18HLT02 AeroTox: Measurements for mitigatin adverse health effects from atmospheric particulate pollutants

• Research unit: METAS
• Project number: F-5235.30113

Key words (English)

Atmospheric aerosols, cell cultures, chemical models, cytotoxicity, lung organoids, optical microscopy, oxidative potential, particulate matter, inflammatory response.

Short description (English)

Atmospheric particulate pollution has been linked to a broad spectrum of adverse health effects including respiratory problems, cardiovascular diseases, cancer and dementia. These effects depend not only on physical, but also on chemical properties of airborne particulate matter (PM) though to date it has proven difficult to disentangle the relative contribution of PM constituents to the reported population-level health effects. To address this issue this project will use "tailored" reference aerosols, combined with high-resolution optical imaging of exposed cells and state-of-the-art cell analysis methods to study the cytotoxic effects of airborne PM in vitro. This will be done in a systematic way to help inform which PM metrics are associated with the induction of toxic mechanisms so that they can then be linked to specific health effects.

This is a joint research project carried out in the framework of the European Metrology Programme for Innovation and Research (EMPIR) (see:http://www.euramet.org/research-innovation/empir/). The EMPIR initiative is co-funded by the European Unions's Horizon 2020 research and innovation programme and the participating states. METAS is one of the project partners in the project.

Project aims (English)

The overall goal of this project is to identify correlations between particle component/properties (metrics) with adverse outcome pathways that are associated with the induction of acute and chronic health effects within the European population. This will be delivered through the development of a new method for studying in vitro cytotoxicity based on the use of "tailored" synthetic ambient aerosols combined with high-resolution optical imaging and state-of-the-art cell analysis methods. The specific objectives of the project are:

1. To develop a stable and reproducible laboratory-based source of well-controlled and chemically defined, synthetic reference aerosol mixtures that mimic real ambient aerosols at high concentrations (at around the limit values of the EU Air Quality Directive and up to a few mg/m3). The aerosol properties should be tunable and the source should be coupled to an oxidation flow reactor (OFR) to mimic atmospheric photochemical "ageing". To improve traceability for the physical and chemical characterisation of the synthetic aerosols using EU reference methods (target uncertainty in mass concentration 15 %, number concentration <15 %, analysis of major chemical components <15 %). Moreover, to quantify uncertainties for emerging techniques, such as Aerosol Mass Spectrometry (AMS) for chemical analysis and Brunauer–Emmett–Teller (BET) for surface area analysis and develop new approaches to ensure reproducibility and quality assurance.
2. To apply novel methods for cell exposure at the air-liquid interface (ALI) in order to mimic and quantify the effects of the in vivo aerosol inhalation routes. To study phenotypic effects using lung organoids. To compare these novel methods with the conventional cell-exposure techniques relying on submerged cell systems, where aerosol particles are collected in water with high-volume samplers.
3. To assess how the composition of the collected aerosols and their ageing impacts on their acellular and cellular oxidative characteristics, both in simple chemical models simulating human respiratory tract lining fluids (in health and disease) and in representative cell lines maintained under near physiologic conditions. To evaluate adverse outcome pathways using proteomics and transcriptomics (high throughput sequencing), to examine known causal pathways, such as pro-/anti-inflammatory responses, cytotoxicity and genotoxicity, as well as novel ‘component-specific’ pathways. The project will work toward improved, validated protocols for harmonising/standardising cell analysis studies, as well as on the integration of multi-omic approaches for statistical analysis of complex data sets on a European level.
4. To push the frontiers of optical imaging and biological image analysis to quantify the effects of particle uptake on single cells and cell populations by using various types of optical microscopy including confocal, structured illumination, light sheet and fluorescence lifetime imaging.
5. To facilitate the take up of the technology and measurement infrastructure developed in the project by the measurement supply chain (accredited laboratories, instrumentation manufacturers), standards developing organisations (CEN, ISO) and end users (e.g. hospitals and health centres).

Abstract (English)

A new oxidation flow reactor, called Organic Coating Unit (OCU), has been developed by FHNW and validated by METAS. The new device (essentially a micro smog chamber) is portable, fully automated and therefore very user-friendly. It includes an automated precursor supply system, a built-in aerosol humidifier, a touch screen for reading/displaying experimental parameters and automatic data-logging. Moreover, it enables inspection of UV-C lamp power and aerosol temperature during measurement. The device is versatile and can be readily combined with various soot generators, such as a miniCAST or a miniature inverted burner. A series of combustion aerosols has been produced in a stable manner, ranging from black carbon aerosols (>95% EC/TC mass fraction) to aerosols containing mostly secondary organic matter (90% OC/TC mass fraction).

