Dishing the Dirt on our Soils

15 December 2015
Presented by Chris Smith, Kat Arney.

This month, the United Nations published its much-anticipated report on the state of the world's soils and the results are not good. We'll be asking why, and taking a down-to-earth look at the consequences to see what we can do to reverse the trend. Plus in the news: why life drawing improves self-esteem; how the asteroid Ceres might be an invader from outer space; and the looming antibiotic apocalypse...

In this episode

01:00 - E-cigs could give you lung disease

The chemical flavours in e-cigarettes could be causing a condition known as 'popcorn lung,' for which the treatment is a lung transplant.

E-cigs could give you lung disease
with Professor Joseph Allen, Harvard T.H. Chan School of Public Health

The e-cigarette has blazed onto the scene recently, and it's become a big hit. They work by using a heating element to boil or vapourise a nicotine-rich mixture, that's then inhaled. An added facet is that there are literally thousands of flavours, which are made by adding scent chemicals to the mixture. Why is it though, Harvard's Joe Allen is wondering, that some of these flavour chemicals are turning up in e-cigarettes but have already been linked to serious lung diseases? Chris Smith reports...

Joe - For over a decade we've known about severe lung disease associated with inhaling flavouring chemicals because of workers in the popcorn packaging industry, many of whom develop severe and irreversible lung disease after inhaling these flavouring chemicals.

So our interest in this topic came from knowing this history of occupational disease for workers in the popcorn industry and then learning that there were over 7,000 flavours of e-cigarettes available to consumers.  And we thought, and it turns out correctly, that these flavoured e-cigarettes would have a lot of the same chemicals that were of concern from the workers over ten years ago.

Chris - Tell us a bit about those workers and how that particular story came to light in the first place and what went wrong for them.

Joe - Sure. It was about in May of 2000 in the United States, 8 workers who worked at a microwave popcorn processing plant reported to have a severe and irreversible lung disease called bronchiolitis obliterans.  It was investigated and determined that this was due to inhaling flavouring chemicals in their workplace. 

So they would mix up butter flavour for the microwave popcorn product and then they would inhale the heated flavouring chemicals.  The disease became known as popcorn lung because this is where it was first discovered in these workers, and what you have is virtually the same thing happening with flavoured e-cigarettes. You have a heating element heating the flavouring chemicals, and the consumer inhaling the chemicals.

Chris - And more critically, are they the same chemicals that you would find in a popcorn factory?

Joe - We found at least one in 92% of the flavoured e-cigarettes we looked at.  IN particular, one of the chemicals that got the most attention, called diacetyl and we detected diacetyl in over 75% of the flavoured e-cigarettes we tested, and this is the chemical that in the United States the investigating agency said "it's highly likely that diacetyl contributed to the occurrence of fixed obstructive lung disease, also known as bronchiolitis obliterans, also known as popcorn lung."

Chris - Now tell us how you did this study first of all and then we can look a bit at what these chemicals are doing in these e-cigarettes, if they've already got this track record.

Joe - Sure. So, our study is very is a very simple design; we tested 51 flavouring chemicals - remember there are over 7,000 available - and we set up in my lab a system to mimic smoking or inhalation.  So we pull out the chemical, just like a user would, and then we capture it on a sampling device and we analyse it according to standardised methods to look at three different flavouring chemicals so, diacetyl, acyteon and 2,3-pentanedione.

Chris - What do they smell like?

Joe - Well, this is what's interesting about the flavouring chemical issue is that it first started, we first became aware of this in the popcorn workers and it was butter flavour, but these flavourings are not limited to just butter.  In fact, diacetyl is used in wide range of flavourings like caramel, butterscotch, pina colada; all sorts of fruit flavours, banana, apple, grapes, strawberry.  So these flavouring chemicals are widely used to flavour a lot of the food products we consume, and actually in our study we found diacetyl and other flavourings in flavoured e-cigarettes that we deem are appealing to children like cupcake and cotton candy flavour e-cigarettes.

