The Impact of Microplastics on Human Health: An Urgent Public Health Concern

Abstract

Microplastics (MPs) have rapidly become one of the most pervasive pollutants in the modern world. Far from being confined to oceans or waste sites, these tiny particles now circulate through the air we breathe, the water we drink, and the food we eat. As everyday plastic items break down over time, they form microscopic fragments that can travel long distances and enter the human body through inhalation or ingestion. Once inside the body, these particles may accumulate in organs and interact with biological systems in ways that scientists are only beginning to understand. This review synthesizes current scientific findings on the formation of MPs, their pathways into and persistence within the human body, and their potential health impacts. Although there is no standardized method for measuring MPs, the main analytical techniques used for biological samples are discussed. Furthermore, the toxicity and environmental impacts of plastic types to which humans are exposed are assessed using the EPI Suite™ program developed by the U.S. Environmental Protection Agency (USEPA). Certain MP types, such as polyethylene and polypropylene, appear more toxic due to their low biodegradability. Although evidence increasingly identifies MPs as a growing public health concern, many questions remain unanswered. Health effects related to gastrointestinal and respiratory health systems are examined, while long-term effects, behavior in human tissues, and associations with chronic diseases—including potential links to cancer—require further multidisciplinary investigation. As global plastic use continues to rise, understanding and mitigating MP exposure will be essential for protecting human health.

Introduction

Formation and Environmental Occurrence of MPs

Plastics are versatile polymers characterized by their low density, malleability, and durability, leading to their ubiquity in modern life.¹ In addition to their use in household goods, vehicles, and industrial production processes, they are also produced extensively for single use in all areas of life.² Plastic production worldwide is increasing every year and has exceeded 400 million tons annually.³ Due to problems in plastic waste management and the global recycling rate being around 10%, the degradation and disintegration of plastic polymers lead to the formation of particles called microplastics (MPs), defined as particles ranging from 1 to 5,000 µm.⁴

Microplastics can be formed by the direct breakdown of plastics released into the environment, as well as through environmental factors, such as sunlight, wind, and long-term weathering and aging processes.⁵ In addition to the widespread presence and use of plastics in all human environments (homes, offices, industrial parks, etc.), direct exposure also occurs. Fabrics made from plastics such as polyester or polyethylene terephthalate (PET) and shoes made from plastic derivatives such as ethylene-vinyl acetate (EVA) demonstrate that plastics are beginning to surround our bodies.^6,7 Empirical evidence has demonstrated that domestic laundry effluent is a significant source of synthetic microfibers.⁸ During the recycling of these plastics, high amounts of MPs are released into receiving water bodies along with washing water.⁹ Similarly, studies have identified domestic and industrial wastewater treatment plants as point sources of MPs.¹⁰ Studies conducted in various water sources worldwide have revealed the presence of MPs at high concentrations, particularly in coastal areas.¹¹ Varying in morphology and composition, MPs can act as vectors for chemical pollutants due to their high surface adsorption capacity.¹²

Studies reported in the literature have demonstrated that the widespread presence of plastics across all environmental media results in the ubiquitous occurrence of MPs.¹³ MPs have been detected in air (both indoor and outdoor), on land (including terrestrial environments and landfills), in marine, oceanic, and freshwater environments, and even in the Arctic.^14–17 Although MPs are not considered a conventional air pollution parameter, fiber MPs have been shown to be transported over distances of several kilometers.¹⁸ Due to poor plastic waste management, particularly in rural regions, MP formation and plastic-related environmental impacts are more pronounced, leading to severe consequences such as open burning, open dumping, landfill burial, and waste imports.¹⁹ Consequently, it has been reported that the transition to a circular economic perspective in plastic waste management is quite difficult, and there are significant barriers to achieving a sustainable waste management model.²⁰

As a result, MPs are constantly transported across all environmental media (air, soil, and water) by environmental factors.²¹ The presence of MPs is not limited to remote areas; they remain in continuous contact along long transport routes. MPs are in constant contact with humans in all areas of life, from seed and medicine packaging or compost used in agricultural fields to serums, syringes, and medications in hospitals.²² Notably, hypertonic fluids are one of the sources of MPs that directly enter the human body via intravenous routes.²³ Therefore, it is necessary to investigate the pathways of MPs after they enter the human body. Crucial to this investigation is the standardization of analytical methodologies for detecting MPs in biological matrices.

