Science Friday - Is Chemical Sunscreen Safe, Slime, Amazon Deforestation. August 2, 2019, Part 2

Episode Date: August 2, 2019

Sunscreen has been on the shelves of drugstores since the mid-1940s. And while new kinds of sunscreens have come out, some of the active ingredients in them have yet to be determined as safe and effective. A recent study conducted by the FDA showed that the active ingredients of four commercially available sunscreens were absorbed into the bloodstream—even days after a person stops using it. Ira talks to professor of dermatology and editor in chief of the Journal of the American Medical Association Dermatology Kanade Shinkai about what the next steps are for sunscreen testing and what consumers should do in the meantime. Often called the planet’s lungs, the trees of the Amazon rainforest suck up a quarter of Earth’s carbon and produce a fifth of the world’s oxygen. The National Institute for Space Research in Brazil has been using satellite images of tree cover to monitor the Amazon’s deforestation since the 1970s—and new data shows a potentially dangerous spike in deforestation. In the first seven months of 2019, the rainforest lost 50% more trees than during the same period last year. That spike in tree loss has coincided with Brazil’s new president, Jair Bolsanaro, taking office in January and slashing environmental protections. Bolsanaro even called the new data a lie. But climate scientists warn deforestation is pushing the Amazon rainforest to a tipping point that would disrupt both its ecosystem and the global climate. Ira talks to Carlos Nobre, a climate scientist at the University of Sao Paulo’s Institute of Advanced Studies, about the new data and why deforestation in the Amazon is so risky for the planet. When you think of algae, one of the first images that might come to mind is the green, fluffy stuff that takes over your fish tank when it needs cleaning, or maybe the ropy seaweed that washes up on the beach. But the diversity of the group of photosynthetic organisms is vast—ranging from small cyanobacteria to lichens to multicellular mats of seaweed. Author Ruth Kassinger calls algae “the most powerful organisms on the planet.” She talks about how this ancient group of organisms produces at least 50% of the oxygen on Earth, and how people are trying to harness algae as a food source, alternative fuel, and even a way to make cows burp less methane. Subscribe to this podcast. Plus, to stay updated on all things science, sign up for Science Friday's newsletters.

This is Science Friday. I'm Ira Flato. Later in the hour, do you know what's in your sunscreen and that it moves from your skin into your blood? We'll talk about that. But first, the Amazon rainforest is often called the planet's lungs in the process of growing and breathing. Its trees suck up a quarter of the Earth's carbon and produce a fifth of the world's oxygen. So new data from the National Institute for Space Research in Brazil is of great concern. Researchers monitoring satellite images of Amazon tree cover found an alarming spike in the Amazon's deforestation. In the first seven months of 2019, the rainforest lost 50% more trees than during the same time last year.

That spike in tree loss coincides with Brazil's new president, Javei Air, Bolon Saro taking office, and since January, he's slashed environmental productions and has reportedly called the new deforestation data a lie. But climate scientists warned deforestation is pushing the Amazon rainforest to a tipping point that would disrupt both its ecosystem and the global climate. Dr. Carlos Nobri is a climate scientist at the University of Sao Paulo's Institute of Advanced Studies. He joins us via Skype. Welcome to Science Friday. Thank you very much.

So put this in perspective, would you? How alarming are these new numbers on deforestation? The numbers are very worrying because Brazil and most of the other Amazonian countries for about 10 years from 2004 to 2012-13. They were declining over 70% deforestation rates. they were really moving towards almost a zero deforestation, and still the production of agricultural products were increasing. So deforestation has nothing to do with agricultural production. So everybody was happy, but after 2014, deforestation rates started to climb back again,

and this year, the last 12 months, have seen a spike, have seen a surge, A very troublesome search, very likely the last 12 months, we will see an increase of 40 to 50% in deforestation rates in Brazil. Also, deforestation rates in Colombia are increasing. So this is a sign that we might be closer to the tipping point for the Amazon. If we defourced more than 25% of the forest in the Amazon basin, we might really, really ruining the Amazon forest would move to a new system in which it becomes

irreversible to maintain the forest over 56% of the basin. And now this spike in deforestation has happened under Brazil's new president, Jaya Bolsonaro. Does he understand this, that this is

