Titans of Science: Richard Thompson
Titans of Science series is back for another run. And to kick us off, marine biologist Richard Thompson, who first brought to the world’s attention 20 years ago the problem that is micro - and now nano - plastic pollution...
In this episode
00:57 - Richard Thompson: Unearthing microplastics
Richard Thompson: Unearthing microplastics
Richard Thompson was born in Nottingham in 1963. He attended Urnell Junior School and Arnold Hill Comprehensive School in the city and later went on to study at Newcastle University and the University of Liverpool. In 2004 Richard was internationally recognised for coining the term 'microplastics' and he's been at the forefront of research that's fundamentally changed our understanding of plastic ocean pollution ever since.
Over the course of his career, Richard has led influential studies on the sources, the distribution and ecological impacts of microplastics, helping to shape global policy discussions on plastic waste and marine conservation. He's currently a Professor of Marine Biology at the University of Plymouth and he leads the university's International Marine Litter Research Unit. He spoke with Chris Smith...
Richard - Hello, thank you for having me on the show.
Chris - Now, why did you end up looking at microplastics at all? Were you already a marine biologist by that point?
Richard - I was studying for my PhD and I'd got experiments set out on the shore, marine ecology experiments, looking at microscopic algae and the molluscs that feed on them, and every day I went to tend these experiments and do the counts and the observations and virtually every day I got items of litter clogging up the experiments because I had to remove them and then the next day there was more. So I joined together with some of the other students and we set up beach cleaning around the local area where we were but something struck me that started off the story really of the microplastics from my perspective. As I was entering all of this data into the sheets I realised that there was something missing. What to me was the most abundant type of litter on the beach was the small fragments of plastic. There was no category for it and this question struck me: I wonder what the smallest bits of plastic are on the beach. A couple of years later when I started to teach undergraduate students myself one afternoon I said let's go and have a look on the beach, I've got this question I want to answer, I wonder what the smallest bits of plastic are. The students said, well, let's look in the sand, and I thought well okay let's look in the sand.
So we brought back some sand samples and pretty much from the first sample we could see bits that didn't look like sand, brightly coloured bits; blues, greens, reds and quite a few that were fibrous in shape and they certainly didn't look natural, let's say. It was then an almost forensic journey to confirm what they were and indeed there were a range of different common polymers that we were finding, some of them smaller than the grains of sand themselves and that's what motivated me then to explore a little bit further how widespread this phenomenon was. We looked at beaches from around the UK, we looked at sediments from the seabed and in all of these samples we could see these strange bits and we could confirm common polymers, polyethylene, PVC, polystyrene, polypropylene, all of the everyday common polymers we were finding. Then, I was curious of course. Has this problem got worse over time because we've only really been mass producing plastics since the 1950s and again I was looking for ways to do this and it was about the time that I relocated to Plymouth, I got my first lecturing post there in a permanent position and I work with the Marine Biological Association who hold this continuous plankton record where they've got archived samples of plankton that have been collected over the last 70 years and what we showed was there was a significant increase over the decades. So this information really was gathering almost as a trickle, it wasn't my regular line of research. One of my supervisors when I was a postdoc was saying to me, ‘It's all right we're really happy for you to do this work on the plastics but you know you need to keep it a bit for the evenings and weekends because it's not quite what the grant is paying you to do!’ which was fine and it was it was said in very good humour.
Chris - But when did it dawn on them and you that this was actually the thing to spend your life working on and commit the other stuff to the evenings and weekends because this is absolutely massive?
Richard - A pivotal moment would have been in the late 90’s, probably about 1998-1999 I presented this seminar at lunchtime to some of the postdocs and PhD students in the lab, mainly marine ecologists. It was OHP slides on a projector and a few photographs and one of the researchers who was a bit more senior than me said to me - he's Italian and he said it with quite some panache and charisma - ‘This is your boat, Richard. This is the thing that nobody is working on. This is what you should pursue.’ And I thought, well maybe Paolo. But this kept coming back into my head when we were pushing on with this story. He saw it as a career boat if you like as something that nobody else was working on.
Chris - Had you by then considered the problem internationally or was this very much looking at UK samples, so it's very local. You obviously must have thought well this is everywhere so we must spread our wings internationally and then make it a global problem and then I'm almost certainly going to get more support for this?
