Aerosol Particle Size Research Articles

The thermostated medical jet nebulizer: Aerosol characteristics.

The sudden expansion of gas at the outlet of the jet (pneumatic) nebulizer significantly reduces the temperature of the solution, which may provoke bronchospasm, therefore it is recommended to use modern pneumatic inhalers equipped with a thermostat or a universal thermal attachment that allow to obtain a higher temperature aerosol, i.e. thermo-aerosol. The research was carried out for model Newtonian fluids. The droplet diameters of the aerosol spray were investigated using a Spraytec aerosol particle size measurement system. Analysis of the obtained results showed that the increase in solution viscosity caused a decrease in mean droplet diameters and prolonged nebulization time. The analysis of experimental data made it possible to propose a correlation equation describing the mean diameter of the droplets depending on the properties of the liquid and the flow conditions in the thermostated medical nebulizer. The obtained data contributes to a better understanding of the complex liquid atomisation process and can be helpful in the design of medical nebulizers and pharmaceutical preparations.

Stratospheric aerosol characteristics from space-borne observations: extinction coefficient and Ångström exponent

Abstract. Stratospheric aerosols are of a great importance to the scientific community, predominantly because of their role in climate, but also because accurate knowledge of aerosol characteristics is relevant for trace gas retrievals from remote-sensing instruments. There are several data sets published which provide aerosol extinction coefficients in the stratosphere. However, for the instruments measuring in the limb-viewing geometry, the use of this parameter is associated with uncertainties resulting from the need to assume an aerosol particle size distribution (PSD) within the retrieval process. These uncertainties can be mitigated if PSD information is retrieved. While occultation instruments provide more accurate information on the aerosol extinction coefficient, in this study, it was shown that limb instruments are more sensitive to the smaller particles in the visible–near-infrared spectral range. However, the sensitivity of occultation instruments improves if the UV part of the wavelength spectrum is considered. A data set containing PSD information was recently retrieved from SCIAMACHY limb measurements and provides two parameters of the unimodal lognormal PSD for the SCIAMACHY operational period (2002–2012). In this study, the data set is expanded by aerosol extinction coefficients and Ångström exponents calculated from the retrieved PSD parameters. Parameter errors for the recalculated Ångström exponents and aerosol extinction coefficients are assessed using synthetic retrievals. For the extinction coefficient the resulting parameter error is within ±25 %, and for the Ångström exponent, it is better than 10 %. The SCIAMACHY aerosol extinction coefficients recalculated from PSD parameters are compared to those from SAGE II. The differences between the instruments vary from 0 % to 25 % depending on the wavelength. Ångström exponent comparison with SAGE II shows differences between 10 % at 31 km and 40 % at 18 km. Comparisons with SAGE II, however, suffer from the low number of collocated profiles. Furthermore, the Ångström exponents obtained from the limb-viewing instrument OSIRIS are used for the comparison. This comparison shows an average difference within 7 %. The time series of these differences do not show signatures of any remarkable events (e.g., volcanic eruptions or biomass burning events). In addition, the temporal behaviour of the Ångström exponent in the tropics is analyzed using the SCIAMACHY data set. It is shown that there is no trivial relation between the Ångström exponent value at a single wavelength pair and the PSD because the same value of Ångström exponent can be obtained from an infinite number of combinations of the PSD parameters.

Extinction-related Angström exponent characterization of submicrometric volume fraction in atmospheric aerosol particles

The AEAOD– ΔAEAOD grid proposed by Gobbi et al. (2007) is a graphical method used to visually represent the spectral characterization of aerosol optical depth (AOD), i.e. Angström exponent (AE) and its curvature, in order to infer the fine mode contribution (η) to the total AOD and the size of the fine mode aerosol particles. Perrone et al. (2014) applied this method for the wavelengths widely used in lidar measurements. However, in neither case does the method allow for a direct relationship between η and the fine mode fraction contribution to the total aerosol population. Some discussions are made regarding the effect of shape and composition to the classical AE-ΔAE plot. The potential use of particle backscatter measurements, widely used in aerosol characterization methods together with extinction measurements, is also discussed in the AE-ΔAE grid context. A modification is proposed that yields the submicron contribution to the total volume concentration by using particle extinction data, and a comparison to experimental measurements is made. Our results indicate that the use of a modified AE-ΔAE grid plot to directly obtain submicrometric and micrometric mode fraction to the total aerosol population is feasible if a volume-based bimodal particle size distribution is used instead of a number-based one.

