Micro Plastics

I came across and interesting paper on micro-plastics. Previous papers have shown that microplastics do accumulate in human tissues including the brain, liver, kidney, placenta, and colon (see sources cited below). However the paper we are about to discuss is the first paper I have come across which followed individuals with microplastics found in their tissues, compared them to individuals that did not have microplastics in those tissues, and looked at health outcome data.

Spoiler Alert: You don't want microplastics in your tissues.

Let's get into the study.

This was a prospective observational cohort study published in the NEJM in March of 2024 that analyzed 304 patients undergoing carotid endarterectomy, comparing the risk of myocardial infarction, stroke, or death over an average of just under 3 years between those with microplastics and nanoplastics detected in their carotid plaques and those without.

What a sentence! Let's break it down.

A prospective observational cohort study is a research study that follows a group of people over time to determine how a factor (in this case having plastics in their carotid artery plaque) affects an outcome (in this case having a heart attack, stroke, or all cause mortality).

Visual Representation of Prospective Observational Cohort Study. Credit for Image: https://elearning.fondation-merieux.org/africarami/epidemiologie/en/chapter-2/page-26.php

The study looked at 304 patient that had plaques removed from their carotid artery. The carotid artery is a larger artery in your neck that delivers blood to your brain. Just like every other artery it is subject to the atherosclerotic disease process and can accumulate plaques.

Carotid Artery with Plaque. Credit for Image: https://www.harbourvascular.com.au/conditions/stroke-mini-stroke-carotid-artery-disease/

Because the carotid arteries are so large, doctors can go in and remove the plaque in a procedure called a carotid endarterectomy. These plaques can then be stained and looked at under a microscope. The image below is a key figure from the paper showing that the plaque tissues that contained micro and nano plastics had a marked increase in inflammatory factors and a decrease in collagen, as well as an increase in CD3 and CD68 both of which are markers of lymphocyte and macrophage infiltration, which again indicates inflammation.

The authors went on to use electron microscopy actually procure images of the micro and nano plastics in the tissues.

Wow! look at those plastics!

Now for the outcomes.

As I said in my spoiler alert, you don't want microplastics in your tissues.

The study found that the primary end-point event (nonfatal myocardial infarction, nonfatal stroke, or death from any cause), occurred in 8 of 107 patients (7.5%) in the group that did not have evidence of micro and nano plastics in their carotid artery sample(2.2 events per 100 patient-years) and in 30 of 150 patients (20.0%) in the group that had evidence of micro and nano plastics in their carotid artery sample (6.1 events per 100 patient-years) at 33.7±6.9 months (just under 3 years).

Using this information we can calculate the hazard ratio, which is a measure of how often a particular event happens in one group compared to how often it happens in another group, over time. Patients with micro and nano plastics in their carotid artery sample had a higher risk of having a primary end-point event than patients with no evidence of micro and nano plastics in their carotid artery sample by 353 percent. (hazard ratio, 4.53; 95% confidence interval [CI], 2.00 to 10.27; P<0.001)

353% increase is startling. Let's put that in perspective. The hazard ratio for eating red meat and processed meats on colon cancer was 1.35, meaning that there was a 35% increase in the rate of colon cancer in those that ate the highest amounts of these meats compared to those that ate the lowest amounts of these meats. Poor dentition has a hazard ratio to all cause mortality of 1.13 to 1.59, meaning that people with poor dentation have an increased risk of death between 13% to 59%. It's really not until you get to big factors like smoking that you start to get into the realm of this 353% increase. Smoking has a hazard ratio on lung cancer somewhere between 14 and 26, meaning that smokers have a 1,300% to 2,500% increase in the rates of lung cancer.

Remember that when looking at a study it is incredibly important to look both at the relative difference in the occurrence of events between groups as well as the actual difference in the occurrence of events between groups. Only then can you get the full picture of risk. As an example of how you can get tricked by only looking at one of the metrics: let's say a study found that you had a 200% increase in the rate of a bad outcome having had a certain exposure. The relative difference in occurrence sounds quite alarming. But when you look at the actual difference in occurrence, it occurs in 1 out of 1,000,000 patients without the exposure vs 3 out of 1,000,000 patients with the exposure. This would give it a hazard ratio of 3.0 and thus an increased risk of 200% between the 'unexposed group' and 'exposed group'. However, this difference of 2 events per 1,000,000 patients in most cases would be clinically meaningless and thus would change how we would integrate the 200% increased event rate of the study into clinical practice. This study is different.

