Combined effects of nanoparticles and other environmental contaminants on human health - an issue often overlooked

Effects of Mixtures of Engineered Nanoparticles and Cocontaminants on Anaerobic Digestion

The widespread application of nanotechnology inevitably leads to an increased release of engineered nanoparticles (ENPs) into the environment. Due to their specific physicochemical properties, ENPs may interact with other contaminants and exert combined effects on the microbial community and metabolism of anaerobic digestion (AD), an important process for organic waste reduction, stabilization, and bioenergy recovery. However, the complicated interactions between ENPs and other contaminants as well as their combined effects on AD are often overlooked. This review therefore focuses on the co-occurrence of ENPs and cocontaminants in the AD process. The key interactions between ENPs and cocontaminants and their combined influences on AD are summarized from the available literature, including the critical mechanisms and influencing factors. Some sulfides, coagulants, and chelating agents have a dramatic "detoxification" effect on the inhibition effect of ENPs on AD. However, some antibiotics and surfactants increase the inhibition of ENPs on AD. The reasons for these differences may be related to the interactive effects between ENPs and cocontaminants, changes of key enzyme activities, adenosine triphosphate (ATP) levels, reactive oxygen species (ROS) production, and microbial communities. New scientific opportunities for a better understanding of the coexistence in real world situations are converging on the scale of nanoparticles.

An integrated approach to occupational health risk assessment of manufacturing nanomaterials using Pythagorean Fuzzy AHP and Fuzzy Inference System

Nanomaterials (NMs) have the potential to be hazardous owing to their unique physico-chemical properties. Therefore, the need for Health Risk Assessment (HRA) of NMs is expanding. In this study, a novel HRA was developed by the Pythagorean Fuzzy Health Risk Assessment (PFHRA) approach. Risk is considered to be the outcome of parameters including Occurrence Likelihood (OL), Potential Exposure (PE) and Toxic Effects (TE). In our proposed method, priority weights of sub-factors in Pythagorean Fuzzy-Analytical Hierarchical Process (PF-AHP) were determined by pairwise comparison based on expert judgment. After determining parameter scores, both RM and risk class (i.e., negligible, minor, major and critical) were reported as Fuzzy Inference System (FIS) output. Ultimately, a risk management strategy is presented for NMs manufacturing workplaces. This proposed method provides experts with more flexibility to express their opinions. The PFHRA approach was applied for two scenarios. The production scenario for SiNPs can create minor (5%) and major (95%) occupational health risks; the production scenario for ZnONPs can create minor (100%) concerns. However, the production SiNPs and ZnONPs utilizing the CB Nanotool technique had a major and minor risk class, respectively. The results of the present study confirmed the reliability and applicability of this approach.

Application of a novel exposure limit approach for co-exposure of ‎chemicals: a field study by in-vitro design

This study has suggested an occupational exposure limit (OEL) based on the co-exposure approach in an iron-foundry industry. Respirable dust was collected in an iron casting industry using the NIOSH 0600 method. The DNA damage was obtained by comet assay. The lower confidence interval of the benchmark dose (BMDL) was employed for exposure limit evaluation. The estimated BMDL of the cell line was extrapolated to human subjects. Based on the Hill model, a BMDL 1.65 µg for chemical mixture has been estimated for the A549 cell line. According to uncertainty factors, permitted daily exposure (PDE) was predicted in humans. However, PDE of 3.9 μg/m3 was specified as the time-weighted average limit for toxic respirable dust in the casting industry. In this study, OEL for active respirable dust in the casting industry has been proposed. The industry-based standard for active respirable dust has been proposed for better management of co-exposure.