Rapid Clogging of High-Efficiency Particulate Air Filters During In-Cell Solvent Fires at Reprocessing Facilities

Recent Japanese nuclear regulations have focused on the hazards of in-cell solvent fires at reprocessing facilities. In this work, a mixture of tributyl phosphate and dodecane-based solvents was burned to generate an aerosol composed of soot and unburned solvent that was then loaded onto a high-efficiency particulate air filter simulating the ventilation system of reprocessing facilities. A radical increase of differential pressure occurred in the filters during these tests after the dodecane burned out from the solvent in a phenomenon we named as rapid clogging, likely caused by the burnout of dodecane. This relationship provides valuable insight into the establishment of new regulations for reprocessing facilities. Moreover, an analysis of the aerosol revealed an increase in unburned solvent content and aerosol particle size generated during the rapid clogging. As such, the rapid clogging may be caused by the unburned solvent release or interactions between the soot and unburned solvent vapor. Overall, this work indicates that clogging of ventilation filters during solvent fires may occur more rapidly than previously estimated.

Efficiency of electrostatic precipitation of NiO nanoparticles dispersed by atomization

ABSTRACT The dispersion of metal oxide nanoparticles by pneumatic atomization of oxide suspensions has rarely been used in laboratory-scale research on electrostatic precipitation, due to the insolubility of the oxides under ambient conditions, the particle agglomeration and sedimentation in aqueous mixtures. Therefore, the aim of this work was to evaluate the performance of a wire-plate electrostatic precipitator in the collection of NiO nanoparticles produced by nebulization of suspensions pretreated with ultrasonic bath, which resulted in reproducible aerosol concentrations and particle size distributions. Increase of the voltage and decrease of the gas flow rate improved the charging and collection efficiencies.

Charging efficiency of nanoparticles in needle-to-plate chargers with micro discharge gaps

Simple chargers, based on needle-to-plate configuration with micro gap distance of several hundred micrometers, for the direct charging of aerosol particles, have been designed and constructed. Charging efficiency and particle deposition loss (electrostatic and diffusional) of this type of chargers have been evaluated systematically for particles (polystyrene) with diameters ranging from 28.9 to 287 nm, at different applied voltages, different aerosol flow rates, and different gap distances. The charging efficiency increases with particle size, applied voltage, and mean residence time of aerosol particles in the charger, while decreases with gap distance. As a consequence of the small effective volume of the chargers, a negligible diffusional loss of particles was obtained. The electrostatic loss of charged particles within the chargers was relatively large for smaller particles at higher applied voltage, but a charging efficiency of 82% was achieved for 28.9-nm particles using the charger with a gap distance of 150 μm. The chargers can charge nanoparticles effectively and are easy to be integrated into minimized devices such as sensor chips.

Biophysical model to predict lung delivery from a dual bronchodilator dry-powder inhaler

A biophysical lung model was designed to predict inhaled drug deposition in patients with obstructive airway disease, and quantitatively investigate sources of deposition variability. Different mouth-throat anatomies at varying simulated inhalation flows were used to calculate the lung dose of indacaterol/glycopyrronium [IND/GLY] 110/50 µg (QVA149) from the dry-powder inhaler Breezhaler®. Sources of variability in lung dose were studied using computational fluid dynamics, supported by aerosol particle sizing measurements, particle image velocimetry and computed tomography. Anatomical differences in mouth-throat geometries were identified as a major source of inter-subject variability in lung deposition. Lung dose was similar across inhalation flows of 30–120 L/min with a slight drop in calculated delivery at high inspiratory flows. Delivery was relatively unaffected by inhaler inclination angle. The delivered lung dose of the fixed-dose combination IND/GLY matched well with corresponding monotherapy doses. This biophysical model indicates low extra-thoracic drug loss and consistent lung delivery of IND/GLY, independent of inhalation flows. This is an important finding for patients across various ages and lung disease severities. The model provides a quantitative, mechanistic simulation of inhaled therapies that could provide a test system for estimating drug delivery to the lung and complement traditional clinical studies.

Case Study: A Practical Application of an Aerosol Treatment in a Commercial Mill.

