Development and characterization of a single particle laser ablation mass spectrometer (SPLAM) for organic aerosol studies

A single particle instrument was developed for real-time analysis of organic aerosol. This instrument, named Single Particle Laser Ablation Mass Spectrometry (SPLAM), samples particles using an aerodynamic lens system for which the theoretical performances were calculated. At the outlet of this system, particle detection and sizing are realized by using two continuous diode lasers operating at λ = 403 nm. Polystyrene Latex (PSL), sodium chloride (NaCl) and dioctylphtalate (DOP) particles were used to characterize and calibrate optical detection of SPLAM. The optical detection limit (DL) and detection efficiency (DE) were determined using size-selected DOP particles. The DE ranges from 0.1 to 90% for 100 and 350 nm DOP particles respectively and the SPLAM instrument is able to detect and size-resolve particles as small as 110–120 nm. During optical detection, particle scattered light from the two diode lasers, is detected by two photomultipliers and the detected signals are used to trigger UV excimer laser (λ = 248 nm) used for one-step laser desorption ionization (LDI) of individual aerosol particles. The formed ions are analyzed by a 1 m linear time-of-flight mass spectrometer in order to access to the chemical composition of individual particles. The TOF-MS detection limit for gaseous aromatic compounds was determined to be 0.85 × 10<sup>−15</sup> kg (∼4 × 10<sup>3</sup> molecules). DOP particles were also used to test the overall operation of the instrument. The analysis of a secondary organic aerosol, formed in a smog chamber by the ozonolysis of indene, is presented as a first application of the instrument. Single particle mass spectra were obtained with an effective hit rate of 8%. Some of these mass spectra were found to be very different from one particle to another possibly reflecting chemical differences within the investigated indene SOA particles. Our study shows that an exhaustive statistical analysis, over hundreds of particles, and adapted reference mass spectra are further needed to understand the chemical meaning of single particle mass spectra of chemically complex submicrometer-sized organic aerosols

Importance of size representation and morphology in modelling optical properties of black carbon: comparison between laboratory measurements and model simulations

Black carbon (BC) from incomplete combustion of biomass or fossil fuels is the strongest absorbing aerosol component in the atmosphere. Optical properties of BC are essential in climate models for quantification of their impact on radiative forcing. The global climate models, however, consider BC to be spherical particles, which causes uncertainties in their optical properties. Based on this, an increasing number of model-based studies provide databases and parameterization schemes for the optical properties of BC, using more realistic fractal aggregate morphologies. In this study, the reliability of the different modelling techniques of BC was investigated by comparing them to laboratory measurements. The modelling techniques were examined for bare BC particles in the first step and for BC particles with organic material in the second step. A total of six morphological representations of BC particles were compared, three each for spherical and fractal aggregate morphologies. In general, the aggregate representation performed well for modelling the particle light absorption coefficient σabs, single-scattering albedo SSA, and mass absorption cross-section MACBC for laboratory-generated BC particles with volume mean mobility diameters dp,V larger than 100nm. However, for modelling Ångström absorption exponent AAE, it was difficult to suggest a method due to size dependence, although the spherical assumption was in better agreement in some cases. The BC fractal aggregates are usually modelled using monodispersed particles, since their optical simulations are computationally expensive. In such studies, the modelled optical properties showed a 25% uncertainty in using the monodisperse size method. It is shown that using the polydisperse size distribution in combination with fractal aggregate morphology reduces the uncertainty in measured σabs to 10% for particles with dp,V between 60-160nm. Furthermore, the sensitivities of the BC optical properties to the various model input parameters such as the real and imaginary parts of the refractive index (mre and mim), the fractal dimension (Df), and the primary particle radius (app) of an aggregate were investigated. When the BC particle is small and rather fresh, the change in the Df had relatively little effect on the optical properties. There was, however, a significant relationship between app and the particle light scattering, which increased by a factor of up to 6 with increasing total particle size. The modelled optical properties of BC are well aligned with laboratory-measured values when the following assumptions are used in the fractal aggregate representation: mre between 1.6 and 2, mim between 0.50 and 1, Df from 1.7 to 1.9, and app between 10 and 14nm. Overall, this study provides experimental support for emphasizing the importance of an appropriate size representation (polydisperse size method) and an appropriate morphological representation for optical modelling and parameterization scheme development of BC

Development of a portable reference aerosol generator (PRAG) for calibration of particle mass concentration measurements

International audienceThe tapered element oscillating microbalance with filter dynamics measurement system (TEOM-FDMS) is an instrument commonly employed by the French air quality monitoring network. This instrument is currently calibrated with calibration weights traceable to SI but having value and mass differences between each of them that are not representative of real atmospheric particle mass measurements. Moreover, these calibration weights do not allow detection of any technical problems associated with either the TEOM-FDMS sampling system upstream of the mass measurement or the intrinsic TEOM-FDMS filtration system. Therefore, a calibration method was developed using a portable reference aerosol generator (PRAG) that produces known and stable particle mass concentrations over time. Here, we present the characterization of the PRAG system in terms of a reference range of particle masses between 30 ± 10 and 3456 ± 83 μg at three sampling times. Its coupling with the TEOM-FDMS and a global comparison between the defined reference range of particle masses and the measured masses obtained with each TEOM-FDMS implicated in this study are also presented. © 2017 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Science

