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Prepared by Ana Boischio
April 30th 2012


La erupción del volcán Puyehue, ubicado a 90 kilómetros al noroeste de San Carlos de Bariloche, se produjo el 4 de junio 2011 y generó una lluvia de cenizas que afectó vastas zonas de las provincias de Río Negro y Neuquén. Además de las devidas precauciones tomadas inmediatamente después de la erupción, otras acciones a mediano y largo plazo deben dar seguiemento. Esta nota tiene como objectivo indicar las preguntas claves para orientar estas acciones.

The Ingeniero Jacobacci town, located in the Patagonia, with around 6,000 people, has been aftected by the volcanoes ash. A railway town in the 1920s, nowadays has the economic activity of exploiting a diatomite rock, in addition to the tourism industry.

Diatomite rock exploitation is an important consideration, considering the potential synergies with volcanoes ashes. Diatomite is composed by crystallite silica, built from water by micro-organisms in ancient times by diatomaceas. Crystallite silica is considered an occupational respiratory hazard, often present in blasting operations (see reference 1).

The technical note below provides first information regarding volcanoes ashes in general, with some specific questions for Puyehue in particular; then general overview of volcanoes ahs health effects, and additional information on environmental management for on livestock, assuming this is also an economic activity affected by the volcanoes ashes.

I. Ash particles size and distribution factors

Ash particle size and tickeness - decreases exponentially with increasing distance from the volcano; the smalles the particle size the deepest it can go into the respiratory system; i.e., the smallest particles can reach alveolos, whereas the largest will stay on the upper areas, like nasal and throat;

Ash distribution will depend on the initial particle-sizes of the volcanoes eject, height of eruption column, rate and duration of eruption, and prevailing wind conditions — considering the distance between the Puyetec volcanoes and ing Jacobacci, considerations regarding winds direction and speed, in relation to the exposed population, seems relevant;

Eruption style - controlled by magma - determines the chemistry, particle size distribution and physical and chemical components of volcanic ash;

Volcanic eruptions range from (1) effusion of lava fountains and flows with very little ash erupted, typical of basaltic magma eruptions; to (2) extremely explosive eruptions that inject large quantities of ash high into the stratosphere, typical of rhyolite and dacite magmatic eruptions. What kind of eruption or magma had the Puyehue volcano? Is that balsatic?

Ash particle components — physical factors

Pumice, glass shards, crystals, and lithic particles; pumice fragments may form temporary mats of floating material if deposited on water. Since coarser and more dense particles are deposited close to source, fine glass and pumice shards are relatively enriched in ash fall deposits at distal locations.

Minerals within volcanic ash have not been shown thus far to cause any long term adverse health effects in humans, but they will affect the composition of soil into which they become incorporated possibly affecting livestock and agriculture.

Crystobalite is a type of silica crystal often present in volcanoes ash. Crystobalite is known to cause silicosis in humans, depending on time and intensity of exposure, often contracted by people working for prolonged periods in industries that expose workers to fine rock dust. See the health section below for more information on health effects of ash, including who is most at risk from ash inhalation and how to minimize exposure to volcanic ash. Consider other exposures among those people working or living near the diatomite exploitation rock. These people accumulating occupational exposure with volcanoes ashes should be considered vulnerable for priority actions. Also, if the families of these workers live nearby the diatomite rock blastings, then the whole family should be considered.

Ash chemical factors

Ash chemistry is directly related to the chemistry of the source magma. Volcanic glass is relatively high in silica compared to mineral crystals, but relatively low in non-silica elements (especially Mg and Fe). Both glass and most minerals almost always contain Si, Al, K, Na, Ca, Mg and/or Fe.

Freshly fallen ash grains commonly have surface coatings of soluble components (salts) and/or moisture. These components can make ash mildly corrosive and potentially conductive. The volcanic-gas aerosols may be composed of sulphuric and hydrochloric acid droplets with absorbed halide salts. That is a relevant health concern.

Soluble components of ash particles

Volcanic eruptions inject water vapour (H2O), carbon dioxide (CO2), sulfur dioxide (SO2), hydrochloric acid (HCl), hydrofluoric acid (HF) and ash into the atmosphere. HCl and HF will dissolve in water and fall as acid rain whereas most SO2 is slowly converted to sulphuric acid (H2SO4) aerosols. Ash particles can change soil and water chemistry and hence quality.

