with tectonic plate margins. Most volcano eruptions in history have occurred on continental margins or island arcs where the edge of one tectonic plate drops beneath another (7). Most of these volcanoes are tall cones with summit craters and tend to erupt infrequently but violently. Examples from the so-called ‘Ring of Fire’, i.e. around the Pacific Ocean include Pinatubo (Philippines). Mt St Helens (United States) and Mt Fuji (Japan). European volcanoes include Vesuvius in Italy, whose catastrophic eruption in AD 79 destroyed Pompeii and Santorini in Greece (7). Volcanoes are also found where tectonic plates are separating, e.g. those in the African Rift Valley (3, 7). Some volcanoes are not related to tectonic plates and instead to deeper seated convective processes occurring within the Earth's mantle. They can be found in both oceanic and continental regions. Examples are the volcanoes of Hawaii Islands and Yellowstone (United States) (1, 3, 4, 7). Iceland is on the tectonic plate margin. There volcanic eruptions occur every 3–4 years, with more than half occurring beneath glaciers. (Fig. 1) In Iceland, by far, the greatest majority of explosive events are phreatomagmatic explosive eruptions. These often occur in volcanic systems that are partly covered by ice caps such as the Grímsvötn and Katla volcanoes (7, 8).

Figure 1.

The volcanic eruption at Fimmvorduhals from March to April, 2010. This was a popular attraction for tourists. Photo by Arni Tryggvason.

Tephra and ash falls

Tephra is a general term for any fragmentary material emitted from volcanoes, while ash refers to tephra particles that are less than 2 mm across. (1, 3, 4, 7). The factors influencing tephra distribution can be divided into those governed by (i) the type, intensity and magnitude of the eruption, including height of the eruption column; (ii) the duration of the eruption; and (iii) those governed by external factors such as wind strength, wind direction and changes in wind direction during an eruption (1, 3, 6–8). The location of a volcano relative to inhabited areas is also important with respect to potential hazards from tephra fallout. It is more likely that inhabited areas that are close to the volcano will be more affected. This could be from social factors such as disruption of daily life activities and also from health effects because of likelihood of more exposure to volcanic ash. Freshly erupted ash differs from other natural dusts in several ways. The particle surfaces are unweathered and are therefore not oxidised and can carry condensed volatiles such as acids, polycyclic hydrocarbons and trace metals (1). Those compounds adhering to the surface of tephra particles can cause pollution of water supplies and grazing lands in areas remote to the erupting volcanoes (1, 3). Drinking water may become contaminated by fluorine, but fluorine poisoning in humans is thought to be rare (3). However, grazing animals can ingest toxic quantities of fluorine. Heavy falls of tephra can damage vegetation, including agricultural crops. Tephra by itself can present many types of health hazard (1, 3). Health hazards are most commonly through inhalation and abrasion of skin and mucus membranes such as conjunctiva, but also from loading on roofs causing buildings to collapse and through impacts on environments (1, 3, 6).

Volcanic gases

Volatiles that can be emitted during volcano eruptions include CO and CO2, SO2, HCl, HF, H2S and radon (3, 4, 6). Exposure to acidic gases without wearing respiratory protection, especially if repeated frequently, may lead to irritant-induced asthma including reactive airways dysfunction syndrome (3, 4).