Chris - I mean that's a whole different ball game isn't it whether or not this acts as a gateway into smoking behaviour.  But when you inhale these flavours from an e-cigarette, I think one critical question is, if you are going to link this to the same sort of damage that the popcorn workers got, is there evidence that what's coming out of the vaporiser in an e-cigarette is going to be particles, which are the same sort of size, the same chemical characteristic, as those popcorn workers would have been breathing in in the factory?

Joe - Right.  So this is one of the follow-up questions that we're starting to look at and I know others are, but it's the characterisation of these at a bit finer scale.  So we don't know much at all right now about the hazard associated with these flavoured e-cigarettes and that was one of our goals of our study, is to be sure that when we start talking about e-cigarettes and safety and risk, is that flavouring chemicals are part of that conversation.

Chris - To be clear here, you're not saying these chemicals cause this lung disease, but what you are saying is there's very strong evidence from other situations that there is a strong association between exposure to them and getting lung disease.  Therefore, it's reasonable to be prudent and say there could be a risk here, we need to do something about this.

Chris - That's exactly right Chris.  So this wasn't a study of a health effect, it's simply designed to show that we have the presence of these flavouring chemicals that didn't just cause minor diseases, they caused severe and irreversible lung disease in workers.  We don't have the same kind of warnings or knowledge reaching consumers of flavoured e-cigarettes.  Many of these consumers are children, and many of these flavoured eCigarettes that we've shown in our study, we feel, are even marketed towards kids.

Chris - So what would you like to see change?

Joe - Well I think at a minimum we should be regulating e-cigarettes as carefully as we regulate cigarettes.

06:34 - Body concious? Life drawing could help

The naked truth of life drawing is that it could make you feel much more comfortable in your own skin...

Body concious? Life drawing could help
with Professor Viren Swami, Anglia Ruskin University

90% of us have experienced moments of low body confidence at some point; and life drawing class these feelings are linked with the development of depression, anxiety and eating disorders. One way to boost body image is by participating in physical activities, such as dance and martial arts. But, for the more artistically-inclined, new research has shown that attending life drawing classes has similar benefits. Viren Swami, from Anglia Ruskin University, sketched out the findings for Felicity Bedford...

Viren - We had two studies; in the first study we look at attendance at life drawing sessions and the association with women's and men's body image, and we found that greater attendance at these life drawing sessions was associated with a higher body appreciation or positive body image among both women and men. 

In the second half our study, we followed a group of women who had never attend life drawing classes before, and we measured their state body image, their current feelings about their body image, both before and after the class, and we found that attending the life drawing class for about 2½ hours had as significant effect on their body image.  They felt better about their body image immediately after attending the class.

Felicity - That's great news for anybody considering going to life drawing classes, that you can have a fairly immediate impact upon attending just a few classes.

Viren - Exactly, so we think that the effect is both short term, but also is you continuously attend a life drawing classes, it seems to have a long term effect as well.

Felicity - How did you measure people's feelings about their bodies?

Viren - We measured three different types of body image, both women and men.  We measured social physique anxiety; this is how anxious they feel about showing their bodies in public.  We measured body appreciation, which is a measure of positive body image, and we measured in women's drive for thinness, this is how much they feel a drive to be thin, and in men we measured the drive for muscularity, which is a drive to feel muscular.

Felicity - You were looking at the attitudes of people attending the classes.  How might drawing somebody else naked, make you feel better about your own body?

Viren - Well I think it's about embodiment.  So a theory in body image research is that any activity that promotes embodiment will result in a more positive body image, so embodiment is any activity that promotes greater respect for your body or greater feelings of love and openness towards your body. 

Typically embodiment is looked at in terms of actually doing something so, for example, you might actually do dance rather than just watching dance, but life drawing might be one activity where you can experience embodiment vicariously.  In life drawing sessions, in particular, you're not just looking at another body, you're also to experiment with that body in terms of reproducing it in a form of art.

The other thing that life drawing sessions might do is that they might provide a safe space in which to explore your own feelings about your own body in relation to other people, or just in relation to yourself.

Felicity - What about if the models are really attractive?  Could this have the opposite effect?

Viren - It's possible but I think one of the things about life drawing sessions is that you are exposed to a whole range of different types of bodies; it's not just attractive people who are life models. 