a danger? I'm not sure the current president and he's mostly the ministers associated, particularly the minister of the environment, have a full understanding of the risks that are Brazil and the Amazon countries are under, because you see the forest is a, the Amazon forest,

provides a lot of ecosystem services. For instance, recycling, water vapor and increasing rates, keeping temperatures to three degrees cooler than without the forest. So this is all benefits, even for agricultural production south of the Amazon. And so if the forest disappears, the life, the agriculture, the life of the people will be much worse without the forests. So I don't think the president and his minister of agriculture understand the full consequences. consequences of continuing to de-force the Amazon. I think their policies are aimed at a very short-term

gains in pushing the agricultural frontier cattle farms and also soy plantations into the Amazon. So is it all about the money then? It's about short-term gains. It's about really seeing opportunities to increase. increase production of those goods, agricultural goods. But this is very short term because without the Amazon forest, even the productivity of cattle farms or crops will be diminished up to the point that you might not have suitable agricultural crop lands or grazing lands for cattle in the near future in less than 20, 30 years. And what about the indigenous communities and their land in the Amazon? What are his policies on their rights?

He comes, actually, even when he was a House member for 28 years, the President was a House member. For a long time, he has defended the idea that the indigenous lands are too large in extent. they should not be demarcated anymore. And also now as a president, he's trying to convert indigenous cultures into a different culture, into, let's say, our culture, farmers, cattle ranchers. But that really goes very much against the cultural inheritance of this more than 300 different indigenous communities in the Brazil. in Amazon they want to keep their culture which is a standing force culture which is not only good for them for their culture but it's also very important for the maintenance of climate stability

for the planet if the Amazon forest disappears we will almost impossible to reach the targets of the Paris Agreement to keep the temperature of the planet less than two degrees warmer. Well, is there going to be a tipping point in the rainforest where that happens? A lot of scientific studies, and I've been involved in those studies for almost 30 years, they indicated that if we exceeded 20 to 25% of deforestation in the whole Amazon, Or if we keep global warming unchecked and the temperature in the Amazon region increased 4 degrees Celsius, we might really exceed and tip this balance and transform 50, 60, up to 70% of the forest into a degraded savannah,

which much less carbon, with much less biodiversity. So we are now currently at total deforestation is about 15, 16 percent in the basin, and the Amazon is about 1.5 degrees warmer. So if we continue the deforestation rates, as they are in the last few years, the tipping point will be exceeded, reached in something like 20 years. And do you find, you know, anything besides President Bolsonaro in your way or in the way of making sure that doesn't happen? Well, we hope that he will listen to the voices of the people, of the Brazilian people, the Amazonian people, because all polls conducted the last 20 years, including Poles conducted after. he was elected, 90% of Brazilians are against Amazon deforestation. So we hope democracy will have the last word. Every Brazilian, almost all Brazilians, 9 out of 10, are against Amazon

deforestation. So I hope eventually democracy will prevail and he will listen to the voice of the people, including, including his electors, his voters. Also against Amazon deforestation. Well, let's talk about it. If the rainforest does become a savannah, what does happen to the global climate? Well, initially, there will be, over the course of this transition, which might take between 30 and 50 years, a tremendous loss of carbon. The forest stores a lot of carbon in underground, in the trunks, branches, etc. It's a lot of carbon.

It's about 120 to 150 tons of carbon per hectare per 10,000 square meters. A savannah, a degraded savannah that might replace the forest, store something like 30 to 40. So we lose 70 to 80 tons. of carbon per hectare that will end up in the atmosphere as carbon dioxide again complicating the global global climate crisis so if all these carbon ends up in the atmosphere the keeping meeting the targets of the Paris accord will become much much less difficult perhaps even impossible so this is a fact a very

important fact and also savannas degraded savannas contain much less biodiversity so we are talking about extinction of tens of thousands of species that exist only the tropical forest and the last but not less important is the fact that you know perhaps one million people living in indigenous lands with their culture their forest culture might be at the risk of losing the forest Are you hopeful about this? It seems very scary. Well, I'm hopeful that loss. First, of course, you know, Brazil and all other Amazonian countries, there are democracy.

