Despite the World Health Organization’s warning last Friday that Icelanders and Europeans may have to stay inside to avoid respiratory problems once the Icelandic volcanic ash begins to settle, most experts agree that the effects should be minimal.  “There is a massive diluting effect in the atmosphere as it gets dispersed by wind which means the amount reaching land is very small,” said Ken Donaldson, professor of respiratory toxicology at the University of Edinburgh in Scotland.  He added that little impact has been seen in people’s health from prior volcanic eruptions, except for in those with lung problems in the immediate vicinity of the volcano.

Volcanic ash is composed of fine particles of fragmented volcanic rock.  Only very small particles measuring less than 10 microns in size are able to reach the lower respiratory tract in humans and cause adverse effects such as wheezing and coughing.  Analysis of the ash that has been released thus far suggests that less than 25% of the particles are small enough to cause problems.

So long as the volcanic ash remains in the upper atmosphere, respiratory toxicologists maintain, there will be no increase in people’s exposure and little to no added health risk.  If the ash drops to ground level due to vertical movement of air masses, those with chronic respiratory problems such as emphysema and asthma could experience a slight increase in respiratory symptoms.  Rainfall could mitigate the problem, however, by removing the ash particles altogether from the atmosphere.

For now, the World Health Organization is monitoring the situation, and will issue more substantial warnings if the eruption continues for many more weeks and the volcanic ash, now drifting above 20,000 feet, begins to settle over Iceland and Northern Europe.