Characterization of aerosols generated from nine nanomaterial powders reliability with regard to in vivo inhalation toxicology studies

International audienceIn experimental toxicology, when simulating human exposure to aerosols in the working environment, inhalation is the route of administration of choice for evaluating the toxicity of a given material (in aerosol form) in animals. In this context, this work aimed to contribute to the establishment of recommendations concerning the characterization of aerosol tests in inhalation toxicology studies. In particular, the work consisted of experimentally characterizing test aerosols using a given generation method to be used for inhalation toxicology studies. Nine nanomaterial powders have been investigated (four types of TiO2, two types of SiO2, ZnO, CeO, and BaSO4). The aerosols produced cover the particle size range from a few tens of nanometers up to several micrometers and are mainly composed of aggregates and/or agglomerates. The work carried out shows that generation and characterization of test aerosols for inhalation toxicology studies is a complex but essential element of inhalation studies, for which the conditions required (stability, repeatability, level of concentration) are sometimes difficult to obtain. Moreover, this study highlights the necessity to carry out preliminary tests to ascertain the performances of the chosen devices and their suitability for inhalation toxicology. © 2018, Springer Nature B.V

In vivo evaluation of the potential neurotoxicity of aerosols released from mechanical stress of nano-TiO2 additived paints in mice chronically exposed by inhalation

Engineered Nanomaterials (ENM) provide technical and specific benefits due to theirphysical-chemical properties at the nanometer scale. For instance, many ENM are used to improveproducts in the building industry. Nanoscaled titanium dioxide (TiO2) is one of the most used ENM inthis industry. Incorporated in different matrix, cement, glass, paints… TiO2 nanoparticles (NPs) providethe final product with anti-UV, air purification and self-cleaning properties, thanks to theirphotocatalytic activity. However, ageing processes of such products, as photocatalytic paints, during amechanical stress have been shown to release TiO2 NPs from this matrix associated with sanding dust.Thus, workers who sand painted walls could be exposed to TiO2 NPs through inhalation. As inhalationmay lead to a translocation of particulate matter to the brain via olfactory or trigeminal nerves, there isan urgent need for evaluating a potential neurotoxicity. In order to provide new knowledge on this topic,we developed a dedicated experimental set-up using a rodent model exposed via inhalation. The aerosolreleased from a mechanical stress of photocatalytic paints containing TiO2 NPs was characterized andcoupled to an exposition chamber containing group of mice free to move and chronically exposed(2 hours per day for 5 days a week during 8 weeks)

: Travaux LCSQA 2017 (Convention n°2201070603)

Note technique rendant compte de l’opportunité d’établir un protocole pour la caractérisation métrologique en laboratoire de micro-capteurs pour la mesure indicative des particules (au sens de la Directive européenne "Qualité de l'air 2008/50/CE")

Analyse des fractions granulométriques utilisées pour l’évaluation des expositions par inhalationd’aérosols - Pertinence et comparaison des fractions environnementales - PM10 , PM2,5 - et professionnelles - inhalable, thoracique, alvéolaire

