Around the world, companies produce hundreds of millions of tons of plastic waste every year, all of which will eventually break down into smaller pieces of plastic known as microplastics. While scientists have found these wee bits on nearly every corner of the planet—from Arctic ice to deep sea trenches—studies are now shifting focus to explore the more complicated question of what that ubiquitous pollution means for human health. And what they’ve found thus far about microplastics in humans is enough to raise the alarm.
The limits of what we know
Papers published as recently as 2023 note that knowledge about the toxicity of microplastics in humans is still limited.1 But more researchers are asking the right questions, despite significant challenges, says Robert C. Hale, an environmental chemist and professor at the Virginia Institute of Marine Science. To begin with, we are not good at measuring microplastics, particularly the smallest ones, otherwise known as nanoplastics. “Actually trying to measure these things, we don’t do it right yet,” Hale says. “Small is the thing we’re worst at measuring and classifying.”
Additionally, experiments related to harm caused by microplastics can only go so far. While scientists can use laboratory animals to try to gauge exposure impacts, it’s unsafe and unethical to subject humans to such experiments. It can also be difficult to compare lab-based scenarios to real life, where people may be exposed to a wider variety of plastics and chemicals and scenarios over a prolonged period of time, explains Hale. Another challenge with figuring out the human health risks of microplastics is separating what ailments trace back to microplastics from those caused by exposure to other environmental or behavioral factors, like smoking or drinking.
How are people exposed to microplastics?
Microplastics can be found in household dust, local rivers and creeks, and even Arctic sea ice. Their ubiquitous presence means it’s likely people will get exposed to them in some way, but it’s typically through ingesting contaminated food and beverages or inhaling microplastics-rich air.
Microplastics on land and water
Scientists believe the majority of microplastics found in the environment come from the deterioration of larger plastic (macroplastic) products from a variety of sources.2 Those smaller pieces of microplastics can infiltrate the soil where we grow our fruits and vegetables as well as waterways that provide both drinking water and aquatic habitats to the seafood people consume.3 Some of those microplastics (especially the ones that break down into even smaller pieces known as nanoplastics) can even make their way into our bodies through what we ingest as they’re absorbed by fruits and vegetables, eaten by fish and shellfish, and taint our drinking water.
Microplastics indoors
While many headlines have focused on microplastics in extreme environments or contaminating the world’s waterways, Hale says people should be far more concerned about the microplastics pollution surrounding them inside their homes and businesses. “We’re encased in an environment that’s really rich in plastics,” he said. “We’re kind of doing a little experiment on ourselves.” Since most people spend about 90% of their lives indoors, he says, the exposure to microplastics inside is far greater than exposure to what’s swirling around in the middle of the Pacific Ocean.
Not only does the indoor environment contain more plastic products, but those products are also “highly engineered” plastics, Hale says, referring to the additive chemicals that are intended to make them more resistant to things like fire, water, and mold and mildew.
“At a certain point, even something that’s not really toxic, you pass the threshold for toxicity.”
Robert C. Hale, environmental chemist, Virginia Institute of Marine Science
Researchers like Hale and his colleagues have found that indoor dust is quite rich in potentially toxic plastic additives, oftentimes at much higher concentrations than what can be found outside.4 Dust also contains microplastics, particularly polyester fibers, and studies have indicated that people are inhaling microplastics on a daily basis.5
“From a human standpoint, the indoor exposure from additives and potentially from microplastics [themselves], that’s really the biggest concern,” Hale says. “At a certain point, even something that’s not really toxic, you pass the threshold for toxicity.” It’s like the old adage, “the dose makes the poison,” he said. If you’re exposed to too much of something for a long enough time, it can become toxic.
Microplastics in the workplace
Hale notes that, much like the home environment, people who work in industrial settings that handle plastics also face increased risks. The federal Occupational Safety and Health Administration has published a swath of information about hazards and solutions for the plastics industry, although no specific information on microplastics-specific hazards is readily available. The American Lung Association has found that workers who are exposed to small plastic fibers “can have lung problems and reduced lung capacity, perhaps due to damage caused by inflammation.”
