Particle distribution in lung and lymph node tissues of rats and dogs and the migration of particle-containing alveolar cells in vitro

Prevention through design: insights from computational fluid dynamics modeling to predict exposure to ultrafine particles from 3D printing

Fused filament fabrication (FFF) 3D printers are increasingly used in industrial, academic, military, and residential sectors, yet their emissions and associated user exposure scenarios are not fully described. Characterization of potential user exposure and environmental releases requires robust investigation. During operation, common FFF 3D printers emit varying amounts of ultrafine particles (UFPs) depending upon feedstock material and operation procedures. Volatile organic compounds associated with these emissions exhibit distinct odors; however, the UFP portion is largely imperceptible by humans. This investigation presents straightforward computational modeling as well as experimental validation to provide actionable insights for the proactive design of lower exposure spaces where 3D printers may be used. Specifically, data suggest that forced clean airflows may create lower exposure spaces, and that computational modeling might be employed to predict these spaces with reasonable accuracy to assist with room design. The configuration and positioning of room air ventilation diffusers may be a key factor in identifying lower exposure spaces. A workflow of measuring emissions during a printing process in an ANSI/CAN/UL 2904 environmental chamber was used to provide data for computational fluid dynamics (CFD) modeling of a 6 m2 room. Measurements of the particle concentrations in a Class 1000 clean room of identical geometry were found to pass the Hanna test for agreement between model and experimental data, validating the findings.

Translocation of particles deposited in the respiratory system: a systematic review and statistical analysis

Many epidemiological studies have demonstrated that ambient particulate matter poses consistent risks for respiratory and cardiovascular disorders. The translocation of inhaled particles is one hypothesis that could explain such systemic effects. The objectives of this study were to conduct a systematic review of previous reports on particle translocation from the respiratory system and to discuss factors important for translocation. A PubMed search was conducted in August 2011 for the period from 1967 with four main keyword domains (particle, translocation, detection site, and exposure route). The systematic review identified 61 original articles written in English that met the specified criteria (i.e., information on experiment and particle detection). Categorical regression analysis was performed with the site of particle detection as the objective variable, and particle size, particle material, animal species, and exposure route as the explanatory variables. All explanatory variables showed statistically significant effects. The effects for particle size and particle material were large, while the effects for animal species and exposure route were relatively small. There was a broad relationship between particle size and detection site: ≤50 nm for brain and remote organs; ≤1 μm for blood; and ≤10 μm for lung tissues. However, these results should be considered within the context of several limitations, such as deficiency of information.

Estimating the lung burden from exposure to aerosols of depleted uranium

Following exposure to aerosols of depleted uranium (DU), biological samples show the presence of a synthetic mixture of natural uranium and DU. By partitioning the uranium in the 24-h urine sample along the isotopic fractions of natural uranium and DU, one can study the kinetics of these subpopulations independently. A linear model is developed to estimate the lung burden of DU from measurements of DU in 24-h urine samples, years after inhalational exposure to aerosols of DU. This model takes into account the intracellular dissolution of the retained particles and the precipitation of a significant fraction of the dissolved DU as insoluble uranyl phosphates.

Evaluation of phagocytic activity in human monocyte-derived dendritic cells

Dendritic cells play a central role in initiation of primary T lymphocyte responses to foreign antigens. Their potency in antigen presentation vis-à-vis reported low or lack of ability to phagocytize particulate matter has limited our understanding of the role that they play in inducing immunity to particulate antigens. One hypothesis is that dendritic cells may possess a high phagocytic capacity when immature and located in peripheral tissues, which they lose on maturation. Our goal was to characterize the phagocytic capacity in human immature dendritic cells. The phagocytic capacity of human monocyte-derived immature dendritic cells was studied by morphological and morphometric means, and compared to that of professional phagocytes, human alveolar macrophages, their progenitors, the peripheral blood monocytes, and mature dendritic cells. Phagocytic index (proportion of phagocytic cells) was decreased by 42.8% (immature dendritic cells) and 74.2% (mature dendritic cells) with respect to monocytes. Similarly, the phagocytic index was decreased by 46.5% (immature dendritic cells) and 75.9% (mature dendritic cells) with respect to macrophages. Volume density of phagocytized particles was decreased by 76.1% (immature dendritic cells) and 96.7% (mature dendritic cells) with respect to the monocytes. However, volume density was decreased by 34.3% (immature dendritic cells) and 91% (mature dendritic cells) with respect to alveolar macrophages. These results show that human monocyte-derived immature dendritic cells possess a phagocytic capacity that is lower than that of peripheral blood monocytes and alveolar macrophages but higher than that of mature dendritic cells.

Combined influence of quartz dust, ozone and NO2 on chemotactic mobility, release of chemotactic factors and other cytokines by macrophages in vitro

In this study the single as well as combined effects of quartz, ozone and nitrogen dioxide (NO2) on some immunofunctions of bovine alveolar macrophages (BAM) were investigated. After incubation with 10 micrograms/ml of particles the chemotactic response of BAM is increased nonspecifically, whereas after incubation with 100 micrograms/ml of quartz chemotaxis is specifically decreased. In addition, quartz induces tumor necrosis factor alpha (TNF-alpha) and chemokines to be released dependent on the concentration. Ozone by itself is also a very potent inducer of the release of chemokines and TNF-alpha, but in combination with ozone, quartz has not more than an additive effect. NO2 alone suppresses drastically the release of TNF-alpha. The results show that quartz, ozone and NO2 alter some immunofunctions of BAM and that by combining toxic particles such as quartz with these gases, additive but not synergistic effects might be expected.

Pulmonary retention of ultrafine and fine particles in rats

In aerosol research, particle size has been mainly considered in the context of the role it plays in particle deposition along the respiratory tract. The possibility that the primary particle size may affect the fate of particles after they are deposited was explored in this study. Rats were exposed for 12 wk to aerosolized ultrafine (integral of 21 nm diameter) or fine (integral of 250 nm diameter) titanium dioxide (TiO2) particles. Other rats were exposed to TiO2 particles of various sizes (12, 21, 230, and 250 nm) by intratracheal instillation. After the rat lungs were extensively lavaged, analysis of particle content in the lavaged lungs, lavage fluid, and of lymphatic nodes was performed. Electron and light microscopy was also performed using unlavaged lungs. Both acute instillation and subchronic inhalation studies showed that ultrafine particles (integral of 20 nm) at equivalent masses access the pulmonary interstitium to a larger extent than fine particles (integral of 250 nm). An increasing dose in terms of particle numbers and a decreasing particle size promoted particle access into the interstitium. The translocation of particles into the interstitium appeared to be a function of the number of particles, and the process appeared to be related to the particle size, the delivered dose, and the delivered dose rate. A net effect of the preferential translocation of the smaller particles into the interstitium was a prolongation in their lung retention. After the 12-wk inhalation exposure, pulmonary clearance of ultrafine particles was slower (t1/2 = 501 days) than of larger particles (t1/2 = 174 days).(ABSTRACT TRUNCATED AT 250 WORDS)