This study investigates the impact of fatty acids on the cloud condensation nuclei (CCN) activity of sea salt aerosol of initial size 30, 50, 70 or 90 nm. Two of the major fatty acids in the marine ...environment, palmitic acid (C16) and stearic acid (C18), were investigated along with their unsaturated analogues palmitoleic acid and oleic acid, respectively. Sea salt seed particles were generated by aeration through a diffuser placed inside a sea spray tank. Fatty acids were added to the particles via condensation of fatty acid vapours in a heated flask at different temperatures. The diameters and CCN activity of particles before and after condensation of fatty acids were monitored. Based on the change in mobility diameter, a coating thickness and an organic volume fraction were inferred. Addition of the unsaturated acids to the core sea salt particles did not result in hindered water uptake for any organic volume fractions studied (25-96%) and critical supersaturations generally followed the kappa addition rule assuming a kappa value of zero for the fatty acids and assuming a constant surface tension equal to that of water. For the saturated fatty acids, a deviation from the Zdanovskii, Stokes and Robinson assumption (kappa mixing rule) in the direction of hindered water uptake was observed for organic volume fractions corresponding to thick (25-29 nm) coatings of palmitic acid and even thinner coatings of stearic acid.
Particulate matter (PM) air pollution is a central concern for public health. Current legislation relies on a mass concentration basis, despite broad acceptance that mass alone is insufficient to ...capture the complexity and toxicity of airborne PM, calling for additional and more comprehensive measurement techniques. We study to what extent scanning electron microscopy coupled with energy dispersive X-ray spectroscopy (SEM/EDS) can be applied for physicochemical characterization of complex aerosols, and investigate its potential for separating particle properties on a single particle basis, even for nanosized particles. SEM/EDS analysis is performed on impactor samples of laboratory generated aerosols, consisting of either NaCl, Halloysite fibers, soot-like Printex90 agglomerates, or their combination. The analysis is automated and performed as EDS maps, covering a statistically relevant number of particles, with analysis times of approximately one hour/sample. Derived size distributions are compared to scanning mobility particle sizer (SMPS) and electric low-pressure impactor (ELPI) results. A method is presented to estimate airborne number concentrations and size distributions directly from SEM results, within a factor 10 of SMPS and ELPI outcomes. A classification scheme is developed based on elemental composition, providing class-specific information with individual particle statistics on shape, size, and mixing state. This can identify primary particles for source apportionment and enables easy distinction between fibrous and dense particle classes, e.g. for targeted risk assessments. Overall, the SEM/EDS analysis provides a more detailed physicochemical characterization of PM than online measurements, e.g. SMPS and ELPI. The method has the potential to improve assessments of PM exposure and risk, and facilitates source identification, even without prior knowledge at sampling.
The composition and carbon nanostructure of soot are important parameters influencing health and climate effects, and the efficacy of soot mitigation technologies. We used laser-vaporization, ...electron-ionization aerosol mass spectrometry (or SP-AMS) to systematically investigate relationships between aerosol mass spectra, carbon nanostructure (HRTEM), and composition (thermal-optical carbon analysis) for soot with varying physicochemical properties. SP-AMS refractory black carbon concentrations (based on C≤5+ clusters) were correlated to elemental carbon (r = 0.98, p < 10−8) and equivalent black carbon (aethalometer) concentrations. The SP-AMS large carbon (C≥6+, midcarbons and fullerene carbons) fraction was inversely correlated to fringe length (r = −0.97, p = 0.028) and linearly correlated to the fraction of refractory organic carbon that partially pyrolize during heating (r = 0.89, p < 10−4). This refractory organic carbon material was incompletely detected with conventional aerosol mass spectrometry (flash vaporization at 600 °C). This suggests that (SP-AMS) refractory carbon cluster analysis provides insight to chemical bonding and nanostructures in refractory carbon materials, lowcarbons (C≤5+) indicate mature soot and large carbons indicate refractory organic carbon and amorphous nanostructures related to C5-components. These results have implications for assessments of soot particle mixing state and brown carbon absorption in the atmosphere and enable novel, on-line analysis of engineered carbon nanomaterials and soot characteristics relevant for climate and health.
