Evaluation of Pulmonary Effects of 3-D Printer Emissions From Acrylonitrile Butadiene Styrene Using an Air-Liquid Interface Model of Primary Normal Human-Derived Bronchial Epithelial Cells.

This study investigated the inhalation toxicity of the emissions from 3-D printing with acrylonitrile butadiene styrene (ABS) filament using an air-liquid interface (ALI) in vitro model. Primary normal human-derived bronchial epithelial cells (NHBEs) were exposed to ABS filament emissions in an ALI for 4 hours. The mean and mode diameters of ABS emitted particles in the medium were 175 ± 24 and 153 ± 15 nm, respectively. The average particle deposition per surface area of the epithelium was 2.29 × 107 ± 1.47 × 107 particle/cm2, equivalent to an estimated average particle mass of 0.144 ± 0.042 µg/cm2. Results showed exposure of NHBEs to ABS emissions did not significantly affect epithelium integrity, ciliation, mucus production, nor induce cytotoxicity. At 24 hours after the exposure, significant increases in the pro-inflammatory markers IL-12p70, IL-13, IL-15, IFN-γ, TNF-α, IL-17A, VEGF, MCP-1, and MIP-1α were noted in the basolateral cell culture medium of ABS-exposed cells compared to non-exposed chamber control cells. Results obtained from this study correspond with those from our previous in vivo studies, indicating that the increase in inflammatory mediators occur without associated membrane damage. The combination of the exposure chamber and the ALI-based model is promising for assessing 3-D printer emission-induced toxicity.

Pulmonary and systemic toxicity in rats following inhalation exposure of 3-D printer emissions from acrylonitrile butadiene styrene (ABS) filament.

BACKGROUND: Fused filament fabrication 3-D printing with acrylonitrile butadiene styrene (ABS) filament emits ultrafine particulates (UFPs) and volatile organic compounds (VOCs). However, the toxicological implications of the emissions generated during 3-D printing have not been fully elucidated. AIM AND METHODS: The goal of this study was to investigate the in vivo toxicity of ABS-emissions from a commercial desktop 3-D printer. Male Sprague Dawley rats were exposed to a single concentration of ABS-emissions or air for 4 hours/day, 4 days/week for five exposure durations (1, 4, 8, 15, and 30 days). At 24 hours after the last exposure, rats were assessed for pulmonary injury, inflammation, and oxidative stress as well as systemic toxicity. RESULTS AND DISCUSSION: 3-D printing generated particulate with average particle mass concentration of 240 ± 90 µg/m³, with an average geometric mean particle mobility diameter of 85 nm (geometric standard deviation = 1.6). The number of macrophages increased significantly at day 15. In bronchoalveolar lavage, IFN-γ and IL-10 were significantly higher at days 1 and 4, with IL-10 levels reaching a peak at day 15 in ABS-exposed rats. Neither pulmonary oxidative stress responses nor histopathological changes of the lungs and nasal passages were found among the treatments. There was an increase in platelets and monocytes in the circulation at day 15. Several serum biomarkers of hepatic and kidney functions were significantly higher at day 1. CONCLUSIONS: At the current experimental conditions applied, it was concluded that the emissions from ABS filament caused minimal transient pulmonary and systemic toxicity.

In vitro toxicity assessment of respirable solid surface composite sawing particles.

Solid surface composites (SSCs) are a class of popular construction materials composed of aluminum trihydrate and acrylic polymers. Previous investigations have demonstrated that sawing SSC releases substantial airborne dusts, with a number-based geometric mean diameter of 1.05 µm. We reported that in mice, aspiration exposure to airborne SSC dusts induced symptoms of pulmonary inflammation at 24-h postexposure: neutrophilic influx, alveolitis, and increased lactate dehydrogenase (LDH) and pro-inflammatory cytokine levels in lavage fluid. The particles appeared to be poorly cleared, with 81% remaining at 14-day postexposure. The objective of this study was to determine the toxicity specifically of respirable particles on a model of human alveolar macrophages (THP-1). The relative toxicities of subfractions (0.07, 0.66, 1.58, 5.0, and 13.42 µm diameter) of the airborne particles were also determined. THP-1 macrophages were exposed for 24 h to respirable particles from sawing SSC (0, 12.5, 25, 50, or 100 µg/ml) or size-specific fractions (100 µg/ml). Exposure to respirable SSC particles induced THP-1 macrophage toxicity in a dose-dependent manner. Viability was decreased by 15% and 19% after exposure to 50 and 100 µg/ml SSC, respectively, which correlated with increased cell culture supernatant LDH activity by 40% and 70% when compared to control. Reactive oxygen species (ROS) production and inflammatory cytokines were increased in a dose-dependent manner. A size-dependent cytotoxic effect was observed in the cells exposed to subfractions of SSC particles. SSC particles of 0.07, 0.66, and 1.58 µm diameter killed 36%, 17%, and 22% of cells, respectively. These results indicate a potential for cytotoxicity of respirable SSC particles and a relationship between particle size and toxicity, with the smallest fractions appearing to exhibit the greatest toxicity.