In recent years, there has been an increasing interest and need for alternatives to structural fumigations, and one alternative that has been used across the industry is aerosol insecticides. Previous tests inside a pilot-scale mill demonstrated that aerosol particle size, delivery method, and the spatial configuration of the mill all influenced effectiveness. However, there is no research conducted inside large commercial facilities. The objective of this research was to evaluate a pyrethrin-plus-methoprene aerosol application inside a commercial mill on adult Tribolium confusum Jacquelin duVal, confused flour beetle, directly exposed to the aerosol and residual effects on larvae. Additionally, five aerodynamic particle sizer spectrometers were placed in the facility and recorded instantaneous spray concentration and estimated aerosol deposition. Adult T. confusum exposed nearest to the aerosol application points had the highest percentage of affected adults (>60%). The aerosol also had vertical movement when released at the top of a three-story open room; instantaneous concentrations were recorded on the ground floor. The aerosol residual was highly effective after 6-weeks post aerosol exposure, as 80% of the bioassays did not have any adult emergence from exposed larvae. This research demonstrates a practical use of aerosol insecticides and their potential to be an effective alternative to structural fumigations.

Precise size distribution measurement of aerosol particles and fog droplets in the open atmosphere.

A precise measurement for the aerosol particle size distribution and fog droplet size distribution simultaneously in the open atmosphere is proposed. The extinction coefficient and small-angle forward scattering measurement are integrated into the detection for particle size distribution in the open atmosphere, and can achieve the fine detection of the particles in the atmosphere with radius between 0.1 to 30 μm. The key technology including optimal scattering angle in small-angle forward scattering measurement and optimal wavelengths selection are discussed and solved in detail. The fourteen different particle size distributions including aerosol size distributions and fog droplet size distributions are used for the determination of optimal forward scattering angle and wavelengths. The optimal forward scattering angle is calculated to be 1.1°. Seven wavelengths for extinction coefficients and five wavelengths for forward scattering coefficients are chosen for the retrieval of particle size distribution in the measurement. The regularization inversion of optical parameters for the retrieval of particle size distribution is described. The aerosol particle size distributions measured by particle spectrometer and actual fog particle size distributions are used for the method test and the reconstructions of particle size distributions. The inversion results show that the method can achieve the precise measurements of aerosol particle size distribution and fog droplet size distribution. The error influence on the inversion results of distributions is discussed. Based on the sensitivity analysis of inversion results, the feasibility of measurement in the real atmosphere is analyzed and discussed, and the scheme of detection system is provided.

A New Angular Light Scattering Measurement of Particulate Matter Mass Concentration for Homogeneous Spherical Particles.

Under the condition of ultra-low emission for power plants, the particulate matter concentration is significantly lower than that of typical power plants a decade ago, which posed new challenges for the particulate matter monitoring of stationary emission. The monitoring of particulate matter mass concentration based on ensemble light scattering has been found affected by particle size. Thus, this study develops a method of using the scattering angular distribution to obtain the real-time particle size, and then correct the particulate matter concentration with the real-time measured particle size. In this study, a real-time aerosol concentration and particle size measurement setup is constructed with a fixed detector at the forward direction and a rotating detector. The mass concentration is measured by the fixed detector, and the particle size is measured from the intensity ratio of the two detectors. The simulations show that the particle size has power law functionality with the angular spacing of the ripple structure according to Mie theory. Four quartz aerosols with different particle size are tested during the experiment, and the particle size measured from the ripple width is compared with the mass median size measured by an electrical low pressure impactor (ELPI). Both techniques have the same measurement tendency, and the measurement deviation by the ripple width method compared with ELPI is less than 15%. Finally, the measurement error of the real-time mass concentration is reduced from 38% to 18% with correction of the simultaneously measured particle size when particle size has changed.

DEVELOPMENT OF CALCULATION TOOL FOR RESPIRATORY TRACT DEPOSITION DEPENDING ON AEROSOLS PARTICLE DISTRIBUTION.

Inhalation exposures occur by inhaled radioactive nuclides depositing in the various locations in the respiratory tract (International Commission on Radiological Protection Publication 66). Respiratory tract deposition depends on particle size. The sensitivity to ionising radiation is different among respiratory regions. Under actual atmospheric environments, the radionuclides attach to aerosols of various size in the atmosphere, so the particle size of radionuclides changes differently. Therefore, it is important for the estimation of health impact to calculate the respiratory tract deposition under atmospheric environment wherein the various sizes of radioactive nuclides (i.e. polydisperse particles) exists. In this study, a tool which can calculate the respiratory tract deposition on the basis of polydisperse particle size distribution was developed to estimate dose depending on variable aerosol particle sizes.