While the prevalence of MPs is well documented, specific toxicological modeling of human exposure remains sparse. In preparing this review, research and review publications from the last 10 years were selected from the perspective of each author, including studies on MP formation and occurrence in environmental samples, MP analysis and toxicity in humans, and associated health effects. This review differentiates itself as a case study by applying EPI Suite™ to assess the biopersistence of common polymers. A focused analysis of the mechanisms of respiratory and gastrointestinal degradation is also provided. An interdisciplinary approach was employed to explore the relationship between environmental and medical sciences.

CLINICAL AND RESEARCH CONSEQUENCES

Calculation of Environmental Toxicity of MPs Using EPI Suite™

In this research, the twelve most frequently utilized MPs were analyzed. To gather insights into the toxicological impacts and biodegradability of MPs in the environment, the EPI Suite™ (Estimation Programs Interface) created by the U.S. Environmental Protection Agency (EPA) was employed to assess human toxicity.²⁴ Biodegradability parameters were evaluated using the BIOWIN module of the software, while toxicity metrics such as effective concentration (EC₅₀) and lethal concentration (LC₅₀) were determined using the ECOSAR module.²⁵ This program operates based on the principles of Quantitative Structure-Activity Relationships (QSAR), predicting the physical and chemical effects of substances on living organisms according to their molecular characteristics. Unlike basic toxicity screening tools, EPI Suite™ enables a comprehensive assessment of both environmental fate (e.g., partitioning and biodegradation) and toxicological endpoints based on the specific molecular geometry and functional groups of polymers. The integration of BIOWIN™ and ECOSAR™ models provides a standardized regulatory framework developed by the U.S. EPA, ensuring that the predictive data are aligned with internationally recognized environmental safety benchmarks.

Characterization and Detection of MPs in Biological Samples

Numerous studies have analyzed MPs using different methods. Variations in MP extraction processes, as well as in the instrumentation and analytical techniques employed, significantly increase the diversity of analyses.^26,27 The analysis of MPs in biological samples is complicated by the difficulty of isolating polymer particles from organic matrices. Because plastics are polymeric organic chemicals, selectively separating them from biological samples that also contain organic material is difficult and may lead to analytical errors.

Separation processes such as digestion, oxidation, or density gradient techniques used to remove the organic matrix from the analyte can result in analyte loss.²⁸ Therefore, it is essential to avoid the use of overly strong solvents or oxidants during sample separation. Recently, enzymatic digestion has emerged as a particularly suitable pre-separation method for biological samples. This approach has been reported to achieve high digestion efficiency using very low concentrations of trypsin or proteinase K, without analyte loss.²⁹

Given the heterogeneity of sample matrices and polymer types, a universal “gold standard” for MP analysis remains elusive. Method selection should be strategically determined based on sample type (e.g., water, sediment, or tissue) and the targeted particle size range. Analytical methods can be broadly divided into two categories: spectroscopic and thermo-analytical approaches.^26,27

The fundamental distinction in MP characterization lies between particle-based methods, such as Fourier Transform Infrared Spectroscopy (FTIR) or Raman spectroscopy, and mass-based methods, such as pyrolysis gas chromatography/mass spectroscopy (Py-GC/MS). FTIR and Raman analyses report data on a “pieces/liter” or “pieces/m³” basis, quantifying pollution levels by particle number. Py-GC/MS, on the other hand, provides mass-based values such as µg/L. In the literature, it is debated whether mass-based data are more stable indicators than particle counts for determining ecotoxicological risks. Microscopic techniques are limited by the wavelength of light. FTIR generally experiences signal loss for particles smaller than 20 µm, whereas Raman spectroscopy can detect particles down to 1 µm. Py-GC/MS, in contrast, is size independent.^26,27 The advantages and disadvantages of each method are summarized in Table 1.^26–29

Table 1.

