Most laboratory studies on microplastics rely on high doses and simplified conditions, raising questions about how accurately they reflect real-world human exposure and health risks.
Research: The gap between laboratory experiments and real-world exposure: Toxicity assessment of microplastics is based on insufficient evidence. Image credit: Floren Horcajo/Shutterstock.com
recent environment and health With a combined perspective of systematic literature review and meta-analysis, we assessed methodological gaps in microplastic toxicity research and proposed an interdisciplinary framework to align laboratory methods with real-world exposure conditions.
Why laboratory evidence on microplastics often doesn’t reflect real-world risks
Microplastics (MPs) are present everywhere from marine sediments and agricultural soils to human blood, lung tissue, and arterial plaque. Several toxicology and epidemiology studies have reported an association between MPs and potential health effects, including an association with oxidative stress, chronic inflammation, neurotoxicity, and increased cardiovascular risk. However, the paper emphasizes that current epidemiological evidence does not prove direct causation, but remains primarily correlational. However, the research informing these assessments has fundamental limitations.
Identifying methodological discrepancies between exposure control studies and real-world situations
The gap between controlled laboratory conditions and real-world exposures has long been recognized but has never been comprehensively quantified or addressed in an integrated practical framework. In this study, we mapped the magnitude of these methodological shortcomings across published studies and used analytical chemistry and artificial intelligence (AI) to build a practical framework to make future research more relevant to real-world settings.
After removing duplicates, 88 studies were included. The meta-analysis highlighted considerable differences between MP toxicity experiments and real-world situations, including a significant overrepresentation of polystyrene, which appeared in almost half of all studies, despite the diverse composition of environmental MPs. Most studies use short-term exposures ranging from 0 to 21 days and ignore chronic effects. Approximately 64% of studies focus on small particles (0–10 μm), ignoring broader environmental size distributions.
Model selection and exposure design further exacerbated these differences. Model organisms have been biased toward insects and arthropods, limiting generalizability across ecosystems, as many studies have failed to reproduce co-exposure to co-occurring pollutants and aging of MPs in laboratory environments.
Bioavailability, which is governed by polymer type, size, shape, surface chemistry, and weathering status, was similarly misrepresented. Although the irregular morphology exhibited greater tissue penetration and a stronger oxidative stress response, the parameters controlling its toxicity remained unresolved, and environmentally realistic morphological criteria for MPs did not exist.
Significant gaps remained in quantifying exposure. Laboratory concentrations were typically 102 to 107 times higher than environmental levels, and few adverse effects were observed at environmentally relevant doses. The lack of standardized metrics further confuses evaluation.
Environmental aging may introduce additional toxicity pathways that were largely absent in laboratory models. The main degradation mechanism, UV-induced photooxidation, released toxic volatile organic compounds (VOCs) unique to polymers, but the paper notes that no studies have quantified VOC emissions during photoaging under real-world environmental conditions. Loosely bound additives such as flame retardants, plasticizers, and antimicrobials can easily leach into the surrounding media and accumulate through bioconcentration.
Microplastics also act as environmental vectors, adsorbing polycyclic aromatic hydrocarbons, polychlorinated biphenyls, heavy metals, and antibiotic-resistant microorganisms through the so-called Trojan horse effect. Polyamide (PA) exhibits the highest heavy metal adsorption capacity, which is determined by surface functional groups and physicochemical conditions.
Accurate biomonitoring of microplastic exposure remained constrained by the absence of standardized sampling, extraction, and quantification methods. Each available analytical tool has its own limitations and cannot reliably distinguish contamination from plastic instruments from true signals in clinical settings.
Although new approaches such as single-particle inductively coupled plasma mass spectrometry (SP-ICP-MS) and pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) have improved sensitivity, and Py-GC/MS is particularly useful for nanoplastics, residual impurities and non-plastic pyrolysis products can still produce misleading signals. These gaps meant that the true exposure levels in humans remained debated, impairing the design of biologically realistic in vitro experiments.
Strategies for reconciling toxicological research and environmental reality
Bridging the gap between laboratory conditions and real-world exposures requires advances in several interrelated areas. It is important to use MPs from natural weathering sources at realistic concentrations and for periods long enough to capture ecologically important effects. Building the foundation for future toxicological research in this context is essential to inform sound environmental management policies.
Standards need to move beyond monodisperse spherical particles to functionalized standards with irregular shapes that incorporate surface oxidation, contaminant loading, and biofilm coatings that more closely reflect real-world environmental conditions.
Given the chemical inertness and ubiquity of microplastics, long-term low-dose exposure protocols are equally important. Understanding the combined toxicity of both soil and aquatic organisms requires studies spanning days to months, supported by epidemiological monitoring and correlation with health data.
Beyond exposure design, mechanical modeling must consider microplastics, which act as both physical stressors and vectors of chemical contaminants. This includes dissolution rates under various pH, temperature, and microbial conditions. Nanoplastics (NPs) are transported across biological barriers such as the blood-brain barrier. The role of the “ecocorona”, a surface layer of organic matter and pollutants that are sequentially adsorbed, must be considered in changes in immune recognition and chronic inflammation.
Microphysiological systems such as microfluidic organ chips and human induced pluripotent stem cell (hiPSC)-derived 3D organoids, combined with multi-omics approaches, provide powerful platforms for high-throughput mechanical screening under realistic exposure conditions.
On the detection side, in situ online tools such as Raman and infrared spectroscopy, flow cytometry with fluorescent labels, surface-enhanced Raman scattering (SERS), hyperspectral imaging, laser-induced breakdown spectroscopy (LIBS), and pyrolysis mass spectrometry enable real-time, field-deployable analysis across complex matrices such as wastewater, sludge, and sediment. Combining single-particle hyperspectral Raman imaging with nanoscale secondary ion mass spectrometry (NanoSIMS) extends resolution further to the cellular level, enabling contaminant tracking and heterogeneity analysis across particle populations.
Artificial intelligence (AI) and machine learning (ML) are integrating these advances into predictive risk frameworks. ML and deep learning (DL) automate particle identification and classification, and transfer learning (TL) bridges model biological data to human organ-specific toxicity prediction. Multidimensional ensemble models that integrate physicochemical properties, environmental aging, and co-pollutant interactions are advancing microplastic risk assessment from a single factor to a dynamic multifactor analysis.
conclusion
Microplastic pollution represents a pressing global environmental and public health concern, but gaps between laboratory conditions and real-world exposure scenarios continue to undermine the reliability of toxicological evidence. Quantitative human exposure data remain lacking, the health effects of chronic low-dose exposure and co-contaminants are poorly understood, and experimental approaches continue to diverge from environmental realities.
Importantly, current evidence does not establish a direct causal link between microplastics and specific human diseases. Bridging these gaps through standardized methods, environmentally realistic research designs, and integrated life cycle assessments is essential to support evidence-based policy and effective regulation.
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Reference magazines:
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Zang, Y. et al. (2026) The gap between laboratory experiments and real-world exposure: Toxicity assessment of microplastics is based on insufficient evidence. environment and health. Doi: https://doi.org/10.1021/envhealth.6c00030. https://pubs.acs.org/doi/10.1021/envhealth.6c00030