The Impact of Changes in Cloud Water pH on Aerosol Radiative Forcing

AbstractOxidation of sulfur dioxide (SO2) in cloud water by reaction with ozone is an important sulfate aerosol formation mechanism and strongly dependent on the acidity of cloud water. Decadal reductions in Northern Hemisphere sulfur emissions have contributed to higher cloud water pH, thereby altering sulfate formation rates. Here we use a global composition‐climate model to show that changes in cloud water pH over the 1970–2009 period strongly affects the aerosol particle size distribution, cloud condensation nuclei concentrations, and the magnitude of aerosol radiative forcing. The simulated all‐sky aerosol radiative forcing (1970–2009) over the North Atlantic is +1.2 W m−2 if pH remains constant at 5.0, as in many climate models. However, the forcing increases to +5.2 W m−2 if pH is assumed to increase by 1.0 unit over this period. Global composition climate models need to account for variations in cloud water pH to improve the representation of sulfate aerosol formation and aerosol radiative effects.

Aerosol Particle Size May Contribute to Varying Health Responses

Particulate matter in the atmosphere derives from industrial and environmental sources. The size of the particle determines how it deposits in the body and leads to different health challenges.

Inversion algorithm for non-spherical dust particle size distributions

Dust particles are the main aerosol component of the atmosphere, and can influence human, environmental, and ecological health. Particle size distribution is an important aerosol micro-physical parameter that denotes the concentration distribution of particles of different radii and can determine the extinction characteristics of these particles. In traditional inversion algorithms, the aerosol is generally assumed to be spherical according to Mie theory, and the relationship between aerosol optical thickness and particle size distribution is described by the Fredholm integral equation of the first kind. For non-spherical dust particles, this spherical assumption is obviously unreasonable and yields unreliable results. Therefore, we developed an algorithm assuming non-spherical particles for inversion of dust particle size distributions. In the case of non-spherical particles, the extinction efficiency factor kernel functions of the ellipsoid were calculated using the anomalous diffraction approximation method, and the kernel function of Mie scattering theory was substituted with these new kernel functions. Moreover, the Phillips–Twomey method was employed to solve the Fredholm integral equation of the first kind using aerosol optical thickness data from a CE-318 sun photometer. To verify the feasibility of the anomalous diffraction approximation method, experiments were carried out under sunny, dusty, windy and hazy weather conditions. These experiments showed that the extinction kernel function for non-spherical particles obtained using the anomalous diffraction approximation method is suitable for inversion of non-spherical dust particle size distributions under different weather conditions in the Yinchuan area.

The distribution, composition, and particle properties of Mars mesospheric aerosols: An analysis of CRISM visible/near-IR limb spectra with context from near-coincident MCS and MARCI observations

The Compact Reconnaissance Imaging Spectral Mapper (CRISM) onboard the Mars Reconnaissance Orbiter (MRO) obtains pole-to-pole observations (i.e., full MRO orbits) of vertical profiles for visible/near-IR spectra (λ= 0.4–4.0 μm), which are ideally suited to identifying the composition and particle sizes of Mars ice and dust aerosols over 50–100 km altitudes in the Mars mesosphere. Within the coverage limitations of the CRISM limb data set, a distinct compositional dichotomy is found in Mars mesospheric ice aerosols. CO2 ice clouds appear during the aphelion period of Mars orbit (Solar Longitudes, Ls ∼ 0–160°) at low latitudes (∼20S–10N) over specific longitude regions (Meridiani, Valles Marineris) and at typical altitudes of 55–75 km. Apart from faint water ice hazes below 55 km, mesospheric H2O ice clouds are primarily restricted to the perihelion orbital range (Ls∼160 – 350°) at northern and southern mid-to-low latitudes with less apparent longitudinal dependences. Mars mesospheric CO2 clouds are presented in CRISM spectra with a surprisingly large range of particle sizes (cross section weighted radii, Reff = 0.3 to 2.2 μm). The smaller particle sizes (Reff ≤1 μm) appear concentrated near the spatial (latitude and altitude) boundaries of their global occurrences. CRISM spectra of mesospheric CO2 clouds also show evidence of iridescence, indicating very narrow particle size distributions (effective variance, Veff ∼ 0.03) and so very abrupt CO2 cloud nucleation. Furthermore, these clouds are sometimes accompanied by altitude coincident peaks in 1.27 μm O2 dayglow, which indicates very dry, cold regions of formation. Mesospheric water ice clouds generally exhibit small particle sizes (Reff = 0.1–0.3 μm), although larger particle sizes (Reff = 0.4–0.7 μm) appear infrequently. On average, water ice cloud particle sizes decrease with altitude over 50–80 km in the perihelion mesosphere. Water ice mass appears similar in clouds over a large range of observed cloud particle sizes, with particle number densities increasing to ∼10 cm−3 for Reff = 0.2 μm. Near coincident Mars Climate Sounder (MCS) temperature and aerosol profile measurements for a subset of CRISM mesospheric aerosol measurements indicate near saturation (H2O and CO2) conditions for ice clouds and distinct mesospheric temperature increases associated with mesospheric dust loading. Dayside (3 pm) mesospheric CO2 clouds with larger particle sizes (Reff ≥0.5 μm) scatter surface infrared emission in MCS limb infrared radiances, as well as solar irradiance in the MCS solar band channel. Scattering of surface infrared emission is most strikingly presented in nighttime (3 am) MCS observations at 55–60 km altitudes, indicating extensive mesospheric nighttime CO2 clouds with considerably larger particle sizes (Reff∼7 μm). Mesospheric CO2 ice clouds present cirrus-like waveforms over extensive latitude and longitude regions (10°×10°), as revealed in coincident Mars Color Imager (MARCI) nadir imaging. Solar tides, gravity waves, and the large orbital variation of the extended thermal structure of the Mars atmosphere influence all of these behaviors. Mesospheric dust aerosols appear infrequently over the non-global (planet encircling) dust storm era of the CRISM limb data set (2009–2016), and exhibit smaller particle sizes (Reff = 0.2–0.7 μm) relative to dust in the lower atmosphere. One isolated case of an aphelion (Ls = 96°) mesospheric dust layer with large dust particle sizes (Reff ∼2 μm) over Syria Planum may reflect high altitude, non-local transport of dust over elevated regions.