Can the impact of micro- and nanoplastics on human health really be assessed using in vitro models? A review of methodological issues

Because of the many advantages they offer (strength, low cost, durability, lightweight, resistance, etc.), plastics are integral part of our daily life with a production constantly rising. However, their waste management is still inadequate, resulting in their release and accumulation in the environment, representing a main source of pollution. Their degradation results in debris of variable size including microplastics (0.1 μm-5 mm) and even nanoplastics (<0.1 μm), whose potential impact on ecosystems and human health have raised concerns. The potential adverse effects they may cause have been evaluated using both in vitro and in vivo models. However, due to some specific characteristics of micro- and nanoplastics, there are challenging questions about whether conventional in vitro tests are appropriate for evaluating their toxicity. For example, low-density plastics float on the surface of the culture medium and cannot come into contact with cells adhering to the bottom of the culture plates, which prevents proper evaluation of potential adverse effects and leads to misinterpretation of toxicological assays. In this review, we discuss the main issues related to the evaluation of micro- and nanoplastics toxicity using conventional in vitro assays. A literature survey has allowed to propose some solutions to circumvent these issues including the use of mathematical models to accurately determine the dose of particles delivered to cells, advanced 3D models (organoids), inverted cell culture models, cell cultures at the air-liquid interface or under dynamic conditions. Finally, we propose some perspectives and recommendations for further research on the in vitro evaluation of micro- and nanoplastics toxicity, underlining the importance of using standardized protocols for comparison purposes and samples and experimental conditions more representative of real-life exposure.

Research Progress of a Pesticide Polymer-Controlled Release System Based on Polysaccharides

In recent years, with the development of the nanomaterials discipline, many new pesticide drug-carrying systems-such as pesticide nano-metal particles, nano-metal oxides, and other drug-carrying materials-had been developed and applied to pesticide formulations. Although these new drug-loading systems are relatively friendly to the environment, the direct exposure of many metal nanoparticles to the environment will inevitably lead to potential effects. In response to these problems, organic nanomaterials have been rapidly developed due to their high-quality biodegradation and biocompatibility. Most of these organic nanomaterials were mainly polysaccharide materials, such as chitosan, carboxymethyl chitosan, sodium alginate, β-cyclodextrin, cellulose, starch, guar gum, etc. Some of these materials could be used to carry inorganic materials to develop a temperature- or pH-sensitive pesticide drug delivery system. Herein, the pesticide drug-carrying system developed based on polysaccharide materials, such as chitosan, was referred to as the pesticide polymer drug-carrying system based on polysaccharide materials. This kind of drug-loading system could be used to protect the pesticide molecules from harsh environments, such as pH, light, temperature, etc., and was used to develop the function of a sustained release, targeted release of pesticides in the intestine of insects, and achieve the goal of precise application, reduction, and efficiency of pesticides. In this review, the recent progress in the field of polysaccharide-based polymer drug delivery systems for pesticides has been discussed, and suggestions for future development were proposed based on the current situation.

Complementary Analysis for Undetectable Microplastics from Contact Lenses to Aquatic Environments via Fourier Transform Infrared Spectroscopy

Although microplastics (MPs) are intrinsically toxic and function as vectors for organic micropollutants, their discharge from wastewater treatment plant effluents and human activity remains unknown owing to the limitations of detection and treatment technologies. It is imperative to quantify MPs from human activities involving the consumption of various plastic products. This study warns that contact lenses can generate MPs and nanoplastics (NPs) after being discharged into aquatic environments. Identification via micro-Fourier transform infrared spectroscopy revealed that the fragmented particles (from a few tens to a few hundred micrometres) could not be detected as poly(2-hydroxyl methacrylate), the component of contact lenses, owing to changes in its chemical properties. After the degradation process, the median size of the contact lens particles decreased from 313 to 85 µm. Approximately 300,600 g of contact lens waste is discharged into sewage systems daily in the United States of America (USA), where 45 million people wear contact lenses and throw away one-fifth of them every day. Contact lens waste (1 g) has the potential to release 5653.3-17,773.3 particles of MPs. This implies that the currently reported MP amounts in the environmental matrix exclude significant amounts of MPs and NPs from discharged contact lenses. The identification method should be examined, and a registration of the disposal process should be established.

