Inhalable Textile Microplastic Fibers Impair Airway Epithelial Differentiation.

Rationale: Microplastics are a pressing global concern, and inhalation of microplastic fibers has been associated with interstitial and bronchial inflammation in flock workers. However, how microplastic fibers affect the lungs is unknown. Objectives: Our aim was to assess the effects of 12 × 31 µm nylon 6,6 (nylon) and 15 × 52 µm polyethylene terephthalate (polyester) textile microplastic fibers on lung epithelial growth and differentiation. Methods: We used human and murine alveolar and airway-type organoids as well as air-liquid interface cultures derived from primary lung epithelial progenitor cells and incubated these with either nylon or polyester fibers or nylon leachate. In addition, mice received one dose of nylon fibers or nylon leachate, and, 7 days later, organoid-forming capacity of isolated epithelial cells was investigated. Measurements and Main Results: We observed that nylon microfibers, more than polyester, inhibited developing airway organoids and not established ones. This effect was mediated by components leaching from nylon. Epithelial cells isolated from mice exposed to nylon fibers or leachate also formed fewer airway organoids, suggesting long-lasting effects of nylon components on epithelial cells. Part of these effects was recapitulated in human air-liquid interface cultures. Transcriptomic analysis revealed upregulation of Hoxa5 after exposure to nylon fibers. Inhibiting Hoxa5 during nylon exposure restored airway organoid formation, confirming Hoxa5's pivotal role in the effects of nylon. Conclusions: These results suggest that components leaching from nylon 6,6 may especially harm developing airways and/or airways undergoing repair, and we strongly encourage characterization in more detail of both the hazard of and the exposure to microplastic fibers.

Air pollution exposure during pregnancy and childhood and brain morphology in preadolescents.

BACKGROUND: Studies investigating the relationship between exposure to air pollution and brain development using magnetic resonance images are emerging. However, most studies have focused only on prenatal exposures, and have included a limited selection of pollutants. Here, we aim to expand the current knowledge by studying pregnancy and childhood exposure to a wide selection of pollutants, and brain morphology in preadolescents. METHODS: We used data from 3133 preadolescents from a birth cohort from Rotterdam, the Netherlands (enrollment: 2002-2006). Concentrations of nitrogen oxides, coarse, fine, and ultrafine particles, and composition of fine particles were estimated for participant's home addresses in pregnancy and childhood, using land use regression models. Structural brain images were obtained at age 9-12 years. We assessed the relationships of air pollution exposure, with brain volumes, and surface-based morphometric data, adjusting for socioeconomic and life-style characteristics, using single as well as multi-pollutant approach. RESULTS: No associations were observed between air pollution exposures and global volumes of total brain, and cortical and subcortical grey matter. However, we found associations between higher pregnancy and childhood air pollution exposures with smaller corpus callosum, smaller hippocampus, larger amygdala, smaller nucleus accumbens, and larger cerebellum (e.g. -69.2mm3 hippocampal volume [95%CI -129.1 to -9.3] per 1ng/m3 increase in pregnancy exposure to polycyclic aromatic hydrocarbons). Higher pregnancy exposure to air pollution was associated with smaller cortical thickness while higher childhood exposure was associated with predominantly larger cortical surface area. CONCLUSION: Higher pregnancy or childhood exposure to several air pollutants was associated with altered volume of several brain structures, as well as with cortical thickness and surface area. Associations showed some similarity to delayed maturation and effects of early-life stress.

Chemistry, lung toxicity and mutagenicity of burn pit smoke-related particulate matter.