Mouse pulmonary response to dust from sawing Corian®, a solid-surface composite material.

Corian®, a solid-surface composite (SSC), is composed of alumina trihydrate and acrylic polymer. The aim of the present study was to examine the pulmonary toxicity attributed to exposure to SSC sawing dust. Male mice were exposed to either phosphate buffer saline (PBS, control), 62.5, 125, 250, 500, or 1000 µg of SSC dust, or 1000 µg silica (positive control) via oropharyngeal aspiration. Body weights were measured for the duration of the study. Bronchoalveolar lavage fluid (BALF) and tissues were collected for analysis at 1 and 14 days post-exposure. Enhanced-darkfield and histopathologic analysis was performed to assess particle distribution and inflammatory responses. BALF cells and inflammatory cytokines were measured. The geometric mean diameter of SSC sawing dust following suspension in PBS was 1.25 µm. BALF analysis indicated that lactate dehydrogenase (LDH) activity, inflammatory cells, and pro-inflammatory cytokines were significantly elevated in the 500 and 1000 µg SSC exposure groups at days 1 and 14, suggesting that exposure to these concentrations of SSC induced inflammatory responses, in some cases to a greater degree than the silica positive control. Histopathology indicated the presence of acute alveolitis at all doses at day 1, which was largely resolved by day 14. Alveolar particle deposition and granulomatous mass formation were observed in all exposure groups at day 14. The SSC particles were poorly cleared, with 81% remaining at the end of the observation period. These findings demonstrate that SSC sawing dust exposure induces pulmonary inflammation and damage that warrants further investigation. Abbreviations: ANOVA: Analysis of Variance; ATH: Alumina Trihydrate; BALF: Bronchoalveolar Lavage Fluid; Dpg: Geometric Mean Diameter; FE-SEM: Field Emission Scanning Electron Microscopy; IACUC: Institutional Animal Care and Use Committee; IFN-γ: Interferon Gamma; IL-1 Β: Interleukin-1 Beta; IL-10: Interleukin-10; IL-12: Interleukin-12; IL-2: Interleukin-2; IL-4: Interleukin-4; IL-5: Interleukin-5; IL-6: Interleukin-6; KC/GRO: Neutrophil-Activating Protein 3; MMAD: Mass Median Aerodynamic Diameter; PBS: Phosphate-Buffered Saline; PEL: Permissible Exposure Limit; PM: Polymorphonuclear Leukocytes; PNOR: Particles Not Otherwise Regulated; SEM/EDX: Scanning Electron Microscope/Energy-Dispersive X-Ray; SSA: Specific Surface Area; SSC: Solid Surface Composite; TNFα: Tumor Necrosis Factor-Alpha; VOC: Volatile Organic Compounds; σg: Geometric Standard Deviation.

Three-dimensional printing with nano-enabled filaments releases polymer particles containing carbon nanotubes into air.

Fused deposition modeling (FDM™) 3-dimensional printing uses polymer filament to build objects. Some polymer filaments are formulated with additives, though it is unknown if they are released during printing. Three commercially available filaments that contained carbon nanotubes (CNTs) were printed with a desktop FDM™ 3-D printer in a chamber while monitoring total particle number concentration and size distribution. Airborne particles were collected on filters and analyzed using electron microscopy. Carbonyl compounds were identified by mass spectrometry. The elemental carbon content of the bulk CNT-containing filaments was 1.5 to 5.2 wt%. CNT-containing filaments released up to 1010 ultrafine (d < 100 nm) particles/g printed and 106 to 108 respirable (d ~0.5 to 2 µm) particles/g printed. From microscopy, 1% of the emitted respirable polymer particles contained visible CNTs. Carbonyl emissions were observed above the limit of detection (LOD) but were below the limit of quantitation (LOQ). Modeling indicated that, for all filaments, the average proportional lung deposition of CNT-containing polymer particles was 6.5%, 5.7%, and 7.2% for the head airways, tracheobronchiolar, and pulmonary regions, respectively. If CNT-containing polymer particles are hazardous, it would be prudent to control emissions during use of these filaments.