So people go out and vote. So I hope, you know, because this issue became so urgent, so critical with the increase in deforestation rates in the last few years. in the last 12 months, that, you know, the voice of the people will be heard by all politicians, not only Brazil, but all Amazonian countries, and that they will eventually start thinking harder and find ways of developing our countries without deforestation. All right. We have to leave it there, and we hope we share your optimism, Dr. Carlos. No break, climate scientist at the University of Sal Palo's Institute of Advanced Studies. We're going to take a

break and when we come back, we're going to talk about sunscreen. How much do you know about it? How much do you know how it's regulated? How much do you know how much of it gets into your bloodstream, even though you put it on your skin? We'll talk all about that stuff after the break. Stay with us. This is Science Friday. I'm Ira Plato. It is summertime. It is a time when doctors have been telling us to wear sunscreen. They've been telling us to do this. for decades now, right? And for good reason, melanoma is one of the most dangerous forms of cancer. And while some of us might slather or spray it on before a day at the beach, others are

even more diligent and use a little bit of sunscreen every day. We asked you to tell us on the Science Friday Voxpop app what you've been told about sunscreen and how you use it. I've been told by my dermatologist to use it, use it, use it. I try to use it, but I don't use it that often. I try and just stay covered up as much as I can. Recently, I read an article suggesting that sunscreen doesn't actually block the cancer-causing UV, but it does block the UV that causes you to get sunburned.

My understanding is that you need both UVA and UVB protection, probably at least SPF 30 or greater, although I've been told that anything above that probably doesn't offer you that much more protection. It's just hype. Well, we're going to talk about that. And those are listeners, Richard in Wisconsin, Andrew in New Zealand, Bill in Oregon on the Science Friday Voxpop app. So I'm asking you, now again, what have you been told about sunscreen? Do you use it? Download the Science Friday Voxpop app and leave us a little voice message there like they did to let us know.

And also you can call us now at 844724-8255, 844-724-Sight-Talk, or, of course, you can tweet us at SciFRI. One thing that we're probably all been told is that sunscreen can prevent sunburn, even skin cancer. But listen to this. A recent study conducted by the FDA put sunscreen safety in question. My next guest was not part of the FDA study, but is here to discuss what we need to know in light of it. Kanada Shinkai is a professor of dermatology and the editor-in-chief of the Journal of the American Medical Association Dermatology. Just to note, we did reach out to the FDA for the segment, but they said no one was available to join us today. Welcome to Science Friday.

Dr. Shinkai. Thank you so much for having me on the show. That's great. We know that we should use sunscreen, but exactly how does it protect our skin from the sun? Well, sunscreen is used for two purposes. The first is to prevent sunburn, and the second is to prevent skin cancer when you are exposed. There's really two types of sunscreens, and I think consumers have noticed this when they go shopping to look for purchasing a sunscreen. The first type is mineral sunscreen.

These are literally minerals, things like titanium dioxide and zinc oxide. They coat the skin, and that causes reflection or refraction of ultraviolet rays. They literally bounce off the skin surface and are blocked from entering the skin. The second type are chemical sunscreens. These are chemical filters that are used typically in combination with each other to provide a broad spectrum, or meaning coverage over the UVA and UVA spectrum, and these absorb ultraviolet light. Now, the FDA tested four chemical sunscreens that are sold in stores today. What did they see?

Well, they used four commercially. available formulations of sunscreen and apply them on a small number of human subjects. There were four groups of six in the study. And these are subjects that were kept in climate-controlled environment and were asked to apply the medication four times a day to 75 percent of body surface area. So akin to what you would do if you followed the sunscreen label and perhaps we're at the beach. So you're basically covering all the exposed areas of skin. And then what they proceeded to do was to measure the blood levels of the specific sunscreen ingredients. They looked at four ingredients, oxybenzone, octochrylene, acampsal, and avobenzone,

and looked at how the body absorbed these sunscreens over time. And the medications were applied four times a day for four days. And what was striking about the study was they saw systemic absorption as early as day one, and they saw absorption that persisted into day seven. So three days after the sunscreen application had stopped. for all of the four sunscreens that were tested. And those are the chemical sunscreens, right? Not the mineral sunscreens.