BACKGROUND: Open burning of anthropogenic sources can release hazardous emissions and has been associated with increased prevalence of cardiopulmonary health outcomes. Exposure to smoke emitted from burn pits in military bases has been linked with respiratory illness among military and civilian personnel returning from war zones. Although the composition of the materials being burned is well studied, the resulting chemistry and potential toxicity of the emissions are not. METHODS: Smoke emission condensates from either flaming or smoldering combustion of five different types of burn pit-related waste: cardboard; plywood; plastic; mixture; and mixture/diesel, were obtained from a laboratory-scale furnace coupled to a multistage cryotrap system. The primary emissions and smoke condensates were analyzed for a standardized suite of chemical species, and the condensates were studied for pulmonary toxicity in female CD-1 mice and mutagenic activity in Salmonella (Ames) mutagenicity assay using the frameshift strain TA98 and the base-substitution strain TA100 with and without metabolic activation (S9 from rat liver). RESULTS: Most of the particles in the smoke emitted from flaming and smoldering combustion were less than 2.5 µm in diameter. Burning of plastic containing wastes (plastic, mixture, or mixture/diesel) emitted larger amounts of particulate matter (PM) compared to other types of waste. On an equal mass basis, the smoke PM from flaming combustion of plastic containing wastes caused more inflammation and lung injury and was more mutagenic than other samples, and the biological responses were associated with elevated polycyclic aromatic hydrocarbon levels. CONCLUSIONS: This study suggests that adverse health effects of burn pit smoke exposure vary depending on waste type and combustion temperature; however, burning plastic at high temperature was the most significant contributor to the toxicity outcomes. These findings will provide a better understanding of the complex chemical and combustion temperature factors that determine toxicity of burn pit smoke and its potential health risks at military bases.

Mechanistic Similarities between 3D Human Bronchial Epithelium and Mice Lung, Exposed to Copper Oxide Nanoparticles, Support Non-Animal Methods for Hazard Assessment.

The diversity and increasing prevalence of products derived from engineered nanomaterials (ENM), warrants implementation of non-animal approaches to health hazard assessment for ethical and practical reasons. Although non-animal approaches are becoming increasingly popular, there are almost no studies of side-by-side comparisons with traditional in vivo assays. Here, transcriptomics is used to investigate mechanistic similarities between healthy/asthmatic models of 3D air-liquid interface (ALI) cultures of donor-derived human bronchial epithelia cells, and mouse lung tissue, following exposure to copper oxide ENM. Only 19% of mouse lung genes with human orthologues are not expressed in the human 3D ALI model. Despite differences in taxonomy and cellular complexity between the systems, a core subset of matching genes cluster mouse and human samples strictly based on ENM dose (exposure severity). Overlapping gene orthologue pairs are highly enriched for innate immune functions, suggesting an important and maybe underestimated role of epithelial cells. In conclusion, 3D ALI models based on epithelial cells, are primed to bridge the gap between traditional 2D in vitro assays and animal models of airway exposure, and transcriptomics appears to be a unifying dose metric that links in vivo and in vitro test systems.

A practical approach to assess inhalation toxicity of metal oxide nanoparticles in vitro.

Exposure of humans to metal oxide nanoparticles (NPs) occurs mainly via air, and inhaled metal oxide NPs may generate inflammation. The aim of this study was to investigate the proinflammatory potential of six metal oxide NPs (CeO2 , Mn2 O3 , CuO, ZnO, Co3 O4 and WO3 ; 27-108 µg ml-1 ) using human primary 3-dimensional airway epithelium (MucilAir™) and dendritic cell (DC) models. Metal oxide NPs were mainly aggregated/agglomerated in the cell media, as determined by dynamic light scattering, scanning electron microscopy and differential centrifugal sedimentation. WO3 and ZnO were highly soluble, both with and without respiratory mucus. Proinflammatory signalling by the epithelium was evaluated after a 24 hour exposure by increased interleukin-6 and -8 and monocyte chemoattractant protein 1 cytokine release, which occurred only for CuO. Moreover, maturation of immature human DCs, which play a key role in the lung immune system, were evaluated by expression of surface markers HLA-DR, CD80, CD83 and CD86 after a 48 hour exposure. Only Mn2 O3 consistently upregulated DC maturation markers. Furthermore, by addition of medium from metal oxide NP-exposed 3-dimensional airway cultures to metal oxide NP-exposed DC cultures, the interplay between lung epithelium and DCs was studied. Such an interplay was again only observed for Mn2 O3 and in one of five DC donors. Our results show that, even when using dosages that represent very high in vivo exposure levels, up to 27 hours of constant human airway exposure, metal oxide NPs cause minimal proinflammatory effects and that epithelial cells not necessarily interfere with DC maturation upon metal oxide NP exposure. The present approach exemplifies a relevant translation towards human safety assessment.

Outdoor air pollution and risk for kidney parenchyma cancer in 14 European cohorts.

