CME: The Effects of Plastics on Human Health
- FibonacciMD
- Aug 14, 2024
- 12 min read
Updated: 6 days ago
Explore the growing concerns about plastics in our environment, their entry into our bodies through food, water, and air, and the potential health risks, from hormone disruption to cancer.
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The Effects of Plastics on Human Health
By Stuart M. Caplen, MD last updated 4/5/2025
Plastic was invented in the 1860s and an initial use was in making combs. Improved plastic formulations became commercially available in the 1940s and production and sale of plastics rapidly increased after World War II.[1] Plastics are now in use all over the world, and humans are ingesting or inhaling plastics in ever increasing amounts. This article will discuss some of the sources of plastics and their known effects on human health. While there can be specific negative health effects to the workers who manufacture plastics, this article will only discuss some of the risks to the general population.
Plastics
Global production of plastics is an exponentially increasing phenomenon that increased from 2 million metric tons in 1950 to 380 million metric tons in 2015. It is estimated that much of the plastic that was ever produced has been released into the environment and remains there in some form. As of 2015, an estimated 6,300 million metric tons of plastic waste had been generated, with about 9% recycled, 12% incinerated, and 79% deposited in landfills, or disposed of into the natural environment such as into rivers, seas or oceans.[2,3]
99% of plastics produced today are from fossil fuels, and contain numerous potentially harmful substances, both chemicals which can leach out of the plastic and plastic particles. The term plastic refers to various types of polymers which are synthesized from monomers and formed into macromolecular chains.[2] Polyethylene is the most widely used plastic in the world, found in bottles, plastic wrap, grocery bags, as well as many other products.
Chemicals, some of which are known to be hazardous, can leach from plastics. Some, which are linked to cancer can be found in polyurethanes (flexible foam in furniture, bedding, and carpet backing), polyvinyl chloride (pipes, packaging, wire, and cable coatings), epoxy resins (coatings, adhesives, and composites, such as carbon fiber and fiberglass), and polystyrene (food packaging, hard plastic in consumer products).[2] Plastics may also contain potentially harmful additives such as brominated flame retardants, lead heat stabilizers and plasticizers (which makes plastic more flexible and durable) such as phthalates. In addition, the hormone-disrupting plasticizer Bisphenol A (BPA) can leach from plastic in water bottles and epoxy beverage can liners.[2]
Chemicals commonly migrate from packaging into food. Some plastic polymers used for food packaging can degrade into toxic monomers when they come into contact with acidic or alkaline foods, ultraviolet light, and heat. Migration of plastics from food and beverage packaging into food products is thought to be one of the highest sources of human exposure.[2]
Plastic particles that are concerning to human health are categorized as microplastics (particles 1000 nanometers to 5 millimeters (mm) in size) and nanoplastics (particles smaller than 1000 nanometers).[4] For reference, a human hair is 50,000 to 100,000 nanometers (0.05mm to 0.1mm) in width.[5]
How Do Plastics Get into the Human Body?
Microplastics and chemical additives enter the human body through drinking water, food, and from the air. In studies of microplastics, some investigators actually test the materials detected to ensure they are plastics, and others report finding anthropogenic (resulting from the influence of human beings on nature) debris that is consistent with microplastics, without actually testing the materials.