That's correct. These are all four chemical sunscreens. Do the mineral ones work differently? I mean, do they get absorbed into the bloodstream like the chemical ones? That has been tested in the answer is clearly no. So titanium dioxide and zinc oxide are not absorbed into the bloodstream. Now, did the FDA say there was any, you know, reason to give up? sunscreens, these chemical ones, after they were found in increasing levels in the bloodstream, and above FDA limits, correct?

That's right. So what's striking about the study is that the levels of sunscreen that were detected in the subjects' blood streams exceeds a level that has been set by the Food and Drug Administration to be a threshold for testing, and that testing is 0.5 nanograms per milliliter of blood. And what that threshold is is that any medication that's sold in the U.S., an over-the-counter medication, that's no matter how it's ingested or taken, if it exceeds that threshold, it needs to undergo a safety testing specifically to look at cancer risk and whether that medication has any impact on reproduction and other biological functions.

Well, now that it has exceeded that threshold, is the FDA going to test these substances? Well, it's important to recognize the Food and Drug Administration is not a testing agency. They're a regulatory agency. So their role in human medicine or in health is to really set the standard for how things should be examined. It's really up to the drug makers to provide the evidence that all of these tests have been done. So the first test is whether or not it's absorbed and whether it exceeds that threshold that we just talked about. And then the second, if it is absorbed, the drug manufacturers are obligated to provide standard testing results, things like the cancer risk and reproduction farm. So are they required now to go out and do these tests?

That's correct. And in fact, there's a proposal that's been put forth by the Food and Drug Administration that they would like this to happen before November of 2019. So that's soon in just a couple of months. However, this conversation has been going on for decades. So the Food and Drug Administration has regulated sunscreen since the 1970s. And in the late 1990s, the Food and Drug Administration asked sunscreen manufacturers to provide the safety data about systemic absorption. And for many years, they've gone back and forth, and for various reasons,

they have not seen the results yet. So this has been a dance that's going on for decades. That's right. It really has to do with, really, it really, gets at the heart of how over-the-counter medications are regulated in the U.S. I'm not an FDA member. I'm not a drug regulatory expert, but my understanding is that all over-the-counter medications are regulated by the Food and Drug Administration. So that's important to recognize. Sunscreen isn't just a cosmetic here in the U.S. It's a medication, and that's different.

In other countries, sunscreen is sold as a cosmetic agent, so it does undergo different testing outside of the U.S. But in the U.S., it's considered a medication, and therefore it does does have to fall under all the same regulations that other medications that we take do here in the U.S. But that retesting has never happened. And it has a lot to do with the fact that sunscreens were initially approved as medications many, many decades ago before a lot of this modern era of drug regulation really took place. It's really now and more recent years that we have clear standards for how all over-the-counter medications are tested. So if I'm just going to assume that we should assume,

that what is past is also going to be happening in the future that we're not going to get these tests, why suddenly should we be getting these tests? And if we're not getting these tests, what do you as a dermatologist recommended people and do about themselves and their kids? Well, what we know right now is that these four, at least, these four chemical sunscreens that were studied in this particular research article are absorbed into the bloodstream. What we don't know, and this is so important for listeners to understand, is that we don't know if they have any human harm in terms of health impacts or health effects. So the first really important issue is that we need to do these studies, either the sunscreen industry needs to do them

or medicine needs to do them. And that's really the first and foremost point I wanted to make. The second is for listeners to recognize that there's many different forms of what we call sun protection or many different steps of how we protect ourselves from the sun. And sunscreen is just one of them. It's very important for people to wear protective clothing. that includes hats, sunglasses, you know, long-sleeve shirts, long pants when we're outdoors, when possible, and then to use sunscreen on the areas that are exposed. People have a lot of control over when they do their exercise, so, for example, avoiding direct sun during the peak hours of the sun,

which are defined as 10 a.m. to 2 p.m. in the afternoon, and seeking shade when possible. So these are all parts of a sort of a sun protection regimen that people can participate in. The other is that there still are sunscreens that we know are safe. These are the mineral sunscreens that I mentioned earlier, the titanium dioxide and the zinc oxide. Those are widely available throughout the U.S. and make up a good portion of the sunscreens that are available here in the U.S. and have been tested and deemed safe.

