Additives influence 3D printer emission profiles: Implications for working safely with polymer filament composites.

It is critical to thoroughly investigate, characterize, and understand the unique emission profiles of common and novel polymer feedstocks used in fused filament fabrication (FFF) 3D printers as these products become increasingly ubiquitous in consumer and industrial environments. This work contributes unique insights regarding the effects of polymer composite feedstocks with metal, ceramic, or carbonaceous particle additives on particulate emissions in a variety of filaments under various print conditions, including print temperature. In addition to active characterization of particulate size and concentration following the ANSI/CAN/UL 2904 method, particulate sampling and subsequent analysis by scanning electron microscopy revealed agglomeration behavior that may have important health implications. Specifically, fine particles (0.3-2.5 µm) generated by certain filaments including acrylonitrile butadiene styrene (ABS) and glycol-modified poly(ethylene terephthalate) (PETG) are shown to be formed via agglomeration of emitted ultrafine particles rather than composed of coherent primary particles; accordingly, transport and behavior of these particulates after inhalation may not follow expected patterns for micrometer-sized particles. Structures resembling carbonaceous additives (e.g., graphene and nanotubes) were also captured by airborne sampling during printing of filaments containing carbonaceous advanced materials.

An Emergency Powered Air-Purifying Respirator From Local Materials and its Efficacy Against Aerosolized Nanoparticles.

We describe an approach used by a rural healthcare provider to convert surgical helmets into emergency powered air-purifying respirators (PAPRs) at the onset of the COVID-19 pandemic. The approach uses common materials and efficacy was demonstrated against aerosols measuring 7 nm to 25 µm in diameter.

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.

Testing of Commercial Masks and Respirators and Cotton Mask Insert Materials using SARS-CoV-2 Virion-Sized Particulates: Comparison of Ideal Aerosol Filtration Efficiency versus Fitted Filtration Efficiency.

Shortages in the availability of personal protective face masks during the COVID-19 pandemic required many to fabricate masks and filter inserts from available materials. While the base filtration efficiency of a material is of primary importance when a perfect seal is possible, ideal fit is not likely to be achieved by the average person preparing to enter a public space or even a healthcare worker without fit-testing before each shift. Our findings suggest that parameters including permeability and pliability can play a strong role in the filtration efficiency of a mask fabricated with various filter media, and that the filtration efficiency of loosely fitting masks/respirators against ultrafine particulates can drop by more than 60% when worn compared to the ideal filtration efficiency of the base material. Further, a test method using SARS-CoV-2 virion-sized silica nanoaerosols is demonstrated to assess the filtration efficiency against nanoparticulates that follow air currents associated with mask leakage.

Use of echocardiography as an essential tool for targeted transcatheter biopsy of cardiac masses.

Echocardiography has emerged as an essential tool to guide targeted, transcatheter biopsy of cardiac masses. Options for imaging include transthoracic or transesophageal echocardiography and intracardiac echocardiography, with appropriate use being dictated by specific patient characteristics and institutional experience. The authors present a case of three-dimensional (3-D) transesophageal echocardiography-guided transcatheter biopsy of a right ventricular mass and review the current use of echocardiography to guide these procedures.

Adrenal insufficiency in neonates after cardiac surgery with cardiopulmonary bypass.