A study of globally sourced tap water found anthropogenic fiber particles consistent with microplastics in 81% of the samples.[6] In other studies, there was great variation in the amount of microplastics found in tap water, depending on the location. For example, no plastics were detected in a study of Norwegian drinking water, while 100% of the samples in a study of Mexico City drinking water contained microplastics.[7,8] Another study of 11 brands of globally sourced bottled water found microplastic contamination in 93% of the bottles. As polypropylene was the most common polymer found, it was theorized that some of the microplastic found could be from the bottlecap, with some entering the water when the bottle was opened. Some glass water bottles were also found to have plastic microparticles which might indicate contamination from the bottling process or from the water itself.[9] A number of studies in the literature from different geographic sites have reported that bottled water typically contains more microplastics than tap water.[10]
A study of school meals packed in aluminum dishes for children aged 3 to 10 found that levels of the phthalates di(2-ethylhexyl)phthalate (DEHP) and di-n-butylphthalate (DBP) in the food increased by more than 100% compared to the initial baseline levels in the food. Aluminum used in food storage is not infrequently coated with plastic. Aluminum cans may also be coated with a plastic epoxy coating.[11]
Polypropylene infant feeding bottles from 48 geographic regions were tested and it was estimated that the average daily consumption for a 1-year-old feeding from them was 1,580,000 polypropylene microparticles, with a range of 14,600–4,550,000 microparticles per day. The numbers were higher in developed countries.[12] In another study, 76% of breast milk tested (26 out of 34 samples) contained plastic microparticles mostly consisting of polyethylene, polyvinyl chloride, and polypropylene.[13]
An Australian study found that 95% of tested rice samples had plastic contamination. There was no difference between rice packed in plastic or paper. Instant rice on average contained four times the plastic content of non-pre-cooked rice.[14] An Italian study looked at apples, pears, broccoli, potatoes and carrots, and found plastic particles in all of them, with apples and pears containing the most.[15] Plastics can be absorbed by plant roots if there is plastic in the water supply or soil.[16] A study testing 16 different types of protein including chicken, shrimp, fish, steak, tofu, and plant-based ground beef found microplastics in all the foods tested at varying levels. The highest levels were found in highly processed foods such as breaded shrimp and fish sticks.[17] Chemical polymer fibers were found in 100% of 19 honey samples from five different countries and five sugar samples.[18] A study of plastic release from plastic triangular tea bags found that one plastic teabag released approximately 11.6 billion microplastics and 3.1 billion nanoplastics into a single cup of the tea. However, while the billion numbers are huge it should be noted that one source calculated that the total amount of plastic released is about 60 millionths of a gram.[19,20]
Microplastics have been found in varying percentages in fish and other seafood around the world which potentially may be ingested by humans.[21,21A] Multiple studies have found varying percentages of microplastics in sea salts.[6,22] Annual plastic flows to the ocean are expected to increase from 11 million metric tons in 2016 to 29 million metric tons in 2040.[23] One dire estimate is that if the use of plastic and management of refuse remains unchanged there could be more plastic by weight in the oceans than fish by 2050.[24] While there are many sources of ocean plastic, one surprising estimate is that about 8.6% of microplastics in the oceans comes from tire dust.[23] In addition to plastic waste products and dust entering water, sunlight can break down plastics and further contribute to smaller plastic particles being released into the water.[25]
Plastic cutting boards can also be source of plastic in food, and also when washed off a source of plastic in waste water.[27]
Organic food may also contain substances from plastic. Organic fertilizer frequently has been found to contain plastic particles.[28,29]
In 2024, Consumer Reports tested for and found phthalates in both organic food and nonorganic food products.[30] Phthalates were used in the past in the U.S. in many enteric-coated medications to help control drug release, and in 2012 the FDA recommended they no longer be used.[31,32] In 2022 the FDA removed 23 phthalates no longer being used in the food industry from food contact situations, such as tubing or packaging, but in a controversial decision, left nine still available for use.[33,34] Phthalates have been associated with increased insulin resistance[35,36,37], arteriosclerosis[37], hypertension[36], fertility problems[38,39], behavioral disorders and impaired motor skills in children[40,41], pregnancy loss[42,43], endometriosis[43A,43B], male infant genital abnormalities[42], and cancers.[31,44]
Plastics in the Human Body
When searched for, plastic compounds have been found nearly everywhere in the human body.