Comparison of microplastic (MP) analysis methods

Evaluation criteria	Spectroscopic methods			Thermo-analytical methods
Analysis methods	Stereomicroscopy	FTIR spectroscopy	Raman spectroscopy	Py-GC/MS
Chemical analysis	Not possible	Yes	Yes	Yes
Nanoplastic detection	Not possible	Limited	Possible	Possible (mass-based)
Operational complexity	Very low	Moderate	Expertise required	Moderate
Matrix effects	High	Low	Low	Very Low

FTIR: Fourier transform infrared spectroscopy; Py-GC/MS: Pyrolysis gas chromatography-mass spectrometry.

For the quantitative and qualitative analysis of MPs in biological samples, the PY-GC/MS method is recommended, as it does not require pretreatment and minimizes analyte loss.³⁰ This method is based on the thermal treatment (pyrolysis) of the sample at high temperatures (600 °C) in an oxygen-free environment, followed by separation of the resulting pyrolysates in a GC column and detection using an MS detector. Qualitative and semi-quantitative analyses can be performed by comparison with GC-MS libraries.³⁰ Additionally, fully quantitative analyses can be achieved when analyte standards are prepared and appropriate calibrations are performed. The flowchart of the proposed method is shown in Figure 1.

Figure 1.

Gas chromatography-mass spectrometry (GC-MS) system equipped with a pyrolyzer.

Routes of Human Exposure

Recent studies have identified MPs such as polyvinyl chloride (PVC), polyethylene terephthalate (PET), polypropylene (PP), polyethylene (PE), polystyrene (PS), and polymethyl methacrylate (PMMA) in various human samples, including urine, breast milk, blood, semen, meconium, otitis media fluid, placenta, lung tissue, and heart tissue.^31–33 Therefore, the possible routes of entry into the human body are discussed with respect to ingestion and inhalation.

Ingestion

Microplastic ingestion represents a significant and prevalent pathway for human exposure to these ubiquitous environmental contaminants.^34,35 Humans routinely ingest MPs through various dietary sources, including packaged foods, bottled water, beverages, fruits, fish, sea salt, seafood, and agricultural crops.^34,36 Both aquatic ecosystems and agricultural activities serve as pathways through which MPs enter the human food chain.^36,37 Once ingested, MPs are absorbed primarily via transcytosis in enterocytes, with larger particles may be internalized through gaps in the intestinal lining.³⁸ Evidence indicates the widespread presence of MPs within the human body, as they have been detected in tissues and excreta such as stool, saliva, colon, and placenta.^39,40 Although ongoing research seeks to determine the full extent of health impacts, immediate concerns include long-term accumulation leading to intestinal damage, liver infection, microbial imbalance, and metabolic disorders.^34,35,41

Inhalation

Humans are chronically exposed to airborne MPs, which are ubiquitous in both indoor and outdoor environments, with indoor settings representing a substantial source due to the amount of time individuals spend indoors.^34,42,43 The presence of MPs in human respiratory samples, including lung tissues, sputum, and the lower airways, has been confirmed in the literature.^44–46 For instance, polymeric particles and fibers have been observed in human lung tissue samples, with particles typically smaller than 5.5 µm and fibers ranging from 8.12 to 16.8 µm.⁴⁴ The synthetic fiber industry also represents a significant source of occupational inhalation exposure. The presence of MPs in the respiratory system raises concerns about potential adverse health effects, such as alterations in cellular metabolism, impacts on respiratory diseases, and inflammation.^44,45 Although ingestion was historically considered the primary exposure route, emerging evidence underscores the significance of airborne MP exposure in humans.³⁵

CONCLUSIONS – HEALTH EFFECTS ASSOCIATED WITH MP EXPOSURE

Toxicity of Common Plastic Types

Polyethylene and polypropylene stand out for their high toxicity due to their very low LC₅₀ and EC₅₀ values (Table 2). Furthermore, polyethylene terephthalate and Nylon 66 (N-66) MPs are more biodegradable than other plastic types; therefore, prioritizing these materials may be more appropriate when considering alternatives. Additionally, MPs have the potential to adsorb other pollutants, allowing them to enter living organisms and exert synergistic toxic effects. Weathered plastics are continuously transported in the environment and act as vectors for pollutants due to the contaminants they adsorb or are exposed to.⁴⁷ Because these plastics are hydrophobic, they generally exhibit a high adsorption capacity and may accumulate in lipid-rich tissues. Studies have also explored the use of plastics or weathered MPs as adsorbents, as reported by Osman et al.⁴⁸ Consequently, when MPs adsorb pollutants, their potential to transport additional contaminants into the body, beyond the MPs themselves, is considerably high.