Moreover, a portable aerosol mixing chamber was designed and built by METAS. The chamber is cylindrical with an adjustable height of 0.5-1 m and 5 cm internal diameter, and is made of steel. Mixing is achieved by 3 turbulent air-jets located below the aerosol injection ports. The facility is modular, i.e. can be easily assembled/dissembled and has a total weight of about 10 -20 kg depending on the exact height. The mixing chamber is equipped with three sampling outlets. The aerosol spatial homogeneity at the sampling zone was determined to be within 5 % in particle number concentration even for particles in the lower micrometre range. The mixing chamber enables the homogenisation of various aerosol components, such as soot, inorganic salt, dust, and metal particles in order to generate ambient-like aerosols in the laboratory in a controlled way. The mass concentration and chemical composition of the aerosols can be tuned to simulate different urban, suburban, and rural aerosols. This new facility can be applied in health-related studies, aerosol research and instrument calibration.

Transfer and application (English)

The new oxidation flow reactor, OCU, has been used in several studies. Kalbermatter et al. Atmos. Meas. Tech., 15, 561–572, (2022) performed an inter-comparison of black carbon- and aerosol-absorption-measuring instruments with laboratory-generated soot particles coated with controlled amounts of secondary organic matter (SOM). SOM was generated by the OCU. Nilofar Faruqui (National Physical Laboratory) combined the miniCAST and the OCU to produce a series of well-defined soot aerosols for controlled cell exposure studie (manuscript in preparation). The University of Lund have used the OCU to produce well-defined aerosols for a bird exposure study (manusciprt in preparation). The University of Applied Sciences Northwestern Switzerland (FHNW) has sold already four OCU units to research institutes across Europe.

The portable aerosol homogeniser is currently being equipped with an air compressor and an optical particle counter and will be used in the near future as a transfer standard for the calibration of particle counters in the field. METAS is currently building a second prototype, which will be sold to a research institute institute in Europe for R&D purposes.

Publications / Results (English)

Karin Lovén et al., Toxicological effects of zinc oxide nanoparticle exposure: an in vitro comparison between dry aerosol air-liquid interface and submerged exposure systems, Nanotoxicology https://doi.org/10.1080/17435390.2021.1884301

Anna Löfdahl et al., Silver Nanoparticles Alter Cell Viability Ex Vivo and in Vitro and Induce Proinflammatory Effects in Human Lung Fibroblasts, Nanomaterials https://doi.org/10.3390/nano10091868

M. Ess et al., Laboratory-generated coated-soot particles with tunable, well-controlled properties using a miniCAST BC and a micro smog chamber, Journal of Aerosol Science https://doi.org/10.1016/j.jaerosci.2021.105820

Mariam Bagher et al., Crosstalk between Mast Cells and Lung Fibroblasts Is Modified by Alveolar Extracellular Matrix and Influences Epithelial Migration, International Journal of Molecular Sciences https://doi.org/10.3390/ijms22020506

Russell, C. & Shaw, M., mmSIM: An open toolbox for accessible structured illumination microscopy, Philos. Trans. R. Soc. A https://doi.org/10.1101/2021.01.18.427184

Daniel Kalbermatter et al., Response of black-carbon and aerosol absorption measuring instruments to laboratory-generated soot coated with controlled amounts of secondary organic matter, Atmospheric Measurement Techniques https://doi.org/10.5194/amt-15-561-2022

Alejandro Keller et al., The organic coating unit, an all-in-one system for reproducible generation of secondary organic matter aerosol, Aerosol science and Technology https://doi.org/10.1080/02786826.2022.2110448

Stefan Horender et al., A portable aerosol flow tube homogenizer for mixing particles in the sub-micrometre and lower micrometre size range, Measurement Science and Technology https://doi.org/10.1088/1361-6501/ac81a1

Daniel Geißler et al., Analyzing the Surface of Functional Nanomaterials – How to Quantify the Total and Derivatizable Number of Functional Groups and Ligands, Microchimica Acta https://doi.org/10.1007/s00604-021-04960-5

Zaira Leni et al., Role of Secondary Organic Matter on Soot Particle Toxicity in Reconstituted Human Bronchial Epithelia Exposed at the Air–Liquid Interface, Environmental Science and Technology https://doi.org/10.1021/acs.est.2c03692