Several studies have indicated weakly increased risk for kidney cancer among occupational groups exposed to gasoline vapors, engine exhaust, polycyclic aromatic hydrocarbons and other air pollutants, although not consistently. It was the aim to investigate possible associations between outdoor air pollution at the residence and the incidence of kidney parenchyma cancer in the general population. We used data from 14 European cohorts from the ESCAPE study. We geocoded and assessed air pollution concentrations at baseline addresses by land-use regression models for particulate matter (PM10 , PM2.5 , PMcoarse , PM2.5 absorbance (soot)) and nitrogen oxides (NO2 , NOx ), and collected data on traffic. We used Cox regression models with adjustment for potential confounders for cohort-specific analyses and random effects models for meta-analyses to calculate summary hazard ratios (HRs). The 289,002 cohort members contributed 4,111,908 person-years at risk. During follow-up (mean 14.2 years) 697 incident cancers of the kidney parenchyma were diagnosed. The meta-analyses showed higher HRs in association with higher PM concentration, e.g. HR = 1.57 (95%CI: 0.81-3.01) per 5 µg/m3 PM2.5 and HR = 1.36 (95%CI: 0.84-2.19) per 10-5 m-1 PM2.5 absorbance, albeit never statistically significant. The HRs in association with nitrogen oxides and traffic density on the nearest street were slightly above one. Sensitivity analyses among participants who did not change residence during follow-up showed stronger associations, but none were statistically significant. Our study provides suggestive evidence that exposure to outdoor PM at the residence may be associated with higher risk for kidney parenchyma cancer; the results should be interpreted cautiously as associations may be due to chance.

Diesel exhaust alters the response of cultured primary bronchial epithelial cells from patients with chronic obstructive pulmonary disease (COPD) to non-typeable Haemophilus influenzae.

BACKGROUND: Exacerbations constitute a major cause of morbidity and mortality in patients suffering from chronic obstructive pulmonary disease (COPD). Both bacterial infections, such as those with non-typeable Haemophilus influenzae (NTHi), and exposures to diesel engine emissions are known to contribute to exacerbations in COPD patients. However, the effect of diesel exhaust (DE) exposure on the epithelial response to microbial stimulation is incompletely understood, and possible differences in the response to DE of epithelial cells from COPD patients and controls have not been studied. METHODS: Primary bronchial epithelial cells (PBEC) were obtained from age-matched COPD patients (n = 7) and controls (n = 5). PBEC were cultured at the air-liquid interface (ALI) to achieve mucociliary differentiation. ALI-PBECs were apically exposed for 1 h to a stream of freshly generated whole DE or air. Exposure was followed by 3 h incubation in presence or absence of UV-inactivated NTHi before analysis of epithelial gene expression. RESULTS: DE alone induced an increase in markers of oxidative stress (HMOX1, 50-100-fold) and of the integrated stress response (CHOP, 1.5-2-fold and GADD34, 1.5-fold) in cells from both COPD patients and controls. Exposure of COPD cultures to DE followed by NTHi caused an additive increase in GADD34 expression (up to 3-fold). Importantly, DE caused an inhibition of the NTHi-induced expression of the antimicrobial peptide S100A7, and of the chaperone protein HSP5A/BiP. CONCLUSIONS: Our findings show that DE exposure of differentiated primary airway epithelial cells causes activation of the gene expression of HMOX1 and markers of integrated stress response to a similar extent in cells from COPD donors and controls. Furthermore, DE further increased the NTHi-induced expression of GADD34, indicating a possible enhancement of the integrated stress response. DE reduced the NTHi-induced expression of S100A7. These data suggest that DE exposure may cause adverse health effects in part by decreasing host defense against infection and by modulating stress responses.

Cellular response of mucociliary differentiated primary bronchial epithelial cells to diesel exhaust.

Diesel emissions are the main source of air pollution in urban areas, and diesel exposure is linked with substantial adverse health effects. In vitro diesel exposure models are considered a suitable tool for understanding these effects. Here we aimed to use a controlled in vitro exposure system to whole diesel exhaust to study the effect of whole diesel exhaust concentration and exposure duration on mucociliary differentiated human primary bronchial epithelial cells (PBEC). PBEC cultured at the air-liquid interface were exposed for 60 to 375 min to three different dilutions of diesel exhaust (DE). The DE mixture was generated by an engine at 47% load, and characterized for particulate matter size and distribution and chemical and gas composition. Cytotoxicity and epithelial barrier function was assessed, as well as mRNA expression and protein release analysis. DE caused a significant dose-dependent increase in expression of oxidative stress markers (HMOX1 and NQO1; n = 4) at 6 h after 150 min exposure. Furthermore, DE significantly increased the expression of the markers of the integrated stress response CHOP and GADD34 and of the proinflammatory chemokine CXCL8, as well as release of CXCL8 protein. Cytotoxic effects or effects on epithelial barrier function were observed only after prolonged exposures to the highest DE dose. These results demonstrate the suitability of our model and that exposure dose and duration and time of analysis postexposure are main determinants for the effects of DE on differentiated primary human airway epithelial cells.

