How and Where Microplastics End Up in Our Bodies

Even our drinking water contains microplastic (credit: Orakunya on Shutterstock)
Even our drinking water contains microplastic (credit: Orakunya on Shutterstock)

In my book "A Guide to a Healthier Planet", I explain how microplastics that have ended up in the environment harm aquatic animals. These microplastics come from improperly disposed of plastic products, which slowly break down into tiny particles. These particles are called microplastics when they are smaller than 5 mm. Also, I explain how these microplastics can enter the food chain and eventually end up on our plates. When we eat this food, microplastics end up in our bodies and harm us too.
As microplastics cannot only be found in aquatic environments, but also in sediment, soil, dust, air, and even - for example - beer, sea salt, and tap water and the number of these particles is growing, we are becoming more and more likely to take microplastics in through our food. Currently, it is estimated that we eat 39,000–52,000 particles per person per year! This is about a credit card per week!
We are eating about a credit card's worth of microplastics a week (credit: LightField Studios on Shutterstock)
We are eating about a credit card's worth of microplastics a week (credit: LightField Studios on Shutterstock)

Also, we are inhaling these particles. How deeply these particles enter our lungs depends on their size and density, with smaller and less dense particles penetrating the lungs deeper. As these particles can harm our lungs, a natural defense mechanism called mucociliary moves these particles out of the lungs, towards our throats. When they have reached our throats, we usually swallow them. Alternatively, microplastics can be broken down by a type of white blood cells, and enter the bloodstream or the lymphatic system.
With the growing number of microplastics, this is a great concern because this means that the potential negative impact on our health is growing as well. This is because microplastics may contain toxic substances and adsorb harmful chemicals. As a result, they can for example cause inflammations and change the activity of microorganisms in our guts. These microorganisms are very important for our health (further reading: 3 Ways To Take Care Of Your Gut To Prevent (Eco-)Depression).
Also, they can end up in many different parts of our bodies. In fact, microplastics have already been found in many different parts of our bodies. Microplastics have for example been found in:


One location in which microplastics have been found in our bodies is blood. Microplastics smaller than 0.7 μm have been found in blood samples from healthy persons:
  • PET (polyethylene terephthalate) was found most often - in over half of the tested individuals. PET is the most commonly used type of plastic, for example for plastic bottles and clothes.
  • PA (polyamide) was also found often - also in about half of the tested individuals. This type of plastic is used for example in textiles, kitchen utensils, and sportswear because of its durability.
  • PS (polystyrene) was found in about 1/3 of the individuals, which is often used for insulation and packaging material.
  • PE (polyethylene) was found in about a quarter of the individuals. Polyethylene is also used for plastic bottles, but also for instance for plastic bags and knee joints.
  • PMMA (polymethyl methacrylate) was found relatively seldom (5% of the individuals). This type of plastic is used as an alternative to glass as it doesn't shatter, for example for windows and aquariums.
While the effects of these plastics on our health are not known yet, the potential impact is large as blood is crucial in staying healthy and it transports microplastics through the body. Also, the size and presence of microplastics in blood samples before and after surgery differ, which means that these particles seem to interact with medication. For example, in one study, PET was found most often before the surgery and PA after the surgery; and before surgery, the diameter of the microplastics was between 30 and 50 µm but 20 to 30 µm after surgery. What the consequences are for our health, our recovery from illness, and the environment needs to be investigated further.
Microplastics have been found in our blood (image is illustrative only, not showing any plastic particles; credit: UGREEN 3S on Shutterstock)
Microplastics have been found in our blood (image is illustrative only, not showing any plastic particles; credit: UGREEN 3S on Shutterstock)


Another location in which microplastics have been found in our bodies is the heart. These microplastics were found in all types of heart tissue that were investigated: the sac that surrounds the heart, the fat that sits on the surface of the heart muscle and is surrounded by this sac, the heart's muscle tissue, and the small appendix of the heart muscle.
The type of plastic that was found most often differed between muscle tissue. For example, PET was found most often in all tissues apart from the appendix. In the appendix, PU (polyurethane) was found most often. This type of plastic is for example used for foam in seatings and insulation panels. Also, apart from tiny particles, microplastics in various shapes were found such as threads and rods.
Having found microplastics in the heart is a critical finding as it shows how well microplastics can enter the cardiovascular system. The cardiovascular system consists of the heart and blood vessels. The exact effect on humans is unclear yet, but in aquatic animals they negatively impacted the heart rate of larvae and embryos, suggesting that microplastics can also interfere with normal heart function in humans, potentially contributing to heart and blood vessel diseases.