BACKGROUND: Cardiopulmonary bypass (CPB) may lead to adrenal insufficiency (AI). Emerging evidence supports association of AI with morbidity after cardiac surgery. AIMS: The aim of this study was to define AI incidence in neonates undergoing complex cardiac surgery with CPB and its association with intraoperative post-CPB outcomes. METHODS: Forty subjects enrolled in a prior randomized control trial who received preoperative methylprednisolone as part of our institutional neonatal bypass protocol were included. No intraoperative steroids were given. ACTH stimulation tests were performed: preoperatively and 1 h after separation from CPB. AI was defined as <9 µg·ml-1 increase in cortisol at 30 min post cosyntropin 1 mcg. Clinical outcomes were collected up to 90 min after CPB. RESULTS: 2/40 (5%) subjects had preoperative AI vs 13/40 (32.5%) post-CPB AI, P ≤ 0.001. No significant difference was observed in age, gestational age, weight, CPB time, circulatory arrest, or STAT category between subjects with or without post-CPB AI. ACTH decreased from preoperative values 127.3 vs 35 pcg·ml-1 [median difference = 81.8, 95% CI = 22.7-127.3], while cortisol increased from 18.9 vs 75 µg·dl-1 [median difference = 52.2, 95% CI = 36.3-70.9]. Post-CPB AI was associated with increased median colloid resuscitation, 275 vs 119 ml·kg-1 [median difference = 97.8, 95% CI = 7.1-202.2]; higher median peak lactate, 9.4 vs 6.9 mg·dl-1 [median difference = 3.2, 95% CI = 0.04-6.7]; median post-CPB lactate, 7.9 vs 4.3 mg·dl-1 , [median difference 3.6, 95% CI = 2.1-4.7], and median lactate on admission to CICU, 9.4 vs 6.0 mg·dl-1 [median difference = 3, 95% CI = 1.1-4.9]. No difference was observed in blood pressure or vasoactive inotrope score at any time point measured in operating room (OR). Higher initial post-CPB cortisol correlated with decreased cosyntropin response. CONCLUSIONS: Neonatal cardiac surgery with CPB and preoperative methylprednisolone leads to AI as determined by low-dose ACTH stimulation test in one-third of patients. AI is associated with increased serum lactate and colloid resuscitation in OR. Impact of preoperative methylprednisolone on results is not defined. Benefit of postoperative steroid administration in neonates with post-CPB AI warrants further investigation.

Nanotechnology in the real world: Redeveloping the nanomaterial consumer products inventory.

To document the marketing and distribution of nano-enabled products into the commercial marketplace, the Woodrow Wilson International Center for Scholars and the Project on Emerging Nanotechnologies created the Nanotechnology Consumer Products Inventory (CPI) in 2005. The objective of this present work is to redevelop the CPI by leading a research effort to increase the usefulness and reliability of this inventory. We created eight new descriptors for consumer products, including information pertaining to the nanomaterials contained in each product. The project was motivated by the recognition that a diverse group of stakeholders from academia, industry, and state/federal government had become highly dependent on the inventory as an important resource and bellweather of the pervasiveness of nanotechnology in society. We interviewed 68 nanotechnology experts to assess key information needs. Their answers guided inventory modifications by providing a clear conceptual framework best suited for user expectations. The revised inventory was released in October 2013. It currently lists 1814 consumer products from 622 companies in 32 countries. The Health and Fitness category contains the most products (762, or 42% of the total). Silver is the most frequently used nanomaterial (435 products, or 24%); however, 49% of the products (889) included in the CPI do not provide the composition of the nanomaterial used in them. About 29% of the CPI (528 products) contain nanomaterials suspended in a variety of liquid media and dermal contact is the most likely exposure scenario from their use. The majority (1288 products, or 71%) of the products do not present enough supporting information to corroborate the claim that nanomaterials are used. The modified CPI has enabled crowdsourcing capabilities, which allow users to suggest edits to any entry and permits researchers to upload new findings ranging from human and environmental exposure data to complete life cycle assessments. There are inherent limitations to this type of database, but these modifications to the inventory addressed the majority of criticisms raised in published literature and in surveys of nanotechnology stakeholders and experts. The development of standardized methods and metrics for nanomaterial characterization and labelling in consumer products can lead to greater understanding between the key stakeholders in nanotechnology, especially consumers, researchers, regulators, and industry.

Gaining a Critical Mass: A Dose Metric Conversion Case Study Using Silver Nanoparticles.

Mass concentration is the standard convention to express exposure in ecotoxicology for dissolved substances. However, nanotoxicology has challenged the suitability of the mass concentration dose metric. Alternative metrics often discussed in the literature include particle number, surface area, and ion release (kinetics, equilibrium). It is unlikely that any single metric is universally applicable to all types of nanoparticles. However, determining the optimal metric for a specific type of nanoparticle requires novel studies to generate supportive data and employ methods to compensate for current analytical capability gaps. This investigation generated acute toxicity data for two standard species (Ceriodaphnia dubia, Pimephales promelas) exposed to five sizes (10, 20, 30, 60, 100 nm) of monodispersed citrate- and polyvinylpyrrolidone-coated silver nanoparticles. Particles were sized by various techniques to populate available models for expressing the particle number, surface area, and dissolved fraction. Results indicate that the acute toxicity of the tested silver nanoparticles is best expressed by ion release, and is relatable to total exposed surface area. Particle number was not relatable to the observed acute silver nanoparticle effects.