Chemical speciation determines combined cytotoxicity: Examples of biochar and arsenic/chromium

As both electron donors and acceptors, biochars (BCs) may interact with multivalent metal ions in the environment, causing changes in ionic valence states and resulting in unknown combined toxicity. Therefore, we systematically investigated the interaction between BCs and Cr (Cr(III) & Cr(VI)) or As (As(III) & As(V)) and their combined cytotoxicity in human colorectal mucosal (FHC) cells. Our results suggest that the redox-induced valence state change is a critical factor in the combined cytotoxicity of BCs with Cr/As. Specifically, when Cr(VI) was adsorbed on BCs, 86.4 % of Cr(VI) was reduced to Cr(III). In contrast, As(III) was partially oxidized to As(V) with a ratio of 37.2 %, thus reaching a reaction equilibrium. Meanwhile, only As(V) was released in the cell, which could cause more As(III) to be oxidized. As both Cr(III) and As(V) are less toxic than their corresponding counterparts Cr(VI) and As(III), different redox interactions between BCs and Cr/As and release profiles between BCs and Cr/As together lead to reduced combined cytotoxicity of BP-BC-Cr(VI) and BP-BC-As(III). It suggests that the valence state changes of metal ions due to redox effects is one of the parameters to be focused on when studying the combined toxicity of complexes of BCs with different heavy metal ions.

Nanomaterial Ecotoxicology in the Terrestrial and Aquatic Environment: A Systematic Review

This systematic review analyzes the studies available on the ecotoxicity of nanomaterials (NMs) in the environment to understand where future research should be addressed for achieving Agenda 2030 goals on sustainable development and environmental safety. We discuss the status of NMs ecotoxicological effects across different organisms that are representative of all natural environments (land, air, water). A total of 1562 publications were retrieved from the Web of Science (all databases) by using the search criteria “nanomaterials” and “ecotoxicology”; among them, 303 studies were included in the systematic review because they met any of the following criteria: (i) focalize on both search criteria; (ii) deal with terrestrial, or aquatic environment; (iii) address models (organisms, cells) for the nano environmental risk assessment and exposure. The knowledge gaps are identified together with novel insights that need to be further investigated to better understand the ecotoxicological environmental impacts of NMs.

Establishment of Repeated In Vitro Exposure System for Evaluating Pulmonary Toxicity of Representative Criteria Air Pollutants Using Advanced Bronchial Mucosa Models

There is mounting evidence that shows the association between chronic exposure to air pollutants (particulate matter and gaseous) and onset of various respiratory impairments. However, the corresponding toxicological mechanisms of mixed exposure are poorly understood. Therefore, in this study, we aimed to establish a repeated exposure setting for evaluating the pulmonary toxicological effects of diesel exhaust particles (DEP), nitrogen dioxide (NO2), and sulfur dioxide (SO2) as representative criterial air pollutants. Single, combined (DEP with NO2 and SO2), and repeated exposures were performed using physiologically relevant human bronchial mucosa models developed at the air−liquid interface (bro-ALI). The bro-ALI models were generated using human primary bronchial epithelial cells (3−4 donors; 2 replicates per donor). The exposure regime included the following: 1. DEP (12.5 µg/cm2; 3 min/day, 3 days); 2. low gaseous (NO2: 0.1 ppm + SO2: 0.2 ppm); (30 min/day, 3 days); 3. high gaseous (NO2: 0.2 ppm + SO2: 0.4 ppm) (30 min/day, 3 days); and 4. single combined (DEP + low gaseous for 1 day). The markers for pro-inflammatory (IL8, IL6, NFKB, TNF), oxidative stress (HMOX1, GSTA1, SOD3,) and tissue injury/repair (MMP9, TIMP1) responses were assessed at transcriptional and/ or secreted protein levels following exposure. The corresponding sham-exposed samples under identical conditions served as the control. A non-parametric statistical analysis was performed and p < 0.05 was considered as significant. Repeated exposure to DEP and single combined (DEP + low gaseous) exposure showed significant alteration in the pro-inflammatory, oxidative stress and tissue injury responses compared to repeated exposures to gaseous air pollutants. The study demonstrates that it is feasible to predict the long-term effects of air pollutants using the above explained exposure system.

Experimental and Computational Nanotoxicology-Complementary Approaches for Nanomaterial Hazard Assessment

The growing development and applications of nanomaterials lead to an increasing release of these materials in the environment. The adverse effects they may elicit on ecosystems or human health are not always fully characterized. Such potential toxicity must be carefully assessed with the underlying mechanisms elucidated. To that purpose, different approaches can be used. First, experimental toxicology consisting of conducting in vitro or in vivo experiments (including clinical studies) can be used to evaluate the nanomaterial hazard. It can rely on variable models (more or less complex), allowing the investigation of different biological endpoints. The respective advantages and limitations of in vitro and in vivo models are discussed as well as some issues associated with experimental nanotoxicology. Perspectives of future developments in the field are also proposed. Second, computational nanotoxicology, i.e., in silico approaches, can be used to predict nanomaterial toxicity. In this context, we describe the general principles, advantages, and limitations especially of quantitative structure–activity relationship (QSAR) models and grouping/read-across approaches. The aim of this review is to provide an overview of these different approaches based on examples and highlight their complementarity.