Long-term Exposure to Particulate Matter Constituents and the Incidence of Coronary Events in 11 European Cohorts.

BACKGROUND: Long-term exposure to particulate matter (PM) has been associated with increased cardiovascular morbidity and mortality but little is known about the role of the chemical composition of PM. This study examined the association of residential long-term exposure to PM components with incident coronary events. METHODS: Eleven cohorts from Finland, Sweden, Denmark, Germany, and Italy participated in this analysis. 5,157 incident coronary events were identified within 100,166 persons followed on average for 11.5 years. Long-term residential concentrations of PM < 10 µm (PM10), PM < 2.5 µm (PM2.5), and a priori selected constituents (copper, iron, nickel, potassium, silicon, sulfur, vanadium, and zinc) were estimated with land-use regression models. We used Cox proportional hazard models adjusted for a common set of confounders to estimate cohort-specific component effects with and without including PM mass, and random effects meta-analyses to pool cohort-specific results. RESULTS: A 100 ng/m³ increase in PM10 K and a 50 ng/m³ increase in PM2.5 K were associated with a 6% (hazard ratio and 95% confidence interval: 1.06 [1.01, 1.12]) and 18% (1.18 [1.06, 1.32]) increase in coronary events. Estimates for PM10 Si and PM2.5 Fe were also elevated. All other PM constituents indicated a positive association with coronary events. When additionally adjusting for PM mass, the estimates decreased except for K. CONCLUSIONS: This multicenter study of 11 European cohorts pointed to an association between long-term exposure to PM constituents and coronary events, especially for indicators of road dust.

Generation and characterization of diesel engine combustion emissions from petroleum diesel and soybean biodiesel fuels and application for inhalation exposure studies.

Biodiesel made from the transesterification of plant- and animal-derived oils is an important alternative fuel source for diesel engines. Although numerous studies have reported health effects associated with petroleum diesel emissions, information on biodiesel emissions are more limited. To this end, a program at the U.S. EPA assessed health effects of biodiesel emissions in rodent inhalation models. Commercially obtained soybean biodiesel (B100) and a 20% blend with petroleum diesel (B20) were compared to pure petroleum diesel (B0). Rats and mice were exposed independently for 4 h/day, 5 days/week for up to 6 weeks. Exposures were controlled by dilution air to obtain low (50 µg/m(3)), medium (150 µg/m(3)) and high (500 µg/m(3)) diesel particulate mass (PM) concentrations, and compared to filtered air. This article provides details on facilities, fuels, operating conditions, emission factors and physico-chemical characteristics of the emissions used for inhalation exposures and in vitro studies. Initial engine exhaust PM concentrations for the B100 fuel (19.7 ± 0.7 mg/m(3)) were 30% lower than those of the B0 fuel (28.0 ± 1.5 mg/m(3)). When emissions were diluted with air to control equivalent PM mass concentrations, B0 exposures had higher CO and slightly lower NO concentrations than B100. Organic/elemental carbon ratios and oxygenated methyl esters and organic acids were higher for the B100 than B0. Both the B0 and B100 fuels produced unimodal-accumulation mode particle-size distributions, with B0 producing lower concentrations of slightly larger particles. Subsequent papers in this series will describe the effects of these atmospheres on cardiopulmonary responses and in vitro genotoxicity studies.

Health effects of soy-biodiesel emissions: bioassay-directed fractionation for mutagenicity.