Table 2.

Toxicity properties of the most commonly used microplastics (MPs)

Polymer type	LC50/test organism (mg/L)	EC50/test organism (mg/L)	Biodegradability
Polyester (PS)	6.896/Mysid	8.691/green algae	No
Polyethylene (PE)	4.270×10-16/Mysid	6.480×10-9/green algae	No
Polypropylene (PP)	3.111×10-16/Mysid	5.200×10-9/green algae	No
Polyvinyl chloride (PVC)	9.925/Mysid	27.439 /green algae	No
Polyethylene terephthalate (PET)	1031.740/Daphnid	2567.640/green algae	Yes
Polycarbonate (PC)	1.041/Mysid	4.216/green algae	No
Polyurethane (PUR)	131.680/Fish	1.435/green algae	No
Nylon 6 (N-6)	16.420/Mysid	10.095/green algae	No
Nylon 66 (N-66)	10.426/Mysid	6.382/green algae	Yes
Polymethyl methacrylate (PMMA)	0.039/Daphnid	7.892/green algae	No
Styrene-butadiene rubber (SBR)	0.107/Mysid	0.911/green algae	No
Acrylonitrile-butadiene-styrene (ABS)	0.273/Fish	0.157/green algae	No

Gastrointestinal Health

Microplastic exposure to the human gastrointestinal system is a growing concern, as humans are estimated to ingest significant amounts of MPs weekly, with particles detected in various human biological samples, including feces, saliva, sputum, lungs, liver, and breast milk.⁴⁹ Once ingested, these MPs can enter the human body and translocate to the lymphatic and circulatory systems, accumulating in various organs.⁵⁰ Indeed, MPs have been detected in human colectomy specimens and have also been identified in human blood and even brain tissue, with increasing concentrations reported over time.^51–54 Current evidence suggests that MPs are not easily excreted from the body after ingestion, leading to their accumulation in human tissues and organs, with particularly high concentrations observed in the colon and liver.^35,55 While the exact long-term impacts are still under investigation, these findings highlight the pervasive nature of MPs within the human body and their potential interactions with the gastrointestinal system.

Once ingested, MPs may accumulate in the gastrointestinal tract, leading to significant disruption of the gut microbiome.⁵⁶ This disruption often manifests as dysbiosis, characterized by alterations in the diversity and composition of beneficial bacteria and a potential increase in harmful bacterial population.^56,57 Studies indicate that MP exposure can negatively affect functional pathways and metabolic activity of the gut microbiota, contributing to oxidative stress, inflammation, and compromised intestinal barrier function.^57–59 Alterations to the gut microbiome may trigger a range of health problems, including digestive disorders and widespread inflammation. These changes can influence gut health, and, consequently, the rest of the body through its connections with the brain and the immune system.^56,60

The liver and gastrointestinal tract serve as the primary sites for nutrient absorption and metabolic detoxification. MPs disrupt the gut-liver axis by triggering oxidative stress, inflammation, and programmed cell death (apoptosis).⁶¹ These particles may further interfere with hepatic glucose and lipid regulation and exert indirect effects on the gut-brain axis by altering the intestinal microbiota.⁶¹ Zhang et al.⁶² reported in a meta-analysis that MPs can cause hepatocellular injury, oxidative stress, and elevated inflammatory markers, as well as increased liver enzyme levels and decreased antioxidants, such as superoxide dismutase, catalase, and glutathione peroxidase, in animal models. Jin et al.⁶³ reported that MPs induce cellular toxicity in an in vitro human intestinal cell model. Ozsoy et al.⁶⁴ demonstrated the presence of MPs in stomach cells from 26 cadavers.