Display omitted
Recent findings show that cerium oxide (CeO2) nanoparticles may undergo in vivo-induced size transformation with the formation of smaller particles that could result in a higher translocation ...following pulmonary exposure compared to virtually insoluble particles, like titanium dioxide (TiO2). Therefore, we compared liver deposition of CeO2 and TiO2 nanoparticles of similar primary sizes 1, 28 or 180 days after intratracheal instillation of 162 μg of NPs in female C57BL/6 mice. Mice exposed to 162 μg CeO2 or TiO2 nanoparticles by intravenous injection or oral gavage were included as reference groups to assess the amount of NPs that reach the liver bypassing the lungs and the translocation of NPs from the gastrointestinal tract to the liver, respectively. Pulmonary deposited CeO2 nanoparticles were detected in the liver 28 and 180 days post-exposure and TiO2 nanoparticles 180 days post-exposure as determined by darkfield imaging and by the quantification of Ce and Ti mass concentration by inductively coupled plasma-mass spectrometry (ICP-MS). Ce and Ti concentrations increased over time and 180 days post-exposure the translocation to the liver was 2.87 ± 3.37% and 1.24 ± 1.98% of the initial pulmonary dose, respectively. Single particle ICP-MS showed that the size of CeO2 nanoparticles in both lung and liver tissue decreased over time. No nanoparticles were detected in the liver following oral gavage. Our results suggest that pulmonary deposited CeO2 and TiO2 nanoparticles translocate to the liver with similar calculated translocation rates despite their different chemical composition and shape. The observed particle size distributions of CeO2 nanoparticles indicate in vivo processing over time both in lung and liver. The fact that no particles were detected in the liver following oral exposure showed that direct translocation of nanoparticles from lung to the systemic circulation was the most important route of translocation for pulmonary deposited particles.
Display omitted
•The stepwise addition of HNTs and CNFs efficiently removes anionic dye from water.•Both HNTs and CNFs participate in the dye capture.•CNFs also aggregate the dye-loaded colloidal ...clay particles.•The size and morphology of the clay mineral determine the dye removal efficiency.
The synergistic combination of different nanomaterials for improved performance in environmental applications such as the removal of aqueous micropollutants has attracted increasing interest in recent years. This study demonstrates a novel sequential adsorption–aggregation concept that harnesses tubular halloysite nanotubes (HNTs) and flexible cellulose nanofibrils (CNFs) for the removal of a small, anionic dye molecule, chrome azurol S, from water. Hollow HNTs were first allowed to interact with the aqueous dye solution, after which the dye-loaded colloidal nanotubes were aggregated and separated from the water phase with cationized CNFs. The combination of 25 mg CNFs with 1 g HNTs at pH 7 resulted in efficient removal of dye (80%) and turbidity (~100%) and the removal of dye was further promoted in more acidic conditions (within the pH range of 6–8.5) because of the attractive electrostatic interactions. Cationic CNFs not only enabled the separation of dye-loaded clay particles from the water phase through a rapid aggregation but also participated in dye removal through adsorption (~20%). In comparison with nano-sized HNTs, the dye removal performance of micro-sized and chemically similar kaolin was poor (43%). Given the good availability of both HNTs and CNFs and the low consumption of the more expensive component (i.e., CNFs) in the process, the concept is straightforward, readily applicable, environmentally benign, and potentially cost-effective.
In the indoor environment, people are exposed to several fungal species. Evident dampness is associated with increased respiratory symptoms. To examine the immune responses associated with fungal ...exposure, mice are often exposed to a single species grown on an agar medium. The aim of this study was to develop an inhalation exposure system to be able to examine responses in mice exposed to mixed fungal species aerosolized from fungus-infested building materials. Indoor airborne fungi were sampled and cultivated on gypsum boards. Aerosols were characterized and compared with aerosols in homes. Aerosols containing 10(7)CFU of fungi/m(3)air were generated repeatedly from fungus-infested gypsum boards in a mouse exposure chamber. Aerosols contained Aspergillus nidulans,Aspergillus niger, Aspergillus ustus, Aspergillus versicolor,Chaetomium globosum,Cladosporium herbarum,Penicillium brevicompactum,Penicillium camemberti,Penicillium chrysogenum,Penicillium commune,Penicillium glabrum,Penicillium olsonii,Penicillium rugulosum,Stachybotrys chartarum, and Wallemia sebi They were all among the most abundant airborne species identified in 28 homes. Nine species from gypsum boards and 11 species in the homes are associated with water damage. Most fungi were present as single spores, but chains and clusters of different species and fragments were also present. The variation in exposure level during the 60 min of aerosol generation was similar to the variation measured in homes. Through aerosolization of fungi from the indoor environment, cultured on gypsum boards, it was possible to generate realistic aerosols in terms of species composition, concentration, and particle sizes. The inhalation-exposure system can be used to study responses to indoor fungi associated with water damage and the importance of fungal species composition.
