By Phornrak Sriphon, Board Certified ophthalmologist
What are plastics?
Plastics are synthetic materials made from polymers. These substances are typically synthesized from petrochemicals, such as natural gas or petroleum. The key characteristics of plastics are their durability and ability to be shaped to suit various applications, such as packaging, household items, cosmetics, and medical tools, among others.
Types of Plastics based on Chemical Structure and Properties:
Polyethylene (PE) – Commonly found in water bottles or plastic bags.
Polypropylene (PP) – Used in the packaging industry and automotive manufacturing.
Polyvinyl chloride (PVC) – Found in the production of pipes and medical tubing.
Polystyrene (PS) – Used in the packaging industry.
Polyethylene terephthalate (PET) – Found in food and beverage packaging.
While plastics are beneficial in various industries due to their durability, strength, and long lifespan, their poor biodegradability creates severe environmental pollution issues. When plastics break down into microplastics or nanoplastics, they pose significant concerns in the medical, health, and environmental fields. This issue has raised serious concerns about the impact on human health and ecosystems.
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What are Microplastics?
Microplastics refer to small plastic particles less than 5 millimeters in size and can be categorized into two main types:
Primary Microplastics: These are small plastic particles produced directly by factories, often used in industries such as cosmetics and products that require small plastic particles from the start.
Secondary Microplastics: These result from the breakdown of larger plastic items through natural processes like water, heat, or environmental factors, which cause the plastic to fragment into smaller pieces.
Due to their tiny size, microplastics can easily disperse throughout the environment. They can be found in various locations, including the ocean, rivers, soil, and air.
Moreover, microplastics are released from everyday plastic products and from the breakdown of plastic waste in nature, leading to contamination in the environment. This contamination impacts marine life, such as fish and small marine creatures, which may unknowingly ingest microplastics, causing them to accumulate in the food chain.
For humans, consuming seafood or coming into contact with microplastics can have health impacts. The accumulation of microplastics in the body may increase the risk of inflammation, tissue damage, and chronic diseases. These risks will be further detailed in this article.
Microplastics in the Human Body
Microplastics can enter the human body through three main routes:
Inhalation
Ingestion
Skin contact
Several studies have investigated the amount of microplastics humans are exposed to, including:
A study by Bai et al. (2022) suggested that humans are exposed to the equivalent of 50 plastic bags per year.
A study by Gruber et al. (2022) found that humans are exposed to the equivalent of one credit card per week.
A study by Mohamed Nor et al. (2021) reported that adults ingest an average of 4.1 micrograms of microplastics per week.
A study by Senathirajah et al. (2021) showed that adults are exposed to an average of 0.1–5 grams of microplastics per week.
Additionally, Martin Pletz’s research questioned whether humans truly ingest the equivalent of a credit card per week, analyzing and critiquing this finding. Pletz argued that the actual amount of microplastics humans consume may not be that high, possibly aligning closer with Mohamed Nor et al.'s findings of an average of 4.1 micrograms per week, which is relatively low.
However, even though the amount of microplastics humans are exposed to is not large, it cannot be denied that microplastics may have long-term health impacts. Several studies suggest that microplastics may cause various health issues, including oxidative stress, which is linked to diseases like neurodegenerative disorders and cancer (Jambeck et al., 2015). Microplastics can also affect the reproductive system, metabolism, and cellular functions in the body (Lusher et al., 2017).
Moreover, research shows that microplastics can accumulate in organs such as the lungs, liver, and brain, potentially leading to long-term health problems, especially in individuals who are continuously exposed to plastics from food, beverages, and other products.
Toxic Substances from Microplastics
Plastics are materials with various properties that make them useful in a wide range of industries. However, when plastics degrade into microplastics, which are smaller than 5 millimeters, the chemicals that were embedded in the plastic can be released and contaminate the environment. This can be harmful to human health, especially when certain types of plastics contain chemicals that are dangerous to the body and cannot be easily excreted through sweat or urine. Examples of such chemicals include Bisphenol A (BPA) and Per- and Polyfluoroalkyl Substances (PFAS).
BPA (Bisphenol A) is a chemical found in polycarbonate plastics and epoxy resins, which can contaminate food and beverages when plastics degrade or come into contact with high temperatures. BPA is an endocrine disruptor, meaning it affects the hormone system in the body. This can lead to various health issues, such as an increased risk of cancer, reproductive disorders, and developmental problems in children.
PFAS (Per- and Polyfluoroalkyl Substances) are chemicals in the fluorine group used in some plastics, known for their resistance to water, fat, and heat. These chemicals can accumulate in the body and are difficult to eliminate, increasing the risk of diseases such as cancer, liver problems, weakened immune systems, and reproductive disorders.
When plastics degrade into microplastics in the environment, these chemicals can be released and spread throughout ecosystems, including in water, air, and soil. This has harmful effects on both animals and humans. Microplastics can accumulate in the human body through the consumption of food and water, with studies showing that microplastics can accumulate in various organs such as the lungs, liver, and brain. They may also affect reproductive functions and the development of children.
Health Effects
Studies have shown that microplastics can be found in almost every part of the body, including:
Placenta
Lungs
Liver
Breast Milk
Urine
Blood
In fact, it can be said that microplastics or nanoplastics can be detected in nearly every organ in the body.
Respiratory System
A study by Shumin Huang provides interesting evidence that microplastics can be inhaled into the human body and found in sputum, indicating that microplastics can enter the respiratory system. However, this research has some limitations, such as the possibility that the discovery of microplastics in sputum could be due to environmental contamination, which has not been definitively confirmed.
