If you’ve seen the classic 1967 film, The Graduate, you’ll surely remember the infamous graduation party scene when family friend Mr. McGuire offers bewildered young Ben Braddock (Dustin Hoffman) a bit of advice:
“I just want to say one word to you…..just one word,” says McGuire. “Are you listening? Plastics! There’s a great future in plastics.”
Ol’ Mr. McGuire could not have known back then that 50 years later, microplastic particles would be detected in human blood. But that is exactly what has happened.
Late last March, headlines around the world announced that for the first time microplastics had been identified in human blood.
Toxicologists at the Vrije Universiteit Amsterdam analyzed blood samples from 22 healthy adults, and found plastic residues in 17 of them (77%). Half contained traces of polyethylene terephthalate (PET), a common material for food containers and beverage bottles, and one quarter showed microparticles of polyethylene (Leslie HA, et al. Environment International. 2022).
This new Dutch study builds on earlier evidence, including a 2009 paper documenting plastic additives, especially phthalates, in the urine of 242 pregnant women (Meeker JD, et al. Philos Trans R Soc Lond B Biol Sci. 2009), and a 2019 study showing an average of 20 different microplastics in feces from eight healthy human volunteers (Schwabl P, et al. Ann Intern Med. 2019).
Toxicologists at the Vrije Universiteit Amsterdam analyzed blood samples from 22 healthy adults, and found plastic residues in 77% of them.
One particularly troubling study published last year showed that per kilogram of body weight, the presence of microplastics in feces was significantly higher in infants than in adults (Zhang J, et al. Environ Sci Technol Let. 2021).
Though these studies are shocking, they should not be surprising.
Awash in Plastic
Microplastics defined as polymer fragments under 5 mm in size, and often in the nanometer range, are byproducts of plastic production, but also result from the gradual breakdown of plastic debris in the environment. And there’s a lot of plastic in our environment.
Plastic bottles, containers, bags, packaging materials, fishing nets, synthetic fabrics, and other polymer flotsam float around in the oceans and waterways, pile up in landfills, and burn in incinerators. Gradually large pieces break down into tiny fragments.
According to a 2014 estimate, there are between 15 and 51 trillion individual bits of microplastic in the world’s oceans. They’re estimated to weigh between 93,000 and 236,000 metric tons.
Though researchers are just beginning to study the impact of microplastics on human health, there’s already reason for concern. Some types of microplastic can disrupt and destabilize the lipid bilayers comprising cell membranes. Others increase oxidative stress, trigger apoptosis, and alter immune system function (Danopoulos E, et al. J Hazardous Materials, 2022).
“From animal studies it’s already known that microplastic causes changes in the gut microbiome. When you feed mice with microplastic they develop microbiome changes. And when you look at this microbiome it looks like that of somebody who is obese or has cancer, or has some other diseases like diabetes.”–Vanessa Stadlbauer-Köllner, MD, Medical University of Graz
Toxicologists, environmental scientists, and endocrinologists have long known that plastic-related compounds like bisphenol-A, phthalates, and polyfluoroalkyls, are hormone mimics which can be disruptive to the endocrine system.
Plastic breakdown products might also be harmful to our gut microbial ecology, says Vanessa Stadlbauer-Köllner, MD, a clinical gastroenterologist in the Department of Gastroenterology & Hepatology at the Medical University of Graz, Austria.
“From animal studies it’s already known that microplastic causes changes in the gut microbiome. When you feed mice with microplastic they develop microbiome changes. And when you look at this microbiome it looks like that of somebody who is obese or has cancer, or has some other diseases like diabetes. You see a loss in diversity, an increase of potentially pathogenic species. Could it be that microplastic in our environment is one of the factors that causes obesity and metabolic disorders?”
Researchers at the Medical University of Graz are planning studies to look into the impact of microplastics on the human microbiome, and by extension on human metabolism, to see if the alarming changes seen in the rodent experiments occur in humans.
Microplastics are not biodegradable and they are likely to persist as environmental pollutants for centuries, unless we figure out ways to not only reduce our production and use of plastics, but to clear the existing debris.
Though the situation looks grim, given the amount of plastic already in our environment, there’s some hope that the microbial world holds potential solutions to the problem.
Dr. Stadlbauer-Köllner pointed to some studies outside of the medical field showing that certain bacteria are able to trap water-borne microplastics. “This was research done at waste treatment plants. They found there are certain types of bacteria that can really get rid of the plastic.”
This work, led by Professors Song Lin Chua and James Kar-Hei Fang at the Hong Kong Polytechnic Institute, was presented at the 2022 annual international meeting of the Microbiological Society.
The process involves creation of biofilm “nets” using a strain of Pseudomonas aeruginosa, which are able to ensnare and bind the tiny plastic particles.
Stadlbauer-Köllner says she and her colleagues are planning early-stage studies to look at bacterial strains that could potentially digest microplastics.
“There are some enzymes present in some bacteria that can digest certain kinds of plastics. And some of these bacteria belong to families that occur in the human gut microbiome. So, we will screen common gut commensals to see whether they have the genes to produce the enzymes that digest plastic. Then we will feed them with plastic and see if they can really degrade it,” she told Holistic Primary Care.
“This would be really, really cool because unfortunately we can’t entirely get rid of plastic. What we are going to do now is to find out whether microplastic really damages the human microbiome, and if yes, can we find probiotic bacteria that degrade the microplastic? We won’t be able to solve this problem soon, but we will be able to get some initial data.”
In any future remake of The Graduate, perhaps Mr. McGuire will have a slightly different bit of one-word advice for young Ben Braddock: Microbiome!