In a recent study, asymptomatic patients who required a carotid endarterectomy had their carotid plaques excised and tested for embedded plastics. 58% of those plaques had detectable amounts of polyethylene, and 12% had polyvinyl chloride. Electron microscopy demonstrated jagged foreign particles among plaque macrophages and also scattered in the plaque itself. Subjects who had plastic particles in their carotid plaques had 4.5 times the risk of having a stroke, myocardial infarction or death in the next 34 months compared to those that did not. The majority of the particles found were nanoparticles as it has been suggested that larger particles may not be absorbed as easily into the blood from the gastrointestinal (GI) tract.[4] Other researchers looked at arterial thrombi removed after emergency surgery of the lower extremities or aorta. It was reported that microplastics were found in 61.5% of the 26 thrombi they examined.[45]
Cardiac tissue samples were taken during surgery in another study, and although not in 100% of the samples, microplastics were found in some of the pericardial and epicardial fat, myocardial and pericardial tissue, and in the left atrial appendage. As another part of the study, microplastics were noted in the blood of patients prior to surgery. After surgery, the patients’ blood samples revealed two additional types of microplastic particles and also smaller sized microplastics compared to pre-surgical blood samples. This suggests that medical procedures might be another way plastic enters the body.[46]
In another study, lung tissue removed during thoracic surgery was examined and microplastic particles were found in 85% (11 out of 13 tissue samples).[47] Inhalation of plastic particles can occur after burning plastics in waste disposal, exhaust from plastic production, or plastic particles floating in the air. A large source of plastic particles in the air comes from automobile and truck tires as they wear down from road friction. Plastic textile fibers can also be released into the air.[2] Extended respiratory exposure to microplastics such as polypropylene can potentially cause asthma and pneumoconiosis. (lung disease caused by the lung's reaction to inhaling certain dusts.)[48]
A study of human and canine testicular tissue found microplastics in all samples with the levels in human testes three times higher than in the dog testes.[49] In an Italian study, microplastics were found in 60% of ten samples of human semen, while a Chinese study found microplastics in 100% of 36 semen samples tested.[50,51] There has been a world-wide decrease in fertility and it is suspected that microplastics could be a factor. (Other substances, such as herbicides, have also been found in semen samples suggesting the etiology of the infertility problem may be multifactorial.[52])
In a study looking at six human post-partum placentas, microplastics were found in four of the samples or 66.7%.[53]
Scientists looking at human post-mortem liver, kidney and frontal cortex brain samples found micro- and nanoplastics in the brain at 7-to-30 times the concentrations measured in the livers or kidneys. They also compared results from 2024 to similar samples from the year 2016 and found significantly more plastic material in the 2024 liver and brain tissue than in the 2016 samples. The most common plastic found was polyethylene.[54]
Most ingested plastic is eliminated from the body in feces. The first report of researchers documenting microplastics in the stool was in 2018 when microplastics were found in all eight of the subjects who lived in various places in Europe and Asia. The median amount of plastic discovered in those subjects was 20 microplastic particles in 10 grams of stool (0.35 ounces).[55] A study comparing microplastics in infant stools to adult stools found that the infants’ stool contained up to 14 times the amount of microplastics per gram of stool than the adults, indicating higher infant exposure to microplastics. All six infant and ten adult stool specimens tested were positive for microplastics.[56] In vitro studies with simulated human intestinal models have found that ingestion of plastics can change the gut microbiome, with potentially negative effects on health.[57] A study comparing patients with irritable bowel syndrome (IBS) to controls found higher levels of microplastics in the patients’ feces with IBS suggesting that higher levels of plastic exposure might possibly contribute to the development of the disease.[58] Another study examined colon tissue removed during surgery and found microplastics embedded in normal colonic tissue as well as higher amounts of microplastics embedded in colonic adenocarcinoma tissue samples.[58A] Although not proven, researchers are looking into the connection between microplastic ingestion and the noted increase in colorectal cancers in young adults.[59]
In vitro experiments have demonstrated impaired lipid digestion and metabolism when microplastics are present. It was found that microplastics could cause smaller lipid particles to aggregate creating larger, less absorbable lipid particles. Microplastics also changed the structure of lipase which decreased its activity and impaired fat digestion.[60,61]
The chemical additive BPA, in some studies, has been found in the urine of up to 86% of adults and over 90% of children.[62] BPA migrates out of polycarbonate water or beverage bottles into the water at levels that increase with heat. Migration of BPA in liquids also occurs with epoxy-coated beverage cans. BPA has been found in either animal or human studies to have a number of adverse effects. BPA has been shown to increase the chance of having insulin resistance and contracting type-2 diabetes. There is also some data that BPA may interfere with thyroid hormone metabolism.[63] BPA has weak binding affinity to estrogen receptors, and exposure is hypothesized to lead to accelerated puberty and may also worsen estrogen sensitive tumor growth. BPA has been found to potentially damage DNA. It may also alter immune responses. Elevated BPA levels in pregnant women may be a risk factor for male autism.[64] Finally, in vitro studies demonstrated BPA may increase a cancer’s resistance to some chemotherapeutic drugs.[65]
Addendum: Two recent studies have discovered microplastics in additional parts of the body. Microplastics were found in 100% of bone marrow samples in one study[65A]. Another study found the widespread presence of microplastics in the synovium (membrane lining) of hip and knee joints in patients undergoing arthroplasty.[65B]
Animal Studies
Microplastics have been reported in animals to migrate from the GI tract and have been found in the lungs, liver, kidneys, muscles, intestines and brain[60,66].
