#332 - AMA #67: Microplastics, PFAS, and phthalates: understanding health risks and a framework for minimizing exposure and mitigating risk

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Ask Me Anything episode. Welcome to ask me anything AMA episode 67. For today's AMA, we're going to focus on something that's gotten a lot of attention lately in the news, online, social media. And as a result, we've received an endless stream of questions, not only from our audience, but also from our patients. And that topic is microplastics and all other accompanying chemicals such as BPAs, PFAs, and phthalates. Given the interest, we decided to dedicate an AMA to this topic. In this conversation, we dive deeply into what we know and what we don't know about these chemicals. Why they seem to appear all of a sudden everywhere, how we're exposed to them, how much exposure we have, and how dangerous they may or may not be to our health. Ultimately, and perhaps most importantly, I think we propose a framework for how someone can think about avoiding and mitigating exposure to these chemicals. If you are a subscriber and you.

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The Show Notes page. If you're not a subscriber, you can watch a sneak peek of the video on our YouTube page. So without further delay, I hope you enjoy AMA67.

Peter, thanks for coming back for another ama. How are you doing?

Good. Thank you for having me.

Before we get started today, quick question. Do you have a beverage in front of you?

I do.

What type of glass is that in? Is it a plastic? Is it glass?

It is plastic.

Huh? Okay, interesting. Then that will be interesting for this ama, which is going to cover one topic, which is something that seems to be growing in interest. We've been getting a ton of questions on ton of conversation online. That's microplastics and other chemicals such as BPAs, PFAs, and phthalates. So what we did, gathered all these questions that have come through, pulled them together, and are ultimately going to try and help people understand. Should they be worried? What should they be worried about? What's dangerous based on all that, what can they do about it? Before we get started, Anything you want to add?

I think there's actually a lot I need to say before we dive into this for context, so I'll preface maybe by saying the following. Obviously, people who are regular listeners of the AMA can appreciate that these are not off the cuff remarks that we make here. And we put a lot of work into doing this. When I sit up here and do these AMAs, I'm doing them based on the work that me and a team of analysts have done for usually about a month in preparation for them, I think it would be safe to say that in the six years we've been doing this, or is it seven or eight now, I've lost track, to date at least, this will go down as the AMA that has required the most work, that has probably generated the most swear words and probably resulted in the secretion of the most adrenergic compounds from the adrenal glands. In other words, this has been a royal pain in the ass to prepare for. And as recently as last night at 10 o', clock, I was emailing you saying, what the fuck? Why are we doing this? It's a never ending morass of information, most of which is incomplete. There's so much I could say on this. And then the most wonderful thing happened, which always happens. Anyone has experienced this if they think back to being in college. Even the night before the exam, you're like, I don't know what the hell is going on. And the best advice is usually just go to bed, get a good night's sleep, get up nice and early, fresh cup of coffee. And I think that sort of happened this morning. Me and a couple of the other analysts went to bed, got up this morning, and all of a sudden I just had more clarity about, in my words, how to land the plane. And I took to writing a couple of pages out, and I think I've got kind of a sensible way to make sense of something that is incredibly noisy. So what I'm gonna say at the outset is if you are listening to this thinking that there is a punchline and a one word answer, I'm gonna spare you the disappointment. This is a very nuanced topic. If I could answer this in a word, I promise you I would, and I would never try to go through the 75 pages of notes that our team has assembled to help me think about this topic. I swear to you, there are a hundred things I'd rather be doing than going through this. However, it is important in an area where there is so much uncertainty, so much asymmetry and such complete and incomplete information that we have to understand the boundary conditions so that we can each make a reasonably informed decision. So with that as my preamble, let's do our best to guide people on a journey that we've been on and acknowledge our shortcomings, acknowledge where we wish we knew more, where. Where maybe others do know more. But leave people with a framework such that at the end of this ama, which will hopefully be sometime today and not tomorrow, everyone can sort of make a risk based decision for themselves, for their families.