Reducing bacterial aerosol emissions from membrane bioreactors: The impact of SRT and the addition of PAC and calcium

Bacterial aerosols resulting from membrane bioreactor (MBR) processes, which require excessive aeration in a confined space, are important to investigate because of their possible adverse effects on human health. This study investigated the influence of solid retention time (SRT) on bacterial aerosols from MBRs. Moreover, powdered activated carbon (PAC) and calcium were used to attenuate bacterial aerosol emissions from MBRs. The particulate matter (PM) emitted from the MBRs was reduced by 30.5 and 25.2% at SRTs of 20 and 80 d, respectively, compared to the level emitted at an SRT of 10 d. Total cell counts were similarly reduced at SRTs of 20 and 80 d. Longer SRTs also led to greater reductions in the particle size distribution of the sludge within 10 μm. Several factors in the MBR influenced the behavior of the bacterial aerosol emissions from the MBRs. This study showed that changes in viscosity and particle size induced by the SRT influenced the bacterial aerosol emissions in MBRs. Therefore, SRT was identified as an important design parameter affecting bacterial aerosol emissions in MBR processes. The amounts of particulate matter and bacterial aerosols were reduced in MBRs using PAC and calcium, both of which exerted an immediate effect on the bacterial aerosol emissions in MBRs by increasing the aerosol-particle size.

Contribution to column-integrated aerosol typing based on Sun-photometry using different criteria

This study analyses the aerosol optical and microphysical properties obtained by the Aerosol Robotic Network (AERONET) in seven different sites operating in the Iberian Peninsula during three coincident years (2010−2012) with the objective of studying different aerosol typing approaches. This area is of interest due to its location between the Sahara desert (the largest source of natural aerosols in the world) and mainland Europe (a relevant source of anthropogenic aerosols). In particular, we study the aerosol optical depth (AOD), Angström parameter (α440–870) and fine mode fraction (FMF), which are estimated from direct sun irradiance measurements. Additionally, the single scattering albedo (ωo) and aerosol particle size distribution (PSD), which are computed using additional sky radiances measurements under cloudless skies, are used in our analyses. The analyses show aerosol seasonal patterns in the AOD with maximum values in summer/spring and minimum values in winter/autumn for all the analysed stations. For α440–870, there are differences from site to site, with maximum values in winter and minimum values in summer for the southern locations, while there is not a remarkable pattern for the eastern locations close to the Mediterranean coast. The frequent and intense Saharan dust outbreaks over the southern Iberian Peninsula and the intense anthropogenic activity in the eastern urban locations are behind these seasonal patterns in the AOD and α440–870. In this work, two of the most employed classification schemes of aerosol type in the literature are used: one is based on the AOD and α440–870, the other one is based on ωo at 440 nm and the FMF and a new classification scheme based on ωo at 440 nm and FMF is proposed. The results revealed that the new classification method is more appropriate for distinguishing the aerosol types that affect the Iberian Peninsula. The relationship derived here between Δωo = ωo (440)- ωo (1020) and the FMF is demonstrated to be useful for aerosol type classification when no measurements of the sky radiances, and consequently of ωo(440), are available. Alternatively, the relationship between the ratio Δωo/ωo(440) and the FMF can be used because (Δωo/ωo) provides information about both the spectral ωo and the absolute values.