In this study both the relative difference as represented by the hazard ratio of 4.35 and the actual difference represented by the rate 8 of 107 patients (7.5%) in the group that did not have evidence of micro and nano plastics in their carotid artery sample vs in 30 of 150 patients (20.0%) in the group that had evidence of micro and nano plastics in their carotid artery sample are material and I would argue are clinically significant.

To be clear, because of the nature of the study, it cannot determine causality. That is we cannot conclude that it is the plastics that are causing the markedly increased risk in nonfatal myocardial infarction, nonfatal stroke, or death from any cause.

This is where common sense comes in. Perhaps it's not the plastics driving the events. Perhaps the plastics are a proxy for another nefarious process that is occurring which actually driving the negative outcomes, perhaps they are the driver, perhaps they have nothing to do with it at all. It is unclear, but given that we are humans that have to make real time decisions with imperfect information, I think it is reasonable to take steps to avoid microplastic exposure.

Now, with the knowledge that we are mere mortals and we have decided to live in an interconnected society over which we have limited control, we have to accept that we are not going to be able to limit all exposure. That is to say, we are looking at reducing our exposure with the knowledge that eliminating exposure completely is not feasible. AND we need to mitigate the negative affects of anxiety and social withdraw that can occur when pursuing such exposure reductions.

It does an individual no good to completely cloister oneself off from society and it is unproductive to live with a mindset that everything in my environment including my food, water, and air are trying to actively kill me. Imagine a scenario where pursuing such behaviors had the unlikely effect of adding 5 more years to your life... Would you really want to live that life of isolation and constant terror? I bet not.

So instead, we are going to be reasonable and do what we can, with what we got, when we got it, and take discrete reasonable steps to significantly cut down exposure while still living the meaningful connected life we want.

Some steps I have taken:

• I use reverse osmosis water filter for drinking and cooking water.

• I store food in glass or stainless steel containers.

• I swapped out kiddos plastic lunch box containers for stainless steel metal containers.

• I cook on ceramic or stainless steel pots and pans and threw out all my teflon coated non stick pans. (teflon is actually a plastic!)

• I swapped out for bamboo or silicon cooking utensils and cutting boards.

• I rarely drink from plastic water bottles.

• I avoid drinking from the cardboard cups at restaurants, as they are all lined with plastic.

• I never heat food in plastic container or use saran wrap in the microwave.

• My mouthguard I use in sports is silicone and does not contain plastics.

I am not draconian about this. If you are going to take this on, remember first of all that this is a long term battle vs a sprint. Don't get too stressed and don't beat yourself up for slipping up every now and again.

And again, I cannot reiterate enough, don't become afraid of everything around you! The human body is amazingly resilient. Do what you can, take care of all aspects of your health, and let the rest flow. Remember that life is suffering, just make sure you are fighting the good fight, and let that be enough.

Microplastics and Nanoplastics in Atheromas and Cardiovascular Events 2024 Marfell et al.p

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Paper this article focuses on:

• Marfella R, Prattichizzo F, Sardu C, et al. Microplastics and Nanoplastics in Atheromas and Cardiovascular Events. N Engl J Med. 2024;390(10):900-910.

Selection of papers showing microplastics in human tissue:

• Nihart AJ, Garcia MA, El Hayek E, et al. Bioaccumulation of microplastics in decedent human brains. Nat Med. Published online February 3, 2025.

• Garcia MA, Liu R, Nihart A, et al. Quantitation and identification of microplastics accumulation in human placental specimens using pyrolysis gas chromatography mass spectrometry. Toxicol Sci. 2024;199(1):81-88.

• Ibrahim YS, Tuan Anuar S, Azmi AA, Wan Mohd Khalik WMA, Lehata S, Hamzah SR, Ismail D, Ma ZF, Dzulkarnaen A, Zakaria Z, Mustaffa N, Tuan Sharif SE, Lee YY. Detection of microplastics in human colectomy specimens. JGH Open. 2020 Nov 21;5(1):116-121.

• Massardo S, Verzola D, Alberti S, et al. MicroRaman spectroscopy detects the presence of microplastics in human urine and kidney tissue. Environ Int. 2024;184:108444.