For more information see reference 2.

II. Health aspects — common respiratory symptoms

Potential respiratory symptoms from the inhalation of volcanic ash depend on a number of factors, including airborne concentration of total suspended particles, proportion of respirable particles in the ash (less than 10 microns in diameter- i.e., the total suspended particles, particulate material of 10, or 2.5 or < 1.0 micrometers), frequency and duration of exposure; also, free crystalline silica and volcanic gases or aerosols mixed with the ash, meteorological conditions; exposed people conditions, for example those suffering asthma or bronchitis conditions; the use of fine masks for respiratory protection is key.

Acute respiratory symptoms commonly reported by people during and after ash falls:

  • nasal irritation and discharge (runny noses)
  • throat irritation and sore throat, sometimes accompanied by dry coughing
  • people with pre-existing chest complaints have developed severe bronchitic symptoms which lasted some days beyond exposure to ash (for example, hacking cough, production of sputum, wheezing, or shortness of breath)
  • airway irritation of people with asthma or bronchitis; common complaints of people with asthma include shortness of breath, wheezing, and coughing
  • breathing becomes uncomfortable

These are short-term effects that affect people differently according to their exposures levels and vulnerable conditions

Eye symptoms

Because volcanic ash is abrasive, people typically experience eye discomfort or irritation during and after ash fall, especially among those that use contact lenses. Commonly reported symptoms of ash 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 conjunctiva sac that surrounds the eyeball due to the presence of ash, which leads to redness, burning of the eyes, and photosensitivity

Individuals with Dry Eye Syndrome may also experience ailments due to the presence of ash.

Skin irritation

Depending on the chemical components of ash, skin irritation combined with eyes symptoms might request additional medical attention.

Free crystalline silica in volcanic ash

Volcanic ash may contain varying proportions of free crystalline silica (silicon dioxide, SiO2) in the form of quartz, cristobalite, or tridymite minerals. The minerals are described as "free" silica because the silicon dioxide compound is not attached to another element to create a new mineral; for example, magnesium to form the mineral olivine. Over time, exposure to respirable particles of free crystalline silica can lead to silicosis, for which dose responses are well established as occupational hazards.

The U.S. National Institute for Occupational Safety and Health (NIOSH) recommended in 1974 the exposure to respirable free silica be limited to 50 micrograms/m3 of air for workers up to a 10-hour work day, 40-hour work week over a lifetime. Historical data suggests that this exposure has been exceeded for brief periods of time (hours to days) in certain locations, but not over the working lifetime of people (2-3 decades).

Principal health effects of ash and main preventive measures (reference 2)


Health effect


Preventive measure


Inhalation of ash less than 10 microns in diameter

Exacerbation of pre-existing lung disease

Monitor total suspended particulate (TSP)
Monitor ash particles <10 micron in diameter

Wear high-efficiency masks
Protect home and offices from ash infiltration

Inhalation of free silica in volcanic ash

Silicosis—chronic silicosis is a fibrous (scarring) reaction of the lungs caused by inhalation of crystalline silica

Determine free silica content of respirable ash
Monitor exposure in high exposure individuals and jobs

Respiratory protective equipment


Ocular (eyes)

Foreign bodies in eyes

Conjunctivitis, corneal abrasions

Monitor wind direction and ash production for early warning to people downwind

Goggles for heavy exposure



Roof collapse and ashfalls from roofs

Trauma, including death

Prevent excessive accumulation of ash on roofs

Automobile accidents from slippery roads and poor visibility

Trauma, including death

Monitor areas that will receive ash fall and issue public announcements regarding expected conditions and road closures

Traffic control
Pre-eruption notification of what to do during an ash fall

III. Livestock

Survival of livestock exposed to ash falls

Feed availability - When ash falls destroy pastures, livestock need to be supplied with all of their feed in order to survive in the short-term. The supply of dry feed must be maintained until the livestock are either evacuated or slaughtered, or pasture is re-established.

Even with very light ash falls that do not destroy existing pastures, animals may need to be provided with uncontaminated feed. For example, if the ash contains a high level of fluorine adsorbed onto the tiny particles and livestock consume both ash and fluorine, there is a risk of fluorosis.

