Philip Demokritou: Ingestion is the primary route of exposure, and we are consuming about 5 grams of micronanoplastics per week; that’s the equivalent of a credit card.

Samantha Laine Perfas: Our planet is filled with plastic. On average, we produce 430 million tons every year, most of which is used only for a short period of time and then discarded. But plastic isn’t just in the environment: it’s now in our bodies. Microplastics have been found in our bloodstreams, lungs, and other organs, and we’re only recently beginning to understand how this affects our health.

How destructive is our relationship to plastic?

Welcome to “Harvard Thinking,” a podcast where the life of the mind meets everyday life. Today, I’m joined by:

Demokritou: Philip Demokritou. I’m the founding director of the Harvard Nanotechnology and Nanotoxicology Center at the School of Public Health.

Laine Perfas: His current research focuses on how nanomaterials and particles affect our health and safety. Then:

Don Ingber: Don Ingber. I’m the founding director of the Wyss Institute and a professor both in the Medical School and School of Engineering, as well as Boston Children’s Hospital.

Laine Perfas: He’s also a cell biologist and a pioneer in the field of bionics. And finally:

Mary Johnson: Mary Johnson. I am a research scientist in the Environmental Health Department of the School of Public Health.

Laine Perfas: Her work focuses on immune health and investigates how the effects of air pollution, wildfires, and other environmental exposures affect our bodies.

And I’m Samantha Laine Perfas, your host and a writer for the Harvard Gazette. Today, we’ll take a close look at the plastic problem.

I want to start off by asking why are we so obsessed with plastic?

Demokritou: I think plastics have become an integral part of modern life because of their low cost, amazing properties, and they definitely made our life easier. We found one of the very first ads that the industry put together and it starts with, “Plastic is fantastic.” So, I guess we live in the age of disposable living. We are all addicted to plastics.

Ingber: It’s basically our culture’s heroin. It does everything you’d want it to do at incredibly low cost with high fidelity, reproducibility, manufacturability. It’s useful in every way, as Philip was saying. It’s a fantastic product, it’s just getting rid of it is the problem. It’s killing us over time; I mean the whole planet, not just humans. I mean, marine life, animals. In the last 15, 20 years, it’s really reached the point where it’s obvious when you see large expanses of ocean filled with plastic trash, that doesn’t degrade in landfills and so forth, but it was always there. We just weren’t aware.

Demokritou: When we don’t manage plastics in a sustainable way, then it becomes a problem. And that’s the case for every chemical we’re using, every material we’re using. And unfortunately, the modus operandi of our society when it comes to chemicals is, let’s put them out there and we’ll worry and clean the mess 20, 30 years later when scientists like myself, Don, and Mary discover that they are causing harm to the environment and human beings.

Laine Perfas: So I want to talk a little bit about microplastics and nanoplastics specifically. What are they and why are they so concerning to our health?

Johnson: So the plastics are wonderful when they’re being used, but then they decompose. And as they decompose, the microplastics are small plastics, less than 5 millimeters, and they can further degrade into nanoplastics, which are even smaller. And the concern, obviously, is not only is it destroying our environment, a few years ago we found out it’s in our blood, and now we’re finding out it’s in a lot of our organs and tissues and really it’s everywhere. I think that has heightened our concern and our awareness that we really have to figure out a way to prevent this degradation and exposing ourselves to the microplastics.

Laine Perfas: How is it getting into our bodies?

Ingber: I was in meetings 15, 20 years ago when the field of nanotoxicology sort of initiated when people realized that these particles are getting — this was all types of nanoparticles, not just plastics — getting into every organ in the body, and it was hard to understand how this could be happening because we have barriers in our tissues. Maybe 14 years ago we developed devices called organs-on-chips that have human cells oriented in little engineered devices that have hollow channels that could have flow of fluids to mimic blood and air. And we lined it by the lung cells that line our air sac. And we put particles that were some of the more plastic particles in the lung. And what we found is that actually breathing motions increase their absorption enormously, and it’s analogous, I think, to like viruses going across, which are similar size, going across the barrier of these tissues. They’re being picked up the way we pick up other things that are small and transport them. It wasn’t like tearing apart the tissue at all. It really made me think, whoa, I mean, the idea that this can cross all the tissue barriers got really worrisome to me.

