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Wednesday, March 5, 2008

Hydrogen Sulfide May Kill Us, Bring Us Back to Life

Peter Ward tells the crowd at TED 2008 about the perils of hydrogen sulfide, which he says wiped out 90 percent of Earth's species during the Permian period.
Courtesy Ted Conferences

Millions of years before the dinosaurs were apparently killed by an asteroid hitting our planet, the Earth experienced another mass extinction that was far more devastating. The cause for that, paleontologist Peter Ward says, was actually homegrown: Hydrogen sulfide in the oceans and atmosphere turned the sky green and choked off oxygen for plants, animals and marine life.

Ward, who teaches at the University of Washington and who spoke at the Technology, Entertainment and Design (TED) conference last week, says that global warming caused by humans could reproduce the same hydrogen sulfide gas conditions that killed more than 90 percent of life during the Permian period, when the extinction occurred. And we might just do it faster than nature did.

Ward, who published a book about the extinctions last year called Under a Green Sky, is involved in a project with Arizona State University to design a $60 million atmosphere chamber to reproduce the Earth's atmospheric conditions from the Permian period--as well as any other period they want -- and recreate the die-off with plants grown in the chambers. The aim is to see what kinds of signs are left behind so they can then look for them in nature today and see what they tell us about evolution.

Although hydrogen sulfide has the potential to be a mass murderer, researchers have recently discovered a possible medical use for the deadly gas that could, ironically, also save millions of lives. Tests have only been conducted on mice, but so far they show that hydrogen sulfide injected directly into the heart of mice suffering a medically induced heart attack puts their bodies into a state of suspended animation and results in the heart cells sustaining less damage than those of mice who did not receive the injections.

Ward spoke with Wired.com about the possible risks and benefits of hydrogen sulfide and how gas masks may be in our future.

Wired: Explain how the Permian mass extinction occurred.

Peter Ward: Step one is, there's an enormous release of flood basalts coming out of cracks in the earth, and huge amounts of magma from the deep Earth comes out. These things go on for millions of years, and the volume of lava is extraordinary. It may have covered an area the size of the continental U.S.

Now, the lava doesn't kill much, except the poor, stupid animals that were crazy enough to be around there. But as the lava comes out, carbon dioxide bubbles out with it and a lot of carbon dioxide goes into the atmosphere to the point that we estimate the carbon dioxide levels hit 3,000 parts per million. [Current carbon dioxide levels are about 380 parts per million.]

This causes the oceans and the planet to warm, and once you do that you stop ocean currents. Once you stop currents, you lose oxygen in the ocean, because it's circulation that keeps the ocean oxygenated. This allows a type of bacteria to take over that creates hydrogen sulfide (H2S). Animal life cannot live in water that has a lot of hydrogen sulfide in it. When you have concentrations of greater than 80 ppm of hydrogen sulfide, or you get up to 200 ppm, which is easily done, you'll kill every animal [in the ocean]. Eventually so much hydrogen sulfide leaks into the atmosphere that it kills animals and plants.

Wired: How many land species were there at the time and how many were killed?

Ward: On land you had hundreds of species of mammal-like reptiles -- the first stage of mammals. It was over 90 percent extinction, not just of land animals but of ocean animals and plants. Only 50 percent [of species] in the asteroid-dinosaur stage died. So this was way, way worse.

Wired: How long did it take for this to happen?

Ward: It occurred slowly, over thousands of years. We still do not know precisely how long.

Wired: It's believed that hydrogen sulfide was the cause of at least two other mass extinctions, right?

Ward: Actually, I think it's up to 12. Every mass extinction except the dinosaur extinction seems to have been caused by this. It's all about when the Earth decides to spit out these big burps of magma that come to the surface. But a big mass extinction from global warming has not happened in 100 million years.

Wired: We place the blame for our current global warming situation on rising CO2 levels created by man. But the previous episodes of global warming and mass extinctions were entirely the cause of nature. It seems as if we could do everything in our power to reduce man-made global warming and still face global warming and mass extinction from nature if we have flood basalts at the level that occurred during the Permian period.

Ward: Not really -- those past episodes were from very rare flood basalts. There may not be another of these, as the Earth is cooling as it ages.

But we've had these mass extinctions [from hydrogen sulfide] when carbon dioxide has hit 1,000 ppm. We have not hit that [level] for 100 million years. But we are currently at 380 ppm -- and climbing rapidly at 2 ppm a year and accelerating -- and this is the highest CO2 I think in the last 40 million years. The only time [these extinctions] ever happened in the past is when these big flood basalts happened. But now we're making it happen far faster than the flood basalts ever did. This is a unique event in the history of the planet.

