Lobar evenness of deposition/retention in rat lungs of inhaled silver nanoparticles: an approach for reducing animal use while maximizing endpoints

BackgroundInformation on particle deposition, retention and clearance are important for the evaluation of the risk of inhaled nanomaterials to human health. Recent revised OECD inhalation toxicity test guidelines require to evaluate the lung burden of nanomaterials after rodent subacute and subchronic inhalation exposure (OECD 412, OECD 413). These revised test guidelines require additional post-exposure observation (PEO) periods that include lung burden measurements that can inform on lung clearance behavior and translocation. The latter being particularly relevant when the testing chemical is a solid poorly soluble nanomaterial. Therefore, in the spirit of 3 R's, we investigated whether measurement of retained lung burden of inhaled nanoparticles (NPs) in individual lung lobes is sufficient to determine retained lung burden in the total lung. If it is possible to use only one lobe, it will reduce animal use and maximize the number of endpoints evaluated.ResultsTo achieve these goals, rats were exposed nose-only for 1 or 5days (6h/day) to an aerosol of 20nm well-dispersed silver nanoparticles (AgNPs), which is the desired particle diameter resulting in maximum deposition in the pulmonary region when inhaled as singlets. After exposure, the five lung lobes were separated and silver concentration was measured using inductively coupled plasma-mass spectrophotometer (ICP-MS). The results showed that the retention of deposited silver nanoparticle in the different lung lobes did not show any statistically significant difference among lung lobes in terms of silver mass per gram lung lobe. This novel finding of evenness of retention/deposition of inhaled 20nm NPs in rats for all five lobes in terms of mass per unit tissue weight contrasts with earlier studies reporting greater apical lobe deposition of inhaled micro-particles in rodents. The difference is most likely due to preferred and efficient deposition of inhaled NPs by diffusion vs. additional deposition by sedimentation and impaction for micron-sized particles.ConclusionAgNPs following acute inhalation by rats are evenly retained in each lung lobe in terms of mass per unit lung tissue weight. Accordingly, we suggest sampling any of the rat lung lobes for lung burden analysis can be used to determine deposited or retained total lung burden after short-term inhalation of NPs and using the other lobes for collecting and analyzing bronchoalveolar lavage fluid (BALF) and for histopathological analysis. Therefore, by combining lung burden measurement, histopathological tissue preparation, and BALF assay in the same rat will reduce the number of animals used and maximize the number of endpoints measured.This research was supported by the Industrial Technology Innovation Program (10052901), Development of highly usable nanomaterial inhalation toxicity testing system in commerce through the Korea Evaluation Institute of Industrial Technology by the Korean Ministry of Trade, Industry & Energy and NIH/NIEHS grants U19ES019545, P30ES007033 and EPA grant RD83573801

Development of a toroidal-shaped differential mobility analyzer for effective measurements of airborne particles: Experiment and modeling

A toroidal-shaped differential mobility analyzer (DMA), called toroidal Hanyang-DMA (toroidal Hy-DMA), was developed for particle characterization. The height, width, and weight of the newly developed toroidal Hy-DMA are 8 cm, 14 cm, and 1.2 kg, respectively, indicating that it is much more compact and lighter than the TSI long-DMA; nevertheless, the classifiable particle size range is up to 400 nm. Therefore, the toroidal Hy-DMA can be useful for many applications in a limited space owing to its small size. The performance of the Hy-DMA was evaluated using tandem differential mobility analyzer (TDMA) experiments with two identical Hy-DMAs and numerical simulations using a single-particle tracking analysis in a Lagrangian framework. To simulate particle behaviors, a flow-rate-weighted particle injection method, which is more realistic, was employed, and the proposed particle tracking method can be widely applied to any non-plug flow conditions. The obtained experimental data and numerical results of central particle sizes are consistent with each other. Empirical and numerical transfer functions of the toroidal Hy-DMA were obtained and compared with those of other types of well-known DMAs. It is concluded that the toroidal Hy-DMA has an empirical transmission probability ranging from 0.5 to 0.9 and a sizing resolution ranging from 5.5 to 9.0, which indicates acceptable performance in classifying monodisperse particles within the test size range of 20 to 400 nm. Copyright (c) 2019 American Association for Aerosol ResearchThis work was supported by the research fund of Hanyang University (HY-2019-P)