Laine Perfas: I mentioned at the top of the episode too that we’re also literally eating them; and I guess that was surprising to me, that from consuming them it was also entering our bodies because like you said, Don, I would have thought that our bodies were able to just digest it. And there it goes. And it’s no longer in us. But that’s not the case. So I’d love to hear more about that as well.

Demokritou: That’s what I call the two I’s in terms of the exposure: inhalation, of course, but also ingestion. Actually, if you look at the human population data, you will see that ingestion is the primary route of exposure, and we are consuming about 5 grams of micronanoplastics per week; that’s the equivalent of a credit card. So ingestion is a major route. And we have a grant from USDA, and we’re looking also at how these micronanoplastics from soil make it to edible plants. And also through the trophic transfer, they can make it through the food chain. Now, I think Don put it nicely, anything in the nanoscale, it’s very clear that they can bypass biological barriers. When it comes to micronanoplastics, especially nanoplastics, they are everywhere. It’s the byproduct of degradation over 50, 60 years that we throw them out there. We have many evidence that these nanoplastics in particular, because of their hydrophobic nature, they can really become systemic. We found them everywhere. Every organ, every week, it’s a study that we found them. In this organ, in that organ. Of course, for those of us that were doing toxicology, we know that the dose makes the poison. So it’s not just the identification in organs, it’s also in certain quantities that they can really cause harm. And that’s the question we’re trying to address right now.

Johnson: I’d like to also bring up microplastics in the air, I think [that] is underappreciated, and we don’t have a standardized method for measuring it, especially on a populational level. And we do research looking at how wildfires, how the smoke impacts your immune system. We know that there’s also microplastics being inhaled with the smoke. But the standardization of measurements isn’t there yet to be able to accurately quantify how much we are inhaling, especially in those special circumstances with increased air pollution or wildfire smoke.

Ingber: I learned that one of the biggest sources of microplastics is tires; as tires run on the road and you’ll see those little black marks, it’s leaching into the air. And then also textiles. We’re just surrounded, we’re bathed in them. The other point I think that’s important, it may not be obvious, is that, when we ingest foods, we digest them, right? We break them down to small molecules that could be absorbed, and those that are not digested usually go out in feces or urine. But plastics are not broken down to their individual links, if you like, we call them monomers. Yes, their small bits are released through breakdown, but that’s more physical breakdown over time and not chemical breakdown. And that’s what makes them really so dangerous.

Laine Perfas: It seems like a study every day is coming out, oh, we found microplastics here in the body, or in this organ, or here. So we know that it’s very commonly present in our bodies. What do we know so far about the health risks, about how that actually is affecting our bodies, and some of the dangers that it can cause?

Demokritou: In public health, usually we use epidemiology to come up with the associations of exposures to whatever disease. And that’s an area that when it comes to micronanoplastics, we don’t have many studies out there. So we need to do more of these kind of studies to link the associations between exposures and diseases. Now, in terms of the toxicology of micronanoplastics, that’s a little bit more mature field. I’ve been studying nanoscale materials and plastics for probably 10 years, especially nanoplastics through the NIH-funded center we had at Harvard. The evidence that nanoscale plastics in particular, that they can bypass biological barriers, I think, that’s very strong. You put them in the lungs, they will translocate, become systemic, they will go to different organs. Also, at the cellular molecular level, we see red flags. We can see them becoming internalized in the gut, for instance, we even found them in the nuclei. We publish a ton of papers on DNA damage, the potential to generate reactive exospecies and interfere with cellular functions. Actually, I’m using one of the organ-on-a-chip platforms that Don developed to understand how they behave in the gut. We have a ton of evidence, but we need to understand mechanistically what’s happening. Not all micronanoplastics are created equal. They have unique properties, different polymers, different sizes, morphologies. So we have a ton of work to do to study potential health effects. We are not there yet.

Ingber: I’m excited to hear you working with intestine-on-a-chip because that would be a great model for this. We’ve also integrated microbiome into these intestine chips. And the microbiome can also modify the plastics, or they can be modified by the plastic. And these plastics can bring toxins along with them, like heavy metals. And that’s a whole area I think that people have explored more in the marine-life area, but it’s probably affecting us as well. In our first paper that I mentioned, where we looked at nanoparticle transport in the lung chip, we could absolutely show activation of inflammation. And inflammation is, you know, at the heart of almost every disease and also even cancer progression. It was the nanoparticles being taken up that drove that.

