Here's How Microplastics Enter Our Bodies

Sam Westreich, PhD

Red Solo cups? Plastic retainers or night guards? Absorbed through our skin?
“Mmm, tasty plastic! Can’t wait to slowly swallow every bit of this retainer!”Photo by Diana Polekhina/Unsplash

Plastics: they’re everywhere, including inside the Arctic ice, in a massive garbage patch in the oceans, and inside the bodies of pretty much every living creature — including ourselves.

That’s right: you have plastic inside you. Specifically, every person on Earth now has increasing concentrations of microplastics found in their tissues.

What are microplastics, versus regular plastics? Microplastics are just very small pieces of plastic. They’re defined as any piece of plastic that is smaller than 5 millimeters (0.2 inches) in length. They come in a variety of shapes, from tiny little beads or spherical particles, to long threads, to irregularly shaped fragments.

We’re still not fully certain of all the effects that they might have in our bodies, but they’re unlikely to make us healthier.

How are they getting into us? Should we be worried about using plastic items, like retainers, because they could leach microplastics into our bodies?

The potential health risks of “life is plastic” (it’s not fantastic)

It’s easier to spot plastic in our bodies than to determine exactly what harm it causes. Microplastics presence may be a contributing factor to larger symptoms or conditions, but it’s difficult to always trace that condition back to microplastics as a source.

One challenge is the sheer variety of molecules that we label as “plastic”. There are more than 10,000 unique chemicals used in various plastics, about a quarter of which are of potential health concerns to humans.

We’re exposed to those chemicals both through microplastics but also through our interactions, day to day, with regular plastics. Even if you show that cancer-causing chemicals leeched from plastic were responsible for a disease, how do you determine whether those came from internal microplastics, or from external exposure (drinking from plastic water bottles, wearing clothing with synthetic fibers, etc.)?

In a laboratory setting, microplastic exposure has led to cell allergic reactions, inflammation, and cell death. Microplastics may also damage specific organs, like reducing lung function and contributing to irritation or asthma.

There’s also a possibility that, for some people, microplastics may prompt an immune response, with the body reacting as if it’s a foreign invader. This could aggravate auto-immune conditions or lead to widespread long-term damage from inflammation.

You’re not going to be able to avoid microplastics. Just in the oceans, there’s currently an estimated 578,000 TONS of microplastic floating around.
This statue weighs 225 tons. Imagine 2,500 of these statues in the ocean, shattered into tiny fragments.Photo by Avi Werde/Unsplash

For comparison’s sake, that’s equivalent to 2,500 copies of the Statue of Liberty, all in tiny plastic fragments, distributed throughout the ocean.

How does microplastic get into our bodies?

You can’t fully avoid microplastics, but you can definitely try to lessen the amount that you ingest. What’s the biggest sources of these tiny particles?

Let’s consider three sources: our food, the environment around us, and direct from larger plastic objects (retainers, etc.).

Microplastics in our food

Yep, our food has microplastics. It’s been found in pretty much everything, including salt, tea, meat, seafood, milk, honey, sugar, beer, and soda.

For some foods (like rice), you can reduce the amount of microplastics by washing it with water — but guess what? Water, including tap water, also has microplastics! So you better be using specially filtered water to wash it.

In most food, the microplastics are either from the packaging, the processing (the factory where that rice was hulled and sealed up), or from the food chain (fish tissues contains microplastics because the fish eat other sea creatures with microplastics).

For a long time, diet was thought to be the main way that microplastics entered our bodies. But more recent studies suggest that this is only responsible for about half the total plastic in our bodies.

Interestingly, while you can’t avoid the microplastics, some choices can have a big impact. For example, if you drink (plastic) bottled water, you’re ingesting an estimated 90,000 microplastic particles per year. Tap water? Only 4,000 particles per year.

Contribution: 40–60%, depending on diet and choices

Microplastics in our environment

We were sleeping on this one for a while, but recent studies are suggesting that inhalation of airborne microplastic particles may be the single biggest source of microplastics in our body.

The biggest sources of environmental microplastics that become airborne:

  • Road dust. Tires break down and shed dust every time they are driven, which spreads through the air and is inhaled.
  • Synthetic textiles (carpets, furniture) are the major sources of microplastics in indoor air.
  • Waste incineration and landfills also leak microplastics into the air. Living near a waste disposal facility increases the amount of inhaled microplastics.

Contribution: 50–60%, depending on location and environment

Microplastics from direct-contact plastics

The question that spurred this article: I put in a retainer each night, in order to keep my teeth from shifting out of position. That retainer, like the one pictured at the start of this article, is made of plastic.

Am I poisoning myself with microplastics?

The answer here is no — or at least, the level is low in comparison with other sources of plastic that enter our bodies. Microplastics are generated through either physical abrasion (tires rubbing against the road) or through chemical breakdown (sunlight breaking down the plastic in water bottles, leaching microplastic bits into the water).

There will be some leaching and degradation. Your mouth is warm, and you may grind your teeth together as you sleep.

But in comparison to the total average ingested microplastics, the amount is small. One recent WWF study suggested that we consume about 5 grams of plastic per week; that’s the equivalent of eating a credit card per week.

Most retainers weigh less than 5 grams, so even if parts of that retainer are shed as microplastics, it will be significantly less than what we consume weekly from food, water, and inhalation.

Contribution: minimal

What should we do to minimize microplastic ingestion?

The bad news is that you cannot totally avoid plastics. They are literally everywhere around you; if you drive, have carpets, go to an office, or even drink water, you’re going to get some level of ingested microplastics.

But you can take some easy actions:

  1. Stop drinking water from disposable plastic water bottles. Get a refillable water bottle — ideally, a metal or glass one.
  2. Consider a water filtration system for your home.
  3. Wear non-synthetic clothing (cotton or wool, avoiding nylon and polyester).
  4. Avoid food in plastic, including microwaving food in plastic containers or drinking from to-go cups (which are paper with a plastic lining to make them waterproof).
  5. Avoid tea bags (which are made with plastic).
  6. Lobby to reduce the amount of plastic used in society. Here in Mountain View, for example, we passed a ban on plastic to-go containers.

We still don’t know all the potential health effects of microplastics ingestion, and they are likely to vary among individuals. Overall, however, better to minimize the amount of foreign material being added to your body.

But it’s okay to keep using your retainer at night.

Do you worry about microplastics? Have you taken any steps to reduce your microplastics consumption?

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A microbiome scientist working at a tech startup in Silicon Valley, Sam Westreich provides insights into science and technology, exploring the strangest areas of biology, science, and biotechnology.

Mountain View, CA

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