Exploring the potential and challenges of developing physiologically-based toxicokinetic models to support human health risk assessment of microplastic and nanoplastic particles

Synergistic Toxicity of Combined Exposure to Acrylamide and Polystyrene Nanoplastics on the Gut-Liver Axis in Mice

Acrylamide (AA) and nanoplastics (NPs) are common food toxicants. However, their combined toxicity and health risks call for further studies. This study aimed to investigate the combined toxicity of AA and polystyrene NPs (PS-NPs) in mice through drinking water exposure. Co-exposure to AA and PS-NPs aggravated colon and liver damage, including more severe inflammatory infiltration, higher levels of colonic and hepatic pro-inflammatory cytokines, and elevated serum content of lipopolysaccharide and activities of diamine oxidase, alanine aminotransferase, and aspartate aminotransferase compared to single exposures. Co-exposure also significantly downregulated the expression of colonic tight-junction genes ZO-1 and Claudin-5. Metabolomics revealed that co-exposure induced more profound metabolic disorders in the liver, particularly affecting amino acid and carbohydrate metabolism. 16S amplicon sequencing showed that co-exposure caused more drastic gut microbiota dysbiosis, characterized by a decrease in beneficial bacteria (unclassified_f__Oscillospiraceae, Roseburia, UCG-005, Ruminiclostridium, unclassified_o__Clostridia_UCG-014, Fournierella, and Acetatifactor) and an increase in pathogenic bacteria (Eubacterium_xylanophilum_group and Eubacterium_nodatum_group). Correlation analysis indicated a negative correlation between beneficial bacteria and intestinal-liver toxicity indicators and a positive correlation between pathogenic bacteria and these indicators. Overall, our findings showed that AA and PS-NPs exerted synergistic toxicity to the gut-liver axis in mammals, highlighting the higher health risks of their combined ingestion.

Regional and population-scale trends in human inhalation exposure to airborne microplastics: Implications for health risk assessment

Growing evidence shows that breathing microplastics (MPs)-polluted air increases the risk of pulmonary health effects. However, a complete understanding of how inhaled MPs distribute within the human respiratory tract (HRT) remains insufficient. This study developed a physiologically-based kinetic HRT model to evaluate the deposition and clearance of MPs over time and at varying concentrations based on their aerodynamic diameter (AD). We quantified the contributions of AD-specific MPs to inhalation exposure trends using literature-based atmospheric MP pollution data from 2015 to 2022. Exposure assessments were conducted in data-rich settings, including megacities, urban-rural, and age-specific populations. Our analysis revealed that all suspended MPs had ADs less than 70 μm, with fragments, fibers, and spheres in decreasing order of prevalence. Modeling results demonstrated a pronounced variation (∼1010 magnitudes) in internal MP burdens across airway regions during long-term exposure. On average, inhaled MPs larger than 40 μm accumulated exclusively in extrathoracic and bronchi regions, whereas MPs with ADs of 0.1-5 μm were the primary contributors to internal burdens. We identified nasal airflow rate as the most sensitive factor influencing internal burdens of MPs larger than 1 μm. Furthermore, our findings showed that infants, children, and the elderly were more vulnerable to short-term exposure, whereas adolescents and adults were of greater concern with long-term exposure. These insights provide valuable guidance for policy decisions on targeting interventions to at-risk regions or susceptible populations.

Artificial intelligence: A key fulcrum for addressing complex environmental health issues

Environmental health (EH) is a complex and interdisciplinary field dedicated to the examination of environmental behaviours, toxicological effects, health risks, and strategies for mitigating harmful environmental factors. Traditional EH research investigates correlations between risk factors and health outcomes through control variables, but this route is difficult to address complex EH issue. Artificial intelligence (AI) technology not only has accelerated the innovation of the scientific research paradigm but also has become an important tool for solving complex EH problems. However, the in-depth and comprehensive implementation of AI in the field of EH still faces many barriers, such as model generalizability, data privacy protection, algorithm transparency, and regulatory and ethical issues. This review focuses on the compound exposures of EH and explores the potential, challenges, and development directions of AI in four key phases of EH research: (1) data collection, fusion, and management, (2) hazard identification and screening, (3) risk modeling and assessment and (4) EH management. It is not difficult to see that in the future, artificial intelligence technology will inevitably carry out multidimensional simulation of complex exposure factors through multi-mode data fusion, so as to achieve accurate identification of environmental health risks, and eventually become an efficient tool for global environmental health management. This review will help researchers re-examine this strategy and provide a reference for AI to solve complex exposure problems.

A physiologically based toxicokinetic model for microplastics and nanoplastics in mice after oral exposure and its implications for human dietary exposure assessment

Evidence of microplastics (MPs) and nanoplastics (NPs) in foods and daily-use products, along with their frequent detection in the human body, has raised concerns regarding their potential impact on human health through dietary ingestion. However, there is a lack of quantitative tools to simulate their bioaccumulation and tissue distribution following environmental exposure. To address this gap, we developed the first physiologically based toxicokinetic (PBTK) model for predicting the biodistribution of MPs and NPs in mice following oral exposure under various exposure scenarios. This novel model incorporated key kinetic mass transport processes, such as membrane permeability, albumin binding, and cellular uptake. We identified that the absorption rate in the gastrointestinal tract and fecal excretion rate constant had significant impacts on organ dosimetry. Our regression analysis indicated that the size-dependent dissociation constant and urine clearance rate constant sharply increased by a factor of 3 as NPs particle size increased to 1 µm. Finally, we developed a graphical user interface to enable interactive visualization and analysis for future applications, supporting human dietary exposure and risk assessment using available food consumption data and MPs/NPs residue data. The simulation results offer a mechanistic perspective, enhancing understanding of the internal organ dosimetry burden and health impacts from dietary exposure to MPs and NPs.