Recent volcano activity in Iceland

During the 11 centuries of settlement in Iceland, volcanic activity has repeatedly affected the population (8). Most part of Iceland is sparsely populated with no permanent settlements in the interior highlands. Population clusters mainly occur along the coast, with about 70% of the 300 000 inhabitants living in the greater Reykjavík area and along the shore in southwest Iceland (8). The Reykjavík metropolitan area is located just outside the margins of the active volcanic zone (8). Eyjafjallajökull is a glacier on the southern shore of Iceland about 150 km from Reykjavik that rises to 1666 m above sea level. There is agricultural land on its southern slopes, with farms located as close as 7 km from the summit. An explosive eruption started on 14 April 2010 and was located within the ice-capped summit of the volcano (Fig. 2) (9–11). Erupting from beneath the ice cap, ash was formed by the contact of magma (at over 1000°C temperature) with water and ice. It was the interaction between the magma and water that gave rise to the explosivity generating large volumes of finely comminuted ash. The eruption plume reached heights of almost 10 km on the first day of the eruption (9).Three days of sustained tephra production followed, leading to ash dispersal towards the southeast (Fig. 3). Many farms are located in that area and several hundred people were exposed to the ash (10–13) (Fig. 4). The volcano eruption halted by the end of May, 2010. Since then, on windy days, this ash is resubmitted into the air; as a result, particulate matter concentration levels have been unusually high in southern and south-western part of Iceland, including Reykjavik (12). This has occurred on several occasions, causing alert to be given to people with respiratory illnesses. The volcano ash from Eyjafjallajökull when fresh was found to have up to 25% respirable particles (i.e. less than 10 microns; Fig. 5). The main constituents were 60% SiO2 (silicon dioxide), 16% AlO3 (aluminium oxide) and 10% FeO (iron oxide). Crystalline silica content was negligible (12).

Figure 2.

The volcanic eruption in Eyjafjallajökull in April 2010. Photo by Arni Tryggvason.

Figure 3.

Seljavellir, the cultivated fields that had the most volcanic ashfall during the Eyjafjallajökull eruption in 2010. Photo by Gunnar Gudmundsson on 31 May 2010.

Figure 4.

Satellite view of Iceland on 17 April 2010 showing the volcanic ash plume heading towards Europe. Photo by NASA Goddard Photo and Video.

Figure 5.

An image from scanning electron microscope of the volcanic ash from Eyjafjallajökull in Iceland showing respirable particles. Provided kindly by Birgir Johannesson, Innovation Center Iceland.

Aviation hazards and effects of Eyjafjallajökull eruption on global aviation

Ash clouds can pose a risk to aviation through abrasion, e.g. of cockpit windows and damage to jet engines (3, 14). An International Airways Volcano Watch (; last accessed 5 September 2010) responsible for monitoring ash clouds and provision of warnings to the aviation community was established by the International Civil Aviation Organisation. To date, there have been no reported air crashes arising from encounters with volcanic clouds, but there have been several near misses (3, 14). Ash from the Eyjafjallajökull eruption was carried towards Europe by prevailing winds in April and May, 2010 (15). The height of the plume was used as the main indicator of mass transfer, a crucial input parameter in atmospheric models to define no-fly zones (10). A no-fly zone was reinforced over large parts of Europe for several days in April and May of 2010 (9, 12). As a consequence of the eruption both in Europe and more distant destinations, many thousands of travellers were stranded and the economic impact was profound (9, 11, 12). Air transport of sick patients was disturbed, causing longer transport times and inconvenience for many patients. The rules for no-fly zones were thought to be too strict and based on limited research and measurements and too much on the use of atmospheric models. This will most likely be changed in the near future because of new information that was obtained during the eruption and afterwards. Such major disruption of flights is therefore unlikely to happen again.

Previous effects of volcano eruption In Iceland on global health

Laki or Lakagígar (Craters of Laki) is a volcanic fissure situated in the south of Iceland. On 8 June 1783, a fissure with 130 craters opened with explosions(8, 16). The eruption continued until February 1784. It has been estimated that it produced 14 km3 of lava, and the total volume of tephra emitted was 0.91 km3. The outpouring of gases, including an estimated 8 million tons of hydrogen fluoride and estimated 120 million tons of sulphur dioxide, gave rise to what has since become known as the ‘Laki haze’ across Europe. The gases were carried to altitudes of about 15 km(8, 16). Sulphurous air pollution was widely reported in Europe throughout the summer of 1783. Poor air quality and acid deposition caused widespread damage to vegetation and crop failures. Impacts upon human health were just as severe, with extensive asthma-like symptoms and eye irritation reported (17). In England, mortality was more than 10% in excess of the 50-year mean and there were 10 000 more deaths than would be expected for an average year (18). In parts of France, the summer death rate in 1783 was 38% above average (19). Over 50% of Iceland's livestock population was killed, leading to famine which killed approximately 25% of the population of Iceland. However as pointed out, if Laki emissions caused all the estimated national mortality increase in England, then three times as many people died in England as a result of the eruption than in Iceland itself (20).

