Why We Need a Strong Global Agreement on Plastics Pollution

Yale Environment 360: How did you first become interested in microplastics?

Richard Thompson: I was conducting experiments on the shore that were accumulating lots of little pieces of plastic. I mobilized the students, and we organized beach cleans. I started asking the question, “What are the smallest pieces?” My students went out on the beach, and they brought back samples of sand. When we looked at them with a microscope, we saw pieces that didn’t look like sand, that turned out to be plastic. We discovered that microplastics, including many smaller than the diameter of a human hair, contaminated waters around the U.K.

In a 2004 paper published in Science, we showed that they were biologically available to a range of marine organisms. We also showed, using archived samples, that the abundance of these small fragments, which we named microplastics, had increased significantly since the 1960s.

e360: We’ve known about plastic pollution for a long time. Why did it take so long for scientists to look into this question of microplastics?

Thompson: There were some studies of plastic pollution in the 1960s and 70s. But nobody was recording small bits. And it wasn’t until our 2004 paper that this really started to attract attention. I suppose it was kind of out of sight, out of mind, particularly for what I was describing, which was truly microscopic. You wouldn’t have been able to see it without a microscope.

e360: Did you immediately sense how important a discovery was?

Thompson: Probably not. I mean, I thought it was important enough to submit to Science. When I got back from holiday [after the paper was published,] my computer was full of media inquiries. Almost nothing else that morning. The phone was ringing constantly.

Since then, we’ve looked from Mount Everest down to the deep sea, from the poles to the equator. We’ve found this material everywhere. I recently came back from a major scientific conference [MICRO 2024 in Lanzarote, Spain] just about microplastics. I would never have dreamt of that 20 years ago. There were 700 scientists from all around the world registered at the conference just to discuss microplastics. So interest has grown phenomenally.

e360: In your latest paper, you cite polls that show that people rate plastic pollution as a more pressing issue for the oceans than climate change. How do you account for that?

Thompson: The [microplastics] problem is going to be irreversible. And the predictions are that we’ll see wide-scale ecological harm from microplastics in the next 70 to 100 years. We’ve already got clear evidence of ecological harm. They’re not going to degrade, they’re persistent contaminants. And because of their small size, it’s going to be kind of irreversible. So I don’t know, have the public got that level of concern right or wrong?

Climate change is a major issue that we need to grapple with. I’d argue that maybe tackling the problem of plastic pollution, although incredibly complex is, I’m hesitant to say, simpler. I would argue that a lot of the societal benefits that we get from plastics could be realized without the harm by starting to use plastics more sustainably. We’ve failed to design plastics [for recycling and reuse] for example. So that’s part of the problem with producing colossal quantities, well over 400 million tons of plastic every year, 40 percent of it is destined for single use.

e360: There are a lot of different sources of these microplastics. Do we know what the main ones are?

Thompson: The biggest source overall accounting for about two-thirds of all microplastics is the larger items of litter that are accumulating in the environment. The packets, the bottles, all of those things will fragment over time into smaller and smaller pieces. There are also fragments and fibers that wear away from larger items like car tires and clothing. The other third is direct emissions of small pieces to the environment. For example, the small bits of plastic that are intentionally added to products such as cosmetics and paints.

e360: You are a marine biologist. A lot of attention has been paid to the question of microplastics ending up in the ocean. After 7,000-plus studies, what do we now know about the impact on the ocean ecosystem?

Thompson: Well, it’s clear that microplastics are incredibly biologically available to a wide range of creatures. I think well over 1,000 species have been shown to ingest them. And there’s clear evidence of harm to individuals. There are also experiments that demonstrate effects on communities and also on ecosystem services, things like gas exchange between sediment and seawater. So we’re seeing evidence of harm across all levels of biological organization, from cellular to ecosystem.

e360: I’ve read that microplastics have been found even in plankton and algae. Is there any evidence that, as with heavy metals like mercury, they accumulate as they go higher up in the food chain?

Thompson: Good question. No, there’s not. There’s evidence of transfer along food chain, but there isn’t biomagnifcation as we see with mercury, for example, from the best evidence that we’ve got at the moment. Now, where I think we may see a change to that is as we start to work on smaller and smaller particles.

e360: Are these very tiny particles even more dangerous than the larger ones which, when they are ingested, generally just pass through the digestive system and get excreted out?

Thompson: The scientific consensus is yes, they are, because they’re not only going to go into the gut, they’re going to pass into the circulatory system. The gut handles foreign material from time to time. It’s a barrier in its own right. But once we’re inside the circulatory system in organisms, then I’d say the potential is quite different. So I think small is certainly more biologically available.

e360: There have been reports that say that the quantities of plastics entering the environment far exceed the quantities we’re actually finding in the environment. Where are these missing plastics as they call them?

Thompson: Yeah, this question of the missing plastics, it’s interesting. Back in 2004 when I published that first paper, I entitled it “Lost At Sea: Where Is All The Plastic?” Because what I did not see at that time in any of the data that was coming from beach cleans was the increase in abundance that you might expect to see. And neither did I see it from surface trawl data. But the reason I believe is that we weren’t yet recording the small bits, so we were missing a fraction. And also there are sinks, places of accumulation that we’re not yet looking at. The deep sea looks like it’s got a lot in it, but we don’t have all that much data from it.