Johnson: There was a recent study that did come out that I thought was pretty exciting, where they looked at patients who are undergoing carotid endarterectomies, so they were scraping the plaque out of the arteries, and then they analyzed the plaque for microplastics. And they found that those who had microplastics in the plaque, I believe it was at least 50 percent, I think it was more than 50 percent, they were able to associate the microplastic levels with morbidity and mortality three years later. And to my knowledge, it’s one of the first studies that were able to show basically a clinical outcome associated with the presence of the microplastics.

Demokritou: One additional point, Sam. All the plastics that we’re currently using, they are loaded with additives. And those additives have plenty of literature, historical, epidemiological, and toxicological data that they can cause harm. We know the phthalates, that they’re there to make the plastic soft, they’re endocrine-disrupting chemicals. And these micronanoplastics now, when they’re taken up by our cells and the body, they are the carriers of these additives so they can more efficiently deliver chemicals into our body. So, it’s kind of a Trojan horse of delivering chemicals from the plastics themselves. We have a paper now in review that as these micronanoplastics wandering in the environment, they carry other environmental pollutants on their surface because of their hydrophobic nature. And also they can really deliver these environmental pollutants more effectively in our bodies.

Ingber: It’s like the cumulative exposure to chemicals of any type that matters, not just whether you saw it for a short time. And these particles, when they’re ingested, are what we call sustained-release vehicles, meaning they’re just sitting there and every day they’re releasing a little bit for the rest of the lifetime of those cells in your gut or other organs, and so that makes it even more dangerous.

Laine Perfas: That actually gets to a clarifying question I wanted to ask, which is: Is it the plastic itself that’s dangerous, or is it all the additives and chemicals that are in the plastic?

Demokritou: I think it’s a combination of the two. I mean, you cannot rule one or the other. And that is one of the major knowledge gaps that we have in toxicological studies of micronanoplastics. Actually, in my labs right now, we have developed platforms that enable us to simulate what happens to a plastic material across its life cycle as it goes through these stressors, which can be mechanical, it can be weathering, UV photo oxidation, thermal stressors. We can shorten what happens to plastic material over 50 years and we make what we call reference micronanoplastic materials that are environmentally relevant. And those are the ones we use in our toxicological studies.

Laine Perfas: Mary, I actually wanted to ask you, with microplastics, I saw some of your work was actually looking at different communities who are at higher risk of being affected than others. Could you talk about that a little bit?

Johnson: A lot of our research has looked at communities that are disadvantaged and are typically exposed to high levels of chronic air pollution and/or wildfire smoke. We don’t have hard data yet, but within that context, it is thought that those groups would also be more exposed to microplastics. A similar concept would be those who are living next to industries, and those also tend to be the disadvantaged populations, and so those types of vulnerable populations are probably going to fall fairly similar to what we see for those exposed to chronic air pollution and exposure to wildfire smoke. There have been a limited amount of studies, not our own, that have found that, at least in the indoor environment, infants are more at risk for exposure, and the second category would be preschoolers, and as you go up, you become less and less exposed to the microplastics. As we’re able to monitor indoor or outdoor air for actual microplastic numbers, we’ll have a better idea of the different age ranges and vulnerabilities.

Ingber: Do they think that infants and small children have greater exposure because everything that you give to a kid is plastic because it tends to be cheap and safer and they put everything in their mouths? Is that why or something about absorb from air?

Johnson: I do believe that the younger populations are exposed to a lot more plastics, but I believe that particular study was focusing on indoor dust, which is where the microplastics were primarily found.

Laine Perfas: I guess I’m surprised. I would have thought that people who are older, who’ve been on earth longer, would be more at risk.

Johnson: Yeah, I believe it was, they were referring to the inhalation basically of the dust in the indoor home, which makes sense, and the younger they are and they’re on the floors and not washing their hands and crawling and closer to the dust itself in the home. But it’s a very limited amount of research that’s come out so far, looking at those associations. So I do think much more needs to be done looking at which populations are truly vulnerable and we should be targeting to try to prevent exposure as much as possible.