Microplastics in food, water, and beverages
More than 100 studies have found microplastics from a wide variety of plastic types in seafood, drinking water (from the tap and the bottle), beer, wine, milk, soft drinks, iced tea, breast milk, honey, sugar, salt, eggs, meat, fruits and vegetables, and processed food.6 By ingesting contaminated food, water and beverages, people eat upwards of 52,000 microplastic particles every year, according to some estimates.
Microplastics in the air
While studies typically find higher concentrations of airborne microplastics in indoor environments, researchers have detected them outdoors as well. People might ingest upwards of 121,000 microplastic particles annually when factoring inhalation as well as consumption.7 In Spring 2023, international publications highlighted a “plastic weather forecast” coming to Paris as an awareness campaign highlighted the existence of microplastics in rain.
Dermal exposure
It’s possible that microplastics, in the tiniest forms, can penetrate the skin from the use of personal care products such as toothpaste, face wash, scrubs, soap, and makeup. This can also happen when people interact closely with contaminated water, soil, or microplastics themselves, but it really depends on individuals and their susceptibility, researchers say.8
Bioaccumulation and biomagnification
While bioaccumulation (the buildup of a substance in the body) of microplastics is of some concern, environmental chemist Hale says microplastics don’t bioconcentrate the same way that toxic chemicals, like the pesticide DDT or metals like lead, typically do. However, some chemical additives in plastics, like some flame retardants, could be more concerning when it comes to bioaccumulation and biomagnification through the food chain. A review of more than 1,000 studies found that as far as we know microplastics don’t biomagnify, or increase levels of concentration, as they move up the food chain.9 Typically, people don’t eat the digestive systems of animals, and therefore it’s unlikely that microplastics in the guts of animals like fish end up in humans. One exception, though, is shellfish that are eaten whole.
Proof of plastics in the human body
Because of ethical concerns with experimenting on human health and the mixture of plastic types and additives chemicals that people are exposed to, it has been difficult to definitively pinpoint human health risks of plastics contamination. Studies have found plastics in the human body, which has spurred researchers to raise the alarm that those unnatural additions may be linked to alarming outcomes.
Human placenta and breast milk
A study published in 2021 provided the first instance of plastics in human placentas, raising concern about long-term health effects from both plastics and endocrine disruptors.10 Other studies have also found microplastics in human breast milk, indicating that vulnerable infants may also be exposed not only to plastics but the potentially toxic and harmful chemical additives as well.11
Microplastics in blood
A 2022 found several different types of plastics in the blood of 77 percent of 22 “healthy volunteers.”12 The study merely cataloged the presence of microplastics in those blood samples, noting that more research is needed to understand how that exposure impacts public health. Researchers concluded that the data they collected raises important questions related to how plastics in the blood can impact immune regulation. An earlier study by Chinese researchers also found potentially toxic amounts of microplastics from PVC in a protein found in blood plasma.13
Gastrointestinal system
Microplastics made of polystyrene have been found to negatively impact the digestive system and metabolic processes in mice, but those results don’t translate immediately to the same results in humans.14 Both polystyrene- and PVC-based micro- and nanoplastics have been studied for impacts on cultured models of human intestines, and researchers found that the combination of inflammation and exposure to those plastics could play a key role in the ultimate health outcomes for people suffering from both.15 One recent simulation also found that microplastics like those derived from PET products may spur the gut microbiome to form a biofilm resulting in “digestive-level health effects.”16
Endocrine system
Plastic additives such as BPA, phthalates and other chemicals have been identified as endocrine disruptors, which means they mess with the body’s hormones.17 Potential hazards from microplastics themselves also exist, but a review of research published in the journal Frontiers of Endocrinology concluded that the body of work hasn’t found a clear link between microplastics and the disruption.18
Respiratory system
The tiniest microplastics can become airborne, and have been found in cities like in Shanghai, Paris, and London. A small study of bodies undergoing routine autopsies found microplastics in the lung tissue of 13 out of 20 samples. All samples were collected from nonsmokers and were most commonly from polyethylene and polypropylene.19
Immune system
Because of a complex combination of interactions among molecules, immune cells, and receptors in the body, researchers say more studies in this area are “urgently needed” to figure out the immunological hazards and risks of microplastics exposure. But scientists do believe the combined exposure with bacteria, viruses, chemicals, and other pollutants may increase the risk of microplastics affecting our immune systems.20
Do microplastics cause cancer?