Definitely. And it kind of reminds me of what Bob Kaplan always used to say. Right. Which is further from the shore, the deeper the water. So as we've kind of like gone deeper and deeper on this, it seems more complicated. More complicated. The last question I'll ask before we get started. That coffee you drank this morning, was that in a glass mug or like a Starbucks paper mug with the plastic lid on top?

It was actually in a metal yeti camping coffee cup. That's sort of my favorite way to drink coffee.

All right, so you redeemed yourself a little bit there, which is good. Starting off, I think it'd be helpful, as we kind of typically do, definitions. What are microplastics? What's bpa? What are these chemicals we're talking about? Let's just define them now so as we say them going forward, people understand what we're talking about.

Part of this is you just have to suck it up through the semantics. And part of the challenge is that some of the definitions are not very helpful. So starting with microplastics, they're typically defined as any particles of plastic that are smaller than 5 millimeters. Now, again, I realize that not everybody is facile with the metric system, but anybody who is will realize 5 millimeters is huge. You can see 5 millimeters, that's half a centimeter. So we're not really talking about that. I think most current studies would really classify microplastics as those smaller than 1 millimeter, 1/10 of a centimeter, about 1/25 of an inch. And then of course we talk about what are called nanoplastics, which are particles that are smaller than one micrometer or micrometer. So one one thousandth of a meter. So we abbreviate these as MNPs or micro nanoparticles. And we should just acknowledge that these things are completely ubiquitous. They're found anywhere that we have looked for them, which is to say we find them in water, we find them in food, we find them in fruit, on fruit, in vegetables, on vegetables, in meat, in the air, and therefore micro nanoplasticles or MNPs are completely ubiquitous. Okay, you asked about BPA. Now, there are lots of these bisphenol chemicals, but bisphenol A or BPA is the one that most people are familiar with. Ironically, the presence of bpa, at least being used actively, has been reduced quite a bit over the past 15 years. But just understand that there's a whole family of these bisphenols, and typically we substitute one for the other. But what are they? They're chemicals that are used to make polycarbonate plastic. Polycarbonate plastic is the hard plastics we have in our world. So if you think about all the places where you use plastic and it's hard, I think of the Nalgene type, water bottles, epoxies, resins, things like that, that's where you're going to have historically found a lot of bpa. Of course, today this is less than the case, but the truth of the matter is they're now replaced by other bisphenols. So BPS and bpf, and the truth of the matter is not clear that we know if those are any better than bpa. So when I say bpa, I think it's just easiest to sort of think of the broad category of these families. Another thing that we're going to talk a bit about, and I've talked quite a bit about this in the past, is actually particulate matters of the 2.5 or smaller variant. These are abbreviated PM 2.5, and again, it refers to particulate matters in the air that are smaller than 2.5 micrometers. So why is that important? Well, there's something relevant about a particle that's that small, which is that if inhaled, it has the potential at least to become systemic. And the reason for that has to do with the anatomy of the lungs and the size of both the alveolar air sacs and the epithelial linings of them, which, again, it's not necessarily that intuitive that you could breathe something, but that it is small enough that it could actually get across a cell barrier at the innermost part of the lungs and enter the systemic circulation just as though it had been injected into you. A PM2.5 refers to any particulate matter that is inhaled in the air that is of that size or smaller. Now, are there some microplastics or micro nanoplastics that fit that description? Yes, but most are not. So most PM2.5s are not microplastics. I forget the exact number. I know it's somewhere. We did look it up. It's on the order of a few percent. I would say that the greatest contribution to PM2.5 is probably come from air pollution. So anything that has to do with when there's a fire burning wood, obviously burning fossil fuels, but coal being, hands down, the leader of this. I mean, natural gas combustion produces much less of this. And then we'll talk about phthalates, which are another class of chemicals that are kind of like. I think of them as sort of the opposite of the BPAs. So these are the things that are used in plastics to make plastic more flexible, to have more bend in it. They're also found in products that we use like shampoos, lotions, laundry detergents. It makes fragrances last longer. Now, there's been a constant regulatory shuffling around all of these things, and I'm not going to get into it because I could just put everybody to sleep right now. We're going to leave a ton of this in the show notes section where we're going to kind of go through the regulatory machinations on this and which of these products were banned and when and what got substituted in. But the bottom line is that the use of phthalates are still currently allowed in food content application, but many companies have undergone voluntary reductions in this. There doesn't appear to be any restriction in the use of phthalates for personal care products. And I think this is probably where people are going to see their greatest exposure to them. So I guess I'll stop there, Nick. But that's the whirlwind tour of what all these different compounds are.