Physical chemical properties and cell toxicity of sanding copper-treated lumber.

To protect against decay and fungal invasion into the wood, the micronized copper, copper carbonate particles, has been applied in the wood treatment in recent years; however, there is little information on the health risk associated with sanding micronized copper-treated lumber. In this study, wood dust from the sanding of micronized copper azole-treated lumber (MCA) was compared to sanding dust from solubilized copper azole-treated wood (CA-C) and untreated yellow pine (UYP). The test found that sanding MCA released a much higher concentration of nanoparticles than sanding CA-C and UYP, and the particles between about 0.4-2 µm from sanding MCA had the highest percentage of copper. The percentage of copper in the airborne dust from sanding CA-C had a weak dependency on particle size and was lower than that from sanding MCA. Nanoparticles were seen in the MCA PM2.5 particles, while none were detected in the UYP or CA-C. Inductively coupled plasma mass spectrometry (ICP-MS) analysis found that the bulk lumber for MCA and CA-C had relatively equal copper content; however, the PM2.5 particles from sanding the MCA had a higher copper concentration when compared to the PM2.5 particles from sanding UYP or CA-C. The cellular toxicity assays show that exposure of RAW 264.7 macrophages (RAW) to MCA and CA-C wood dust suspensions did not induce cellular toxicity even at the concentration of 200 µg PM2.5 wood dust/mL. Since the copper from the treated wood dust can leach into the wood dust supernatant, the supernatants of MCA, CA-C and UYP wood dusts were subjected to the cellular toxicity assays. The data showed that at the higher concentrations of copper (≥5 µg/ml), both MCA and CA-C supernatants induced cellular toxicity. This study suggests that sanding MCA-treated lumber releases copper nanoparticles and both the MCA and CA-C-treated lumber can release copper, which are potentially related to the observed in vitro toxicity.

On the Characterization of the Generation Rate and Size-Dependent Crystalline Silica Content of the Dust from Cutting Fiber Cement Siding.

A laboratory testing system was developed to systematically characterize the dust generation rate and size-dependent crystalline silica content when cutting or shaping silica containing materials. The tests of cutting fiber cement siding in this system verify that it provides high test repeatability, making it suitable for the targeted characterizations. The mass-based size distributions obtained from a gravimetric-based instrument and a direct reading instrument both show bimodal lognormal distributions with a larger mode ~13 µm and another mode <5 µm for the dusts from cutting four different brands of fiber cement siding. The generation rates of respirable dust obtained from the two instruments are comparable, and the results from each instrument are similar for the four brands. The silica content in the airborne dusts, however, strongly depends on the amount of silica used in the respective product. It is also observed that the silica content in the airborne dust from cutting the four brands of fiber cement siding showed the same trend of an increase with the aerodynamic diameter of the dust, approaching the silica content levels found in their respective bulk samples. Combining the results for both the dust size distribution and size-dependent silica content, it is found that most of the respirable crystalline silica (RCS) resides in the dust ~2.5 µm in aerodynamic diameter. These results would help guide the development of specific engineering control measures targeted at lowering workers' exposure to RCS while cutting fiber cement siding. With the high repeatability using the laboratory testing system, the dust generation rate could then be characterized under different operating conditions, and with the deployment of various engineering control measures. This would greatly facilitate the systematic evaluation of the control effectiveness and the selection of the optimal control solutions for field trials.

Characterizing Dust from Cutting Corian®, a Solid-Surface Composite Material, in a Laboratory Testing System.