Respiratory effects of volcanic ash

Interest in the health effects of the inhalation of volcanic ash has grown ever since the eruption of Mt St Helens in the north-western United States that set ashfall over populated areas in 1980. Since then, several studies have been performed on the health of populations affected by eruptions and on ash in laboratory settings. Very detailed reviews are available on this subject and interested readers are referred to these reviews (1, 3–6).

Several factors are important when evaluating the health effects of volcano ash. The first issue is the concentration and size of the ash particles inhaled, particularly the percentage of finer particles able to penetrate deeply into the lung, and coarser particles that mostly affect the upper airways. The second thing is the mineralogic composition, particularly the free silica content and the third is surface properties, especially Fe2+ content – higher iron resulting in more free radical generation in toxicological studies, with fresh ash generating more radicals than weathered samples (1, 3, 21).

The acute respiratory manifestations seen after heavy ashfalls include irritation of the chest and nose and throat discomfort. Acute exacerbations of asthma and bronchitis are seen. These patients present with increased cough, breathlessness, chest tightness and wheezing. Inhalation of fine ash can also exacerbate other previously present disease such as chronic obstructive pulmonary disease or chronic heart problems such as ischemic heart disease (1, 3). A recently published study from New Zealand showed that in 1996 diffuse volcanic ashfall from Mt Ruapehu may have contributed to increased mortality observed in the time period after the ashfall in the city of Hamilton i.e. 166 km from the volcano (22).

For long-term respiratory problems, there are concerns for silicosis, a nodular type of pulmonary fibrosis to occur. For this, three conditions have to be in place: first, a high proportion of fine particles in the ash; second, a high concentration of crystalline silica; and third, is that there has to be exposure to ash over a period of years to decades in significant amounts. However, there are no reported cases of silicosis in the literature (1). A recent paper describing ash from Chaitén volcano in Chile showed that it contained high levels of the silica polymorph cristobalite and levels increased through the time course of the eruption (23). This site will need close monitoring over the next decades.

The current knowledge on the respiratory effects of volcanic ash can be compared to the available information on the respiratory effects of the attack on the World Trade Center in New York City on 11 September 2001. It produced a massive dust cloud with acute exposure and then several month exposure to burning ruble and dust during the cleaning process. The acute effects were cough, dyspnea and nasal stuffiness (24). Firefighters had significant 1-year decline in spirometry values. It was common to have spirometry values in low normal range and a low forced vital capacity was most common (24). It therefore seems that the World Trade Center incident has had more permanent effects on lung function than volcanic ash has ever been shown to have. One must keep in mind that this population has been studied more than any population that has been exposed to volcanic ash.

Epidemiological studies

Mt St Helens

As well described in previous reviews, the eruption of Mt St Helens in 1980 lead to the first detailed systematic epidemiological and toxicological research into health hazards of airborne volcanic ash (1, 3–5). The eruption occurred on 18 May 1980, and areas of central Washington State in the north-western United States experienced around 10 cm of ashfall. Studies showed that areas with high levels of airborne ash experienced a two- to threefold increase in hospital admissions and three- to fivefold increase in emergency room visits for respiratory conditions, most commonly asthma and bronchitis (25). It was also found in these studies that a third of patients with chronic lung disease had exacerbation of their disease without seeking medical attention (26). Studies on lung function in children found no effects but studies on hospitalisation for asthma found an increase in admission rates (1, 27). Follow-up of those with chronic lung conditions (25) and loggers exposed to the ash because of occupation found short-term increases in respiratory symptoms that persisted in some individuals for months (28). This was thought to be because of resuspension of loose ash deposits on the ground. A small, short-term, reversible decline in lung function was seen in loggers working in the immediate vicinity of the volcano(28). No long-term effects on lung function were found. Toxicological studies found that Mt St Helens ash acted as an irritant on the airways, presenting as an increase in mucous and inflammation (3).