Richard - So at that time it was national. I was looking at beaches around the UK, I was going back in time with the archive plankton samples which again were from UK waters. It was almost a decade from first asking that question about what's the smallest bit of plastic to publishing this first paper using the term microplastics, and indeed my first paper on plastic pollution in 2004. So it was gathering this information over time; what are the polymers, what are the habitats we're finding them in, how common are they, have they accumulated over time, and quite a critical step was do organisms eat them. You might think well, probably for sure they do if they're in the environment, but when you're looking at small particles like this, lots of organisms, filter feeders, have got ways of getting rid of natural particles. They're encountering sediment every day, so maybe they'd get rid of the plastic and wouldn't ingest it. But we showed that a range of creatures, filter feeders, deposit feeders, and detritivores, would all readily eat this plastic. It didn't yet prove harm, but it showed the pathway.
Chris - how did you show that they were eating it? What were you looking at?
Richard - We we did a range of laboratory experiments where we had creatures in tanks and we exposed them to small fragments of plastic, and with some of these creatures, because they had more or less transparent bodies you could actually see the plastic in the digestive tract, for example, of the amphipod and so all of that information went into that first paper in 2004.
07:52 - Richard Thompson: Following the trail of microplastics
Richard Thompson: Following the trail of microplastics
Richard Thompson describes to Chris Smith his work to identify the types and quantities of microplastics infiltrating ecosystems...
Chris - We first met around the time you published that paper and one of the things that galvanized me and I suddenly understood the the risk here was you pointed out to me that these plastics are made of hydrocarbons and, just as birds of a feather flock together, oily chemicals stick together and you made the point, look, these plastics are out there, they are encountering other potentially toxic chemicals at low concentration, and they may well be concentrating them into and onto the plastic and then when they go into microorganisms or bigger organisms they could dump that toxic cargo and that's when I think I had my wake-up moment for this.
Richard - Yes and that was a wake-up moment actually for policy. The first policy related meeting about microplastics was held in in the US actually and there were not only a handful of scientists there. There was myself and one of my early postdocs Emma Tewton, and there was a colleague that's become a lifelong friend called Hideshige Takada from Japan and he'd previously shown in his research this potential for plastics in seawater to absorb and concentrate contaminants. Contaminants, man-made chemicals, persistent organic pollutants, a range of other chemicals present in seawater, would become super concentrated on the surface of plastics because those chemicals were hydrophobic in nature and it's a little bit like if you've ever washed up in a plastic washing up bowl perhaps a spaghetti bolognese or a curry and it's had food dye in it, often that dye latches on to the plastic because it has a greater affinity for the plastic than the seawater.
That was what Hideshige Takada demonstrated was happening with some of these hydrophobic contaminants, and so the question struck me: well, what happens if those plastics move to a different chemical environment, perhaps the guts of an organism, where, if it's a warm-blooded creature, you might have different temperatures, you'd certainly have different chemical conditions, you might have enzymes acting. Would some of those chemicals be released? Indeed, that is what we showed, that if you let plastic acquire a burden of chemicals from the natural environment at concentrations equivalent to what you find those chemicals in the environment, and you then move the plastic to either clean water or clean chemical constituents resembling the contents of the guts of an invertebrate or a warm-blooded creature, what you saw is is the chemicals being released. But the interesting thing was that the rate of release could be up to 30 times greater into a warm-blooded creature than the rate of release back into clean seawater.
Chris - So two questions then. One, if we go and sample seawater, do we see this mechanism happening for real? Having demonstrated it's theoretically possible, have we got evidence that this sort of concentration chemically is occurring? And two, have we got evidence that, with that having occurred, it really does impart into the bodies of marine organisms, therefore dumping the toxic cargo in and concentrating it into them?
Richard - There’s really clear evidence that the phenomenon was occurring in the natural environment. The question was then, we've got this concentration mechanism, we've got the increased release, how much worse does the plastic make it? Because of course here, if you're dealing with chemicals that are already in the environment, marine life is already exposed to them, so the critical step was to understand how much worse does the plastic make it. What we showed interestingly was, yes, the plastics had a role, but compared to the intake by diet, and if you're passing seawater over your gills direct from the water, the role of the plastic was quite trivial at that time in terms of the transfer of chemicals to the creature. So it was part of the picture, but it didn't seem that the plastic was making things all that substantially worse.