I think given the nature of life drawing, I think even if the model was particularly attractive, the function of seeing that body and experimenting with that body in an artistic sense would probably have the same effect. But over the course of a period, say if you went to life drawing classes say for a year, you'd be exposed to a whole range of different bodies - some that you might find attractive, some that you might not find attractive - but it's that process of seeing those bodies and absorbing what those different mean, I think that is the most important.

Felicity - Could it be any drawing, not just life drawing, that's causing this improvement in your body image?

Viren - I think that's an interesting question.  I think it is something about life drawing that promotes embodiment.  I think if you can find a different art form that has the same effect in terms of embodiment, you might find the same effect.  I don't think you would find the same effect if you were just drawing a tree, for example.

Felicity - But generally should we be exposed to more nudity, whether it's our own bodies or other people's?

Viren - I think there are different forms of nudity.  You have nudity in everyday life when you see your partner or when you see yourself, there's nudity in pornography, there's all sorts of nudity.  I don't think it's just being exposed to nudity that matters; I think it's the process of engaging with nudity and exploring what that nudity means, either in an aesthetic sense or in relation to your own self; that's probably the key point here.

Do doc leaves stop stinging?
with Dr Kat Arney, The Naked Scientists

Kat Arney continues her myth busting science...Stinging Nettle

Kat - As a child I would often be dragged out into the local forest to walk the dogs. And, inevitably, I'd end up blundering into some stinging nettles. As soon as I got stung, my mum would delve into the undergrowth in search of a dock leaf to rub on the reddening bumps coming up on my pale legs. But does this actually kill the sting?

Before we find out, let's take a step back and see how nettles actually cause their stings. Their leaves are covered in a multitude of tiny hollow needle-like hairs made of silica - the same stuff that glass is made of. When someone like me brushes up against a plant, the tips of these fragile hairs break off, piercing the skin and injecting a cocktail of nasty chemicals.

One of these if formic acid, which is also found in ant bites. Getting concentrated formic acid on the skin can cause severe irritation, pain and blistering, so it was originally thought to be the major culprit responsible for the pain and misery of nettle stings. But it turns out that the levels of formic acid in the delicate hairs are too low to cause this kind of reaction. There are other acids in the stings too - such as oxalic acid and tartaric acid, found in other types of plants. For example, rhubarb leaves are a potent source of oxalic acid, which can be toxic in high doses. but, like formic acid, they're present at relatively low doses.

So what else is in there that could be responsible for the pain and misery of a nettle sting? The other prime candidates are three chemicals known as histamine, acetylcholine and serotonin, which are all naturally produced in the body. To take a look at each of them in turn, serotonin is produced by nerve cells, and is usually associated with transmitting pleasurable sensations by signalling between nerve cells. But when injected by a nettle leaf, it has much more painful results as it irritates the skin. next is acetylcholine, another chemical that usually transmits signals between nerve cells. Again, when injected directly into the skin by a nettle's barbs, the sensation is far from pleasant.

Perhaps the major culprit is histamine, responsible for triggering pain and inflammation, as well as allergic reactions. That's why people take anti-histamines for allergy-related symptoms, such as skin rashes, wheezing and snuffling. So this is probably one of the prime reasons that nettle stings quickly redden, itch and swell - and also suggests that antihistamine cream might work to relieve the pain. But the skin reaction is probably not just down to a single molecule, but the effects of all the nasty things mixed together, so it's a complex issue.

Now onto the main question - does rubbing a dock leaf on a nettle sting make it better? Sadly for my childhood knees, the answer is no. There have been various claims that the sap in the soft, leafy plant is alkaline, and helps to neutralise the formic acid and other acids in the nettle sting. But the acids are only a small part of the problem, and dock leaves aren't even actually alkaline. So that's definitely not true. There are other claims that they contain natural antihistamines, but there's no evidence to prove that's real either. In fact, it's more likely that dock leaves are just a placebo - creating a distraction from the pain of the sting through the rubbing action of a cool leave on the sore red bumps.

So while my mum may have had the best of intentions with her insistence about searching for dock leaves for my clumsily nettle-stung legs, and it was probably as good as kissing it better, it would have been more effective if she'd had some antihistamines in her handb

15:36 - Why Ceres might be an invader from space

Ceres strange white spots have been demystified this week and it might hold clues as to the asteroid's origins...