Relating high ozone, ultrafine particles, and new particle formation episodes using cluster analysis

We studied the simultaneity of tropospheric ozone (O3) episodes, high ultrafine particle (UFP; diameter < 100 nm) concentrations, and the occurrence of new particle formation at a regional background station in the Western Mediterranean (northeast Spain), which is affected considerably by the transport of pollutants emitted in the Barcelona metropolitan area and nearby populated and industrial areas. Using cluster analysis, we categorized summer and spring days between 2014 and 2018 according to their daily cycles of O3 concentrations, and then studied the evolution of the particle number size distribution, meteorological variables, and black carbon and sulfur dioxide concentrations. The analysis revealed that, in spring and summer, the highest UFP concentrations coincided with the highest O3 episodes, but new particle formation was largely inhibited during these episodes, probably due to the high aerosol pollution load transported from the Barcelona metropolitan area to the station. In contrast, new particle formation episodes were concurrent with the lowest concentrations of O3 and UFPs, including the number of particles in the 9–25 nm size range. Measurements carried out in an intensive field study, using an air ion spectrometer and a particle size magnifier, support these results. In addition, measurements obtained onboard tethered balloons revealed that sea and land breezes transported regional pollutants vertically up to about 400 m above ground level. This coincided with episodes of vertical recirculation of air masses that lasted for several days, which resulted in high O3 and high UFP episodes, while new particle formation was inhibited.The present work was supported by the Spanish State Research Agency – integrated in the Spanish Ministry of Science, Innovation and Universities –, FEDER funds under the project HOUSE (CGL2016-78594-R), and by the Government of Catalonia (AGAUR 2017 SGR41). The work was supported by Academy of Finland via Center of Excellence in Atmospheric Sciences (project 272041), via Biofuture2025 project “Nano BioMass, 304347" European Commission via ACTRIS2 (project 654109). The authors thank the Department of Territory of the Government of Catalonia for maintaining the XVPC air quality network and providing the data for O3, NOx and SO2. The authors also acknowledge the valuable contributions of Miguel Escudero, Enrique Mantilla, Hong-Ku Lee, Hee-Ram Eun and Yong-Hee Park during the tethered balloons measurements. C. Carnerero thanks the Spanish Ministry of Science, Innovation and Universities for her FPI grant (BES-2017-080027)

Numerical simulation of a multi-port differential mobility analyzer(MP-DMA) used in a real-time nano-particle sizer (NPS)

In a recently conducted study, we developed a nano-particle sizer (NPS) that consists of a multi-port differential mobility analyzer (MP-DMA) and two multi condensation particle counters (M-CPCs) for achieving fast measurements of aerosol particles; however, the performance of MP-DMA was not detailed in the study. Therefore, the objective of this study is to perform numerical simulations to obtain the transfer function of each port in the MP-DMA, which is the main component of the NPS. We observed good agreement between the numerically obtained central particle size of each port and the experimental data under the same operating conditions. The transmission probability and resolution of each port were determined and analyzed under various conditions using the transfer function. The findings of this study shall help in understanding the advantages of NPS.This work was supported by the research fund of Hanyang University (HY-2019-P)

Extensive evaluation and classification of low‐cost dust sensors in laboratory using a newly developed test method

An extensive evaluation of low-cost dust sensors was performed using an exponentially decaying particle concentration. A total of 264 sensors including 27 sensors with light-emitting diodes (LEDs) and 237 sensors with laser lighting sources were tested. Those tested sensors were classified into 4 groups based on the deviation from the reference data obtained by a reference instrument. The response linearities of all the tested samples for PM1, PM2.5, and PM10 were in excellent agreement with the reference instrument, except a few samples. For the measurements of PM1 and PM2.5, the lighting source, that is, LED or laser, did not show any significant difference in overall sensor performance. However, LED-based sensors did not perform well for PM10 measurements. The 32, 24, and 16% of all the tested sensors for PM1, PM2.5, and PM10 measurement, respectively, are in the category of Class 1 (reference instrument reading +/- 20%) requirement. The performance of the low-cost dust sensors for PM10 measurement was relatively less satisfactory.The Ministry of Trade, Industry & Energy (MOTIE, Korea)

28-Day inhalation toxicity study with evaluation of lung deposition and retention of tangled multi-walled carbon nanotubes