Lung deposition of multi-walled carbon nanotubes (MWCNT) induces pulmonary toxicity. Commercial MWCNT vary greatly in physicochemical properties and consequently in biological effects. To identify ...determinants of MWCNT-induced toxicity, we analyzed the effects of pulmonary exposure to 10 commercial MWCNT (supplied in three groups of different dimensions, with one pristine and two/three surface modified in each group). We characterized morphology, chemical composition, surface area and functionalization levels. MWCNT were deposited in lungs of female C57BL/6J mice by intratracheal instillation of 0, 6, 18 or 54 μg/mouse. Pulmonary inflammation (neutrophil influx in bronchoalveolar lavage (BAL)) and genotoxicity were determined on day 1, 28 or 92. Histopathology of the lungs was performed on day 28 and 92. All MWCNT induced similar histological changes. Lymphocytic aggregates were detected for all MWCNT on day 28 and 92. Using adjusted, multiple regression analyses, inflammation and genotoxicity were related to dose, time and physicochemical properties. The specific surface area (BET) was identified as a positive predictor of pulmonary inflammation on all post-exposure days. In addition, length significantly predicted pulmonary inflammation, whereas surface oxidation (-OH and -COOH) was predictor of lowered inflammation on day 28. BET surface area, and therefore diameter, significantly predicted genotoxicity in BAL fluid cells and lung tissue such that lower BET surface area or correspondingly larger diameter was associated with increased genotoxicity. This study provides information on possible toxicity-driving physicochemical properties of MWCNT. The results may contribute to safe-by-design manufacturing of MWCNT, thereby minimizing adverse effects.
Display omitted
•Electrostatic spray deposition (ESD) particle emissions are not well characterized.•Emission rates in s−1 and μg s−1 was defined for ESD of a photoactive nanocoating.•Particle ...deposition rates and morphologies of deposited particle were determined.•Emission rates and particle properties are required in exposure modellings.•Recommendations for ESD process exposure modellings is given.
Here, we studied the particle release rate during Electrostatic spray deposition of anatase-(TiO2)-based photoactive coating onto tiles and wallpaper using a commercially available electrostatic spray device. Spraying was performed in a 20.3m3 test chamber while measuring concentrations of 5.6nm to 31μm-size particles and volatile organic compounds (VOC), as well as particle deposition onto room surfaces and on the spray gun user hand. The particle emission and deposition rates were quantified using aerosol mass balance modelling. The geometric mean particle number emission rate was 1.9×1010s−1 and the mean mass emission rate was 381μgs−1. The respirable mass emission-rate was 65% lower than observed for the entire measured size-range. The mass emission rates were linearly scalable (±ca. 20%) to the process duration. The particle deposition rates were up to 15h−1 for <1μm-size and the deposited particles consisted of mainly TiO2, TiO2 mixed with Cl and/or Ag, TiO2 particles coated with carbon, and Ag particles with size ranging from 60nm to ca. 5μm. As expected, no significant VOC emissions were observed as a result of spraying. Finally, we provide recommendations for exposure model parameterization.
Some multi-walled carbon nanotubes (MWCNTs) induce mesothelioma in rodents, straight MWCNTs showing a more pronounced effect than tangled MWCNTs. As primary and secondary genotoxicity may play a role ...in MWCNT carcinogenesis, we used a battery of assays for DNA damage and micronuclei to compare the genotoxicity of straight (MWCNT-S) and tangled MWCNTs (MWCNT-T) in vitro (primary genotoxicity) and in vivo (primary or secondary genotoxicity). C57Bl/6 mice showed a dose-dependent increase in DNA strand breaks, as measured by the comet assay, in lung cells 24 h after a single pharyngeal aspiration of MWCNT-S (1-200 μg/mouse). An increase was also observed for DNA strand breaks in lung and bronchoalveolar lavage (BAL) cells and for micronucleated alveolar type II cells in mice exposed to aerosolized MWCNT-S (8.2-10.8 mg/m
3
) for 4 d, 4 h/d. No systemic genotoxic effects, assessed by the γ-H2AX assay in blood mononuclear leukocytes or by micronucleated polychromatic erythrocytes (MNPCEs) in bone marrow or blood, were observed for MWCNT-S by either exposure technique. MWCNT-T showed a dose-related decrease in DNA damage in BAL and lung cells of mice after a single pharyngeal aspiration (1-200 μg/mouse) and in MNPCEs after inhalation exposure (17.5 mg/m
3
). In vitro in human bronchial epithelial BEAS-2B cells, MWCNT-S induced DNA strand breaks at low doses (5 and 10 μg/cm
2
), while MWCNT-T increased strand breakage only at 200 μg/cm
2
. Neither of the MWCNTs was able to induce micronuclei in vitro. Our findings suggest that both primary and secondary mechanisms may be involved in the genotoxicity of straight MWCNTs.
PDF