Why Ceres might be an invader from space
with Professor David Rothery, Open University

What's black with white spots and half made of water? The rather surprising white spots on Ceresanswer is the solar system's largest asteroid, Ceres, scientists had thought that this spherical body, which measures about 1000km across and orbits out beyond Mars, was made of rocky rubble left over when the planets finished forming. Now, closer inspection by NASA's "Dawn" probe, which is currently orbiting Ceres, has shown that the dark black surface of the asteroid is punctuated with bright white spots, which appear to be made of salts, ammonia and water ice. But finding these means that Ceres might not originally be from the asteroid belt at all but is instead a deep space interloper! Chris Smith spoke to David Rothery about the finding...

David - Ceres is the largest asteroid; it's the largest body in the asteroid belt; it was the first asteroid to be discovered very early in the 19th century. 

The white spots were actually suggested from the best Hubble space telescope pictures you could get that they were just areas that looked brighter than elsewhere.  As the Dawn spacecraft approached, the most obvious one came into view. 

In the middle of this crater that's tens of kilometres across, we have areas kilometres in size which are highly reflective.  People were wondering what they were and people are still not sure.  I went on the "Dawn" mission website just now, and there's a popular pole on the go, you can vote for what you think the white spots are. 

10% of people think it's some sort of volcano - presumably an ice volcano - nobody thinks it's a hot lava volcano; 6% said they're geysers; 6% said they're made of rock of some kind; 28% said ice; 11% said salt and 39% said other, so I don't know what they were thinking.

Chris - But now we do have this week some new data, in the form of these two papers in Nature, which are using data and measurements made by the Dawn spacecraft.  So this gives us a much clearer idea as to what these things are.  So what are those papers saying?

David - Well we do have a better idea.  One paper, which is based on data from the framing camera, they're showing that the central parts of the white spots, probably, are some kind of salt - a hydrated version of magnesium sulphate, and you can see a haze rising about the white spot...

Chris - So that suggest something coming off of the white spot which is scattering light around it?

David - Absolutely, something is coming off the surface and it seems to be water vapour, but sublimed off some ice, carrying dust particles with it.  So the source of the water or the ice available to sublime when sunlight hits it is being replenished each day on Ceres because the available life sublimes when the sunshine hits, then it ceases to the sublime, the haze disappears, you don't see it at dusk.  By the next dawn there's enough water ice arrived at the surface to sublime to produce a fresh haze, so there's some active internal transport going on and that's very exciting.

Chris - So is this water coming from inside somewhere then?

David - Yes, I think the water, which is feeding the haze, must be coming from inside Ceres. 

Now there's no evidence, unlike many of the larger icy moons, that Ceres has an internal ocean of liquid water - that would be very surprising, we can't imagine a heat source to keep it warm enough for there to be liquid water. So it's just ice, not too far below freezing point, that's convecting and moving around maybe. 

To be honest we're flummoxed, we don't really know, but the evidence is stacking up to suggest that the places on the surface where ice is being replenished and able to sublime a way to space, and you get left behind these hydrated salts.

Chris - And why is this important, or how does this remodel, or refashion or view and our understanding of the solar system?  How everything we have and we see today got where it is now?

David - Well, to have so much water inside Ceres is a problem.  Ceres orbits not too far beyond Mars, much closer than Jupiter, and it's this side of the snow line.  Get to about Jupiter's distance from the Sun, it's cold enough for lots of ice to condense directly from the solar nebular when the solar system is forming. 

Where Ceres is now, for most of the time at least, has been too warm for a lot of water ice to condense so it's possible Ceres form further out from the Sun and has migrated inward.  And that probably brings us onto the second paper in the same issue of Nature which is providing us that Ceres is from even further away because it is suggesting that the surface contains what they are describing as ammoniated phyllosilicates - that means clay minerals with ammonia trapped within them. 

But nitrogen or ammonia trapped inside Ceres is a very big problem if Ceres grew where we now see it, and the suggestion from this work is well maybe Ceres started off in the very outer solar system - Pluto or beyond - and somehow found itself way inwards.  So it doesn't look like the archetypal biggest asteroid any more, it is a guest in the asteroid belt, and it's a guest that's the mystery we now need to try and solve.