Lung deposition and retention measurements are now required by the newly revised OECD inhalation toxicity testing guidelines 412 and 413 when evaluating the clearance and biopersistence of poorly soluble nanomaterials, such as multi-walled carbon nanotubes (MWCNTs). However, evaluating the lung deposition concentration is challenging with certain nanomaterials, such as carbon-based and iron-based nanomaterials, as it is difficult to differentiate them from endogenous elements. Therefore, the current 28-day inhalation toxicity study investigated the lung retention kinetics of tangled MWCNTs. Male Sprague Dawley rats were exposed to MWCNTs at 0, 0.257, 1.439, and 4.253 mg/m(3) for 28 days (6 h/day, 5 days/week, 4 weeks). Thereafter, the rats were sacrificed at day 1, 7, and 28 post-exposure and the pulmonary inflammatory response evaluated by analyzing the bronchoalveolar lavage fluid. Plus, the blood biochemistry, hematology, and histopathology of the lungs were also examined. The lung deposition and retention of MWCNTs were determined based on the elemental carbon content in the lungs after tissue digestion. The number of polymorphonuclear cells and LDH concentration were both found to be significantly higher with the medium and high concentrations (1.439 and 4.253 mg/m(3)) and dose dependent. The estimated retention half-life for the high concentration (4.253 mg/m(3)) was about 35 days. The results of this study indicate that tangled MWCNTs seem to have a relatively shorter retention half-life when compared to previous reports on rigid MWCNTs, and the no-observed adverse effect level (NOAEL) for the tested tangled MWCNTs was 0.257 mg/m(3) in a previous rat 28-day subacute inhalation toxicity study.This research was supported by the Industrial Technology Innovation Program [10052901], Development of highly usable nanomaterial inhalation toxicity testing system in commerce through the Korea Evaluation Institute of Industrial Technology by the Korean Ministry of Trade, Industry and Energy

Study on the Influence of Mixing Effect to the Measurement of Particle Size Distribution using DMA and CPC

In the measurement using DMA and CPC in series, there is some time delay for particles classified in DMA to detect in CPC. During this time, the DMA time-response changes due to the velocity profile of sampling tube and the diffusion of particles in the volume that exists between the DMA exit and the detector of ultra-fine CPC. This is called mixing effect. In the accelerated measurement methods like the TSI -SMPS, the size distribution is obtained from the correlation between the time -varying electrical potential of the DMA and the corresponding particle concentrations sampled in DMA. If the DMA time -response changes during this delay time, this can cause the error of a size distributi..

부산항만 드론활용 미세먼지(PM2.5) 농도 관측

선박에서 배출되는 대기오염물질들은 항만 및 주변 도심지역의 대기질에 영향을 미치며, 풍향 및 풍속에 따라 선박기원 대기오염물질은 수평거리로는 1-5km 범위까지, 수직거리로는 1-10km 고도까지 영향을 미친다. 본 연구는 부산항만(북항)에서 드론을 이용한 수직적 미세먼지 PM2.5 농도와 입자 크기별(0.3~0.5 μm, 0.5~1 μm, 1~5 μm) 수 농도를 측정하였다. 드론 관측은 2020년 8월과 11월에 한국해양과학기술원(KIOST, 외항 정점)과 항만 내(내항 정점) 각 정점에서 동시에 고도 150 m까지 이루어졌다. 풍향에 따라, 즉 북동풍(case 1), 남동풍(case 2), 남서풍(case 3), 동풍(case 4)에 따른 수직적 PM2.5 농도, 입자 수 농도 및 풍속변화를 분석하였다. 해상으로부터 바람이 불어오는 case 2와 3의 경우, 항만 내 정점의 특정 고도에서 PM2.5 농도가 높아지며, case 2에 비해 case 3에서 더 높은 고도(약 30~60 m)에서 고농도의 PM2.5 농도가 관측되었다. KIOST 정점은 case 2, 3 및 4에서 해상 대기의 영향을 받으며, 특히 case 4의 30 m 이상 고도에서 PM2.5 농도가 증가하였다. 결과적으로 해상에서 불어오는 풍향에 따라 고도별 PM2.5 고농도 현상은 북항에 위치한 부두 및 남외항 묘박지, 감천항으로 입·출입하는 선박의 영향을 받는 것으로 판단된다.2