Important questions answered on the health effects of volcanic ash
1. Q. Does the Iceland volcanic ash affect health?
A. As long as the volcanic ash remains in the upper atmosphere, there will be no increase in people's exposure and no risks to health. If it reaches the ground in high concentrations, it may have health effects, but these are likely to be minor. Most of the ash cloud is currently high in the atmosphere (3-10 km), although ash is reported to have reached the ground in some countries near the source of emission. Traces of ash have also been registered by high-level air quality monitoring stations in the Alps, as well as in Norway and Scotland.
2. Q. What happens if the ash reaches the ground?
A. If the ash reaches the ground due to vertical movement of air masses, there is a risk of increased air pollution levels, notably of concentrations of respirable particulate matter (particles under 10 µm in diameter or PM10), and of related health effects. This increase in pollution is expected to be small and in the range observed even without volcanic ash. It is normally caused by fluctuations in traffic or other human activities, and depends on weather conditions and the long-range transport of air pollution.
Daily fluctuations in particle concentrations may lead to changes in daily mortality rates and in the number of people being admitted to hospital for treatment of heart or lung disorders.
Air quality monitoring networks are working continuously in European cities, assessing the situation. The European project CITEAIR, which is co-funded by the European Union and implemented in collaboration with several non-project cities and other stakeholders including the European Commission (DG Environment) and the European Environment Agency, provides a daily overview of air quality in 84 European cities. Data from several national air quality monitoring networks are also available online. "Eye on Earth", a system run by the European Environment Agency, publishes the results of monitoring activities combined with modelling and the observation of air quality by citizens.
3. Q. What is the composition of the ash?
A. Volcanic ash is composed of small particles of fragmented volcanic rock, most of which are less than 30-40 µm across, some below 10 µm (which can be inhaled) and some even finer below 2.5 µm. These particles consist mostly of quartz and glass. Chemical analysis from Iceland shows the presence of aluminium, silica and oxygen, as well as some fluoride.
4. Q. What happens if it rains?
A. The main health concern is the potential effects of inhaling respirable particles suspended in the air, if the ash reaches the ground layer of the atmosphere. Volcanic ash poses no health threat in wet weather since the ash particles agglomerate, and it is washed out from the air and cannot be inhaled.
In the event of rain, only very low concentrations of volcanic ash are likely to be deposited on the ground and the general public is unlikely to experience significant health effects once the rain dries.
Nevertheless, because small quantities of volcanic ash could float back up into the air in windy conditions, it would be sensible for people with existing respiratory conditions such as chronic bronchitis, emphysema and asthma to keep their inhalers or other medications with them.
5. Q. Which groups are most at risk?
A. People with chronic respiratory conditions such as asthma, emphysema or bronchitis may be more susceptible to irritation if ash is in the lower atmosphere in high concentrations.
6. Q. Are children and the elderly more at risk?
A. Age does not affect the response to short-term exposure to air pollution, though long-term exposure to air pollution may affect the development of children's respiratory systems and is a risk factor for developing asthma.
Elderly people may suffer more often from short-term exposure to pollution due to their worse health status, particularly if they suffer from respiratory or cardiovascular diseases.
7. Q. What is the health risk for otherwise healthy people?
A. The effects of particulate matter on health occur at the levels of daily exposure currently experienced by most urban and rural populations in the WHO European Region. Long-term exposure to particles contributes to the risk of developing cardiovascular and respiratory diseases, as well as lung cancer. In the European Union (minus Bulgaria and Romania), average life expectancy is calculated to be 8.6 months shorter due to exposure to fine particulate matter produced by human activities.
8. Q. Are there special hours in the day when exposure is more risky?
A. Air pollution fluctuates daily in cities, mainly related to traffic. Since the health risk is proportional to the level of pollution accumulated over the day, local peaks of pollution coinciding with increased traffic intensity should be avoided.
9. Q. What are the symptoms of exposure to the ash?
A. It is important to stress that the concentration of particles that may reach ground level is likely to be low and should not cause serious harm. Part of the ash reaching ground level will be larger than respirable particles but, due to its physical properties, will irritate eyes, nose and throat. Remaining indoors will diminish the risk of these symptoms, since closed doors and windows will partly prevent penetration of the larger, irritating particles inside buildings. Nevertheless, people with chronic respiratory diseases, such as chronic bronchitis, emphysema or asthma, may experience exacerbation of their symptoms. They should keep their medication to hand.
10. Q. How should people protect their health?
A. As long as the volcanic ash remains in the upper atmosphere, it poses no risks to health.
When larger particles reach ground level, or are re-suspended after deposition on the ground, they may cause eye irritation. Staying indoors and avoiding play on fields covered with ash are recommended. Gardeners cutting grass affected by ash falls should wear respiratory protection.
If fine particles reach the ground and increase air pollution, normal precautions for days with high air pollution are advised: people with asthma and respiratory symptoms should avoid strenuous exercise.
Staying indoors can protect only against large particles, since smaller particles can get indoors.
11. Q. What are the long-term effects?
A. Ash particles emitted during volcanic eruptions usually deposit on the ground within three months. When they sediment, they affect air quality at the ground level, possibly increasing population exposure to particulate air pollution and increasing the risk of health effects. If an eruption does not last for a long time, however, the contribution to the average pollution levels and to the health effects of long-term exposure will be minimal, probably below detection level.
In terms of indirect potential long-term effects, volcanic sulphate aerosols, formed as a result of explosive volcanic eruptions, can affect the climate by altering the incoming solar radiation and outgoing thermal radiation that are part of the earth's energy balance. They can also affect global stratospheric ozone distributions for a considerable period after an eruption. The potential health effects are complex and not immediate.
12. Q. What is necessary at this stage?
A. Monitoring of air quality to detect any impact of volcanic ash is necessary to rule out any risk of severe health effects. Besides assessing the PM10 and PM2.5 mass, the composition of the particles should be analysed. Since the situation may vary in different parts of Europe, even within countries, depending on the weather conditions, local information will be important.
13. Q. How will the situation evolve?
A. The ash cloud is spreading all over Europe and the rest of the northern hemisphere, but as particles travel they get more diluted. Therefore even if they reach the ground layers of the air, their impact on air quality will be small. This picture may change if the eruptions of ash continue and if the ash continues to travel towards mainland Europe. This may lead to an increased concentration of particles in the air, and more significant impacts on air quality on the ground.
14. Q. What is WHO doing?
A. WHO/Europe is assessing the health risks of the volcanic eruption in Iceland and providing guidance to its Member States on effective ways to address the situation from a public health perspective, in coordination with partner agencies and national authorities. Experts from many countries are providing information and support. WHO/Europe will continue monitoring the situation, including volcanic activity, the extent of ash reaching the ground and the air pollution in the lower atmosphere, and will provide updates as necessary.