CONTEXT: Soy biodiesel is the predominant biodiesel in the USA, but there is little understanding of the classes of chemicals responsible for the mutagenicity of its emissions. OBJECTIVE: We determined some of the chemical classes responsible for the mutagenicity of the particulate matter (PM) of the emissions from petroleum diesel (B0) and biodiesel containing increasing concentrations of soy methyl esters (B20, B50, and B100). MATERIALS AND METHODS: We subjected organic extracts of the PM to bioassay-directed fractionation by sequential elution on silica gel with solvents of increasing polarity to produce four fractions per fuel. We injected these onto high performance liquid chromatography to produce 62 sub-fractions per fraction based on chemical polarity and evaluated all fractions and sub-fractions for mutagenicity in Salmonella. We correlated the results with the concentrations of 32 polycyclic aromatic hydrocarbons (PAHs) in the fractions. RESULTS: The mutagenicity-emission factors of the fractions generally decreased with increasing concentrations of soy in the fuel. Despite the different chemical compositions of the fuels, the extractable organics of all four emissions had similar features: ∼60% of the mass was nonpolar, non-mutagenic compounds; most of the PAHs were polar; and most of the mutagenicity was due to weakly polar and polar compounds. Some of the mutagenicity of B20 was due to highly polar compounds. CONCLUSIONS: The PM from soy biodiesel emissions was less mutagenic than that from petroleum diesel, and this reduction was associated with reduced concentrations of various weakly polar, polar, and highly polar mutagens, including PAHs, aromatic amines, nitroarenes, and oxy-PAHs.

Health effects of soy-biodiesel emissions: mutagenicity-emission factors.

CONTEXT: Soy biodiesel is the predominant biodiesel fuel used in the USA, but only a few, frequently conflicting studies have examined the potential health effects of its emissions. OBJECTIVE: We combusted petroleum diesel (B0) and fuels with increasing percentages of soy methyl esters (B20, B50 and B100) and determined the mutagenicity-emission factors expressed as revertants/megajoule of thermal energy consumed (rev/MJ(th)). MATERIALS AND METHODS: We combusted each fuel in replicate in a small (4.3-kW) diesel engine without emission controls at a constant load, extracted organics from the particles with dichloromethane, determined the percentage of extractable organic material (EOM), and evaluated these extracts for mutagenicity in 16 strains/S9 combinations of Salmonella. RESULTS: Mutagenic potencies of the EOM did not differ significantly between replicate experiments for B0 and B100 but did for B20 and B50. B0 had the highest rev/MJ(th), and those of B20 and B100 were 50% and ∼85% lower, respectively, in strains that detect mutagenicity due to polycyclic aromatic hydrocarbons (PAHs), nitroarenes, aromatic amines or oxidative mutagens. For all strains, the rev/MJ(th) decreased with increasing biodiesel in the fuel. The emission factor for the 16 EPA Priority PAHs correlated strongly (r(2 )= 0.69) with the mutagenicity-emission factor in strain TA100 + S9, which detects PAHs. CONCLUSIONS: Under a constant load, soy-biodiesel emissions were 50-85% less mutagenic than those of petroleum diesel. Without additional emission controls, petroleum and biodiesel fuels had mutagenicity-emission factors between those of large utility-scale combustors (e.g. natural gas, coal, or oil) and inefficient open-burning (e.g. residential wood fireplaces).

Elemental composition of particulate matter and the association with lung function.

BACKGROUND: Negative effects of long-term exposure to particulate matter (PM) on lung function have been shown repeatedly. Spatial differences in the composition and toxicity of PM may explain differences in observed effect sizes between studies. METHODS: We conducted a multicenter study in 5 European birth cohorts-BAMSE (Sweden), GINIplus and LISAplus (Germany), MAAS (United Kingdom), and PIAMA (The Netherlands)-for which lung function measurements were available for study subjects at the age of 6 or 8 years. Individual annual average residential exposure to copper, iron, potassium, nickel, sulfur, silicon, vanadium, and zinc within PM smaller than 2.5 µm (PM2.5) and smaller than 10 µm (PM10) was estimated using land-use regression models. Associations between air pollution and lung function were analyzed by linear regression within cohorts, adjusting for potential confounders, and then combined by random effects meta-analysis. RESULTS: We observed small reductions in forced expiratory volume in the first second, forced vital capacity, and peak expiratory flow related to exposure to most elemental pollutants, with the most substantial negative associations found for nickel and sulfur. PM10 nickel and PM10 sulfur were associated with decreases in forced expiratory volume in the first second of 1.6% (95% confidence interval = 0.4% to 2.7%) and 2.3% (-0.1% to 4.6%) per increase in exposure of 2 and 200 ng/m, respectively. Associations remained after adjusting for PM mass. However, associations with these elements were not evident in all cohorts, and heterogeneity of associations with exposure to various components was larger than for exposure to PM mass. CONCLUSIONS: Although we detected small adverse effects on lung function associated with annual average levels of some of the evaluated elements (particularly nickel and sulfur), lower lung function was more consistently associated with increased PM mass.