On the other hand, animal studies have shown that microplastics can cause inflammation in the respiratory system and trigger oxidative stress processes, leading to lung diseases in animals. These studies suggest that microplastics can enter the lungs and potentially impact the respiratory system.
Therefore, based on the research regarding the effects on the lungs and respiratory system, it can be believed that microplastics can enter the lungs. However, further studies on the impact on the respiratory tract are needed to gain a deeper understanding of the effects of exposure to microplastics.
Cardiovascular System
Previous studies have shown that microplastics can be found in blood. Currently, animal studies suggest that microplastics may be a risk factor for the cardiovascular system. Laboratory experiments have shown that microplastics can trigger oxidative stress, inflammation, cell death, and disruption of blood vessel walls, potentially leading to cardiovascular disorders.
A study published in the New England Journal of Medicine titled Microplastics and Nanoplastics in Atheromas and Cardiovascular Events by Raffaele Marfella, M.D., Ph.D., was released on March 6, 2024.
Study Methodology
This research examined patients with atherosclerotic plaque who needed carotid endarterectomy to remove plaque from their arteries. The procedure was followed by:
Plaque Analysis: The removed plaque was analyzed for the presence of microplastics.
Grouping of Patients: Patients were divided into two groups based on the analysis:
Group with microplastics found in plaque.
Group with no microplastics in plaque.
Follow-up: Both groups were monitored in a prospective study to analyze the relationship between the presence of microplastics in plaque and the risk of heart attack (myocardial infarction), stroke, or death.
Results: Patients with microplastics in their plaque had higher rates of heart attack, stroke, or death compared to those without microplastics during the 34-month follow-up.
Study Limitations:
No Causal Inference: While the study shows a relationship, it cannot conclude that microplastics in plaque directly cause cardiovascular disease.
Risk of Contamination: Despite precautions, the risk of contamination in the laboratory cannot be entirely ruled out.
Limited Scope:
The study does not address socioeconomic factors or exposure to microplastics through food and water.
Air pollution exposure, such as PM2.5, was not assessed.
The results are limited to patients who underwent carotid endarterectomy and may not be generalizable to the broader population.
The specific types of microplastics found (polyethylene and polyvinyl chloride) in plaque remain unclear.
Animal Data Limitations: Data from animal studies may not directly translate to human health outcomes.
Despite these limitations, the study suggests a potential link between microplastics in carotid artery plaque and cardiovascular health outcomes, indicating the need for further research.
Reproductive System
Semen
Studies have found that microplastics can be detected in human semen samples, with polystyrene (PS) being the most commonly found type of microplastic, one of the eight identifiable types in the study. This research suggests a link between microplastic exposure and a decrease in sperm motility, particularly with exposure to various types of microplastics, which may impact sperm quality and male reproductive potential. These findings highlight the importance of further research into the effects of microplastics on the reproductive system and long-term health, as microplastics are widely present in the environment and may affect human health in many ways.
The study also found that microplastics can accumulate in various tissues of both the mother and fetus, including the placenta, meconium, infant feces, breast milk, and infant formula. Sixteen types of microplastics were identified, with the most common being polyamide and polyurethane, typically ranging from 20 to 50 micrometers in size. The sources of these microplastics may include drinking water, scrubs, or toothpaste used by pregnant women and the use of baby bottles or plastic toys for infants.
This research underscores the need for further studies on the effects of plastic products on microplastic exposure during pregnancy and breastfeeding to better understand the potential health risks for both mothers and infants.
Nervous System and Brain
Studies in animal models have shown that microplastics can accumulate in the brain and negatively impact brain cells.
However, current studies confirm that microplastics can pass into the brain, but the exact effects on the brain are still unclear. Theoretically, microplastics may cause oxidative stress, enzyme inhibition, and behavioral changes, but there is no definitive evidence linking these effects directly to neurological disorders in humans, such as neurodevelopmental conditions or neurodegenerative diseases.
Conclusion
Microplastics are commonly found in the environment, and there is growing concern about their health impacts. Current data indicate that microplastics can accumulate in human tissues, particularly in the respiratory, digestive, and reproductive systems, as well as in the brain. These findings raise concerns about the potential effects on critical organs, including fetal development, the reproductive system, and the immune system.
Research to date links microplastics with inflammatory processes, hypoxia, and hormonal changes, which may cause cellular damage in the body. However, these effects are still being studied in animal models, and further research in humans is needed to understand the mechanisms of microplastic toxicity and its impact on human health.
Reducing Exposure to Microplastics
Avoiding microplastics and reducing exposure can be achieved by making some changes in daily behaviors, such as:
Switch to Non-Plastic Packaging: Opt for glass, ceramic, or stainless steel over plastic in everyday items like drinking glasses, water bottles, and cookware.
Avoid Heating Plastic: Even though some plastics are labeled as "microwave-safe," heating plastic can cause microplastics to leach out.
Choose Natural Fabric Clothing: Avoid synthetic plastic-based fabrics that may release microplastics during washing.
Use Water Filters: This helps reduce exposure to microplastics that may be present in drinking water.
Select Microplastic-Free Products: Look for products labeled "microplastic-free," such as cleaning products and cosmetics.
Regular Dusting at Home: Dust in your home can contain microplastics. Regular cleaning helps reduce exposure.
Avoid Plastic Toys: Choose toys made from natural materials or those that are safe for children.
Conclusion
While microplastics are widespread in the environment and our bodies, there is still no conclusive research confirming that microplastics cause specific health effects or diseases. However, if you're concerned about microplastics, you can reduce your exposure by following the above guidelines.
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