Because microplastics aren’t one thing—they can be a variety of plastic types with a variety of chemical additives—it can be difficult to pinpoint what causes what problems. However, one study published in 2023 found that polypropylene microplastics do promote metastatic features in human breast cancer. Other studies have linked some additives, such as PFAS, to a variety of cancers.21
How do different microplastics potentially harm humans?
While much research is still needed to definitively say how certain microplastics can impact human health, there is still cause for concern. Contaminated food, water, beverages, and even the air we breathe mean people consume thousands of pieces of microplastics—along with the additives they contain—every year. One of the biggest challenges with measuring the human health impact is simply that microplastics can be made from dozens of different plastic types and contain even more different types of chemicals, from pigments to flame retardants.
The actual size of the plastics also influences their impact on health. The smaller the piece, the more places it can possibly fit, like in a person’s lungs or inside cell membranes. That’s why the smallest microplastics, known as nanoplastics, can potentially be more harmful, explains environmental chemist Hale. Because they’re so small and so hard to count, however, it’s hard to track where they end up and how toxic they really might be, researchers note. Meanwhile, their shape can also play a role in how much risk they pose, as shape can influence how microplastics disperse and how they interact with organisms. For example, fibers might hurt a fish’s gills, while that same swimmer could mistake a spherical tiny plastic for food.22
“We’re encased in an environment that’s really rich in plastics. We’re kind of doing a little experiment on ourselves.”
Robert C. Hale, environmental chemist, Virginia Institute of Marine Science
A variety of polymers make up different types of plastic. Some are more toxic or fragile than others because of their composition or the chemical additives needed to make a single plastic product.
The plastisphere
The plastisphere is a biofilm that develops on the surface of plastics of any shape and size, which includes microplastics. This film can include pathogens that can cause human illness, such as members of the genus Vibrio, a bacteria that is known to cause food-borne illness, cholera. It could also include other species of fungi, algae, and viruses that could potentially be harmful to human health.23
Polyethylene
Polyethylene is the most common type of plastic waste, and is used to make a wide variety of products used in packaging, construction, and transportation. It’s a relatively stable plastic, but can be susceptible to some acids, solvents, and high temperatures. Researchers have found it will slowly decompose over time in the environment in part due to UV rays.24 Microplastics derived from polyethylene have been found to be “carriers of other organic poisons” in marine environments.2526 Other studies have shown that earthworms that ingest these microplastics can suffer from abnormal enzyme activity and gene expression.27 The microplastics can inhibit the reproduction and mobility, and even lead to increased mortality, of some insects and bees.28 While there are limited definitive studies on certain plastics’ impact on human health, researchers warn that polyethylene, particularly in microplastic form, poses a threat to human health, possibly in the form of cancer.29
Polypropylene
Polypropylene is used in a variety of products, such as stationary folders, planters and industrial fibers, and disposable medical masks. Some studies have found adverse impacts to aquatic animals, including disruption to the gut microbiome, but little is known about the plastic’s impact on human health.30 One study indicates that polypropylene microplastics did affect human breast cancer cells and promoted “metastatic features.”31
Polyethylene terephthalate (PET or PETE)
Polyethylene terephthalate (PET or PETE) is commonly used to make clear plastic bottles for anything from water to salad dressings to shampoo. Studies have found the phthalates (an endocrine-disrupting chemical) in PET bottles can leach into more acidic products.32
Polyvinyl chloride (PVC)
Polyvinyl chloride (PVC) is a hard, strong plastic used most notably in pipes. At least one study has noted that PVC “is the most toxic polymer type used daily” due largely to the toxic additives it contains and the carcinogenic chemicals such as dioxins that can be released throughout the PVC lifecycle.33 Greenpeace has warned that it is created with “deadly building blocks” (i.e., chlorine) and leaves a “lethal legacy” because of the dioxin compounds left behind from production. Government officials have warned that chemical additives in PVC products, such as phthalates and lead, are toxic to children’s health.
Polystyrene
Polystyrene, which is used to make Styrofoam products, is potentially toxic, largely because of related chemical byproducts. According to the Children’s Environmental Health Network, styrene is believed to cause cancer, and improper disposal of polystyrene by burning can release toxic gasses that can impair the nervous system.