But what I would say to that as a caveat now, because of course our understanding of plastic pollution and these small particles has increased a lot. That we were working at the time on, if you like, a standard gut transit time; the amount of time the plastic was in the body and the amount of time it would have to release those chemicals. Of course what we now know is that the really small particles, down a few microns and certainly into the nanoscale, have the potential to pass from the digestive tract into the circulatory system and to pass around the body very rapidly. We've shown in marine molluscs within six hours of exposure in a fish tank that the nanoparticles of plastic have gone literally everywhere in the tissues, and then, if you move those molluscs to clean conditions, even after 28 days you can still detect the presence of the nanoplastics in them.
In terms of harm, I would say that there's three different routes. There's the physical presence of the plastic causing some sort of disruption: you can picture that easier with a big bit of plastic causing an obstruction in the digestive tract, and there's evidence of that longer-term accumulation in molluscs in the hepatic pancreas, which is analogous. There's also the potential for chemical toxicity where you've got chemicals that are already in the environment, anthropogenic chemicals accumulating on the surface of the plastic becoming super concentrated and then released to a creature upon ingestion. But on top of that there's also the potential for chemical additives that were incorporated into the plastic at the time of manufacture.
Now, these are chemicals that are put there mostly with good reason, but some of them are known to be harmful in the wrong context and for that reason we have certain chemicals such as phthalate plasticisers that are prohibited for use in children's toys and in applications in hospitals because of the known adverse effects of those chemicals. But if we've got plastics that have got these additives in them that have become very small pieces, in the wrong context, there's also the the potential for those chemical additives to be released. Interestingly, what the work where we're looking at the chemicals accumulating from the environment soon showed was that the concentrations of some of these additive chemicals in the plastic could be far greater than you'd ever achieve by this mechanism of the chemicals absorbing to the surface of the plastic.
But the key question there is, what's the exposure pathway? Are there instances where we've got plastics that contain potentially really hazardous substances that are finding their way into the environment already as small particles rather than perhaps having to take years to fragment? The interesting one that's come onto the horizon there most recently is particles from tire wear. Every time you drive along the road, and of course tires aren't food contact material, they're not part of children's toys and there's a wide range of chemicals that are potentially very hazardous incorporated into tires, many of them put there with good reason, but they’re potentially hazardous. What's happening as you drive along the road and put the brakes on is, of course, you're getting that particulate dust arising from the tires immediately and that's washed from roads when it rains, it's carried into watercourses, and we've proved that those tire wear particles can pass through wastewater treatment and into the marine environment. They can also be washed directly into streams and rivers and some of them of course become dust into the air that will then settle back into the environment.
15:29 - Richard Thompson: What harms are microplastics inducing?
Richard Thompson: What harms are microplastics inducing?
Richard Thompson and Chris Smith discuss the evidence that microplastic pollution is causing damage to plant, animal and human health...
Richard – There's now a substantial body of laboratory evidence that microplastics have the potential to cause harm, and I say potential because it's always the dose that's the poison. There’s been recent modelling work done in the Netherlands that’s looked at all of the studies – and you know, there are now over 4,000 studies using the term microplastics. Back in 2004, there was only one that used it in this context.
So, there's a whole range of studies, lab experiments, that have demonstrated harm – that could be reduced growth, reduced ability to put on weight, reduced reproductive output. I mean, only the week before last we heard about potential effects of really small particles on photosynthesis. So there's been a wide range of adverse effects demonstrated.
A key question there is: are those lab experiments done at environmentally realistic concentrations? And the challenge here is that we don't know with absolute certainty what the environmental concentrations of microplastics are. Why? Because they're particles of a whole range of different sizes, and when you get to below a few microns in size, they're almost impossible to pull back from an environmental sample – of sediment or seawater or whatever it might be – and confirm that, hey, I’ve got a piece of polystyrene.
Picture a small piece of plastic that you could see in your hand the size of a sugar cube breaking into two pieces, then four, eight, sixteen, thirty-two, etc. You can predict how many nanoparticles there are, but we don't know with absolute certainty how many there are, or the size distribution down to those really small pieces. But where I'm going with this is that the modelling predictions, based on the best estimates of environmental concentrations – and of course those estimates vary from one place to another, some habitats are more contaminated than others – suggest, linking to the lab studies, that what we're probably seeing in the natural environment at the minute is fairly isolated harm from microplastics.
We already know that larger plastic litter is causing harm, but from microplastics at current concentrations, we're probably seeing harm in the natural environment in a smallish number of isolated places. But the interesting thing is that the modelling predictions suggest if we don't change our ways in the next 70 to 100 years, that problem will escalate – and what we will see is adverse effects in the natural environment on a very wide scale.