So those are a great option for people who have any concerns about the chemical sunscreens. What about bringing in sunscreens from other countries? If you're in Great Britain or wherever you, can you just go into boots or someplace and stock up on them? That's absolutely right. For those who are lucky enough to travel outside of the U.S., they probably noticed that when they try to purchase sunscreen in a different country, that the sunscreen agents that are available there are very different from those that are available here in the U.S. We've really had kind of a standstill in terms of new sunscreen filters being approved by the food and Drug Administration in the U.S., and it wasn't until 2014, under President Obama, that there was

a sunscreen Innovation Act, which really put forth a roadmap for how new sunscreen ingredients would be approved into the U.S. while being regulated. There are many different agents out there in sunscreen ingredients that are available worldwide. That is definitely one option. We also don't know a lot about the testing on those, because as I mentioned before, they are regulated as cosmetics elsewhere. So I think it's really going to set forth a big self-reflection of the sunscreen industry in terms of thinking about how we should be testing these things, how we should be regulating them. And these are all really important questions that have been raised by the current study.

See if we can get a few phone calls in because, of course, everybody's concerned. Michael in Fayetteville, Arkansas. Hi. Hello. Go for it. Hey, yeah, about 10 years ago, I got a sunsfall. on my neck. I think it came back twice. The doctor told me definitely wear a sunscreen. I work outside. I wear a sunscreen. I put it on at least three times a day. I mean, I lathered on

like crazy. I'm concerned that that's not enough. The guess they're kind of answered my question, but is just the sunscreen enough to protect me from, you know, cancer? Should I be, you know, it's hot down here in Arkansas, but I've considered wearing long sleeves and just completely covering my body. If that's the best option, if I do have concerns about cancer, I do have a father and grandmother that attacks cancer spots to move from, you know, their forehead and neck. Okay, good question. Covering up, as you say, even though it's hot, it may be the better thing to do. Well, covering up is definitely an option, and we're lucky to have so many different ways of doing that. You know, and I think of the fashion around it has also improved. There's much more fashionable

sun clothing available and it's widely available at, you know, really common stores, not just the sports stores. So I definitely encourage people to do that. You mention the spot on your neck, and there are things they're called neck buffs. They're like scars, but not made out of wool that we would wear in the winter, but they're made out of different types of lighter, breathable materials that can cover the neck and will really allow you to be able to work outside and under hot conditions. And I really liked what your caller said about reapplying.

What we don't know from the study, as I mentioned, the study showed people who are kept in more climate-controlled environment. But what we don't know is how much of sunscreen is absorbed in real-world conditions. For example, when we are working outside, when we're sweating, when we're swimming, doing exercise. We don't know whether that systemic absorption would go up or down relative to those research subjects that were studied in this article. So definitely love the idea of covering up. I love the idea of reapplying the sunscreen, especially if you're working and sweating. I'm Ira Flato. This is Science Friday from WNIC Studios. Talking about sunscreens with Dr. Kanade-Shinkai.

Tell us about SPF factors. They go from, what, 5 to 100? Well, I remember growing up we had sunscreen. SPF 248 and maybe 15 was the highest it went, and now I've seen sunscreens as high as 110. SPF. SPF is really a factor that allows us to measure how much protection we have in terms of time outdoors. If you're likely to burn within a certain amount of time, SPF2 would allow you to be outdoors or under direct sun exposure for twice the length of your normal burn rate. Obviously,

that's going to be different for every individual who uses sunscreen. But the recommendation is that SPF 30 is a good thing to shoot for when you're out purchasing a sunscreen, because that works for most people and essentially blocks almost 95% to 97% of all the UV that's, that's, you're being exposed to. So you don't have to go for 50 or 70, you're saying, or anything above 30? Well, that's the party line. SPF 30 is definitely the party line. However, we do know from many scientific studies that in real world use, many users don't

apply the sunscreen thick enough. And if you don't apply the sunscreen adequately, you're actually getting less SPF protection, right, because you're just dosing yourself with less of the medication. So one of the purposes of looking at an SPF that's 50 or higher can be that if you use half the amount, you're essentially getting the right amount, right? However, yeah, and I think also, too, that it gives you a little bit more wiggle room in terms of some of the factors that we don't have a lot of control over. For example, how much of your sunscreen gets rubbed off or how much of it washes off when we're

