Why Detecting Nanoplastics in Humans Matters: Exposure Routes, Biological Evidence, and Potential Health Implications

Introduction

Plastics are widely used in healthcare, food packaging,textiles and day-to-day consumer products due to their durability and low cost. The physical and chemical degradation of plastic materials leads to the formation of progressively smaller fragments.^1,2 While microplastics have been extensively studied, attention has increasingly shifted toward nanoplastics because of their greater biological accessibility.^3,4

Nanoplastics occupy a size range comparable to viruses and macromolecular complexes.⁴ These properties enable interactions with cellular membranes and facilitate translocation across epithelial barriers.^3,5 As a result, nanoplastics may access tissues that are typically protected from particulate exposure, including the placenta and central nervous system.^6,7

Over the past several years, multiple independent studies have confirmed the presence of plastic particles in human biological samples.^8-10 Detection in blood, lung tissue, placental tissue, faeces, urine, vascular specimens, and brain tissue has shifted the discussion of plastic exposure from an environmental issue to a clinical and public health concern.^6-7,11-13 Understanding how nanoplastics enter the body, where they accumulate and what effects they may exert is now relevant to medical research.^1,14

Routes of Human Exposure

Ingestion

Dietary intake is considered the primary route of exposure to nanoplastics.² Plastic particles have been identified in drinking water, bottled beverages, seafood, salt and packaged foods.^2,5 Food processing and packaging practices further contribute, particularly when plastics are heated or mechanically stressed.³

Once ingested, nanoplastics encounter digestive enzymes and bile salts that alter particle surface properties.^3,4 Experimental models suggest that these particles can cross the intestinal epithelium through cellular uptake or paracellular transport.^1,5 After translocation, particles may enter systemic circulation and distribute to internal organs.¹⁴

Inhalation

Inhalation represents a second major exposure route.⁹ Airborne nanoplastics originate from sources such as synthetic textiles, traffic-related emissions, industrial activity and indoor dust.⁵ Due to their small size, these particles can reach the distal airways and alveoli.⁹

Human lung tissue analyses have identified common polymers, including polyethylene and polypropylene.⁹ Clearance mechanisms appear limited, and retained particles may trigger local inflammatory responses or translocate into the bloodstream.¹

Dermal exposure (skin exposure)

The skin functions as an effective barrier, but nanoscale materials may penetrate under certain conditions,particularly with repeated exposure or barrier disruption⁴ Nanoplastics are present in some cosmetic and personalcare products.³ While systemic uptake via the skin is likely limited, localised effects and occupational exposure remain areas of concern.⁵

Maternal–foetal transfer

Detection of plastic particles in human placental tissue indicates that nanoplastics can cross the placental barrier.⁶ This finding raises concern regarding prenatal exposure during critical periods of development.^1,6 Although clinical consequences have not yet been established in humans,animal studies suggest potential developmental effects.^3,14

Dermal exposure (skin exposure)

The skin functions as an effective barrier, but nanoscale materials may penetrate under certain conditions,particularly with repeated exposure or barrier disruption⁴ Nanoplastics are present in some cosmetic and personalcare products.³ While systemic uptake via the skin is likely limited, localised effects and occupational exposure remain areas of concern.⁵

Biological Evidence of Nanoplastics in Humans

Nanoplastics and related microplastics have been detected in a growing range of human biological matrices.^1,10 Blood was among the first tissues studied,providing evidence of systemic distribution.^8,10 Placental detection supports the possibility of foetal exposure,⁶ while lung tissue findings confirm inhalation as a relevant route.⁹

Faecal samples indicate widespread dietary exposure,though they do not distinguish between absorbed and excreted particles. ¹⁵ More recent studies reporting plastic particles in urine, vascular tissue, thrombi, joints, semen,and brain samples suggest that some particles may persist or accumulate in the body. ^7,11,16 Microplastics have also been detected in human lower limb joint tissues and saphenous vein samples, further supporting systemic distribution and tissue deposition.^17,18 Identification of plastic particles in brain tissue is of particular concern,as it may reflect passage through or alteration of bloodbrain barrier integrity.⁷

Potential Health Implications

Direct clinical evidence linking nanoplastics to disease in humans is currently limited.¹ However, experimental studies provide insight into possible biological effects.Cellular uptake of nanoplastics has been associated with oxidative stress, mitochondrial dysfunction and inflammatory signalling.^3-4,14 Immune activation following particle exposure may result in chronic low-grade inflammation, a process implicated in cardiovascular, metabolic and respiratory diseases.^1,5 In addition, plastics often contain chemical additives such as bisphenols and phthalates, which are known endocrine disruptors.^1,3 Nanoplastics may act as carriers for these compounds, enhancing cellular exposure.¹⁴ 

Animal studies also suggest potential neurotoxic effects,including neuroinflammation and altered behaviour following exposure.^3,14 The relevance of these findings to human health requires further investigation, particularly through longitudinal clinical studies.¹

Clinical and Public Health Relevance

From a medical perspective, detection of nanoplastics in human tissues is a prerequisite for meaningful risk assessment.¹ Without reliable quantitative data, it is not possible to evaluate exposure thresholds, identify highrisk populations, or assess associations with disease outcomes. 

⁵ Current analytical techniques have enabled important discoveries but are not yet suitable for routine clinical use.^8,19 Challenges include contamination control, limited sensitivity for smaller particles and lack of standardised protocols.^8,10 Harmonisation of detection methods will be essential for future clinical and epidemiological research.¹