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Science News Highlights: Ozone Layer, DNA Swap

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Scientists say nitrous oxide is in line to become the leading threat to the ozone layer. In other news, researchers have swapped DNA between monkey egg cells, correcting certain genetic diseases in the offspring. NPR science correspondent Richard Harris runs through the new research.


This is SCIENCE FRIDAY from NPR News, and I'm Paul Raeburn, sitting in for Ira Flatow. This week, researchers from the National Oceanic and Atmospheric Administration released new findings on the ozone layer. They report in the journal Science that nitrous oxide, which is used widely in agriculture, known to many of us better as laughing gas, was set to become the dominant ozone-depleting substance in the 21st century, and there's probably not much we can do about it.

Joining me now to talk more about the study, and another study about some genetic manipulations in monkeys, is NPR science correspondent and my good friend Richard Harris. Thanks for taking the time, Richard.

RICHARD HARRIS: Sure, good to be with you, Paul.

RAEBURN: So give us a call. Our number is 1-800-989-8255. That's 1-800-989-TALK. If you're on Twitter, you can tweet us your questions by writing @scifri. If you want more information about what we're talking about this hour, go to our Web site at, where you will find links to our topic.

So Richard, nitrous oxide in the ozone layer, I think I understand this study. Dentists are going to destroy the ozone layer. How am I doing?

(Soundbite of laughter)

HARRIS: Well, fortunately, not true. I did get a nervous email from someone saying I love getting laughing gas at the dentist office. Please don't let them take it away. And don't worry, they won't. That's an incredibly tiny, minor source of nitrous oxide, but - so that's not a worry. But the worry is that there are enormous sources of nitrous oxide, and they're very hard to deal with. I don't know where you want to start the story, talking about the ozone layer or where the nitrous oxide comes from.

RAEBURN: Where does it come from? I mentioned that it's used in agriculture, but I don't know exactly how. What is the story there?

HARRIS: Yeah, it's not exactly used in agriculture, but what happens is we put nitrogen-based fertilizers on our fields to make them grow better, and what happens is a small quantity of that nitrogen gets - a lot of it gets picked up by the plants, but some of it actually gets picked up by bacteria in the soil. And they mostly do good things with that nitrogen fertilizer, but a small percentage of it they convert into nitrous oxide. It's just sort of an accident. It's not any particular major function for the bacteria, but, like, a couple percentage of the nitrogen ends up being converted by the bacteria into nitrous oxide.

RAEBURN: This is a byproduct of nitrogen fixation. Is that right?

HARRIS: Yeah. It's a byproduct of - yeah, exactly - these bacteria. And so then the nitrous oxide then gradually wafts up into the atmosphere, and from there, it goes up into the upper atmosphere, the stratosphere. And the chemistry gets a little bit complicated, but in some, what it does is it ends up, or can end up, destroying ozone.

RAEBURN: Now where - I just want to remind myself here. We're talking about the ozone layer. We're not talking about climate change here.

HARRIS: Right, although actually, now that you mention it, nitrous oxide also contributes to global warming, so…

RAEBURN: Do you have any good news today, Richard, or…?

(Soundbite of laughter)

HARRIS: Well, not necessarily on this topic, but so yeah - so at any rate, the ozone layer is a layer of ozone way up in the stratosphere, way above where the airplanes fly, and what it does is it blocks harsh, ultraviolet light from the sun. And that's a really good thing for us because ultraviolet light is the main kind of light that gives us skin cancer, and it can also have other bad effects on life on earth if it's too harsh, too intense.

So basically, the earth is shielded from this by the ozone layer, and we had a near catastrophe on planet earth a couple of decades ago when we started pumping chlorofluorocarbons up into the stratosphere - another man-made chemical, very useful for refrigeration and in many ways an excellent industrial chemical. But unfortunately, what we were slow to realize was that it also destroys these ozone molecules that protect us from ultraviolet light.