We conducted a laboratory test to characterize dust from cutting Corian(®), a solid-surface composite material, with a circular saw. Air samples were collected using filters and direct-reading instruments in an automatic laboratory testing system. The average mass concentrations of the total and respirable dusts from the filter samples were 4.78±0.01 and 1.52±0.01mg cm(-3), respectively, suggesting about 31.8% mass of the airborne dust from cutting Corian(®) is respirable. Analysis of the metal elements on the filter samples reveals that aluminum hydroxide is likely the dominant component of the airborne dust from cutting Corian(®), with the total airborne and respirable dusts containing 86.0±6.6 and 82.2±4.1% aluminum hydroxide, respectively. The results from the direct-reading instruments confirm that the airborne dust generated from cutting Corian(®) were mainly from the cutting process with very few particles released from the running circular saw alone. The number-based size distribution of the dusts from cutting Corian(®) had a peak for fine particles at 1.05 µm with an average total concentration of 871.9 particles cm(-3), and another peak for ultrafine particles at 11.8nm with an average total concentration of 1.19×10(6) particles cm(-3) The small size and high concentration of the ultrafine particles suggest additional investigation is needed to study their chemical composition and possible contribution to pulmonary effect.

Protection of firefighters against combustion aerosol particles: simulated workplace protection factor of a half-mask respirator (pilot study).

The present pilot study investigated the penetration of ultrafine particles originated by combustion of different materials into elastomeric half-mask respirators equipped with two P100 filters. We determined the Simulated Workplace Protection Factor (SWPF) for 11 firefighters wearing elastomeric half-mask respirators and performing activities simulating those conducted during fire overhaul operations. The tests were performed in a controlled laboratory setting. A newly-developed battery-operated Portable Aerosol Mobility Spectrometer (PAMS) was used to measure size-resolved aerosol particle concentrations outside (C(out)) and inside (Cin) of an air-purifying respirator donned on a firefighter, and the SWPF was calculated as C(out)/C(in). Based on the total aerosol concentration, the "total" SWPF ranged from 4,222 (minimum) to 35,534 (maximum) with values falling primarily in a range from 11,171 (25 percentile) to 26,604 (75 percentile) and a median value being ≈15,000. This is consistent with the recently reported fit factor (FF) data base.((1)) The size-resolved SWPF data revealed a dependency on the particle size. It was concluded that a portable device such as PAMS can be used on firefighters during overhaul operations (as well as on other workers wearing elastomeric half-mask respirators) to monitor the aerosol concentrations in real time and ultimately help prevent overexposure.

Water requirement of vegetation and infiltration method for determining the ecological water requirement of dried-up rivers.

Many rivers in the region of northwest China are drying up, and the ecological environment is getting worse. Studying methods of calculating the ecological water requirement (EWR) for dried-up rivers will help to slow down the deterioration of the ecological environment and conserve biodiversity. The water requirement of vegetation and infiltration (WRVI) method is proposed in this paper. This method focuses on dried-up rivers and takes the water requirement of vegetation and river bed infiltration into consideration. This is different from the conventional methods, which only focus on the rivers that have a flow rate. Due to drying, the ecological environment is worsening year by year in the lower reaches of the Zhang River in the Haihe River Basin in northwest China. This river is used as an example to determine the EWR, and the results are compared with another method. The results show that the WRVI method can calculate the EWR more accurately by considering various factors in different years and months for dried-up rivers.

Characterization of the Emissions and Crystalline Silica Content of Airborne Dust Generated from Grinding Natural and Engineered Stones.

In this study, we systematically characterized the airborne dust generated from grinding engineered and natural stone products using a laboratory testing system designed and operated to collect representative respirable dust samples. Four stone samples tested included two engineered stones consisting of crystalline silica in a polyester resin matrix (formulations differed with Stones A having up to 90wt% crystalline silica and Stone B up to 50wt% crystalline silica), an engineered stone consisting of recycled glass in a cement matrix (Stone C), and a granite. Aerosol samples were collected by respirable dust samplers, total dust samplers, and a Micro-Orifice Uniform Deposit Impactor. Aerosol samples were analyzed by gravimetric analysis and x-ray diffraction to determine dust generation rates, crystalline silica generation rates, and crystalline silica content. Additionally, bulk dust settled on the floor of the testing system was analyzed for crystalline silica content. Real-time particle size distributions were measured using an Aerodynamic Particle Sizer. All stone types generated similar trimodal lognormal number-weighted particle size distributions during grinding with the most prominent mode at an aerodynamic diameter of about 2.0-2.3 µm, suggesting dust formation from grinding different stones is similar. Bulk dust from Stone C contained no crystalline silica. Bulk dust from Stone A, Stone B, and granite contained 60, 23, and 30wt% crystalline silica, respectively. In Stones A and B, the cristobalite form of crystalline silica was more plentiful than the quartz form. Only the quartz form was detected in granite. The bulk dust, respirable dust, and total dust for each stone had comparable amounts of crystalline silica, suggesting that crystalline silica content in the bulk dust could be representative of that in respirable dust generated during grinding. Granite generated more dust per unit volume of material removed than the engineered stones, which all had similar normalized dust generation rates. Stone A had the highest normalized generation rates of crystalline silica, followed by granite, Stone B, and Stone C (no crystalline silica), which likely leads to the same trend of respirable crystalline silica (RCS) exposure when working with these different stones. Manufacturing and adoption of engineered stone products with formulations such as Stone B or Stone C could potentially lower or eliminate RCS exposure risks. Combining all the effects of dust generation rate, size-dependent silica content, and respirable fraction, the highest normalized generation rate of RCS consistently occurs at 3.2-5.6 µm for all the stones containing crystalline silica. Therefore, removing particles in this size range near the generation sources should be prioritized when developing engineering control measures.