swimming or sweating. But if you do it the right way, and that's an important thing that you brought up, you have to put enough of it on your skin. Sometimes I think I don't want to waste it or don't want to use the old tube up, so I put a thin layer on, right? That's right. Well, for the average-sized adult, the recommendation is to use one ounce or a shot glass if that helps your listeners kind of visualize how much of that sunscreen would be. And most sunscreens that we purchase in a store, at least a regular-sized tube of sunscreen, would be about, four ounces. So if you can imagine an adult going out to the beach

and they're going to apply the medication to their entire body and they're going to put it on four times a day, which is what it says on the sunscreen label, that that bottle's going to go pretty quickly. It's going to be pretty much used up within a day or two. And as we probably all would admit, that usually doesn't happen. So it means to say

that all of us are probably not using enough. And of course you want to put it on again as it wears off so that bottle's not going to last. Even the whole day. Yeah. That's This is a really interesting stuff. I want to thank you for taking time to be with us today. My pleasure.

After Kanadei Shinkai, it's a professor of dermatology, an editor-in-chief of the Journal of the American Medical Association Dermatology section. We're going to take a break, and afterwards we're going to get slimed. I love that movie, didn't you? We're going to talk about not that kind of slime, algal slime, algae. You might not know it, but algae is key for a healthy planet. We'll talk more about it. It's just about everywhere.

I mean, anywhere there's water, there's algae, green stuff. Even, you know, at the zoo in polar bears, I'll tell you about my first experience with it after the break. Stay with us. We'll be right back. This is Science Friday. I'm Ira Flato. As a kid, the first time I saw a polar bear at the zoo, I was shocked to see that its fur was green. Where did that green come from?

I wondered. Well, years later, I would learn that polar bear fur was. actually hollow. And in the hollows would grow algae, finding its way in from the water polar bears like to swim in. Those bears started me on a lifelong citizen science quest about algae. Do you ever think about algae? If you have a fish tank you do, seeing it growing on the glass and bright green fluffy mats, boy, I encountered that in my fish tank. The fact is that algae is all around us for good and bad. Algae provide 50% of the oxygen that we breathe, but they can also bloom into poisonous and deadly pools.

These ancient organisms are a big part of photosynthesis on our planet, but they usually go unnoticed until something bad happens. My next guest says you won't find algae dressed in flowers, wafting scents or sporting seeds and berries. Plants are the fancy pants photosynthesizes of our world. Algae are the plain janes. And in fact, he says, algae are not plants.

We'll talk about that. In her new book, she gives these plain janes their time in the sun, sharing with us her hunt to see how algae are used around the world for food, alternative fuels, and importantly for a healthy planet. Ruth Cassinger is a science writer based out of Bethesda, and her new book is called Slime, How Algae Created Us, Plague Us, and Just Might Save Us. Welcome to Science Friday. Thank you for inviting me. I'm delighted to be here.

Love how that name rolls off your tongue, when you. It took some while for you to do that. We have an excerpt of your book on our website at Science Friday.com slash slime. Ruth, you might get this a lot, but how did you get interested in algae? I mean, I got interested, and I told you about the zoo, it became a lifelong passion for me. How did it happen for you? Well, I was working on another book, a book about the history of conservatories, glass conservatories, and looking for the most modern representation of one of those,

and that took me to El Paso, Texas in about 2008, where an entrepreneur was growing algae underneath a glass conservatory and growing it in clear plastic panels that were about eight feet tall and four feet wide and a few inches thick and filled with water that had algae growing in it. And he was determined to grow the algae, spin the water out of the algae, and then get the oil out of the algae. And he was doing it. He, his business didn't survive, but I was so fascinated by this because, wow, here we are, making oil instead of taking it out of the ground, and we're doing it without using any arable.

land or any fresh water. It just seemed great to me. And the more I looked into algae, the more I realized that even this wonderful application was just a small part of what algae is all about. Let's talk about that. What algae actually is?