Chris – If it's in the fish and I eat that fish, does that mean that I'm at risk? Is this going up the food chain? We often talk about things concentrating up food chains – mercury, and so on, is one classic example people point to, isn't it?
Do microplastics and nanoplastics behave like mercury?
Richard – No. They'll certainly pass from one creature to another, so they'll pass along the food chain, but there doesn't seem to be any evidence of biomagnification – which is what you're referring to with mercury – that larger creatures are accumulating more than the amount, kilo for kilo. So it's not that as the creature gets bigger the relative amount of plastic is bigger. There's no evidence at the minute of magnification.
But absolutely, microplastics are in the water we drink, they're in the food we eat, and they're in the air we breathe. So they're in us as humans. People ask me, of course, about the harm to humans. At the minute, the evidence that we have is correlative evidence that's pointing towards the potential for adverse effects on humans. What I would say – and I'm not a medical scientist – is that the number of experiments we've got across the rest of the animal kingdom pointing to adverse effects… We are just another animal.
So why would we be surprised to see that evidence of harm to humans, as well as to the rest of nature that’s been studied? Because we could spend a decade trying to establish that direct causal link between micro- and nanoplastics and adverse effects on humans. It could cost millions to establish that, and when we've shown it, what do we do with that information? We're still going to need to address the problem.
So my question is: where is the tipping point here? We've shown that there is harm from plastics of a range of these sizes – particularly the larger stuff – to wildlife, economic harm, and potential harm to human health and well-being. How much more evidence do we need before we start to take action?
And I stress the importance of these larger items of plastic, because once they're in the environment, they fragment progressively over time. So the larger items of plastic litter of today are some of the microplastics of tomorrow. We need to make those changes now. We don’t need to wait for further evidence about effects on humans.
Chris – At least people are beginning to explore new forms of plastic that are more biodegradable, and won’t have this hundreds-to-thousands-of-years-long lifetime where they have the chance to fragment into tiny particles with potentially pathogenic effects. Is that the answer, do you think? Do we just have to make a big shift away from making plastics the way we have, and surrender what is a wonderful material – but one with a toxic legacy – in favour of ones that are much better?
Richard – The biodegradable plastics have a role in this, but they're not in any way centre stage as a solution. If you think of the things that have made plastic materials so successful – it's the fact that they're lightweight, they're inexpensive, they're versatile, and they're very durable. A lemonade bottle – you need to rely on it to hold that lemonade as long as you want it, on the supermarket shelf, on the back of your car on a hot summer's day, or on a cold rainy day.
How is that lemonade bottle going to magically know the minute you've consumed the drink, and it’s somehow become litter in the environment, and now it's time to self-destruct in a meaningful timescale?
If we can make them biodegrade rapidly and harmlessly, and not accumulate in the soil, if we can design polymers in those settings where we’ve got a very specific life expectancy of the polymer – it doesn’t need to be durable beyond a few months in the growing season, for example. Or another example: perhaps where we’ve got food wrappers, maybe served at a large venue – a pop concert, football stadium – where the time the food is needed is quite short-lived, over a few hours. You've got a big venue, with a single organisation controlling the food that comes in, the wrappers that come in, and critically, also the waste that goes out.
There, there’s the possibility for wrapping the hamburgers in a compostable wrapper, and the half-eaten hamburgers and the wrapper can go to a commercial composter. But unless those plastics can get into the right waste stream, they're not going to achieve any beneficial effects.
22:43 - Richard Thompson: Plastic pollution solutions
Richard Thompson: Plastic pollution solutions
Is going back to glass part of the way to mitigate plastic pollution? Richard Thompson and Chris Smith discuss solutions to plastic waste...
Richard – Well, there’s a number of things there. Glass is certainly heavier than plastic, so if you do the assessment of the impacts and look at it from a carbon perspective, the packaging is lighter in plastic than in glass. If we can get those plastic bottles to be more circular – and there’s good evidence of high recyclability for milk bottles, for example – I don’t think it’s necessarily about going back to glass.
The idea of the deposit on the bottle could be an incentive to get people to return them, and we’ve seen that working with deposit return schemes on plastic bottles in other countries – so that could be an advantage. But a key part of getting this circularity to work is going to be simplifying the formulation of plastics.