Hazardous dusts from the fabrication of countertop: a review.

Artificial countertop materials, including solid surface composites (SSC) and engineered stone (ES) may pose significant pulmonary health risks for workers who manipulate them. These materials have rapidly become popular in the multibillion-dollar countertop industry, rivaling that of natural materials such as granite and marble due to their variety of desirable esthetic qualities and reduced costs. Both SSC and ES consist of a mineral substrate bound together in a polymer matrix. For SSC the mineral is about 70% aluminum trihydrate (ATH) while ES contains up to 95% crystalline silica by weight. Both materials emit airborne dusts when being manipulated with power tools during the fabrication process. Several deaths and dozens of cases of silicosis have been identified worldwide in workers who fabricate ES, while a single case of fatal pulmonary fibrosis has been associated with SCC dust exposure. This review examines the current state of knowledge for both SSC and ES regarding the composition, particle emission characteristics, workplace exposure data, particle constituent toxicity, and possible methods for reducing worker exposure.

Revealing the structural and chemical properties of copper-based nanoparticles released from copper treated wood.

Copper-based preservatives consisting of micronized and nanoscale copper particles have been widely used in applications for wood protection. The widespread use of these preservatives along with the potential release of copper-containing nanoparticles (Cu NPs) during the life cycle of treated wood, has raised concerns over the impacts on the environment and occupational exposure. Along with assessing the potential hazards of these materials, a critical step is determining the chemical and morphological characteristics of the copper species released from copper-treated wood. Therefore, a combination of scanning transmission electron microscopy (STEM) and electron energy-loss spectroscopy (EELS) was utilized to characterize and differentiate the released copper-containing particles based on their structures, sizing, and chemical properties. Airborne wood dust samples were collected during the abrasion and sawing of micronized copper (MC) treated wood in a laboratory testing system. Based on the signature Cu L2,3 edge of EEL spectra, three different copper species (i.e., basic copper carbonate, copper, and copper-wood complex) were identified as major components of the embedded particles in wood dust. In addition, two types of individual Cu NPs consisting of basic copper carbonate and copper were identified. The variation of morphologies and chemical properties of copper-containing particles indicates the importance of copper-wood interactions to determine the formation and distribution of copper species in wood components. Our findings will advance the fundamental understanding of their released forms, potential transformation, and environmental fate during the life cycle.

Caution on Using Tetrahydrofuran for Processing Crystalline Silica Samples From Engineered Stone for XRD Analysis.

We conducted laboratory experiments to investigate a suspected effect of tetrahydrofuran (THF) on quantifying crystalline silica in samples collected from working with engineered stone when THF is used to process samples prior to the X-ray diffraction (XRD) analysis. Two groups of samples from grinding either engineered stone or granite were simultaneously taken from a laboratory testing system, with one group of samples using THF for processing and another group using muffle furnace for ashing. For each stone type, we also tested four levels of respirable dust loading on the samples by varying the grinding time from 1 to 8 min. Statistical analysis of the experimental results on crystalline silica contents of the two groups of samples showed that the difference between the two methods was not significant (P ≥ 0.05) for the granite at all four levels of respirable dust loading and for the engineered stone at the two levels of respirable dust loading greater than 0.5 mg. However, the crystalline silica content from using THF processing was significantly lower (P = 0.001) than that from using muffle furnace ashing for engineered stone when the respirable dust loading levels were less than 0.5 mg. For the engineered stone dust samples with grinding times of 1 and 2 min, the average respirable dust loading was about 0.19 and 0.34 mg, respectively; while the crystalline silica content from using THF processing was 30.9 and 21.5% lower than that from using muffle furnace ashing, respectively. Since most full-shift samples from field assessments in this industry are expected to have respirable dust loading less than 0.5 mg, muffle furnace or radio frequency plasma ashing should be specified as the preferred sample processing method instead of the THF processing method for quantification of crystalline silica when engineered stone is expected to present to avoid artificially reduced silica content values, which are likely caused by the reactions between THF and the resins in engineered stone.