Revisiting Total Particle Number Measurements for Vehicle Exhaust Regulations

Road transport significantly contributes to air pollution in cities. Emission regulations have led to significantly reduced emissions in modern vehicles. Particle emissions are controlled by a particulate matter (PM) mass and a solid particle number (SPN) limit. There are concerns that the SPN limit does not effectively control all relevant particulate species and there are instances of semi-volatile particle emissions that are order of magnitudes higher than the SPN emission levels. This overview discusses whether a new metric (total particles, i.e., solids and volatiles) should be introduced for the effective regulation of vehicle emissions. Initially, it summarizes recent findings on the contribution of road transport to particle number concentration levels in cities. Then, both solid and total particle emission levels from modern vehicles are presented and the adverse health effects of solid and volatile particles are briefly discussed. Finally, the open issues regarding an appropriate methodology (sampling and instrumentation) in order to achieve representative and reproducible results are summarized. The main finding of this overview is that, even though total particle sampling and quantification is feasible, details for its realization in a regulatory context are lacking. It is important to define the methodology details (sampling and dilution, measurement instrumentation, relevant sizes, etc.) and conduct inter-laboratory exercises to determine the reproducibility of a proposed method. It is also necessary to monitor the vehicle emissions according to the new method to understand current and possible future levels. With better understanding of the instances of formation of nucleation mode particles it will be possible to identify its culprits (e.g., fuel, lubricant, combustion, or aftertreatment operation). Then the appropriate solutions can be enforced and the right decisions can be taken on the need for new regulatory initiatives, for example the addition of total particles in the tailpipe, decrease of specific organic precursors, better control of inorganic precursors (e.g., NH3, SOx), or revision of fuel and lubricant specifications.

Oxidized carbon black nanoparticles induce endothelial damage through C-X-C chemokine receptor 3-mediated pathway

Oxidation of engineered nanomaterials during application in various industrial sectors can alter their toxicity. Oxidized nanomaterials also have widespread industrial and biomedical applications. In this study, we evaluated the cardiopulmonary hazard posed by these nanomaterials using oxidized carbon black (CB) nanoparticles (CBox) as a model particle. Particle surface chemistry was characterized by X-ray photo electron spectroscopy (XPS) and Fourier-transform infrared spectroscopy (FTIR). Colloidal characterization and in vitro dosimetry modeling (particle kinetics, fate and transport modeling) were performed. Lung inflammation was assessed following oropharyngeal aspiration of CB or oxidized CBox particles (20 μg per mouse) in C57BL/6J mice. Toxicity and functional assays were also performed on murine macrophage (RAW 264.7) and endothelial cell lines (C166) with and without pharmacological inhibitors. Oxidant generation was assessed by electron paramagnetic resonance spectroscopy (EPR) and via flow cytometry. Endothelial toxicity was evaluated by quantifying pro-inflammatory mRNA expression, monolayer permeability, and wound closure. XPS and FTIR spectra indicated surface modifications, the appearance of new functionalities, and greater oxidative potential (both acellular and in vitro) of CBox particles. Treatment with CBox demonstrated greater in vivo inflammatory potentials (lavage neutrophil counts, secreted cytokine, and lung tissue mRNA expression) and air-blood barrier disruption (lavage proteins). Oxidant-dependent pro-inflammatory signaling in macrophages led to the production of CXCR3 ligands (CXCL9,10,11). Conditioned medium from CBox-treated macrophages induced significant elevation in endothelial cell pro-inflammatory mRNA expression, enhanced monolayer permeability and impairment of scratch healing in CXCR3 dependent manner. In summary, this study mechanistically demonstrated an increased biological potency of CBox particles and established the role of macrophage-released chemical mediators in endothelial damage.