Water quality - Where there is a significant ash fall, clean water will likely be in short supply. Natural water sources and human-made ponds may be temporarily contaminated by ash, and water-pumping equipment can be damaged by the abrasive rock particles (covering with tarps may provide protection). Restoring quality water supplies for livestock is typically a high priority if livestock are to remain on land affected by ash fall.

Ash toxicity - Ash falls may be poisonous to livestock and result in acute and chronic clinical diseases, including hypocalcaemia, fluorosis, estomach and intestinal damage, and secondary metabolic disorders.

Fluorine aerosols in the eruption column and cloud that become attached to fine ash particles pose a potentially significant threat to livestock, similarly to humans. As smaller ash particles have large surface areas relative to their mass, the fine particles can transport significant amounts of soluble fluorine onto pastures far downwind from an erupting volcano. The smallest ash particles travel the greatest distance from a volcano; thus a thin layer of fine ash only 1 mm thick can contain potentially toxic amounts of fluorine. Livestock ingest fluorine directly as ash is consumed along with pasture feed and soil.

Fluorine poisoning has occurred in several Icelandic eruptions. Depending on exposure factors (length, intensity etc) chronic fluorosis can be fatal. Fluorine exposures can cause lesions in the nose and mouth, and hair to fall out around the mouth. Other symptoms include nutritional and stress related diseases, convulsive seizures, pulmonary edema, and kidney and liver changes. A tooth condition known as "spiking" may also occur, causing outgrowths to develop on molars and making chewing difficult.

When toxic levels of fluorine on pastures are identified, it is recommended that livestock are removed from the affected areas until sufficient rainfall has leached the fluorine from the ash.
A high sulphur concentration adhered to the ash may induce copper and cobalt deficiencies in the long term.

Other factors

  • Ash components (minerals, volcanic glass).
  • Consistency of the ash (particle sizes, angular vs. rounded).
  • Amount of rainfall immediately following an ash fall. For example, toxicity may be reduced by leaching of fluorine during rainfall and thin coatings of ash on plants may be washed away into the soil.
  • Age (young stock are more at risk than mature animals) and health of livestock.
  • Pasture length (close-grazing animals such as sheep and deer are more likely to be affected by light ash fall) and stocking rate.
  • Long-term soil fertility of pasture.

Evacuation of livestock

When pastures are subjected to ash falls and remobilization of ash by wind, evacuation of livestock to areas with good quality feed and water may be prudent. Even after evacuation, long-term inhalation of ash and exposure to fluorine may result in reduced productivity. In some cases, stock may not recover in the long-term, with humane slaughtering being the best option.
Where ash falls affect a large area, evacuation of stock would be extremely difficult due to the logistics of moving large numbers of stock and sourcing feed in areas unaffected by the ash. This may result in large losses of livestock through dehydration and starvation. Effects on Pasture

Ash thickness

Ash falls greater than 10-15 cm (4-6 in) typically result in the complete burial of pastures and soil. Where soil burial is complete, the soil will become sterile because it is deprived of oxygen; existing pasture species and crops and most soil micro-organisms will die. Where ash is as thick as about 5 cm (2 in), plant survival and re-growth will be dependent on several factors, including the chemical nature of the ash, compaction of the ash after the eruption, degree of continuing disturbance, amount and reliability of rainfall, and length of plant stalks at the time of ash fall.

The impact of weather conditions on ash thickness

The survival of pastoral plants is influenced by the timing of rainfall after ash covers an area. Wet ash will consolidate to approximately one-third of the original thickness of dry ash. If it rains soon after an eruption (within 2-3 days) plant survival may be improved because of the compaction. On steep slopes, rain will wash ash into gullies and low-lying basins, leading to increased erosion and deposition in some areas (for example, deposition often occurs at the base of steep hillsides). Wind erosion may also pile ash into "ash dunes," if the ash is not already consolidated or incorporated into the soil profile.


1. Crystalline Silica in Abrasive Blasting Operations
2. Red Internacional de la Salud Peligro Volcánico publicado guías en español
3. Sitio de Geología EE.UU. ofrece gran cantidad de documentos relacionados con los volcanes en EE.UU.

Additional references