And if we hadn't done anything about that, the earth would be in really serious shape. We would've destroyed so much of this ozone that we would have just major skin-cancer problems and all sorts of other, just really harsh - we would be bathed in really harsh, ultraviolet light.

But fortunately, scientists became aware of this problem and diplomats actually listened and created what's known as the Montreal Protocol, probably the best environmental treaty ever designed, and basically we phased out these synthetic chemicals that destroy ozone. And so what's happened - what we're starting to see around planet earth is since about the year 2000, the ozone layer is actually starting to get thicker again, and it's healing itself.

So that's great, but as a result of losing all those chlorofluorocarbons that were in the stratosphere, we now have - so the problem is mostly solved, but the question is, well, so what else is destroying ozone? And so these scientists at - Avi(ph) Ravishankara was the main scientist, a very accomplished scientist at the NOAA laboratories in Boulder, Colorado. He said well, you know, let's think about other gases that can do nasty things to ozone, and he did this calculation and realized wow, nitrous oxide actually is - now that we've taken care of chlorofluorocarbons and the other similar gases, this is now the big actor. This is actually destroying more ozone than anything else.

The good news - there's good news and bad news. Do you want the good new or the bad news first?

RAEBURN: I want - desperate for good news at this point.

(Soundbite of laughter)

HARRIS: Okay, so the good news is this is a much, much smaller effect than what we could have been facing with the chlorofluorocarbons. He did a sort of back-of-the-envelope calculation for me and figured that it might, compared with pre-industrial levels of ozone, the nitrous oxide levels, if they kept growing the way they are right now, would probably thin our ozone layer by about four percent compared to pre-industrial levels.

Nobody wants it to be any thinner than pre-industrial levels, but four percent means that we're still - pardon me - we're still quite well-protected from ultraviolet light. A little more gets in. It means the increased risk of skin cancer is there still, but it's not, it's not a global catastrophe the way that we could've been facing with these other chemicals. So that's the good news.

The bad news is if you want to try to do something about it, it turns out to be really hard because, as I mentioned, this is generated by these microbes not only in the soil, but also microbes in the ocean also produce this. It is a natural part of earth's nitrogen chemistry. We happen to be amplifying that chemistry because we have put so much nitrogen into the system to help increase agriculture and feed the 6.5 billion people on earth.

So we've dramatically increased the amount of nitrogen, and therefore, these bacteria are producing more nitrous oxide, and short of stopping fertilizing fields…

RAEBURN: We could stop eating and stop growing food, and we'd be just fine.

(Soundbite of laughter)

HARRIS: Yeah, well I mean, obviously there is some misuse of fertilizers. And if we could find better ways to, you know, not overuse fertilizers and ways to prevent fertilizers from running into oceans, then that would help. But it would not make a dramatic difference, as best anyone could tell.

There are, by the way, a couple of other sources of it. There are some industrial processes that produce nitrous oxide. So we could think about that. The other source is, to some extent, your tailpipes. When your car burns its gasoline, there's also a trace of nitrous oxide in that, although there have been efforts over the years to try to reduce. That's part of the NOx thing you hear about, that - yeah.

RAEBURN: All right, let's get to the other story we promised before we promised before we run out of time.

HARRIS: Oh, okay.

RAEBURN: I'm glad to know that our laughing gas with our dentist is safe. That's a relief. So now, the other story, interesting story, one of the other interesting stories this week, was in Nature about correcting some genetic flaws in some rather unusual inherited illnesses. Tell us a little bit about what these guys did.

HARRIS: Okay. This research was done in Oregon at the Oregon Natural Primate Research Center at University of Oregon, and basically - or I guess more technically, at the Oregon Health and Science University - and basically, these guys started with a question, which is that we, you know, we have - almost all of our genes are on our chromosomes, right, and our chromosomes are inside the nucleus inside our cell.