Demokritou: I think it might be worth [discussing] a little bit more what happens on the global scale. There is a very recent paper, came out in Nature, which is the first effort to quantify and come up with an inventory of emissions of plastics around the world. And in high-income countries, generally speaking, we did well, not amazingly well, but we did well in containing and controlling the plastic pollution. That’s not the case in low-income countries. About 50, 60 million tons of plastic waste out of these 250 million metric tons that we’re generating globally, it’s uncontained. And in these countries, you will see open fires and burning plastic. You will see debris everywhere and the populations in those countries are getting exposed at higher levels compared to all of us in the United States, for instance. So we really need to do a little bit more at a global scale because environmental pollutants, they transcend boundaries. So if you put micronanoplastics in the air, they will travel, especially the nanoscale particles. They can go thousands of miles, and they can be everywhere. We need to keep that in mind as we address this global issue.

Johnson: I’d like to also bring up, there was a study that sampled tap water globally and 80 percent of the samples had microplastics in them. It’s certainly another issue that maybe isn’t talked about as much, although there was a study looking at bottled water and levels of microplastics, and it was pretty shocking how high of a concentration that were in the bottles. So many areas, I think that, need to be addressed.

Ingber: It obviously depends on whether you have copper pipes, or nowadays PVC is used all over and actually plastic tubing is used now quite a bit. It probably varies enormously, but it’s hard to escape.

Sam, I think it’s important to note that plastics is a general term that are, you know, materials that can be easily formed and take shapes that you desire and that’s where its initial term came from. In medicine, there are plastics that are biodegradable. That’s very different. Those can be broken down to the individual monomers or links. And so we’re talking about ones that can’t be broken down here, often petroleum industry-based and so forth. There’s a lot of work going on at my institute and other places in terms of both bioplastics, things that are easily even compostable, you can put it in the compost to break it down, or ways to remediate and break down plastics that are all over the place. I think that is really where hope lies.

Laine Perfas: I actually wanted to ask a question about that. How are we doing when it comes to discovering plastic alternatives?

Demokritou: We really need to substitute the non-biodegradable plastics, especially the ones that are single-use. Myself and Kit Parker from Wyss Institute, we have this project trying to extract biopolymers from food waste and then turn them into potential nanofibers to replace food packaging, which is a major source of plastic. And actually most of the food packaging we’re using, it’s single-use. So it will end up in landfills. We developed and we published a paper in Nature, I think a year or two ago, that we developed the first water-soluble, washable plastic material that can be used as an alternative for food packaging.

Ingber: Maybe 10 years ago, we developed a material that was inspired by insect cuticle, right? Think of a lobster, you know, or a beetle, very hard shell, but they’re also flexible. And it turns out that it’s all the same material that’s almost like plywood made up of layers; it’s called chitin in insects. And so we made something we called shrilk, which was the chitin, or breakdown products called chitosan, from shrimp shells, and silk fibroin, from silk. Chitosan is used in medical products for wound healing and silk is in surgical sutures, so it’s safe. And when we recreated the layer-by-layer structure, we actually had material that was optically clear but had the strength of aluminum foil and it could be molded. And so we were really excited about that. The challenges in that world, and I think for even Philip’s technology, is scaling up manufacturing so that you can do this at a cost-effective way.

The other side of this that we’ve had some really exciting recent breakthroughs is breaking down of plastics. And there have been some groups recently published that they can find microbes, bacteria that can degrade one type of plastic. And that’s gotten a huge excitement. We have bacteria that we isolated from the microbiome of a worm that degrades plastic on its own. And it degrades at least four different types of the major classes of plastic, and that’s led to a startup company; that was between my lab and George Church’s at the Wyss Institute. The reason we’re excited about this new startup is that it can work in a complex mixture. It doesn’t need to go through the current recycling pipeline of isolating each bit and then trying to degrade one at a time. And I think that’s the kind of thing that we need.

Laine Perfas: Given what we know and don’t know, are there things that we can do as consumers to reduce our exposure now, while we wait for some of these other changes to happen?