Soufrie're Hills volcano, Montserrat

A volcano eruption has been ongoing since 1995 until this date. Health studies conducted there have used a multidisciplinary approach to evaluate health risks. Soufrie're Hills ash typically contains 13%–20% inhalable particles, but crystalline silica content of these particles has varied between 10–27 wt% and 4–6 wt% (29). Toxicological studies have found the Montserrat ash to be mildly toxic, but less harmful to the lungs than the cristobalite concentration might indicate (1, 30). The risk of developing early radiological changes of silicosis of has been estimated to be 0.1% for the population given 20 years of exposure. Outdoor workers such as gardeners were found to have higher ash exposures, resulting in increased risks of 2%–3% and up to 10% (30). No lung abnormalities have been identified by chest radiographs following the first 9 years of eruption. Two studies of health effects in adults have suggested increased respiratory symptoms, particularly in those with higher exposure to ash (1). An epidemiological study with detailed information on 350 children aged under 12 years and still living on the island in 1998 suggested fourfold increases in prevalence of wheeze in the preceding 12 months, and exercise-induced bronchospasm in children exposed to higher levels of ash (31).

Other sites

Emergency room visits for respiratory conditions in children in Quito, Ecuador increased significantly after Guagua Pichinca volcanic eruption in the year 2000. These were both respiratory infections and asthma-related conditions (32). A cross-sectional study after the Mt Asama eruption in Japan on 1 September 2004 to assess the acute impact of volcanic ash on asthma symptoms and treatment changes was done by using a questionnaire completed by 236 adult asthmatic patients. In the areas where ashfall was over 100 g/m2 area, 43% of asthma patients suffered exacerbations, peak expiratory flow decreased and drug use for asthma increased. These authors suggested that ashfall over 100 g/m2 is harmful, access to such areas by asthma patients needs to be restricted, and these areas need to improve asthma treatment (33). Sakurajima, Japan is a volcano that has been erupting since 1955, with frequent ash falls that have affected a large local population. The ash particles are mostly non-respirable in size and has therefore not had much impact on respiratory morbidity or mortality as shown in several publications (34–37).

Studies on respiratory effects of volcanic ash in Iceland

Because of concerns about the health effects of volcanic ash, the Directory of Health in Iceland in May, 2010 initiated a study on the effects of the Eyjafjallajökull volcanic activity. The population studied were individuals living closest to the volcano and that had suffered the most exposure to the ashfall (38). From 31 May to 1 June 2010 a total of 207 individuals were evaluated: of those, there were 107 males. Most were farmers and immediate family members. The mean age was 44 years with the range from 7 years up to 85 years of age. A total of 60% of the study group reported good health and no symptoms related to volcanic ash at the time of study. About 13% of the group gave a history of previous lung condition, most commonly asthma. Abnormal spirometric values were found in 18% of the total group. Of those that reported a previous lung condition, 38% had normal spirometry. No serious immediate consequences of volcanic ash exposure were found. About 40% of the individuals in the study felt acute effects of the ash fall as discomfort in eyes, nose and throat and felt irritation of the chest. Most reported that the use of protective eye wear and respiratory masks had decreased symptoms (38).


The acute effects of volcanic ash on respiratory health have been well described but can be different based on particle size, content and the amount of exposure. Susceptibility of the host is also an important factor. Characterisation of the grain-size distribution of volcanic ash is therefore an important step in assessing the health hazard of ash. A recent paper analysed 63 ash samples from around the world and showed that the fraction of respirable (<4 micron) material ranges from 0–17 vol%, with the variation reflecting factors such as the type of the eruption and the distance from the source. A strong correlation between the amount of <4 and <10 micron material was found for all ash types. This relationship was stable at all distances from the volcano and with all eruption types and can be applied to volcanic plume and ash fallout models (39).

For those interested in studying the effects of volcano eruptions on respiratory health and health in general further, the International Volcanic Health Hazard Network can be recommended. The website ( contains guidelines and information on a number of health topics for both the general public and professionals.

In conclusion, acute respiratory symptoms after exposure to volcanic ash are well described in the literature and include irritation of the chest and nose and throat discomfort, but no long-term effects have been found.