THE HEALTH HAZARDS OF VOLCANIC ASH
A guide for the public
This document has been prepared by the International Volcanic Health Hazard Network (IVHHN), Cities and Volcanoes Commission, GNS Science and the United States Geological Survey (USGS) to promote the safety of those who experience volcanic ashfall. This guide explains the potential health effects of volcanic ash and gives details on how to protect yourself and your family in the event of a volcanic ash fall.
Indirect Effects of Ash Fall
As well as the short and long term health risks, indirect impacts of large ash falls must also be considered. These mainly arise from the secondary consequences of ash fall.
Effects on roads
The reduction in visibility from airborne ash alone may cause accidents. 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
Effects on Power
Ash fall 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
Ash fall can cause contamination of water or clogging and damage of water supply equipment. Small, open
water supplies such as domestic water tanks with roof drainage are especially vulnerable to volcanic ash fall,
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. During and after ash falls, there is also likely to be extra water
demand for clean-up, resulting in water shortages.
Effects on sanitation
(waste water disposal etc).
The temporary disablement of municipal sanitation systems may lead to increased 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.
If the ash is coated in hydrofluoric acid, the ash can be very toxic to grazing animals if they ingest ash-covered grass and soil.