Do we have any idea why it seems like we're now hearing about microplastics being everywhere? It doesn't seem like that was always the case. So do we know why there's been this huge uptick in this?

Yeah, I think there's two things going on. So the first is that obviously plastics are relatively new, didn't really exist much prior to the 1950s. And if you think about it, I mean, they were pretty remarkable. So incredibly lightweight, remarkable strength to weight ratio, resistant to rotting and corrosion and shattering. I mean, there are lots of reasons we use plastic. So when you combine the fact that they've been increasing in their proliferation over the past 70 years, that would certainly explain why we might be seeing more of them. But there's also a little bit of, what is the expression, the drunk under the streetlight problem. People are also looking at this more and more and more. In fact, if you don't mind, if you could pull up, there's A figure we've got that shows the number of scientific publications focusing on microplastics in the last 20 years. So if you go back, it's showing basically 2000 to 2020. It's a linear scale, but it's still pretty remarkable. It still looks like you're basically watching Bitcoin from 2010 to 2020. That's effectively what's been going on. So I don't doubt that there are more and more microplastics accumulating in the environment. That's likely, but we can't lose sight of the fact that we're also looking for it nonstop. So one of the questions that I didn't come up with a satisfactory answer to was if you just look at the last five years, are we seeing a true increase? I wouldn't doubt that there's more. 2020 versus 1980, that strikes me as, hey, over that 40 year period, I could really see it going up. But 2020 to 2025, is that a real increase or is that an artifact of observation?

You touched on a teeny bit when you were kind of going over the definitions, but I think it'd be helpful to just dive into it a little deeper, which is, how are humans being exposed to microplastics currently?

We should always be thinking about this through the lens of relevant versus not so relevant exposure. But again, we're going to always try to focus on a relevant exposure, which is an exposure that has the potential to accumulate. So the most common route of human exposure is from inhaling plastic dust and fibers and from consuming food and beverages that contain these micro nanoplastics. And again, that's why I prefer to talk about N MPS rather than just microplastics. Why? Because my concern about consuming a 5 millimeter piece of plastic is nil, because it can't be absorbed. It's going to come right out my body the next day. This is not the thing that we need to be afraid of. So what are the foods and beverages we need to be concerned with? The highest places we tend to see these are in seafood, salts, water, both tap water and bottled water, but also in fruits, vegetables, meats, even beverages like milk, beer and wine, which obviously contain water as well. Nanoplastics in soil can accumulate within plants, and obviously the exposure gets magnified as you go up the food chain. This again explains why we would see it in seafood, given that we understand the role of plastics in the oceans. And that's why obviously you can see seafood and land animals accumulating these as well. The epithelial barrier is the first line of defense. Remember, there's an epithelial layer on the outside of your body that we can see, but there's also an epithelial layer on the inside of your body. Everything between your mouth and your anus is also an epithelial layer. And that's why generally, micro nanoparticles don't enter the body through the skin or through the gut unless they are small enough. We've already talked about it. The pulmonary epithelium requires them to be smaller than 2.5 microns. And in the lining of the gut, it could probably be as big as 150 microns to be absorbed.

Do we know how much plastic humans actually consume? And is it even knowable? You often hear numbers thrown around a lot. Curious what we know on that.