Other plastics
Other plastics such as poly methyl methacrylate (used in many cosmetics) and thermoset plastics (which are polymers that don’t melt when heated) like epoxy resins, silicone, vinyl, and melamine may also pose health hazards such as allergic reactions and irritations. But there is far less information related to any severe health risks associated with these more durable plastic products. Because of the chemical composition of thermosets, they permanently remain in a solid state and aren’t prone to the same level of degradation as thermoplastics, which hypothetically makes them less of a risk as a source of microplastics, but also makes them problematic because they are so long-lived.
What about chemical additives?
Aside from the plastic polymers themselves, most plastic products also contain chemical additives that give them flexibility, color, fire and water resistance, and other important properties. When larger plastic products break down into smaller pieces, those additive chemicals can also get released, explains Hale, the environmental chemist. There are more than 10,000 chemicals used as plastic additives, about 2,400 of which have already been classified as harmful to marine and land-based ecosystems and wildlife. 34
Flame retardants
Flame retardants can include a variety of chemicals. These substances have been added to furniture, electronics, and building materials since the 1970s. And since then, experts have found that they can leach from products and may cause a variety of adverse health effects, including endocrine dysfunction, thyroid disruption, and issues with childhood neurological development.35
Pigments
Pigments—especially those found in fast fashion clothing—added to plastic products can contain toxic heavy metals, such as cadmium and lead. At least one study has found pigment microparticles in human blood clots, calling for more research on how this contamination could lead to cardiovascular health risks.36
PFAS
PFAS, or per- and polyfluorinated substances, have been used for decades in a wide variety of products for their nonstick properties. They can be found in the coatings on pans, food packaging, and nearly any item designed to fight stains, grease, heat, and water. PFAS also are ubiquitous in many plastic products. Studies have shown that human exposure to these chemicals has been linked to reproductive health problems, developmental effects or delays in children, increased risk of some cancers, reduced efficacy of the immune system, hormone disruption and increased risk of obesity, and high cholesterol.
BPA
Bisphenol a, or BPA, was actually developed as a synthetic estrogen, but ironically has been shown to interfere with hormone receptors. BPA has been commonly used to make certain plastics, such as those used in beverage containers, vehicle parts, and even toys, more durable. Some manufacturers have stopped using BPA in products because of identified health hazards.
Dioxins
Dioxins are a family of chemicals that’s typically a byproduct of industrial and manufacturing processes such as chlorine bleaching, the uncontrolled burning of waste, and even the manufacturing of plastics like PVC. These chemicals interfere with hormones, can cause cancer, and may disrupt the immune, nervous, and reproductive systems.
Phthalates
Phthalates, which are used to make plastics durable, can be released by multiple types of plastic, including PET and PVC, and have been shown to affect the reproductive system in animals. In the early 2000s, CDC researchers found many phthalate metabolites in the general population through a survey of more than 2,500 people.
How to reduce microplastics consumption
It’s nearly impossible to avoid microplastics in our everyday lives, but people can make some small changes to minimize their own exposure—and keep more plastics from entering the environment. These include simple day-to-day things like avoiding single-use plastics and making sure you spend time outdoors, but it’s important to not discount pushing for big change. Boycotting companies with large contributions to plastic pollution, contacting your local and state elected officials for legislative change, or engaging in grassroots activism efforts to enact plastics-related laws or regulations can all help safeguard the future against more plastic pollution.