Uptake and retention of metallic nanoparticles in the Mediterranean mussel (Mytilus galloprovincialis).

We measured the uptake, distribution and elimination of two types of metallic nanoparticles (MetNPs) by the aquatic mussel Mytilus galloprovincialis in static seawater column exposures. Test MetNPs included polyethylene glycol (PEG) functionalized Fe3O4 nanoparticles (PEG-FeOxNP) and PEG-functionalized cadmium-selenide quantum dots (PEG-Qdot). Exposure water was sampled at various times to assess MetNP clearance, and mussels were serially euthanized to assess uptake of MetNPs into the hemolymph, digestive gland, and remaining carcass. Results indicated that >90% of both types of MetNPs were taken up by mussels within 8h of initial exposure. Nearly the entire retained dose of FeOxNPs and PEG-Qdots was deposited in the digestive gland. Our results provide important insights on the uptake and elimination kinetics of MetNPs in filter-feeding marine bivalves, and will be useful for subsequent development of toxicokinetic models to predict the kinetics of these processes.

Effect of silver nanoparticles and antibiotics on antibiotic resistance genes in anaerobic digestion.

Water resource recovery facilities have been described as creating breeding ground conditions for the selection, transfer, and dissemination of antibiotic resistance genes (ARGs) among various bacteria. The objective of this study was to determine the effect of direct addition of antibiotic and silver nanoparticles (Ag NPs, or nanosilver) on the occurrence of ARGs in thermophilic anaerobic digesters. Test thermophilic digesters were amended with environmentally-relevant concentrations of Ag NP (0.01, 0.1, and 1.0 mg-Ag/L; corresponding to approximately 0.7, 7.0, and 70 mg-Ag/kg total solids) and sulfamethoxazole (SMX) that span susceptible to resistant classifications (1, 5, and 50 mg/L) as potential selection pressures for ARGs. Tetracycline (tet(O), tet(W)) and sulfonamide (sulI, sulII) ARGs and the integrase enzyme gene (intI1) associated with Class 1 integrons were measured in raw sludge, test thermophilic digesters, a control thermophilic digester, and a control mesophilic digester. There was no apparent effect of Ag NPs on thermophilic anaerobic digester performance. The maximum SMX addition (50 mg/L) resulted in accumulation of volatile fatty acids and low pH, alkalinity, and volatile solids reduction. There was no significant difference between ARG gene copy numbers (absolute or normalized to 16S rRNA genes) in amended thermophilic digesters and the control thermophilic digester. Antibiotic resistance gene copy numbers in digested sludge ranged from 10(3) to 10(6) copies per microL (approximately 8 x10(1) to 8 x 10(4) copies per microg) of sludge as result of a 1-log reduction of ARGs (2-log reduction for intI1). Quantities of the five ARGs in raw sludge ranged from 10(4) to 10(8) copies per microL (approximately 4 x 10(2) to 4 x 10(6) per microg) of sludge. Test and control thermophilic digesters (53 degrees C, 12-day solids retention time [SRT]) consistently reduced but did not eliminate levels of all analyzed genes. The mesophilic digester (37 degrees C, 20-day SRT) also reduced levels of sulI, sulII, and intI1 genes, but levels of tet(O) and tet(W) were the same or higher than in raw sludge. Antibiotic resistance gene reductions remained constant despite the application of selection pressures, which suggests that digester operating conditions are a strong governing factor of the bacterial community composition and thus the prevalence of ARGs.

Filter-feeding bivalves store and biodeposit colloidally stable gold nanoparticles.