But it just so happens that there are a handful, just a couple of dozen human genes, that actually don't live in the chromosomes, in the nucleus. They are actually floating around in the rest of the cell, and they are inside little, tiny organelles called mitochondria. And these mitochondria produce power for our cells. They're little energy factories. So we can't live without them at all, but it turns out that you can get mutations in those genes, just the way you can get mutations in the genes in your chromosomes, and those can cause human diseases. Some of those, they're obscure diseases, but nonetheless, they can happen.

So these guys said, well, would there be a way to cure these kinds of diseases? And their concept was if you could find a way to take healthy mitochondria and combine them with a nucleus of somebody who wants to reproduce, then you could - but who has unhealthy mitochondria, then you've managed to sidestep this disease. You prevented these genetic diseases.

And they figured out how to do this in monkeys, and this is what they did. They started with a monkey egg, and they took the nucleus out of the egg. And then they took another monkey egg, and they took the nucleus out of that egg. And they took - they basically transplanted the nucleus from one egg to another egg, and the second egg would essentially have good mitochondria, right?

So what you've done here is you've create the nucleus from the mother monkey that you want to reproduce, and you've put it into a cell that has healthy mitochondria. And they did this a bunch of times, and lo and behold, they have now - reporting that they have four healthy baby monkeys as a result of this.

RAEBURN: So some of the stories this week I saw said, you know, monkeys with two mothers, but that didn't sound quite right to me. It's really - isn't it really one mother and then a few genes from somebody else?

HARRIS: Yes, that's true. Most - you know, the vast majority of the genes come from a single mother. Thirty-seven, or something like that, come from this other female. So yeah, so it's a bit of an exaggeration to say two mothers, but I can understand why people would say that, also.

RAEBURN: Now, we're talking about genetic changes here. They're going to now be in the offspring of these monkeys and their offspring and so forth. And presumably once people find out this is safe and assure themselves it's okay, somebody's going to want to try it in humans. There are human mothers and fathers and potential parents who would like to have this, I'm sure. You know, what about the ethics of this? Is it something we want to condone? Is it something we want to ban? What do you think about that side of this?

HARRIS: Yeah, that's an interesting question because for a long time, geneticists have said, you know, we can - they're comfortable fiddling around with genes and doing some human experimentation if they have some relative assurance of safety, but there's been this sort of bright line that says don't do anything that affects more than the individual you're working on. Don't do something that's going to affect future generations. And there are a couple of reasons for that, one of which is if it turns out that you're wrong, and there is something that you didn't realize, a health effect from doing this, you haven't just affected one individual, you've affected, you know, all of their offspring and all their progeny from that point forward, and that's an important ethical question.

RAEBURN: And - but this is a little different, isn't it, with the mitochondria? We're not changing people's hair color. We're changing these energy factories. Does that potentially make it an easier thing to kind of condone?

Okay, so we'll have more. We lost Richard…

HARRIS: Oh, here I am.

RAEBURN: Richard's back, okay.

HARRIS: I'm back.

RAEBURN: Okay, did you hear my question?

HARRIS: Yes, and I guess I started launching in on an answer without realizing…

(Soundbite of laughter)

HARRIS: …you're not hearing me, so maybe could you re-pose the question so I could…?

RAEBURN: Yeah. You know, if we were manipulating people's genes to change their height, their eye color, all kinds of fundamental things, we'd say whoa, that's a little scary, but this is just these little energy factories. Is this an easier thing to sort of condone? We just have a little bit of time left.

HARRIS: Yeah, I think probably it is an easier thing because you're not creating a whole new human being, but the problem in this country is we really do not have a really good system for having that ethical debate.

RAEBURN: That'll do it, Richard. We'll have to stop right there. I'm sorry.

HARRIS: Okay. Sure.

RAEBURN: My guest has been Richard Harris, NPR science correspondent for NPR News. Thanks for taking the time, Richard, good to talk to you.

HARRIS: Likewise.

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