The widespread accumulation of plastic waste in the environment has led to the generation of microplastics

(MPs; <5 mm) and nanoplastics (NPs; <1 μm), prompting growing concern about their possible effects on human

health. (Andrady, 2017; Geyer et al., 2017). Although microplastics are well characterized, nanoplastics have

only recently gained attention as a potentially more harmful class because their nanoscale dimensions increase

reactivity and permit deeper biological penetration (Gigault et al., 2018; Koelmans et al., 2022; Sharma et al.,

2023). This review critically examines recent advancements (2020–2025) in the sources, environmental

distribution, exposure pathways, analytical detection, and toxicological effects of micro- and nanoplastics, with

a primary focus on nanoplastics (Li et al., 2023; Singh et al., 2025). Comparative evaluation highlights a shift

from physical and carrier-based effects of MPs to molecular and cellular toxicity associated with NPs (Yong et

al., 2020; Jin et al., 2019). Despite growing evidence of their presence in human tissues, significant uncertainties

across ecosystems (Andrady, 2017). Over time, these materials fragment into microplastics (MPs) and eventually

nanoplastics (NPs) through environmental processes such as photodegradation and mechanical abrasion (da

Costa et al., 2016; Guo & Wang, 2019).

While MPs have been extensively studied, NPs are emerging as a critical concern due to their nanoscale size and

enhanced physicochemical properties (Gigault et al., 2018). Microplastics act as a precursor pool for

nanoplastics, yet NPs exhibit greater biological reactivity and the ability to cross cellular membranes, enabling

direct interaction with intracellular components (Koelmans et al., 2022). Recent studies have detected plastic

particles in human blood and placenta, indicating systemic exposure and raising concerns regarding potential

health risks (Leslie et al., 2022; Bhattacharyya et al., 2025).

Sources and Environmental Reservoirs

Expanded Sources of Nanoplastics

Nanoplastics originate from both primary and secondary sources. Primary nanoplastics include industrial

nanopolymers, coatings, and cosmetic formulations, while secondary nanoplastics are generated through the

fragmentation of larger plastics driven by ultraviolet radiation, thermal degradation, and microbial activity

(Gigault et al., 2018; Lambert & Wagner, 2016). Emerging sources such as tire wear particles, synthetic textiles,

food packaging degradation, and indoor dust have also been identified as significant contributors (Kole et al.,

2017; Vianello et al., 2019).

Human exposure occurs primarily through ingestion, inhalation, and dermal contact (Prata, 2018; Cox et al.,

Fig. 1: Pathways of Nanoplastics from environmental sources to human exposure, distribution, cellular

interaction, and associated health effects.

Comparative Toxicity: Microplastics vs Nanoplastics

Microplastics primarily induce physical effects such as tissue irritation and localized inflammation and can act

as vectors for chemical contaminants (Wright & Kelly, 2017; Rochman et al., 2019). In contrast, nanoplastics

demonstrate enhanced cellular uptake via endocytosis and can interact directly with proteins, lipids, and DNA

(Yong et al., 2020). These interactions lead to oxidative stress, mitochondrial dysfunction, and genotoxic effects,

indicating a shift toward molecular-level toxicity (Jin et al., 2019; Koelmans et al., 2022). A comparative

summary of microplastics and nanoplastics is provided in Table 2.

Analytical Challenges and Detection Methods

Detection of microplastics is commonly achieved using FTIR and Raman spectroscopy (Koelmans et al., 2022).

However, nanoplastics remain difficult to detect due to their small size and low concentrations. Emerging

techniques such as AFM-IR and nanoparticle tracking analysis are improving detection capabilities, yet the lack

of standardized methodologies continues to limit comparability across studies (Shukla et al., 2024).

Nanoplastics induce reactive oxygen species (ROS) production, leading to oxidative stress and inflammatory

responses (Lu et al., 2018; Hirt & Body-Malapel, 2020; Thapliyal et al., 2025). They can also cause DNA damage

and chromosomal instability, raising concerns regarding genotoxicity (Jin et al., 2019; Liu et al., 2025). Plastic-

associated chemicals such as bisphenols and phthalates can disrupt endocrine function, with nanoplastics

Recent studies have confirmed the presence of micro- and nanoplastics in human tissues, including blood,

placenta, and feces (Leslie et al., 2022; Ragusa et al., 2021; Schwabl et al., 2019). Emerging epidemiological

evidence suggests possible associations between microplastic exposure and cardiovascular diseases,

inflammation, and metabolic disorders (Otorkpa et al., 2024; Sharma et al., 2023). Furthermore, inhalation of

airborne microplastics has been linked to respiratory stress and lung inflammation, particularly in occupational

settings (Prata, 2018; Dris et al., 2016). However, causal relationships remain unclear due to limitations in

exposure quantification and variability in particle characteristics (Koelmans et al., 2022; EFSA, 2021).

Dose and Risk Assessment

Traditional mass-based metrics used for microplastics may not adequately reflect nanoplastic toxicity.

Parameters such as particle number and surface area are more relevant for assessing risk (Koelmans et al., 2022).

A significant limitation in current nanoplastic research is the reliance on laboratory conditions that may not

accurately reflect environmentally relevant exposure levels. Many studies employ high concentrations and

pristine particles, potentially overestimating toxicity compared to aged and weathered nanoplastics encountered

in real-world scenarios. Future research should emphasize standardized detection methods, long-term

epidemiological studies, and realistic exposure assessments (WHO, 2019; EFSA, 2021).

Nanoplastics are emerging as a critical concern in environmental health due to their nanoscale size, high

reactivity, and ability to penetrate biological systems. Compared to microplastics, which primarily induce

physical and carrier-mediated effects, nanoplastics exhibit enhanced cellular uptake and molecular-level

interactions, leading to oxidative stress, inflammation, and potential genotoxic and endocrine-disrupting effects

improving waste management to mitigate potential risks to human health.

1. Andrady, A. L. (2017). The plastic in microplastics: A review. Marine Pollution Bulletin, 119, 12–22.

2. Besseling, E., et al. (2017). Effects of microplastic on ecosystems. Environmental Science & Technology,

51, 12336–12343.

3. Bhattacharyya, S., et al. (2025). Nanoplastics in human systems. Environmental Science & Technology.

4. Cai, L., et al. (2017). Characterization of microplastics in indoor dust. Environmental Pollution, 221, 141–

149.

5. Cox, K. D., et al. (2019). Human consumption of microplastics. Environmental Science & Technology, 53,

7068–7074.

9. Gewert, B., et al. (2015). Degradation of plastics. Marine Pollution Bulletin, 85, 352–364.

10. Geyer, R., et al. (2017). Production, use, and fate of all plastics ever made. Science Advances, 3, e1700782.

11. Gigault, J., et al. (2018). Current opinion: What is a nanoplastic? Environmental Pollution, 235, 1030–

1034.