- Are microplastics toxic? A review from eco-toxicity to effects on the gut microbiota, Metabolites, Jun. 2023 ↩︎
- A global perspective on microplastics, JGR Oceans, Jan. 2020 ↩︎
- Micro- and nano-plastics in edible fruit and vegetables. The first diet risks assessment for the general population, Environmental Research, Aug. 2020 ↩︎
- A global perspective on microplastics, JGR Oceans, Jan. 2020 ↩︎
- Widespread distribution of PET and PC microplastics in dust in urban China and their estimated human exposure, Environment International, Jun. 2019 ↩︎
- Human Consumption of Microplastics, Environmental Science & Technology, Jun. 2019 ↩︎
- Ibid. ↩︎
- Microplastics Exposure Routes and Toxicity Studies to Ecosystems: An Overview, Environmental Analysis, Health, and Technology, Mar. 2020 ↩︎
- Bioaccumulation and biomagnification of microplastics in marine organisms: A review and meta-analysis of current data, PLoS One, Oct. 2020 ↩︎
- Plasticenta: First evidence of microplastics in human placenta, Environment International, Jan. 2021 ↩︎
- Raman Microspectroscopy Detection and Characterisation of Microplastics in Human Breastmilk, Polymers, Jun. 2022 ↩︎
- Discovery and quantification of plastic particle pollution in human blood, Environment International, May 2022 ↩︎
- Probing the toxic interactions between polyvinyl chloride microplastics and Human Serum Albumin by multispectroscopic techniques, Science of the Total Environment, Sep. 2020 ↩︎
- Impacts of polystyrene microplastic on the gut barrier, microbiota and metabolism of mice, Science of the Total Environment, Feb. 2019 ↩︎
- Investigations of acute effects of polystyrene and polyvinyl chloride micro- and nanoplastics in an advanced in vitro triple culture model of the healthy and inflamed intestine, Environmental Research, Feb. 2021 ↩︎
- PET microplastics affect human gut microbiota communities during simulated gastrointestinal digestion, first evidence of plausible polymer biodegradation during human digestion, Sciencitif Reports, Jan. 2022 ↩︎
- Impacts of plastic products used in daily life on the environment and human health: What is known? Environmental Toxicology and Pharmacology, Nov. 2019 ↩︎
- A review of the endocrine disrupting effects of micro and nano plastic and their associated chemicals in mammals, Frontiers in Endocrinology, Jan. 2023 ↩︎
- Presence of airborne microplastics in human lung tissue, Journal of Hazardous Materials, Aug. 2021 ↩︎
- Impacts of microplastics on immunity, Frontiers in Toxicology, Sep. 2022 ↩︎
- Polypropylene microplastics promote metastatic features in human breast cancer, Scientific Reports, Apr. 2023 ↩︎
- Impacts of plastic products used in daily life on the environment and human health: What is known?, Environmental Toxicology and Pharmacology, Nov. 2019 ↩︎
- Quantifying the importance of plastic pollution for the dissemination of human pathogens: The challenges of choosing an appropriate ‘control’ material, Science of the Total Environment, Mar. 2022 ↩︎
- Impacts of polyethylene microplastics on bioavailability and toxicity of metals in soil, Science of the Total Environment, Mar. 2021 ↩︎
- Nano-plastics and their analytical characterisation and fate in the marine environment: From source to sea, Science of the Total Environment, Aug. 2020 ↩︎
- Environmental toxicity and decomposition of polyethylene, Ecotoxicology and Environmental Safety, Sep. 2022 ↩︎
- Edible size of polyethylene microplastics and their effects on springtail behavior, Environmental Pollution, Nov. 2020 ↩︎
- Acute and chronic ingestion of polyethylene (PE) microplastics has mild effects on honey bee health and cognition, Environmental Pollution, Jul. 2020 ↩︎
- Genotoxic and cytotoxic effects of polyethylene microplastics on human peripheral blood lymphocytes, Chemosphere, Jun. 2021 ↩︎
- Environmental hazard of polypropylene microplastics from disposable medical masks: acute toxicity towards Daphnia magna and current knowledge on other polypropylene microplastics, Microplastic and Nanoplastic, Jan. 2022 ↩︎
- Polypropylene microplastics promote metastatic features in human breast cancer, Scientific Reports, Apr. 2023 ↩︎
- Polyethylene terephthalate may yield endocrine disruptors, Environmental Health Perspectives, Nov. 2009 ↩︎
- Impacts of plastic products used in daily life on the environment and human health: What is known?, Environmental Toxicology and Pharmacology, Nov. 2019 ↩︎
- Deep dive into plastic monomers, additives, and processing aids, Environmental Science & Technology, Jun. 2021 ↩︎
- In utero and childhood polybrominated diphenyl ether (PBDE) exposures and neurodevelopment in the CHAMACOS study, Environmental Health Perspectives, Feb. 2013 ↩︎
- A detailed review study on potential effects of microplastics and additives of Concern on human health, International Journal of Environmental Research and Public Health, Feb. 2020 ↩︎