Because I think people are shocked to learn that algae is not a plant, is it? What exactly is it? Well, you know, it's really hard to say exactly what algae is because it's not a taxonomic category like animalia or homo sapiens. It's actually a catch-all term that refers to three different kinds of organisms. The smallest one is cyanobacteria, and that is a very simple organism

related to bacteria only it photosynthesizes. Then there are microalgae, which are a little bit larger, but still invisible, and they're more complicated inside and can produce a lot. lot more kinds of proteins and vitamins and things that we really appreciate. And then there are macroalgae, which are the seaweeds. Those are the conglomerations of algae that actually have parts like a plant. But as you said in your opening, algae are definitely not part of the plant community. They don't have bark, they don't have stems, they don't have flowers. So they actually are more efficient at taking sunlight and turning it into things that we like, rather than turning it into plant material.

In my quest to study algae over the years, I've learned some interesting facts that I'd like to check with you, for example, 90% of all the green stuff growing in the ocean and not plants. Its algae is 90% including the giant kelp beds, kelp or algae? Kelp or algae? Yep, they're 150 feet tall. and they are algae, macroalgae. And how do they reproduce then? Well, the smallest ones, the cyanobacteria, simply divide.

Microalgae, most of them divide, but some of them reproduce sexually. But don't get any X-rated visions in your head, because all they do is release spores that meet in the ocean and form new individuals. And that's the same thing with seaweed. Now, we're in the summer. We've heard about these deadly algae blooms. What is that? What's going on there?

Well, most of these blooms are really man-made. It's because algae are very happy in warm water, and they love nitrogen and phosphorus, and that nitrogen and phosphorus gets to them in large amounts because we're putting too much fertilizer onto our farmland. And so, for example, in the Midwest, where there are lots of farms, the fertilizer washes off in the spring,

finds its way into the Mississippi, then finds its way into the Mississippi, the mouth of the Mississippi, and into the Gulf of Mexico. And algae with all that food for them, because that's what they eat, nitrogen and phosphorus, they just go crazy and divide. and divide and divide. Can algae live without water at all for any period of time, like bacteria might?

Yes, algae, you know, are pretty remarkable in that they can survive in almost any environment. There are algae that go dormant in the desert and might only reappear, get green and reproduce with spring rains. There are algae that live only in the Arctic. and they're actually pretty important algae. Hikers often see those. They're a kind of algae. The variety is called Nivalis, and they have red pigments that they use to capture sunlight,

and they turn the snow red or pink when they bloom in the spring, when there's just a little bit of free water. Interesting. Our number 8447-24-825-8-8-4-Sai Talk if you'd like to join us. You can also tweet us at SciFri. If algae are that hardy and can survive, I remember seeing algae growing in lakes in Antarctica when I was there many years ago, might we, when we send probes to other planets or the moons of other planets and there are oceans there,

should we be looking possibly for algae? I think it's a possibility. Why not? Algae can survive in very salty waters, and scientists' best guess are that the waters on Mars beneath the surface are extremely salty. That's what helps keep them liquid. So they could be there, and certainly scientists who are interested in colonizing Mars,

do think about taking algae with them to, one, create oxygen, and also they can be full of protein and other vitamins and other good things for human beings. So, you know, we might be wanting to take algae with us to Mars. The title of your book, talking with Ruth Cassinger, is slime, how algae created us, plague us and just might save us. Where does the term slime come from when you talk about algae? Well, the slime that we are not very appreciative of on seaweed, for example, is really a saving grace for the organism.

When algae first evolved, and that was about 3.8 billion years ago, there was no oxygen in the air, and so there was no ozone layer. And their DNA would have been fried if they hadn't developed a kind of sunscreen. And that's exactly what they did. It's a polysaccharide sunscreen that protected cyanobacteria and all other microalgae and seaweeds. And I should add, it is under investigation as a sunscreen for us. Very well. We talked about that earlier in the program. So that's fascinating.

So algae, by creating the sunscreen, allowed life to develop on the planet. Yes, yes. Algae were absolutely critical to making our planet a livable place to be. Of course, they produce, oxygen. And we all obviously benefit from that in all oxygen-breathing creatures. But they also created all the iron oxide on the planet. The seas used to be filled with iron, and it actually

took more than a billion years for the oxygen escaping from algae to oxidize all the iron. So 83 billion tons of iron oxide on the planet is all due to algae. And they were also critical in capturing nitrogen. If algae weren't able to fix nitrogen, then there would be no life on the planet that was more complicated than a single cell. Quite fascinating. Let's go to the phones. Let's go to Priscilla in Baton Rouge. Hi, Priscilla.