If I think even about the plasticisers that help to make plastic bendable, I understand there are over two dozen different formulations of plasticiser. Why have we got those? Because different companies, of course, don’t want to pay exorbitant rights to one initial patent owner, so they’ve tried to develop their own. All well and good so far – but if you’re a recycler faced with this diversity of 20 different chemicals that all do the same job, it makes it quite challenging to recycle that material into a viable product.
And of course, it’s not just the plasticisers. Recent studies have demonstrated there are over 16,000 different chemicals associated with plastics and plastic production – and around 4,000 of those, back to the earlier question about chemical release, are known to be potentially harmful.
So I think if we’re going to aim for increased circularity via recycling, that’s going to have the biggest potential for single-use plastics – where the benefit to society is short-lived, and the potential to turn those end-of-life plastics into new plastics is quite high. Let’s not forget that of the 400 million tonnes of plastic we produce every year, about 40% of that is destined for short-lived applications.
But to get that circularity to work, we’ve got to dramatically simplify the chemical formulations. We’ve got to harmonise the way we do things – so that you can mix lemonade bottle brand A with lemonade bottle brand B, with a container of the same plastic that didn’t contain lemonade, and you can recycle them without resulting in an inferior product.
Recycling is part of the solution, but we’ve got a long way to go to make that work. Less than 10% of all the plastics we’ve produced have been recycled. There are lots of challenges around potentially hazardous chemicals used, and the fact that it’s difficult for a recycler to know what’s coming into their plant.
So we start with reduction, right? And there are clearly plastics – particularly some of the single-use ones – that we don’t need. Or at least, I would say, we can’t afford the luxury of them, given all of these external environmental costs and potential human health costs that I’ve talked about.
If you look at the curves for predicted production alongside our ability to manage the waste, those curves are escalating away from each other. This is not a problem that can be solved by waste management alone.
We can’t afford the luxury of some of this throwaway plastic – whether it’s single-use drinking straws, plastic carrier bags, the microbeads in cosmetics that are now, thankfully, banned in many countries.
So we need to think about developing essentiality criteria for plastic products – because it’s clear they all have the potential to be hazardous if they get into the wrong context. Then, for the plastic items that are essential, we need to make them safer and more sustainable than we have done today – and that sustainability needs to be reflected in either reuse formats or recyclability.
Chris – I was very relieved when we went for a coffee just before we got together that you produced your reusable coffee cup and castigated my single-use! But I didn’t have the forethought to think, "I’m meeting a plastics recycling man – I should be more cognisant about bringing a coffee cup I can reuse."
How do you sleep at night? Because the thing is, now you’ve identified this problem, everywhere you look in the world around us, you see more of the same. You see the problem amplifying. I go shopping and I shudder – and it was you that did it to me – because I look at the shopping and the amount of plastic waste I generate from my weekly shop fills a bin.
It doesn’t seem like we can serve anything anymore without wrapping it up in layers of plastic. So what do you do to relax? Do you get any respite, Richard?
Richard – Plastics aren’t the enemy. Plastics bring immense societal benefit, and can bring environmental benefit. Think of lightweight parts in cars and aeroplanes, the many applications in hospitals and schools. Even the single-use packaging that we might pick on actually extends the life of food and drink in supermarkets and in our homes – and it reduces food wastage, which is another major environmental challenge.
So the solution isn’t about trying to ban plastics from our lives. The consumer will have a key role in that solution, but at the minute, education on how to use plastic more responsibly is lacking. We have a slightly broken system.
We need to go right from the drawing board to design plastics in a way that's safer and more sustainable. We need to make sure when we’re designing a plastic product, we’ve considered its end-of-life fate – how it should be disposed of, what the options might be. That’s going to be very context-specific – different in the UK, where I have the benefit of a quite sophisticated recycling truck arriving at my doorstep once a week, versus communities I visit in Indonesia, where literally the only means of getting rid of rubbish is to burn it – releasing potentially toxic gases – or to throw it into the local river because there is no other collection.
It’s really critical that we think about that at the design stage – that we design plastics that are safer and more sustainable, including what happens at the end of life. And to me, it’s a tragedy when I talk to product designers – even of single-use plastics – and they say to me, “End of life? I was never asked to think about that. I was simply asked to make a product that performed and was attractive to the consumer.”
And that’s a major part of why we’ve got the problem that we have. It’s not that plastics can’t be safe and sustainable – it’s that we fail to even think about making them that way.
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