Contribution of Cancer-Specific Protein Coronas to the Pro-Tumor Effects of Nanoplastics through Enhanced Cellular Interactions

The potential impact of nanoplastics (NPs) on human carcinogenic processes is a matter of growing concern, particularly in light of the global plastic pollution crisis. Although the potential effects of NPs on human health have been well investigated, many uncertainties remain regarding their role in tumor behavior. Upon exposure, NPs can enter the bloodstream and are prone to interacting with plasma proteins to form a protein corona (PC), which can influence their interactions with cancer cells. However, how the PCs adsorbed on NPs affect the particle-to-tumor cell interaction and their effect on the tumor biological behavior remain unclear. To better understand the formation of PCs following NPs exposure in the bloodstream under various clinical conditions, we investigated the PC compositions of NPs derived from thyroid cancer (TC) patients and healthy volunteers. Our data revealed a significant enrichment of fibrinogen in the PCs formed on NPs derived from TC patient plasma, which in turn accelerated the endocytosis of NPs into TC cells. In addition, the uptake pathway of NPs into TC cells differed substantially between the two groups studied due to the different PC compositions in cancer patients and healthy individuals. Moreover, intriguingly alterations in the PCs induced by the clinical pathology status were also found to promote NPs engulfment by human macrophages, resulting in potent pro-inflammatory effects, in turn exerting pro-tumor effects. These findings emphasize the importance of considering the significance of a realistic biological identity on NPs and their interactions with cancer cells and also pinpoint the implications of the carcinogenesis outcomes of NPs exposure in humans.

Impacts of microplastics on ecosystem services and their microbial degradation: a systematic review of the recent state of the art and future prospects

Microplastics are tiny plastic particles with a usual diameter ranging from ~ 1 μ to 5 µm. Recently, microplastic pollution has raised the attention of the worldwide environmental and human concerns. In human beings, digestive system illness, respiratory system disorders, sleep disturbances, obesity, diabetes, and even cancer have been reported after microplastic exposure either through food, air, or skin. Similarly, microplastics are also having negative impacts on the plant health, soil microorganisms, aquatic lives, and other animals. Policies and initiatives have already been in the pipeline to address this problem to deal with microplastic pollution. However, many obstacles are also being observed such as lack of knowledge, lack of research, and also absence of regulatory frameworks. This article has covered the distribution of microplastics in water, soil, food and air. Application of multimodel strategies including fewer plastic item consumption, developing low-cost novel technologies using microorganisms, biofilm, and genetic modified microorganisms has been used to reduce microplastics from the environment. Researchers, academician, policy-makers, and environmentalists should work jointly to cope up with microplastic contamination and their effect on the ecosystem as a whole which can be reduced in the coming years and also to make earth clean.

Addressing the relevance of polystyrene nano- and microplastic particles used to support exposure, toxicity and risk assessment: implications and recommendations

BACKGROUND

There has been an exponential increase in the number of studies reporting on the toxicological effects associated with exposure to nano and microplastic particles (NMPs). The majority of these studies, however, have used monodispersed polystyrene microspheres (PSMs) as 'model' particles. Here we review the differences between the manufacture and resulting physicochemical properties of polystyrene used in commerce and the PSMs most commonly used in toxicity studies.

MAIN BODY

In general, we demonstrate that significant complexity exists as to the properties of polystyrene particles. Differences in chemical composition, size, shape, surface functionalities and other aspects raise doubt as to whether PSMs are fit-for-purpose for the study of potential adverse effects of naturally occurring NMPs. A realistic assessment of potential health implications of the exposure to environmental NMPs requires better characterisation of the particles, a robust mechanistic understanding of their interactions and effects in biological systems as well as standardised protocols to generate relevant model particles. It is proposed that multidisciplinary engagement is necessary for the development of a timely and effective strategy towards this end. We suggest a holistic framework, which must be supported by a multidisciplinary group of experts to work towards either providing access to a suite of environmentally relevant NMPs and/or developing guidance with respect to best practices that can be adopted by research groups to generate and reliably use NMPs. It is emphasized that there is a need for this group to agree to a consensus regarding what might best represent a model NMP that is consistent with environmental exposure for human health, and which can be used to support a variety of ongoing research needs, including those associated with exposure and hazard assessment, mechanistic toxicity studies, toxicokinetics and guidance regarding the prioritization of plastic and NMPs that likely represent the greatest risk to human health. It is important to acknowledge, however, that establishing a multidisciplinary group, or an expert community of practice, represents a non-trivial recommendation, and will require significant resources in terms of expertise and funding.

CONCLUSION

There is currently an opportunity to bring together a multidisciplinary group of experts, including polymer chemists, material scientists, mechanical engineers, exposure and life-cycle assessment scientists, toxicologists, microbiologists and analytical chemists, to provide leadership and guidance regarding a consensus on defining what best represents environmentally relevant NMPs. We suggest that given the various complex issues surrounding the environmental and human health implications that exposure to NMPs represents, that a multidisciplinary group of experts are thus critical towards helping to progress the harmonization and standardization of methods.