Titans of Science: Richard Thompson
PodcastsThe Naked ScientistsTitans of Science: Richard ThompsonA career studying microplastic pollution, and how we can deal with it. . . 15 April 2025Titans of Science series is back for another run. And to. . .
PodcastsThe Naked ScientistsTitans of Science: Richard ThompsonA career studying microplastic pollution, and how we can deal with it. . . 15 April 2025Titans 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. . . Richard Thompson: Unearthing microplasticsRichard 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. Richard Thompson: Following the trail of microplasticsRichard 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.