Yes, more vulcanism related matters, this time health.

One thing I have not seen a deal of in press coverage here are the potential health implications from the current eruption other than the advice of our own health authorities that you should carry your inhaler with you if you use one (you don’t say – I would never have thought of that). Via Pravda (the Russian one not the BBC) I came across a well written article on what happened last time Eyjafjallajoküll got indegestion :

The last time Eyjafjallajokull had an episode was in 1821, pouring tonnes of ash containing toxic fluoride gas into the atmosphere. It lasted not 24 hours, but until 1823, causing the deaths of many cattle and sheep through fluor poisoning. Eyjafjallajokull has had four eruptions in the last thousand years: in 920, 1612, 1821-1823 and now in 2010. All of the previous eruptions were precursors to more massive activity from the neighbouring Katla volcano but as yet geologists have not registered any seismic activity.

Eyjafjallajokull, a glacier covering a volcano of 1,600 metres in height and with a crater of 3 to 4 km in diameter, started becoming unstable at the end of 2009, when a number of small earthquakes fuelled by building pressure seven kilometres beneath the volcano gave rise to a peak in activity – 3,000 earthquakes were registered between March 3 and 5 this year. This in turn was followed by an eruption on March 20.

There were two further eruptions on April 13 and 14, under the glacier causing meltwater floods to force the evacuation of 800 people from the slopes. From Wednesday to Thursday a huge cloud of ash, which continues to billow from the volcano, spread eastwards, causing flights to be cancelled across Western and Northern Europe.

Interesting that the fluoride story has not been widely reported I think which leads me to an article from 2004 on the effects of an eruption of the Laki volcano in 1783 :

SKAFTÁRTUNGA, ICELAND–Hildur Gestsdóttir shovels a heap of fine black soil onto a growing mound beside the unmarked grave, grateful for a breeze from a nearby glacier that’s taking the edge off the strong summer sun. “It’s a lovely day for gravedigging,” a member of her team remarks. Hildur agrees: “Conditions are perfect.”Hildur ought to know, having exhumed about 50 skeletons to date with the Institute of Archaeology in Reykjavik. Usually she’s after the remains of Vikings, who settled the island 1000 years ago, or later medieval inhabitants. This grave is much more recent, dating from the late 18th century. Although the period is not her forte, the skeleton beneath Hildur’s feet on Búland farm could well be a researcher’s treasure, offering clues to why the eruption of the nearby Laki fissure in 1783 was so deadly. One of the largest and least appreciated eruptions in recorded history, Laki killed 10,000 Icelanders–roughly one in five–and recent studies suggest that its billowing plumes led to extreme weather and extensive illness that may have claimed thousands more lives in Britain and on the European continent.

“It’s hard to fathom the impact of Laki,” says volcanologist Thorvaldur Thordarson, a leading expert on the eruption. A similar blast in modern times would pump so much ash and fumes into the upper atmosphere that the ensuing sulfuric haze could shut down aviation in much of the Northern Hemisphere for months, Thordarson and Stephen Self of Open University in Milton Keynes, U.K., argued last year in the Journal of Geophysical Research.

“It’s not a matter of if but when the next Laki-like eruption will happen” in Iceland, says Thordarson, who splits his time between the University of Iceland and the University of Hawaii, Manoa. “We certainly don’t want to be here when another Laki-type event hits,” adds Self. Offering a tame glimpse of what the future may hold, the brief eruption of Iceland’s Grímsvötn volcano earlier this month led to the cancellation or rerouting of transatlantic flights. Still, volcanologists say, the odds of a full-blown fissure eruption in this century are low.

By examining presumed victims of Laki, Hildur and her colleagues, including project leader Peter Baxter, a medical researcher at the University of Cambridge, U.K., are testing a thesis that fluoride in Laki’s emissions poisoned people directly and may account in part for the high death toll. “It was the greatest calamity to affect Iceland since human occupation began there,” says Baxter.

During the eruption, an estimated 1 million tons of hydrofluoric acid were deposited over Iceland, contaminating the country’s food and drinking water supplies. Icelanders who lived through the eruption noted that sheep and other livestock developed knobbly protrusions from their bones that were clearly visible under the skin–a telltale sign of fluorosis. Baxter’s team is the first to exhume presumed victims of Laki to look for abnormal bone growth and high levels of fluoride that could well have led to fatal poisoning in people during the later months of the eruption.

If they are right, Iceland’s fissure eruptions may be much more dangerous than scientists had supposed. And this realization implies that civil-defense planners need strategies for the next Laki-like event. “It’s important to consider what the next one is going to do, and how we can prepare for it,” says Clive Oppenheimer, a volcanologist at the University of Cambridge.

Cancellation of flights, closed airspace – sound familiar?