A third location in which microplastics have been found in our bodies is the placenta. The placenta is a crucial organ during pregnancy, as it provides oxygen and nutrients to the unborn baby, and removes waste products from the baby's blood. The microplastics were found on both sides of the placenta: both on the maternal and fetal sides. Also, they were found in the sac that surrounds and protects the embryo. One of the types of plastic is PP (polypropylene) which is for example used for packaging, plastic parts for machinery and equipment, and textiles.
These plastic particles can interfere with the immune system. The immune system distinguishes between particles and substances that belong in the body or not and is triggered by intruders such as microplastics. This response requires energy, changes how energy reserves are used, causes local toxicity, and can weaken the body's defense against infections. What this as a result means for the placenta and baby needs to be investigated further.

Placenta (credit: Sakurra on Shutterstock)
Placenta (credit: Sakurra on Shutterstock)

Breast milk

A fourth location in which microplastics have been found in our bodies is breast milk. Breast milk provides nutrition and protection for a baby. Nutrients include proteins and sugars; protection includes for example antibodies that help the baby's immune system grow stronger and protect them from illnesses. The investigated milk was provided by women one week after delivery. About ¾ of the women had produced milk with microplastics, usually blue or orange. They were between 2 and 12 µm, so even smaller than very thin hair!
The presence of microplastics in breast milk is probably critical, as this is the baby's only source of nutrition, critical for healthy early development. The exact consequences are unclear yet, but it is clear that some particles are considerably toxic and others are moderately toxic, and that it can impact the baby's immune system.

Testicles and semen

A fifth location in which microplastics have been found in our bodies are testicles and semen. Testicles and semen are part of the male reproductive system, together responsible for producing and transporting sperm cells. About ¾ of the microplastics found were between 20 and 100 µm, so similar to the width of a hair. As the microplastics found in the testicles are smaller than in the semen, it seems like the body gets rid of larger particles and smaller particles build up in the body.
The consequences of these particles on reproductive health and fertility are still unclear. But tests with animals have shown that microplastics can reduce sperm quality, change hormone levels, cause inflammation in the testicles, lower fertility, and change the number of sperm cells. Also, when particles build up, they can damage cells that support sperm cells to develop and the barrier between the testis and blood.


So, microplastics have been found in many different parts of our bodies. These include blood, heart, placenta, breast milk, testicles and semen. The exact consequences on our health are still unclear, but first tests with animals show a wide range of harmful effects.

How we can take action

Here are practical ideas of what you and I can do to prevent microplastics from ending up in our bodies:
  • Preventing plastic waste from ending up in the environment (further reading: How To Prevent Plastics From Reaching Rivers and Oceans)
  • Removing plastics from rivers and oceans (further reading: How Plastics Can Be Removed From Our Rivers And Oceans)
  • Participating in or organizing a local cleanup
  • Plogging (picking up waste while jogging)
  • Disposing of waste properly instead of littering
  • Refraining from using single-use plastic and using reusable products instead
Do you have further ideas of what you and I could do? Thank you in advance for leaving them in a comment to this question for us all to get inspired.
Did you enjoy this article? Then I'm sure you'll love my book "A Guide to A Healthier Planet" as well. Check it out at:

About the author

Dr. Erlijn van Genuchten is a an internationally recognized environmental sustainability expert. She is a science communicator, helpings scientists in the fields of nature and sustainability increase the outreach of their results and allowing us all to put scientific insights into practice and contribute to a sustainable future. Erlijn has inspired thousands of people around the world  — for example — by supporting the United Nations with her expertise, her book “A Guide to A Healthier Planet” published by Springer Nature, her YouTube channel Xplore Nature, and her posts on social media. Further links are included in the comments.


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  • Princess

    3 w

    Very informative 👏

    • Chris Ndungu

      5 w

      Interesting article enenthough it's reality is disquieting.

      • johnte ndeto

        5 w

        Nice piece

        • Marine Stephan

          5 w

          Very interesting article on a very worrying reality

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