The Composition of Emissions from Sanding Corian® with Different Sandpapers.

Laboratory tests were conducted to characterize the composition of emissions from sanding Corian®, a solid-surface composite material mainly composed of alumina trihydrate (ATH) and acrylic polymer. Three sandpaper materials (ceramic, silicon carbide, and aluminum oxide) were tested to distinguish the contribution of aluminum-containing dust in the emission from Corian® and sandpaper itself. The result can help identify the main cause of the pulmonary fibrosis from exposure to aluminum-containing dust while sanding Corian®. Airborne dust samples were measured using direct-reading instruments and collected using a Micro-Orifice Uniform Deposit Impactor (MOUDI) for estimating the normalized dust generation rate. The size-classified dust samples from MOUDI were analyzed for elemental aluminum content. Additionally, air samples were analyzed for characterizing methyl methacrylate (MMA). The results from the direct-reading instruments reveal that the size distribution of particulate from sanding Corian® differs from that of sawing Corian®, showing that the size distribution of dust is affected by the fabrication process. The normalized respirable dust generation rate indicates that more respirable dust was generated during sanding Corian® board. However, the use of aluminum oxide sandpaper does not result in a higher aluminum content in the respirable dust from sanding Corian®, suggesting that the aluminum content of the respirable dust is primarily originated from Corian® itself. The generation rates of MMA from sanding did not vary much among all types of sandpapers, and they were much lower than that of sawing, likely due to the higher temperature in the sawing process.

The Composition of Emissions from Sawing Corian®, a Solid Surface Composite Material.

We conducted detailed analyses of the composition of emissions from sawing Corian®, a solid surface composite material, in a laboratory testing system. The analyses included the aluminum content of size-selective dust samples, semivolatile organic compounds (SVOCs) in respirable dust samples, and volatile organic compounds (VOCs). The normalized respirable dust generation rate found using a Micro-Orifice Uniform Deposit Impactor was 5.9 milligrams per gram (mg g-1) suggesting that 0.59% of the mass removed from sawing Corian® becomes respirable dust. The alumina trihydrate content of the dust was consistently above 85% in most parts of the respirable size range, verifying an earlier finding that it is the dominant composition of the airborne particles of all sizes, including ultrafine particles. VOC analyses revealed that methyl methacrylate (MMA) was the most abundant compound, with a generation rate of 6.9 mg g-1 (0.69% of the mass removed from sawing Corian® became MMA vapor). The SVOC analysis only found a small amount of MMA (0.55%) in the bulk dust.

Toxicological assessment of dust from sanding micronized copper-treated lumber in vivo.

Micronized copper azole (MCA) is a lumber treatment improve longevity. In this study, the in vivo response to PM2.5 sanding dust generated from MCA-treated lumber was compared to that of untreated yellow pine (UYP) or soluble copper azole-treated (CA-C) lumber to determine if the MCA was more bioactive than CA-C. Mice were exposed to doses (28, 140, or 280 µg/mouse) of UYP, MCA, or CA-C sanding dust using oropharyngeal aspiration. Bronchoalveolar lavage fluid (BALF) lactate dehydrogenase activity was increased at 1 day post-exposure to 280 µg/mouse of MCA and CA-C compared to UYP. BALF polymorphonuclear cells were increased by MCA and CA-C. There were increases in BALF cytokines in MCA and CA-C-exposed groups at 1 day post-exposure. Lung histopathology indicated inflammation with infiltration of neutrophils and macrophages. Pulmonary responses were more severe in MCA and CA-C-exposed groups at 1 day post-exposure. MCA caused more severe inflammatory responses than CA-C at 1 day post-exposure. These findings suggest that the MCA and CA-C sanding dusts are more bioactive than the UYP sanding dust, and, moreover, the MCA sanding dust is more bioactive in comparison to the CA-C sanding dust. No chronic toxic effects were observed among all observed sanding dusts.

Acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) filaments three-dimensional (3-D) printer emissions-induced cell toxicity.

During extrusion of some polymers, fused filament fabrication (FFF) 3-D printers emit billions of particles per minute and numerous organic compounds. The scope of this study was to evaluate FFF 3-D printer emission-induced toxicity in human small airway epithelial cells (SAEC). Emissions were generated from a commercially available 3-D printer inside a chamber, while operating for 1.5 h with acrylonitrile butadiene styrene (ABS) or polycarbonate (PC) filaments, and collected in cell culture medium. Characterization of the culture medium revealed that repeat print runs with an identical filament yield various amounts of particles and organic compounds. Mean particle sizes in cell culture medium were 201 ±â€¯18 nm and 202 ±â€¯8 nm for PC and ABS, respectively. At 24 h post-exposure, both PC and ABS emissions induced a dose dependent significant cytotoxicity, oxidative stress, apoptosis, necrosis, and production of pro-inflammatory cytokines and chemokines in SAEC. Though the emissions may not completely represent all possible exposure scenarios, this study indicate that the FFF could induce toxicological effects. Further studies are needed to quantify the detected chemicals in the emissions and their corresponding toxicological effects.

Recirculating air filtration significantly reduces exposure to airborne nanoparticles.

BACKGROUND: Airborne nanoparticles from vehicle emissions have been associated with adverse effects in people with pulmonary and cardiovascular disease, and toxicologic studies have shown that nanoparticles can be more hazardous than their larger-scale counterparts. Recirculating air filtration in automobiles and houses may provide a low-cost solution to reducing exposures in many cases, thus reducing possible health risks. OBJECTIVES: We investigated the effectiveness of recirculating air filtration on reducing exposure to incidental and intentionally produced airborne nanoparticles under two scenarios: while driving in traffic, and while generating nanomaterials using gas-phase synthesis. METHODS: We tested the recirculating air filtration in two commercial vehicles when driving in traffic, as well as in a nonventilation room with a nanoparticle generator, simulating a nanomaterial production facility. We also measured the time-resolved aerosol size distribution during the in-car recirculation to investigate how recirculating air filtration affects particles of different sizes. We developed a recirculation model to describe the aerosol concentration change during recirculation. RESULTS: The use of inexpensive, low-efficiency filters in recirculation systems is shown to reduce nanoparticle concentrations to below levels found in a typical office within 3 min while driving through heavy traffic, and within 20 min in a simulated nanomaterial production facility. CONCLUSIONS: Development and application of this technology could lead to significant reductions in airborne nanoparticle exposure, reducing possible risks to health and providing solutions for generating nanomaterials safely.

The Generation Rate of Respirable Dust from Cutting Fiber Cement Siding Using Different Tools.

This article describes the evaluation of the generation rate of respirable dust (GAPS, defined as the mass of respirable dust generated per unit linear length cut) from cutting fiber cement siding using different tools in a laboratory testing system. We used an aerodynamic particle sizer spectrometer (APS) to continuously monitor the real-time size distributions of the dust throughout cutting tests when using a variety of tools, and calculated the generation rate of respirable dust for each testing condition using the size distribution data. The test result verifies that power shears provided an almost dust-free operation with a GAPS of 0.006 g m-1 at the testing condition. For the same power saws, the cuts using saw blades with more teeth generated more respirable dusts. Using the same blade for all four miter saws tested in this study, a positive linear correlation was found between the saws' blade rotating speed and its dust generation rate. In addition, a circular saw running at the highest blade rotating speed of 9068 rpm generated the greatest amount of dust. All the miter saws generated less dust in the 'chopping mode' than in the 'chopping and sliding' mode. For the tested saws, GAPS consistently decreased with the increases of the saw cutting feed rate and the number of board in the stack. All the test results point out that fewer cutting interactions between the saw blade's teeth and the siding board for a unit linear length of cut tend to result in a lower generation rate of respirable dust. These results may help guide optimal operation in practice and future tool development aimed at minimizing dust generation while producing a satisfactory cut.