21:21 - The antibiotic apocalypse

Why we might be facing a future of bugs we can’t kill...

The antibiotic apocalypse
with Dr Mark Holmes, University of Cambridge and Dr Nick Brown, Addenbrooke's Hospital

News broke recently of bacteria discovered in China that are now resistant to Livestockantibiotics used normally as a last resort, prompting fears we could be on the cusp of an age where bacterial infections are no longer curable. So are we all doomed, or is this scare-mongering? Georgia Mills puts the problem under the microscope for us...

[Transcript to follow]

27:51 - The sorry state of our soils

Just how badly damaged is the earth beneath our feet? And why is it we're only beginning to do something about it now?

The sorry state of our soils
with Professor John Quinton, University of Lancaster

We're dishing the dirt on one of the Earth's most precious, but declining plantsresources; it's not an animal or vegetable but a collection of minerals - more specifically, soil. 2015 was declared the year of soil by the UN, and this week they released a much-anticipated report on the state of the world's soils. Unfortunately the results aren't good. John Quinton is a soil scientist from Lancaster University and he joined Kat Arney to fill her in on what the report said...

John - The highlight from the report was that we really need to stop degrading our soils.  The report suggests that we're losing around a football pitch's worth of soil every five seconds, which is quite mind blowing really.  We also need to stop the decline in soil carbon, so soils hold onto about a third our carbon and we're losing that back up into the atmosphere.  We also need to rebalance the amount of nutrients in our soil, so some soils in some parts of the world have far too many nutrients and in other parts of the world they just don't have enough.  And then the final point that they make is just that some of the data that we have on our soils around the world is just really, really old and we need to update it.

Kat - And in terms of what we do know, given that the data is kind of old, what do we know about the kind of degradation that's facing our soils?

John - The kind of data that we have would suggest that around about a third of the world's soils are degrading, and the biggest threat to them is soil erosion.  So that's either by wind erosion where we've got dry soils, often in arid areas, which are just getting blown away, and then the other form is through water erosion.  So this again is when surfaces are exposed to the elements, and we get a heavy rainstorm, and it's actually washing the soil off hill slopes and down into the rivers and then perhaps out into lakes or even into the ocean.  So those are the two ones we're worried about in agriculture but we're also concerned about the area of soil which is being paved over.  More and more of us are living in cities and as we move into the cities, we cover the soil in concrete.  In Europe, an area round about the size of Cardiff is paved over every year, so that's another threat to the functioning of our soil.

Kat - So can we lay the blame really at the expansion of the population and the expansion of agriculture.  Are these the main drivers of the problem?

John - I think we are clearing a lot of land to produce food.  We're going to have what, around 9 to 10 billion people living on this planet by 2050 and they're going to need feeding and that's going to mean that we're going to need land to grow crops in them, so that's really going to be one of the big pressures and when you convert forest or grassland to agriculture, you degrade the soil.

Kat - And that, I guess, is the problem is what is the risks of losing so much soil like this?  Why should we care?  I mean it's just dirt, isn't it?

John - Just dirt.  Gosh, heathen.  It's the brown gold beneath your feet.  The living skin of the earth.  Scientists that around about 10% yield reduction by 2050 due to erosion, so that's equivalent to losing a 150 million hectares, is no longer going to be productive, so it's serious stuff.

Kat - But is just food that's at risk here?

John - So the other big concerns would be around carbon.  Soils store round about a third of the world's terrestrial carbon, so more than all the forests and all the atmospheric carbon combined so, if you lose the soil, you lose that store.  The other thing that soils do for us is to keep us supplied with clean water.  Most of the water that falls on the terrestrial surface is going to hit the soil before it ends up in rivers and lakes and so soils play a really important role in both buffering and attenuating the flow of water, but also of cleaning it up.  It's also packed with organic matter and soil micro-organisms and those things are actually, you know, pulling out all those nasty chemicals that we don't want to get into our water supply, and helping to produce clean water for people.  So that's another threat we need to be concerned about.