Nanoparticles resistant to salt-induced aggregation are continually being developed for biomedical and industrial applications. Because of their colloidal stability these functionalized nanoparticles are anticipated to be persistent aquatic contaminants. Here, we show that Corbicula fluminea, a globally distributed clam that is a known sentinel of aquatic ecosystem contamination, can uptake and biodeposit bovine serum albumin (BSA) stabilized gold nanoparticles. Nanoparticle clearance rates from suspension were dictated by diameter and concentration, with the largest particles cleared most quickly on a mass basis. Particle capture facilitates size-selective 'biopurification' of particle suspensions with nanoscale resolution. Nanoparticles were retained either within the clam digestive tract or excreted in feces. Our results suggest that biotransformation and biodeposition will play a significant role in the fate and transport of persistent nanoparticles in aquatic systems.

Fractionating nanosilver: importance for determining toxicity to aquatic test organisms.

This investigation applied novel techniques for characterizing and fractionating nanosilver particles and aggregates and relating these measurements to toxicological endpoints. The acute toxicity of eight nanosilver suspensions of varying primary particle sizes (10-80 nm) and coatings (citrate, polyvinylpyrrolidone, EDTA, proprietary) was assessed using three aquatic test organisms (Daphnia magna, Pimephales promelas, Pseudokirchneriella subcapitata). When 48-h lethal median concentrations (LC50) were expressed as total silver, both D. magna and P. promelas were significantly more sensitive to ionic silver (Ag(+)) as AgNO(3) (mean LC50 = 1.2 and 6.3 µg/L, respectively) relative to a wide range in LC50 values determined for the nanosilver suspensions (2 -126 µg/L). However, when LC50 values for nanosilver suspensions were expressed as fractionated nanosilver (Ag(+) and/or <4 nm particles), determined by ultracentrifugation of particles and confirmed field-flow-fractograms, the LC50 values (0.3-5.6 µg/L) were comparable to the values obtained for ionic Ag(+) as AgNO(3). These results suggest that dissolved Ag(+) plays a critical role in acute toxicity and underscores the importance of characterizing dissolved fractions in nanometal suspensions.

Release of metal impurities from carbon nanomaterials influences aquatic toxicity.

Few studies have considered the environmental impacts of impurities and byproducts associated with low-efficiency nanomanufacturing processes. Here, we study the composition and aquatic toxicity of low-purity, as-produced fullerenes (C60) and metallofullerene waste solids, both of which were generated via arc-discharge synthesis. Scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) and inductively coupled plasma mass spectroscopy (ICP-MS) were used to characterize the metals composition of the solid test materials and of aqueous leachates prepared by mixing test materials with waters of varying pH, hardness, and salinity. The aquatic toxicity of the leachates was determined using U.S. Environmental Protection Agency recommended aquatic bioassay protocols with two standard test organisms-Pimephales promelas and Ceriodaphnia dubia. Results indicated that metals associated with the solid test materials became mobilized in our test system upon interaction with waters of circumneutral pH and reached concentrations sufficient to induce toxicity in both test species. Acute (48 h) LC50 values for P. promelas and C. dubia exposed to leachates prepared from metallofullerene waste solids were 54 and 5% (as % leachate in diluent), respectively. Toxicity was eliminated after adding the chelator EDTA to the leachates, implicating divalent transition metals as the toxicity source. Our results demonstrate the aquatic toxicity of metals mobilized from products and byproducts of nanomanufacturing, and they emphasize the need for a global review of nanomanufacturing wastes and low-purity products.

Influence of nanotube preparation in aquatic bioassays.

Knowledge gaps in nanomaterial fate and toxicity currently limit the ability of risk assessments to characterize the environmental implications of nanomaterials. This problem is further complicated by the lack of standardized characterization and preparation methodologies for researchers to gain the needed information to assist risk assessors. In the present study, data were generated to determine if multiwalled nanotube (MWNT) fate and toxicity are altered by engineered surface modifications or by different dispersal methods. While dissolved organic matter was a good dispersing agent of MWNTs in water, the humic acid fraction was a more effective dispersant than the fulvic acid fraction. When stabilized in organic matter, the functional group attached to the MWNT controlled its toxicity. Underivatized MWNTs induced relatively moderate toxicity to Ceriodaphnia dubia after 96 h (25 +/- 19% survival at 26 mg/L), while hydrophilic groups (hydroxyl, carboxyl) reduced this toxicity (93 +/- 12% survival at 48 mg/L). However, other functional groups (alkyl, amine) increased toxicity (0 +/- 0% survival at <15 mg/L). In dispersal method studies, sonication of MWNTs increased fragmentation relative to magnetic stirring. The sonication treatment of MWNTs also slightly reduced the mortality of C. dubia in the water column but increased toxicity in the sediment to Leptocheirus plumulosus and Hyalella azteca. Findings in the present study indicate that nanotubes engineered for specific applications need to be managed independently and that laboratory methods to disperse and test nanotubes in bioassays need to be standardized to obtain repeatable results for comparison of materials.