Development of land use regression models for elemental, organic carbon, PAH, and hopanes/steranes in 10 ESCAPE/TRANSPHORM European study areas.

Land use regression (LUR) models have been used to model concentrations of mainly traffic-related air pollutants (nitrogen oxides (NOx), particulate matter (PM) mass or absorbance). Few LUR models are published of PM composition, whereas the interest in health effects related to particle composition is increasing. The aim of our study was to evaluate LUR models of polycyclic aromatic hydrocarbons (PAH), hopanes/steranes, and elemental and organic carbon (EC/OC) content of PM2.5. In 10 European study areas, PAH, hopanes/steranes, and EC/OC concentrations were measured at 16-40 sites per study area. LUR models for each study area were developed on the basis of annual average concentrations and predictor variables including traffic, population, industry, natural land obtained from geographic information systems. The highest median model explained variance (R(2)) was found for EC - 84%. The median R(2) was 51% for OC, 67% for benzo[a]pyrene, and 38% for sum of hopanes/steranes, with large variability between study areas. Traffic predictors were included in most models. Population and natural land were included frequently as additional predictors. The moderate to high explained variance of LUR models and the overall moderate correlation with PM2.5 model predictions support the application of especially the OC and PAH models in epidemiological studies.

Nano- and microplastic PBK modeling in the context of human exposure and risk assessment.

Insufficient data on nano- and microplastics (NMP) hinder robust evaluation of their potential health risks. Methodological disparities and the absence of established toxicity thresholds impede the comparability and practical application of research findings. The diverse attributes of NMP, such as variations in sizes, shapes, and compositions, complicate human health risk assessment. Although probability density functions (PDFs) show promise in capturing this diversity, their integration into risk assessment frameworks is limited. Physiologically based kinetic (PBK) models offer a potential solution to bridge the gap between external exposure and internal dosimetry for risk evaluation. However, the heterogeneity of NMP poses challenges for accurate biodistribution modeling. A literature review, encompassing both experimental and modeling studies, was conducted to examine biodistribution studies of monodisperse micro- and nanoparticles. The literature search in PubMed and Scopus databases yielded 39 studies that met the inclusion criteria. Evaluation criteria were adapted from previous Quality Assurance and Quality Control (QA-QC) studies, best practice guidelines from WHO (2010), OECD guidance (2021), and additional criteria specific to NMP risk assessment. Subsequently, a conceptual framework for a comprehensive NMP-PBK model was developed, addressing the multidimensionality of NMP particles. Parameters for an NMP-PBK model are presented. QA-QC evaluations revealed that most experimental studies scored relatively well (>0) in particle characterizations and environmental settings but fell short in criteria application for biodistribution modeling. The evaluation of modeling studies revealed that information regarding the model type and allometric scaling requires improvement. Three potential applications of PDFs in PBK modeling of NMP are identified: capturing the multidimensionality of the NMP continuum, quantifying the probabilistic definition of external exposure, and calculating the bio-accessibility fraction of NMP in the human body. A framework for an NMP-PBK model is proposed, integrating PDFs to enhance the assessment of NMP's impact on human health.

Suspension of micro- and nanoplastic test materials: Liquid compatibility, (bio)surfactants, toxicity and environmental relevance.

Micro- and nanoplastics have been detected in environmental compartments from the highest mountains to the deepest seas. They have been shown to be present at almost all trophic levels, and within humans they have been detected in numerous organs and human stool. Whilst their ubiquitous nature is indisputable, little is known about the health risks they may present. Much current research is focussed on the production of test materials with which to perform the necessary health studies. An important aspect of this is the correct storage and suspension of the materials to ensure they remain stable both chemically and with regards to size and shape. In this review, we look at the chemical stability of nine common polymers in a range of liquids; first with the use of commercial compatibility charts and then with a more quantitative approach using Hansen solubility parameters. We then look at stability with regards to particle agglomeration, whether and how stable compositions can be predicted, and which dispersants can be added to increase stability. Finally, we discuss the role of bio-surfactants and the eco-corona and how these may offer a route to both better stability and environmental relevance.

Toxicological evaluation of primary particulate matter emitted from combustion of aviation fuel.