Seasonal Changes in Titan’s Upper Haze Resulting from Saturn’s Eccentric Orbit

Abstract Organic aerosols are produced high in the atmosphere of Titan by complex photochemical pathways starting from the dissociation of CH4 by solar ultraviolet (UV) and N2 by energetic particles. An end product of this photochemistry is the organic haze enshrouding Titan. The solar flux at Titan varies by about 20% between periapsis and apoapsis, thus we expect the dissociation of CH4 and the total production of aerosols to have a similar seasonal dependence. The seasonal cycle in the haze production due to Saturn’s orbital eccentricity is complicated by seasonal changes in dynamics and aerosol particle size due to Saturn’s 27° obliquity. A 3D Titan general circulation model with fully coupled aerosol microphysics, the Titan Community Atmospheres Model, simulates the aerosol haze with and without aerosol production as a function of solar UV. Both simulations display an equatorial seasonal cycle in the haze above about 340 km; however, this cycle is amplified by a factor of 2 in the simulation with production as a function of solar UV. We compare the simulations with published estimates of haze extinction in the upper atmosphere. Current observations of the haze extinction at 400 km cannot distinguish between the two simulations, highlighting the difficulties that complicated dynamics in the upper atmosphere pose for trend detection.

On Ash Deposition Rates from Air and Oxy-Combustion of Pulverized Coal, Petroleum Coke, and Biomass

This paper presents a synthesis of a large body of experimental data on growth rates of ash deposits from the air and oxy-combustion of multiple pulverized solid fuels, including coal, biomass, and their blends. The experimental data were obtained from 35 tests in a 100 kW (rated) entrained-flow combustor that allowed for self-sustained combustion of solid fuels. Ash deposition rates were measured using a wall-temperature-controlled ash deposition probe. The collected deposits were divided into tightly bound “inside deposits” adjacent to the heat transfer surface and loosely bound “outside deposits” that grow further out. Ash aerosol particle size distributions (psd’s) and size-segregated compositions were obtained through electric mobility, light scattering, and impactor methods. Rates of ash deposition for both inside and outside deposits are presented. Rates of growth of the inside deposit were proportional to the sub-micrometer particle (PM1) concentration in the flue gas but correlated poorly with th...

Pulmonary toxicity of inhaled nano-sized cerium oxide aerosols in Sprague–Dawley rats

Cerium oxide nanoparticles (CeO2NPs), used in some diesel fuel additives to improve fuel combustion efficiency and exhaust filter operation, have been detected in ambient air and concerns have been raised about their potential human health impact. The majority of CeO2NP inhalation studies undertaken to date have used aerosol particles of larger sizes than the evidence suggests are emitted from vehicles using such fuel additives. Hence, the objective of this study was to investigate the effects of inhaled CeO2NP aerosols of a more environmentally relevant size, utilizing a combination of methods, including untargeted multi-omics to enable the broadest possible survey of molecular responses and synchrotron X-ray spectroscopy to investigate cerium speciation. Male Sprague–Dawley rats were exposed by nose-only inhalation to aerosolized CeO2NPs (mass concentration 1.8 mg/m3, aerosol count median diameter 40 nm) for 3 h/d for 4 d/week, for 1 or 2 weeks and sacrificed at 3 and 7 d post-exposure. Markers of inflammation changed significantly in a dose- and time-dependent manner, which, combined with results from lung histopathology and gene expression analyses suggest an inflammatory response greater than that seen in studies using micron-sized ceria aerosols. Lipidomics of lung tissue revealed changes to minor lipid species, implying specific rather than general cellular effects. Cerium speciation analysis indicated a change in Ce3+/Ce4+ ratio within lung tissue. Collectively, these results in conjunction with earlier studies emphasize the importance of aerosol particle size on toxicity determination. Furthermore, the limited effect resolution within 7 d suggested the possibility of longer-term effects.