The effects of microplastics depends on the size, shape, quantity and probably individual variation of the response to plastics. Animal experiments indicate that microplastics can cause dysfunction in the liver and intestines. Animal studies have shown that exposure to microplastics may increase oxidative stress.[67] Oxidative stress may cause inflammation which can have numerous deleterious effects on the body.[22] Microplastics have been shown to induce an immune response in animals. In some animal studies, microplastics have been demonstrated to inhibit acetylcholinesterase activity which led to neurotoxicity.[60] Chronic exposure to polystyrene in mice damaged the blood brain barrier, deposited microplastics in brain tissue, and led to learning and memory dysfunction.[68] Mouse studies have shown microplastics can reduce the quality of oocytes as well as sperm quality.[60] An experiment using a rat model of induced rheumatoid arthritis, reported that microplastics could increase inflammation and potentially worsen cartilage damage in rheumatoid arthritis.[69]
Discussion
As a byproduct of plastic manufacturing and use, unfortunately humans now breathe or ingest micro- and nanoplastics daily. Some scientists have labeled this time period as the Plasticene era[70] due to the abundant amount of plastics on the earth. Microplastics are in the oceans, soil, air, drinking water, and food. They can be released from food packaging, clothing, carpets, tires and many other manufactured products.
Some chemicals contained in plastics are potentially carcinogenic, some are endocrine disruptors, some can increase oxidative stress and inflammation. They may increase the chance of miscarriage and may adversely affect brain development in children.
Most ingested plastic is removed in feces, nevertheless microplastics have been found almost everywhere in the body researchers have looked. One study reported that plastic embedded in arteriosclerotic plaque increased negative clinical outcomes.[4] A pre-publication study found plastics in human brain tissue, in increased amounts, compared to specimens from eight years ago.[54] With respect to infants, microplastics have been found in placental tissue, breast milk, in polypropylene infant feeding bottles, and in infant feces, so potentially humans may be exposed for their entire lives. Microplastics can negatively affect the intestinal biome, and also may be playing a part in the world-wide decrease in fertility. Plastics appear to have many other potentially negative effects and scientists are still trying to discover all the connections between plastic ingestion or inhalation and deleterious health effects.
Not all human subjects were found to have plastic particles in the various tissues or organs examined. This may represent an area for further study. It may simply represent a difference in the amount of plastic intake. It also may possibly be due to genetic or other factors that impede plastic absorption into the blood stream from the GI tract or lung, which might lead to therapies that can decrease plastic deposition in the body.
The ubiquitous use of plastic in modern societies is evidenced just by looking in a refrigerator and realizing how much food is packaged in plastic, plastic-coated metal, or plastic-lined paper cartons. In addition, most, if not all the food and liquid in the refrigerator probably already contained microplastics before being packed in their containers.
On an individual level, it is currently nearly impossible to avoid ingesting microplastics and plasticizers. Some suggested methods of reducing plastic intake are decreasing intake of water or beverages bottled in plastic, using food-grade silicon or glass food storage containers instead of plastic, not using cutting boards made of plastic, and not microwaving food in plastic containers. Fresh, minimally processed foods have been found to contain less plasticizers than fast food. It has been suggested that the vinyl gloves worn in the preparation of fast foods may possibly further increase plasticizer levels in the food.[71,72] Filtering drinking water has been shown to reduce microplastic levels, but performance can vary greatly between models. One study reported that water filters that incorporated microfiltration or membrane filtration removed more plastic than those that did not use that technology.[73]
Solving the world-wide problem of reducing human exposure to plastics would be an immense task, requiring an enormous change in the way modern societies function.
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