32:33 - Getting to the root of the issue

It's not just that our soils are being eroded but also degraded. Is this having an impact on the quality of the food we eat?

Getting to the root of the issue
with Professor Chris Collins & Dr John Hammond, University of Reading

One of the biggest reasons we're in this sorry state is because of population carrotsgrowth and the resulting intensification of agriculture. But is the poor quality of soil subsequently impacting our food and ultimately therefore, our health? Graihagh Jackson went digging in the dirt with Reading University's John Hammond...

John -   So we've just dug up some soil here and you can see straight away there's a huge diversity of ingredients in the soil.  The soil provides a number of things, water, but also some mineral elements; nitrogen, phosphorous, potassium, calcium, magnesium, and sulphur are the six main ones, and then there's some micro-nutrients that are in there like iron, and copper, and zinc which go into really important functions in the plant

Graihagh - Like what, because I think I need calcium to make my bones stronger, so does the plant need say, phosphorous or nitrogen for?

John - Nitrogen's the biggest one.  The plant needs that in the greatest quantity and that goes into making things like proteins so, if we don't get enough nitrogen in the plant, then the plant can't make chlorophyll and so the plant starts to look yellow.

Graihagh - How does it get from the soil then, into the plant to make the chlorophyll, and make the plant grow ultimately?

John - The plants take up those nutrients from the soil solution, so it's moving water through the soil, up into its roots and out through its leaves, and with that flow of water it can bring with it some of those nutrients.  In particular, nitrogen and sulphur come through that pathway.  Some of the nutrients like phosphorous and potassium, they are harder to move through the water, so they have to move through a diffusion process.  So they move from a high concentration in the soil to a low concentration so that when the nutrients get to the root surface, there's a number of proteins in the root cell that then transport those nutrients.

Graihagh - And this ultimately enables the plant to grow from a seedling all the way up into an adult crop?

John - That's right.

Graihagh - If there are any toxins in the soil, would they be also taken up just like the nitrogen and the phosphorous you were talking about?

John - Yes.  So some heavy metals that we sometimes find in the soils can be taken up through the same process into the plant and, ultimately, into what we would eat.

Graihagh - That's not the only way you could ingest heavy metals though.  You could eat the soil itself.  I know what you're thinking, I don't eat hunks of soil for dinner but, it's actually a lot more common than you think.

Chris - Usually they say about 1% of the weight of a vegetable is the soil attached to it.

Graihagh -   I know, I was quite surprised too - 1%.  That's a colleague of John's at Reading, Chris Collins.  And think about it, how well do you really wash your veggies?  I'm definitely guilty of not scrubbing as well as I should, so there's probably much more than 1% of my vegetable that's actually soil...

Chris - Carrots, because there in such intimate contact with the soil are often more contaminated than other crops where the edible portion is above, say for example, a tomato would be much less likely to be contaminated than a carrot.

Graihagh - Although that's a little hard to stomach, I can't help but think, how bad can it be?  Surely our soils, and certainly the soils that are used to grow food can't be all that polluted - right?

Chris - They're very common.  In any urban area you will find detectable levels of lead, from old lead piping, lead in petrol and you will also find elevated levels of the organic pollutants mainly associated with transport but also, for example, a lot of people used to put the ash from their fires into their gardens because they thought it had a nutrient value.  What they didn't realise, is there are some of these organic pollutants associated with those ashes.

Graihagh - What Chris researches is what happens when we eat this polluted soil.  He took me to a lab where they're simulating the gut tract from your mouth to your anus.

At one end the polluted soil goes in and is mixed with an acidic solution to recreate the conditions in the stomach.  Next is the small intestines where it's a little bit more alkaline, so the solution in the stomach jar is moved into the intestine jar where something is added to bring that pH up to a more neutral level.  The next bit is the colon and it's where things took a turn for the worse.

Chris - You can get it now.

Graihagh - Oh yes.  I mean it's not great.  It's getting gradually worse, isn't it? 

What could be so bad?  Well, this is where Chris takes his intestinal samples and mixes them with real human poo.  Yes, you did hear me right.  Hominid excrement - and it stinks.

Chris - It's like being on a farm isn't it?