Wired: What would life look like as the Earth's oxygen is slowly choked off by hydrogen sulfide and how long would it take?

Ward: This really is a long way off. This is something that's going to take thousands of years. The oceans take a long time to change from oxygenated to a place where there is no oxygen on the bottom. But once it starts, you can't stop it.

I think sea-level rise is a more imminent danger. The thing that we have to do is, we have to save the ice caps, because if the ice caps go, (the hydrogen sulfide scenario) is the inevitable next step. One thousand ppm (of CO2) is all it would take to get rid of all the ice caps on the planet. We'll be at 1,000 in 200 years or less. Which means good-bye ice caps on planet Earth, which means 240 feet of sea level, which means good-bye San Francisco, Seattle, New York and on and on.

But if losing the ice caps makes us uncomfortable [because of rising water], the hydrogen sulfide is going to make us extinct. In 500 years, I can see a world where everyone will be wearing gas masks. Those that [have] them will live; those that don't will die. We humans are here for the long haul, and if we do not stop heating our atmosphere, we will suffer a very nasty fate.

Wired: Are there any areas on the planet where we can see the beginnings of something like this already happening with hydrogen sulfide?

Ward: Right now off the coast of Namibia there is hydrogen sulfide coming out. Fisheries went in and killed off all the anchovies and sardines. Then the plankton comes up, and there are no fish to eat them and they go to the bottom and rot. That rotting produces hydrogen sulfide and it rises to the surface and is causing all kinds of havoc. Where I live [Washington state] we have hydrogen sulfide hot spots coming from the old logging camps. All the wood waste that was buried in the last two or three centuries is now rotting to the point that well-diggers have to [carry] a gas mask because if they puncture one of these hydrogen sulfide bubbles it will kill them.

Wired: Recently researchers have posited that there's also a possible medical benefit from controlled use of hydrogen sulfide. You've called it the next and best boon for medical science. What are the practical applications of the gas?

Ward: With H2S, a mammal can be turned functionally into a cold-blooded animal and cooled far lower than could otherwise take place [to slow down the progression of injuries]. This could save a lot of lives [in a medical crisis]. The Buffalo (Bills) football player (Kevin Everett) who had the accident -- the reason they were able to do the neurological stuff they did on him was because they were able to cool him [until they could treat him]. In a situation like that, you're buying time.

The critical part of a heart attack, it has been shown over and over, is that if you can get them to a hospital fast enough they will survive. So let's say you're in Iraq and they've just blown your leg off with an IED. You're bleeding out. You're dead. Put the hydrogen sulfide in -- you bleed out, but you're slowed down. You get to the hospital, and they fill you back up again with blood again.

Each cell (already naturally) produces a minute amount of hydrogen sulfide, and it causes that cell to reduce activity. So when you're in a crisis, it's as if [the cells and body] come to the conclusion, "I'm in a crisis; I can't be expending energy, I better go into reserve [mode]."

So [if you give someone hydrogen sulfide] to replace the oxygen, theoretically, instead of that lack of oxygen killing you, your metabolism shuts down so low, your need for oxygen reduces immensely. We're talking about a situation where your heart only needs to beat once a minute or so. What we're really talking about is not suspended animation; we're talking about [medically-induced] death. And then we bring you back. We're going to artificially kill people so it buys us time, and then bring them back alive.

Wired: How long could you stay in that state?

Ward: Four to six hours in mice, and they come back perfectly the same. The trouble is ... we don't know what's going on in the brain cells. And this is the biggest issue with this. How much brain death will there be? There will be some. So here's the ethical dilemma: If I get in a car wreck, my wife who loves me dearly, would she rather have me back as a vegetable, a half-Peter? What if I come back without any memory of her whatsoever? Or what if I can't write? Is it better to have me like that ... or is it better to just let me be dead? Going in, you don't know what you're going to get coming out.

Wired: So why would you say this is the greatest boon to medicine?

Ward: Because for some people, they will come out fine. That woman who had the stroke (Jill Bolte Taylor, who spoke at TED last week), she rebuilt everything. Brains rebuild. Yes, you have all this damage, but there's no reason you can't rebuild right around it to get exactly where you were [before the accident]. But we'll be able to save a hell of a lot of lives.

Original here


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