Demokritou: I think we should start from the societal level. We really need to actually come up with a strategy, and this is what we call the “three R waste hierarchy.” So we need to reduce use of plastics. We need to reuse plastics as much as we can. Of course, recycling has to increase, where 9 percent in the United States, it’s very low, and the single-use plastics that will end up in the environment, we need to substitute them, if possible with biodegradable, nontoxic plastics. Of course, we need to get all stakeholders on board. We need to redesign products, which may add to the cost, and it’s also the question of who is paying this add-on cost? Is it the consumer? Those are fundamental questions that we really need to start discussing. And the most effective approach is to do a source reduction. If we reduce the use, if all of us reduce the use of plastics, myself included, I think that can be a really good start.

Ingber: Think about how quickly solar and wind have changed in terms of energy. It required huge political shifts and financial incentives. And I think it’s got to be at that level. I mean, sure, every individual could stop buying plastic water bottles and using plastic bags and use wood cutting boards, but it’s got to be top-down at the same time.

Demokritou: There is this effort by United Nations to put in place a legally binding global plastics treaty, similar to the climate treaty, which is gaining track actually the last couple years; there are already I think 150 countries, signed this treaty. And again, this is at the global level because we need to see the plastic crisis across the board, not only at the local level, and not only at the high-income countries.

Johnson: I guess I would say, obviously, yeah, everything has to be dealt with at a global level, but even so, as a consumer I feel like I can’t wait, I want to minimize my own exposure. And I think having the mindset of when you purchase something, actually knowing what you’re buying helps. Simple examples would be clothing, synthetic clothing versus buying an all-cotton product or an area rug. Synthetic rugs are really cheap and soft. And wool rugs cost more, but you would be reducing the potential amount of microplastics that you’re being exposed to. You mentioned the kitchen. I do try to have nothing plastic used in the kitchen, if possible, it’s not always possible, and avoid, if there is plastic, it being exposed to heat, which can make the chemicals leach out faster. And I think it would be helpful to consumers to have some type of labeling on products, especially until we get these biodegradable plastics, so people are more educated and can make better choices in trying to minimize their exposure to the plastics.

Laine Perfas: So all of these are good suggestions for minimizing future exposure on a global and personal scale. Is there anything that we know of that we can do to remove the plastic that’s already in our bodies?

Ingber: Yeah. I think that’s something we need to figure out.

Demokritou: Another important element, Sam, is, we need better monitoring. Plastics, micronutrient plastics are not in the list of the chemicals that we’re monitoring in terms of biomonitoring. I know some states like California, they’re trying to include micronanoplastics in their plans. And also the reporting is very important. But we need to develop the methods to be able to do it efficiently, the identification and quantification, because it’s not just the identification. It’s not that I found one microplastic in my bottle of water. So it’s the dose makes the poison. We need to quantify our exposures at the human population level.

Laine Perfas: So if I could give each of you a magic wand that you could wave to either speed up the research on something that’s already happening, or to just solve an aspect of this problem, what do you think are the things that would make the biggest difference on this issue right now?

Ingber: You heard Philip say that we want to reduce, replace, reuse. What I’m seeing out there, and I get to see technologies that are really out there coming down the pipeline at the Institute, I really do think this idea of harnessing the way some organisms can break down plastics. And so it is possible. And so what we have to do is not only find ones that break it down, but link it into a cycle so that you have a full remediation, reuse, replacement cycle. And do it in a cost-effective way. It has to be cost-effective, or it will never get anywhere.

Johnson: I guess for my wish, I think having a scalable method to accurately measure the microplastics, whether it’s air or water or in tissue, would be really advantageous, so we can begin to better understand the exposures obviously, but the health impacts.

Demokritou: I think, definitely we need technologies to clean the mess we created, but we really need to start thinking of how we can reduce the use of plastics, because we can’t just throw toxic compounds out there and then develop the technologies to clean the mess.

Laine Perfas: Thank you all for joining me for this conversation. I learned a lot and I really appreciate it.

Ingber: Thank you.

Demokritou: Thank you.

Laine Perfas: Thanks for listening; to find links to all of our episodes and a transcript of this one, visit harvard.edu/thinking. This episode was hosted and produced by me, Samantha Laine Perfas. It was edited by Ryan Mulcahy, Simona Covel, and Paul Makishima with additional production and editing support from Sarah Lamodi. Original music and sound designed by Noel Flatt. This podcast was produced by Harvard University, copyright 2024.