Graihagh - Yes, but the worst thing is, is I know this is human. Whereas cows, it's slightly more acceptable

Chris - It's slightly sweeter, isn't it?

Graihagh - Why put yourself through hours of lab time surrounded by the sweet scent of excrement I hear you ask.  Well, these pollutants are syphoned off the soil, left to float around in the gut solution and absorbed into your body.  What's known as bio-accessible.

Chris - What we're looking for is the bio-accessible fraction so, that is the amount of pollutant that is desorbed from the soil into the gut solution.

Graihagh - And how much is bio-accessible from your experiment here?

Chris - 10 to 30% goes into the colon solution.

Graihagh - How much of an affect does your microbiome have on how much of these pollutants you absorb.

Chris - We really don't know because this hasn't been tested. One thing we did test is whether using a polluted soil changed the population composition of the microflora, and actually in the soils we used we didnt find a significant difference between the polluted soils and non polluted soil.

Graihagh -   Does it make a difference to how accesible those pollutants are?

Chris - That might make a superficial difference. They might break them down and turn them into more benign compounds, so they might hydoxilate them for example, which makes them more water soluble and then more likely to be passed out.

Graihagh -   Is there any evidence to suggest that that whole 10 or 30% is then absorbed into the blood?

Chris - Truth is we really don't know.  There's been tests in pigs, but there's a lot of metabolism of organic compounds when they're in the body, so it's really difficult to test it.

Graihagh - But I suppose the danger of it being in the bloodstream is that blood goes everywhere.  So equally, if it's not metabolised elsewhere in your liver and excreted through your urine, it could end up in your brain or whatever?

Chris - There is some sort of secondary activity on that, so it's unlikely that the whole amount would be exposed to one particular target organ, if you like, but there is the potential.

Graihagh - I'm not sure how much more of it I can stomach in here.  I can feel myself holding my breath slightly.

Chris - It's not the most pleasant place to work - but good science.

40:02 - Stopping erosion in its tracks

We need to change the way we farm our foods but with a growing population, how will we do it?

Stopping erosion in its tracks
with Professor Richard Bardgett, University of Manchester

The plea to take our soil health seriously is a strong one - our food, our safety andcatipilla our climate depend on it - but how do we go about taking better care of our soils? Is it possible to rejuvenate our soils and if so how? Soil ecologist Richard Bardgett from Manchester University took Kat Arney through the options...

[Transcript to follow]

43:43 - The trials and tribulations of truffles

Truffles are one of the hardest crops to cultivate but by studying the relationship between the soil and fungi, one man has figured it out.

The trials and tribulations of truffles
with Al Blaker, Manjimup Truffles

Studying the relationships between plants and the soil has reaped some benefits A trufflein the commercial world. And one winner is Al Blaker - Australia's first truffle farmer. Truffles are a highly prized food delicacy, but they're very hard to farm - sapling trees need to be inoculated with the fungus when they're young; this sets up what's known as a mycorrhizal relationship between the two. The fungus brings nutrients to the tree, and the tree roots feed the fungus sugars in return. The fungus fruits by producing buried golf-ball sized structures full of spores, otherwise known as truffles. Chris Smith went along to see how Al does it at the Manjimup Truffles in southwest corner of Western Australia...

[Transcript to follow]

49:48 - Save our soils: Why we need to act now

If no action is taken, we'll lose 1.5 million km2 of land from crop production by 2050. So, act now or the very ground beneath us will die.

Save our soils: Why we need to act now
with Professor Richard Bardgett, University of Manchester & Professor John Quinton, University of Lancaster

If no action is taken, we'll lose 1.5 million km2 of land from crop production by Gardening2050 - that's equivilant to all the arable land in India. But it's not just down to policy makers, there are things we can all do as individuals to help save our soils, as John Quinton and Richard Bargett explained to Kat Arney...

[Transcript to follow]

52:27 - Why do I sleepwalk?

What causes sleepwalking and is there anything that can be done to prevent this strange nocturnal behaviour?

Why do I sleepwalk?

Felicity Bedford has trying to find out the answer to this one with Dr Ian Smith from the sleep clinic at Papworth Hospital...

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