Recently, Sustainable Aviation Fuel (SAF) blends and novel combustion technologies have been introduced to reduce aircraft engine emissions. However, there is limited knowledge about the impact of combustion technology and fuel composition on toxicity of primary Particulate Matter (PM) emissions, comparable to regulated non-volatile PM (nvPM). In this study, primary PM was collected on filters using a standardised approach, from both a Rich-Quench-Lean (RQL) combustion rig and a bespoke liquid fuelled Combustion Aerosol Standard (CAST) Generator burning 12 aviation fuels including conventional Jet-A, SAFs, and blends thereof. The fuels varied in aromatics (0-25.2%), sulphur (0-3000 ppm) and hydrogen (13.43-15.31%) contents. Toxicity of the collected primary PM was studied in vitro utilising Air-Liquid Interface (ALI) exposure of lung epithelial cells (Calu-3) in monoculture and co-culture with macrophages (differentiated THP-1 cells). Cells were exposed to PM extracted from filters and nebulised from suspensions using a cloud-based ALI exposure system. Toxicity readout parameters were analysed 24 h after exposure. Results showed presence of genotoxicity and changes in gene expression at dose levels which did not induce cytotoxicity. DNA damage was detected through Comet assay in cells exposed to CAST generated samples. Real-Time PCR performed to investigate the expression profile of genes involved in oxidative stress and DNA repair pathways showed different behaviours after exposure to the various PM samples. No differences were found in pro-inflammatory interleukin-8 secretion. This study indicates that primary PM toxicity is driven by wider factors than fuel composition, highlighting that further work is needed to substantiate the full toxicity of aircraft exhaust PM inclusive of secondary PM emanating from numerous engine technologies across the power range burning conventional Jet-A and SAF.

Microplastic Index-How to Predict Microplastics Formation?

The presence of microplastics in environmental compartments is generally recognized as a (potential) health risk. Many papers have been published on the abundance of microplastics at various locations around the globe, but only limited knowledge is available on possible mitigation routes. One of the mitigation routes is based on the choice of plastic materials used for products that may unintentionally end up in the environment. As a first approach, this paper presents a method to calculate the tendency of polymers to form microplastics, based on their mechanical and physical properties. A MicroPlastic Index (MPI) that correlates the microplastic formation to polymer properties is defined for both impact and wear of polymers via a theoretical particle size and the energy required to form these particles. A first comparison between calculated and experimental particle size is included. The MPI for impact and wear follow the same trend. Finally, these MPIs are correlated to the respective abundance of the microplastics in the environment, corrected for global production of the corresponding polymers: the higher the MPI, the more microplastics are found in the environment. Thus, the MPI can be used as a basis for choice or redesign of polymers to reduce microplastic formation.

Measuring DNA modifications with the comet assay: a compendium of protocols.

The comet assay is a versatile method to detect nuclear DNA damage in individual eukaryotic cells, from yeast to human. The types of damage detected encompass DNA strand breaks and alkali-labile sites (e.g., apurinic/apyrimidinic sites), alkylated and oxidized nucleobases, DNA-DNA crosslinks, UV-induced cyclobutane pyrimidine dimers and some chemically induced DNA adducts. Depending on the specimen type, there are important modifications to the comet assay protocol to avoid the formation of additional DNA damage during the processing of samples and to ensure sufficient sensitivity to detect differences in damage levels between sample groups. Various applications of the comet assay have been validated by research groups in academia, industry and regulatory agencies, and its strengths are highlighted by the adoption of the comet assay as an in vivo test for genotoxicity in animal organs by the Organisation for Economic Co-operation and Development. The present document includes a series of consensus protocols that describe the application of the comet assay to a wide variety of cell types, species and types of DNA damage, thereby demonstrating its versatility.

Chemiluminescent reductive acridinium triggering (CRAT)--mechanism and applications.

Acridinium esters traditionally are triggered using basic hydrogen peroxide. By serendipity, we have found that acridinium esters can also be triggered with emission of chemiluminescence by reductive triggering, e.g., by zinc metal or reduced forms of ferric and cupric salts. Furthermore, organic reducing compounds like dithiothreitol, tricarboxyethylphosphine or glutathione could be used in combination with organic oxidants like quinones or inorganic ferric or cupric salts. Mechanisms are proposed which involve the intermediacy of superoxide. Two forms of reactive oxygen species (i.e., hydrogen peroxide and superoxide) could be discriminated based on differences in kinetics. Some applications (improved detection of acridinium ester, use of acridinium ester as redox probes) are discussed.