How are you? Fine. How are you? I'm good. First time ever calling any kind of show. I'd like your show a lot. I appreciate all that you do. Here is my question. Okay. Like in the definition of a plant, right, don't we usually think of a plant as something that makes its own food through the process of photosynthesis? Yet your guest was saying that, like, well, they're not really plant. So I'd like an answer to why it's not a plant if, in fact, it does produce its own food through the process of photosynthesis.

Because you asked for it, we're going to answer to that. Ruth Cassinger, thanks for calling. Thanks for being a listener. Ruth? Well, plants have roots, and they have what are known as vascular systems, which are tubes, which are tubes inside, that carry water up and food down to the roots and to the leaves. Algae don't have those things. Algae, because they float in the water, although they do photosynthesize,

they don't need those kinds of systems because the nutrients that they are getting come not from the earth, but they just pass right through the algae cell, cell walls. So that's the critical difference between algae and plants. We're talking about algae with Ruth Cassinger, author of Slime, how algae created us, plague us, and just might save us on Science Friday from WNIC Studios. And, you know, like we talk about bacteria in the plural, algae is also the plural term, right? It is. Alga is the singular. Yeah, I know. We confuse those.

Use them interchangeably. Now, algae forms something called mucilage. Doesn't sound very appetizing? No, that's that stuff that is the slime that keeps them from getting their DNA fried. It's not very pleasant to touch, although I have to say after years of touching seaweed, actually it's perfectly fine. Now, let's talk about how where algae, it's all over the place. For example, the famous white clips of Dover are not made out of little quartz sand particles. It's all dead algae.

Right? That's right. It's algae and some other microscopic creatures. But yes, algae, after they photosynthesize and divide and eventually die, they sink to the bottom of the ocean, taking their carbon with them, which is a very good thing for our atmosphere. They constantly are cleaning the atmosphere of carbon dioxide. But after millions, in some cases billions of years, with 10,000. tectonic plate movements and volcanoes and other shifts in the ocean crust, those layers become visible again, and that's exactly what happened with the white cliffs of Dover.

That's many, many feet of dead algae and other creatures. Now, I know I used to have a coral reef, a small coral reef in my fish tank in my house, and I used to notice have the colors in there, and I learned that algae are crucial for the livelihood of coral, correct? And that if they lose their algae, they die off. Yes, you know, it's impossible to imagine you cannot have a coral reef without algae. Corals are actually animals. And what we see and think of the coral part is really the calcium carbonation,

shell that they build up over time. But inside the calcium carbonate is a little animal. It looks a bit like an anemone, and it's called a polyp. And that polyp comes out of the coral at night, chiefly, and snags little microscopic creatures, zooplankton. But that's not enough to feed a polyp. That's only about 10% of the polyps diet. The rest of the food, the polyp gets from the algae that are living inside it. And those algae photosynthesize, produce sugars, and share them with the polyp. Fascinating. Thank you.

Fascinating. But we've run out of time so much in Ruth Cassinger's book. Ruth is a science writer based in Bethesda. Her new book is Slime, How Algae Created Us, Plague Us, and Just Might Save a Save a lot of great reading, great research on this, Ruth. Thank you for doing this for one algae lover to another. Thank you very much for having me. You're welcome, and you can read an excerpt up on our website at science friday.com slash slime.

Quick, a program note a few weeks ago in our degrees of change segment, we asked you to tell us on the SciFri Voxpop app, if you've changed what you eat in response to climate change, and here's what Marilia in Oregon had to say. At our home, we have made some changes. to our diet, we now try to find foods that are grown local. And we also try to make dishes that include foods that are in season and not just the foods that are provided year-round. And we want to continue gathering your opinions and ideas on all kinds of topics for upcoming

shows. So share with us your ideas, just like she did. All you have to do is download the Science Friday Vox Pop app wherever you get your apps and just leave us a little message on there like she did, and you can join us each week. Have a great weekend. We'll see you next week. I'm Ira Flato in New York.