Citation suggérée : Anses. (2023). Analyse des fractions granulométriques utilisées pour l’évaluation des expositions par inhalation d’aérosols. Pertinence et comparaison des fractions environnementales - PM10, PM2,5 - et professionnelles - inhalable, thoracique, alvéolaire-. (saisine 2018-SA-0076). Maisons-Alfort : Anses, 177 p.Il existe un grand nombre de termes utilisés couramment dans la littérature scientifique et dansla réglementation pour décrire et étudier la pollution atmosphérique particulaire. Le termegénérique « aérosols » désigne un mélange de particules solides et/ou liquides en suspensiondans un milieu gazeux. Les particules sont habituellement classées par taille en fonction deleur diamètre aérodynamique équivalent et réparties statistiquement sous forme de distributions granulométriques. Le diamètre aérodynamique permet de différencier les particules qui sédimentent rapidement de celles qui peuvent pénétrer facilement dans les voies respiratoires.La proportion de matière particulaire qui est inhalée par un être humain dépend des propriétésdes particules dont la taille mais également de la vitesse et de la direction de l’air près du corpsainsi que de la fréquence respiratoire et du mode de respiration (par le nez ou par la bouche).Les particules inhalées peuvent alors soit se déposer dans différents compartiments des voiesrespiratoires soit être éliminées. Le site de dépôt et la probabilité d’expiration dépendent entreautres des propriétés des particules, des voies respiratoires et du régime respiratoire. D´unepersonne à l´autre, une variation importante de la probabilité d´inhalation, de dépôt, de réaction au dépôt, et d´élimination des particules est observée.La surveillance des particules dans l’air ambiant ou l’air des lieux de travail, à des fins d’évaluation de l’exposition de la population générale et/ou professionnelle, nécessite des méthodes reproductibles de prélèvement des aérosols et permettant de prélever des fractions d’aérosols pertinentes au regard des effets sanitaires. Des conventions ont donc été établies pour l´échantillonnage sélectif en taille des particules en suspension dans l’air. Il s’agit despécifications pour les échantillonneurs en terme d’efficacité de prélèvement en fonction dudiamètre aérodynamique des particules.La surveillance des particules dans l’air ambiant prend communément en considération lesfractions d’aérosol appelées PM10 et PM2,5 (norme NF EN 12341).La surveillance des expositions professionnelles aux agents chimiques sous forme d’aérosolsprend en considération différentes fractions massiques particulaires : inhalable, thoracique etalvéolaire. Ces fractions sont définies (normes NF EN 481 et NF ISO 7708) en relation avec la probabilité de pénétration des particules dans le tractus respiratoire, cette probabilité étantcroissante avec la diminution de la taille des particules.Les référentiels d’évaluation des expositions aux particules par inhalation diffèrent suivant lecadre réglementaire et s’appuient sur ces conventions d’échantillonnage :• S’agissant de la population générale, l’article R221-1 du Code de l’environnement définit les termes et « normes de qualité de l’air »1 établies par polluant dans le cadre de la surveillance de la qualité de l'air ambiant qui pour les particules s’appliquent aux fractions granulométriques PM10 et PM2,5;• S’agissant de la qualité de l’air auquel sont exposés les travailleurs dans des locaux à pollution spécifique, l’article R4222-10 du Code du travail définit les valeurs limites de « concentrations moyennes en poussières totales et alvéolaires » à respecter.A l’occasion de différents travaux d’expertise conduits par l’Anses, les scientifiques se sont heurtés aux difficultés liées à la coexistence de ces référentiels différents pour caractériser la pollution atmosphérique particulaire et les risques sanitaires qui en résultent, selon que les travaux s’intéressaient à la population générale ou aux travailleurs. Est ainsi soulevée la question de la pertinence tant du point de vue scientifique que du point de vue réglementaire des caractéristiques de ces deux référentiels d’évaluation des expositions

VUV photoionization of gas phase adenine and cytosine: A comparison between oven and aerosol vaporization

International audienceWe studied the single photon ionization of gas phase adenine and cytosine by means of vacuum ultraviolet synchrotron radiation coupled to a velocity map imaging electron∕ion coincidence spectrometer. Both in-vacuum temperature-controlled oven and aerosol thermodesorption were successfully applied to promote the intact neutral biological species into the gas phase. The photoion yields are consistent with previous measurements. In addition, we deduced the threshold photoelectron spectra and the slow photoelectron spectra for both species, where the close to zero kinetic energy photoelectrons and the corresponding photoions are measured in coincidence. The photoionization close and above the ionization energies are found to occur mainly via direct processes. Both vaporization techniques lead to similar electronic spectra for the two molecules, which consist of broadbands due to the complex electronic structure of the cationic species and to the possible contribution of several neutral tautomers for cytosine prior to ionization. Accurate ionization energies are measured for adenine and cytosine at, respectively, 8.267 ± 0.005 eV and 8.66 ± 0.01 eV, and we deduce precise thermochemical data for the adenine radical cation. Finally, we performed an evaluation and a comparison of the two vaporization techniques addressing the following criteria: measurement precision, thermal fragmentation, sensitivity, and sample consumption. The aerosol thermodesorption technique appears as a promising alternative to vaporize large thermolabile biological compounds, where extended thermal decomposition or low sensitivity could be encountered when using a simple oven vaporization technique

Metrological Characterization of an Aerosol Exposure Chamber to Explore the Inhalation Effects of the Combination of Paraquat and TiO2 Nano-objects

International audienceAgriculture emits a significant quantity of airborne contaminants, and the prospective environmental release of nanopesticides, a new type of agrochemical that employs engineered nanomaterials (ENMs) as either active substances or additives in a pesticide formulation, raises concerns about the risks of inhalation which are still unknown. Although the adverse effects of pesticides have been studied extensively, the potential synergistic toxicity between these substances and ENMs has rarely been investigated. To this end, toxicological models are essential to estimating the health consequences of such aerosols. Thus, to assess the respiratory hazards of titanium dioxide nano-objects (specifically, AEROXIDE (R) TiO2 P25 nanopowder [nTiO(2)]) in combination with paraquat (PQ), we developed a dynamic whole-body exposure chamber for rodents in compliance with guidelines for inhalation toxicity testing (Organization for Economic Cooperation and Development (OECD)) and animal welfare. First, we metrologically characterized the generated test aerosols by determining their mass and number concentrations, size distributions and atmospheric homogeneity at the laboratory. Then, we evaluated the reproducibility and proper functioning of the chamber during a preliminary field campaign, which validated the consistency of the aerosols' mass and number concentrations between the laboratory characterization and the rodent exposure sessions. Finally, we examined the inhalation effects on the rodents