Respiratory Health

Microplastics have been detected in sputum, bronchoalveolar lavage fluid, and lung tissue. These findings highlight direct exposure routes and the accumulation of MPs within the human respiratory system.^31,45,46

Evidence from both in vitro and in vivo models indicates that MPs may impair respiratory function. These effects are characterized by pulmonary inflammation, metabolic alterations at the cellular level, and dysregulation of proteins associated with apoptosis.⁴⁶ Airborne MPs are increasingly recognized as emerging contributors to respiratory diseases and may significantly influence their onset and progression.⁶⁵ Specifically, MP fibers can trigger alveolar macrophages and airway epithelial cells to produce pro-inflammatory cytokines, potentially resulting in chronic airway inflammation.⁶⁶ Collectively, these findings highlight the potential for broad respiratory health implications associated with MP exposure.⁶⁷

According to Paplińska-Goryca et al.,⁶⁶ MP stimulation elicits distinct responses in the airway epithelial cells of patients with obstructive lung diseases compared to healthy controls. This differential response is associated with Th2-mediated inflammation, altered stress response pathways, and potential carcinogenic processes. Epithelial cells from patients with asthma and chronic obstructive pulmonary disease (COPD) are more susceptible to damage from MP fiber exposure. Anuar et al.⁶⁸ demonstrated that polyethylene MPs may adversely affect airway function by enhancing tissue contractile responses, mimicking pathophysiological features observed in asthma, chronic cough, and chronic obstructive pulmonary disease.

The main findings and conclusions can be summarized as follows:

• Polyethylene and polypropylene were identified as high-toxicity risks based on EPI Suite™ prediction (LC₅₀/EC₅₀ values), whereas PET and Nylon 66 were highlighted as safer and more biodegradable alternatives.

• Hydrophobic MPs act as chemical vectors by adsorbing environmental pollutants and facilitating their transport into lipid-rich tissues.

• Ingested particles can translocate beyond the gastrointestinal tract into the lymphatic and circulatory systems, accumulating in organs such as the liver, blood, and brain.

• MP-induced gut dysbiosis disrupts the intestinal-hepatic axis, contributing to oxidative stress, liver injury, and metabolic disorders, including insulin resistance.

• Inhaled fibers stimulate pro-inflammatory cytokine production, with significantly higher risks of damage in patients with asthma and COPD.

Knowledge Gaps and Future Research Directions

Human exposure routes to MPs are not yet fully understood. Therefore, further studies are needed to elucidate their effects on various organs or tissues after entering the human body. Additionally, research focusing on the long-term effects of MPs, as well as their behavior and degradation within human tissues, is required. Although associations between certain plastic types or the presence of MPs and various cancers have been reported, more in-depth studies are necessary to establish causal relationships.

Microplastics are now known to be ubiquitous in the environment; therefore, it appears that they may have serious impacts on human health. Humans are in constant contact with plastics in daily lives, and because plastics eventually decompose into MPs, human exposure via air, water, and food is inevitable. In addition to affecting the respiratory and digestive systems, the effects of MPs on other systems of the human body, particularly vital organs such as the brain and heart via the bloodstream, need to be investigated. While some waste management strategies emphasize waste prevention and reduction through hierarchical approaches, it is hypothesized that legislative restrictions on plastic production could play a critical role in mitigating MP exposure.

Ethics Committee Approval

Ethics approval was waived for this study because no patient data were reported.

Informed Consent

Written informed consent was not required for this study.

Conflict of Interest

The authors have no conflicts of interest to declare.

Financial Disclosure

The authors declared that this study received no financial support.

Use of AI for Writing Assistance

Jenni AI and Palpaper were used for arrangement and grammar of the article. Also, corresponding author used Gemini (Google Inc.) for grammar check and paraphrasing.

Author Contributions

Concept – KK, HM, İU; Design – KK, İU; Supervision – KK; Resource – KK, HM, İU; Materials – HM; Data Collection and/or Processing – HM; Analysis and/or Interpretation – KK, HM, İU; Literature Review – KK, HM, İU; Writing – İU; Critical Review – İU.

Peer-review

Externally peer-reviewed.

Data Availability Statement

The data supporting the findings of this study are available from the corresponding author upon reasonable request.