Laki - The Biggest Atmospheric Pollution Event in History
If you think our air is polluted today, spare a thought for those living in Iceland in 1783, when an eruption in the Laki fissure caused "the biggest atmospheric pollution event in history". We spoke to John Grattan from the University of Wales, Aberystwyth.Chris - So if this volcano were industry, the government would have shut it down on health and safety grounds?John - Absolutely, it emitted about 17 times more sulphur than all of Europe today put together.Chris - So tell us about the events that led up to this eruption, how it got documented and what the consequences were.John - Well it all began in early June 1783 in Iceland, which was a very remote place at that time. A very astute pastor called John Steingrimsson started to notice a dark cloud building to the north, and that was followed by what he describes as iron filings falling to the earth and burying the plants. That was quickly followed by the smell of sulphur, and within a day or two the animals started to die, then people started to die. Within a few days, the livestock had gone. By the end of the event three quarters of Iceland's livestock (sheep, cattle, horses) had all died, along with about a quarter of Iceland's population. It was bad in Iceland.Chris - So what was the reason that those people and their animals succumbed?John - Well, there are several causes. The first one, as far as the animals are concerned, is the eruption threw out fluorine which landed on the vegetation which was eaten by the animals. That released the fluorine into their bodies, poisoning them. Essentially, their stomachs became blocked up with ash, they couldn't ruminate and the fluorine triggered uncontrollable bone growth. Sheep's teeth grew uncontrollably and they developed 'fangs' that restricted their ability to eat. Their joints developed growths which meant they couldn't walk, it was really an apocalyptic vision. The people in Iceland at the time saw it as the end of the world; as God's judgement on a sinful nation.Chris - Is it a one off, or have there been lots of examples of volcanoes having this kind of catastrophic effect before?John - I think there was an eruption on a slightly bigger scale in the 10th century, an eruption called Eldgjá which was even bigger. Probably, there's an eruption like this in Iceland, on this scale, every 500 years or so. Small eruptions in Iceland still do release fluorine and they do kill livestock, as recently as 2000 the eruption of Hekla killed livestock in Iceland. It's not just the impact in Iceland that is the problem. The Laki fissure released hundreds of millions of tonnes of sulphur into the atmosphere, and it was transported around the world. A lot of it was transported to Europe, where it also had terrible impact.Chris - So if you add up how much comes out of one volcano, how does it compare with mankind's activities? I've got an email here from Eric Taylor in the USA. He wants to know how volcanoes compare to cars, houses, or industry in terms of their emissions.John - You've put me on the spot there and that figure has slipped out of my head! But I can tell you that mount Etna, in a typical year, emits as much sulphur as all of France's industry, so it is a significant contribution. You have to remember that the planet's ecosystem has evolved with volcanoes doing this, and the problem with mans' emissions is that they are extra to this, and they often have concentrated local impacts, in cities or forests which aren't expecting to receive a contribution of sulphur dioxide. Where a volcano is emitting sulphur, the ecologies around it have grown an adapted to tolerate that.Chris - If you look further afield than just the local environment though, as you said these gases get spread right the way around the world, what can we say happens to the Earth's atmosphere, the environment and climate as a consequence of volcanoes?John - Typically, from a low intensity eruption the gases get emitted into the troposphere, they're diluted by atmospheric processes, they're rained out as very dilute acid rain and there's really no significant impact from them. Where we have large scale eruptions (which are less common, at one in five hundred years for instance) then we're dealing with hundreds of millions of tonnes of sulphur being emitted in a relatively short time. These then can be concentrated by atmospheric processes and can have a really severe impact. In 1783, when the Laki fissure eruption was taking place, a sulphurous dry fog formed all over Europe, and people were describing how their crops were being killed, leaves were falling off trees, people were complaining of the smell of sulphur, coughing and people were dying in great numbers. We think that in the summer of 1783 something like 20,000 extra people died in England alone, as a result of the environmental impact of this [eruption].We've got two things going on, the normal background typical year on year eruptive activity and these once in 500 years events which do significantly stress the environment.Chris - We've had similar things with the "London Smogs" in the 1950s though, we know that atmospheric pollution is bad for you.John - We do, and that's certainly what was the case in the 1950s. When I was beginning to investigate the Laki fissure I turned to these smog events to try and get an understanding of what may happen when you get significant concentrations of sulphur on the ground. Certainly, when you're dealing with an event like the Laki fissure, where it erupted for 8 months - people don't always realise this, they have this idea that eruptions last a few spectacular days, then it dies down. Throughout that 8-month eruption it's throwing material into the atmosphere and so there's a long-term environmental stress from something like this. In our world today if something like this were to happen we can imagine the scenario where we have atmospheric pollution in London, or Birmingham or any significant conurbation and then one morning, courtesy of an Icelandic volcano another 2 million tonnes of sulphur are delivered. That's going to push the environmental thresholds significantly, and then I think we can expect to see the significant health impacts and mortality crises.Chris - So you could actually say, because this thing blows up in Iceland you would be able to trace a health effect in the UK, in France, perhaps even further afield in Russia, China, Japan even?John - Absolutely. We've traced this, day by day, from the moment the eruption began all the way through to 1784 when the eruption ended. We've got a day by day history of the eruption and people's health, and we can see the arrival of the smog, the destruction of crops and plants and then the people dying. People begin to die in great numbers in August, September and October 1783. The people writing at the time were amazed by this, the sulphurous smog that meant you couldn't see across the valley, and they were clearly linking the arrival of the smog with deaths. There were some French priests who wrote "when the fog arrived, a third of the men of my parish were swept to their tombs". People were really scared, there's one letter which tells of the people of one parish being so afraid of this smog that they thought the end of the world was here, the gates of Hell had opened and the Devil was walking the Earth. They dragged the priest out of his house, made him put on his vestments and perform a service of exorcism on it.We've got all of this happening in the 18th century where there is relatively little industrial pollution. If an event like this were to happen now or in the future when we have significant industrial pollution and pollution in cities because of cars and industry, we're dealing with an event where the thresholds for human health impacts are much closer.