It's difficult to know, but I think we can probably put some brackets around it. So, first, there's a huge amount of variability based on a lot of factors. So where you live, what type of food you eat, and what your source of drinking water is would probably be the three biggest determinants of your exposure to MNPs. That's worth noting again, and I think it's worth stating your geography. Your source of food, your source of water plays the biggest role. If you aggregate the data from all of the studies, it would suggest that humans are consuming. And this is a broad range. So that's just, unfortunately, the nature of this stuff. Somewhere between 10 and 300 micrograms a week. This is 10 to 300 thousandths of a gram per per week. Now, a study that was published in 2021 estimated that, on average, we consume about 4 micrograms per week from fish and other sea things like crustaceans, mollusks, tap water, bottled water, beer, et cetera, et cetera. The study simulated the expected exposure to amounts that agreed with measured quantities in microplastics and stool. So I think this is probably an underestimate, given that it didn't look at some of the other areas that have already been found to contain some mmp, such as fruits, meat, vegetables, potentially plastic off cutting boards, utensils, plastics. That may come from things we'll talk about like reheating food and things like that. So the point is that the mass of these things is pretty small, and that might not be the right way to think about it. And we can talk about some of the misinterpretations of that stuff. There was a recent study published in 2023, it was in Korea, and it estimated that the population was consuming somewhere between 140 and 310 micrograms per week. That's a nice narrower band. It also ports with largely the upper limit of the US based study as well. I think that's probably the ballpark of where people are consuming.

How do those numbers compare to the credit card worth of plastic that was all over the news? I think you couldn't go anywhere without seeing that we're eating or consuming a credit card worth of plastic a week. So the numbers that we're seeing in those studies compared to what that would be, how do those compare?

Not even in the same zip code. So that soundbite that humans consume a credit card worth of plastic refers to a report that estimated Weekly consumption was 5 grams of mmps. That has been largely debunked, despite what you've said, which is the prevalence in popular media. But, and I don't remember who famously stated that a lie will travel around the world or halfway around the world before the truth has a chance to.

Pull its boots on.

I don't even need to go into that. We'll link in the show notes to both. The original analysis, which came out of the University of Newcastle, commissioned by the WWF, was released I think in 2019. And then obviously the rebuttals to that. But yeah, the long and short of it is I don't think any serious person believes that we're consuming 5 grams.

Of plastic a week based on what we consume. What do we know about how they're eliminated from our body?

The main way that these things are eliminated is largely through coughing and sneezing them out. So anything that's coming into our lungs, we can get it out by a cough or a sneeze, as well as urine and stool. So the largest particles, those that are greater than 10 microns, will generally be removed with relatively high efficiency, regardless of how they enter the body. It's really the smaller particles that are eventually going to make their way to the immune system. If you were going to do a mass balance on this stuff, the majority, to the tune of 99% of ingested microplastics, are going to be eliminated through stool. And this is a relatively short transit time. We're talking about 24 to 72 hours. Plastics have a very difficult time crossing the GI epithelium. So when you look at animal studies, we would see that it's about 0.3%, maybe with a ceiling of about 1.7% of microplastics have the capacity to be absorbed across the GI epithelium and of course it's heavily, heavily size dependent. So it's the particles that are going to be less than 10 microns, which remember, that's four times larger than what is required to get into the lung. So again, just think in the lung we're anchoring to 2.5 microns or less in the gut, even though in theory the gut could absorb something close to maybe a hundred. I think that's more theoretical. And in practical terms, we tend to see it as 10 micron or four times that size. So the bottom line is this, if you're encountering a microplastic that's less than 2.5 microns, you could absorb it both in your gut or via your lungs. Now, when we go through this type of analysis in urine, we again see that we also excrete microplastics through the urine, but this is less than what we do through the gut.

For the things that are not eliminated, where do they end up and why are there growing concerns about that?

So this is really the crux of.

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