Factors influencing the partitioning and toxicity of nanotubes in the aquatic environment.

Carbon nanotubes (NTs) may be among the most useful engineered nanomaterials for structural applications but could be difficult to study in ecotoxicological evaluations using existing tools relative to nanomaterials with a lower aspect ratio. Whereas the hydrophobicity and van der Waals interactions of NTs may suggest aggregation and sedimentation in aquatic systems, consideration regarding how engineered surface modifications influence their environmental fate and toxicology is needed. Surface modifications (e.g., functional groups and coatings) are intended to create conditions to make NTs dispersible in aqueous suspension, as required for some applications. In the present study, column stability and settling experiments indicated that raw, multiwalled NTs (MWNTs) settled more rapidly than carbon black and activated carbon particles, suggesting sediment as the ultimate repository. The presence of functional groups, however, slowed the settling of MWNTs (increasing order of stability: hydroxyl > carboxyl > raw), especially in combination with natural organic matter (NOM). Stabilized MWNTs in high concentrations of NOM provided relevance for water transport and toxicity studies. Aqueous exposures to raw MWNTs decreased Ceriodaphnia dubia viability, but such effects were not observed during exposure to functionalized MWNTs (> 80 mg/L). Sediment exposures of the amphipods Leptocheirus plumulosus and Hyalella azteca to different sizes of sediment-borne carbon particles at high concentration indicated mortality increased as particle size decreased, although raw MWNTs induced lower mortality (median lethal concentration [LC50], 50 to >264 g/kg) than carbon black (LC50, 18-40 g/kg) and activated carbon (LC50, 12-29 g/kg). Our findings stress that it may be inappropriate to classify all NTs into one category in terms of their environmental regulation.

Characterization of airborne particles during production of carbonaceous nanomaterials.

Despite the rapid growth in nanotechnology, very little is known about the unintended health or environmental effects of manufactured nanomaterials. The development of nanotechnology risk assessments and regulations requires quantitative information on the potential for exposure to nanomaterials. The objective of this research isto characterize airborne particle concentrations during the production of carbonaceous nanomaterials, such as fullerenes and carbon nanotubes, in a commercial nanotechnology facility. We measured fine particle mass concentrations (PM2.5), submicrometer size distributions, and photoionization potential, an indicator of the particles' carbonaceous content, at three locations inside the facility: inside the fume hood where nanomaterials were produced, just outside the fume hood, and in the background. The measurements were not selective for engineered nanomaterials and may have included both engineered nanomaterials and naturally occurring or incidental particles. Average PM2.5 and particle number concentrations were not significantly different inside the facility versus outdoors. However, large, short-term increases in PM2.5 and particle number concentrations were associated with physical handling of nanomaterials and other production activities. In many cases, an increase in the number of sub-100 nm particles accounted for the majority of the increase in total number concentrations. Photoionization results indicate that the particles suspended during nanomaterial handling inside the fume hood were carbonaceous and therefore likely to include engineered nanoparticles, whereas those suspended by other production activities taking place outside the fume hood were not. Based on the measurements in this study, the engineering controls at the facility appear to be effective at limiting exposure to nanomaterials.

An empirical test of the kin selection hypothesis for male homosexuality.

The current investigation, following Bobrow and Bailey (2001), aimed to test the kin selection theory of homosexuality in human males using a survey design. A total of 60 heterosexual and 60 homosexual men from England completed items measuring psychological and behavioral indices of "special design" as predicted by adaptation due to kin selection. There were no significant differences between heterosexual and homosexual men in general familial affinity, generous feelings (willingness to provide financial and emotional resources), and benevolent tendencies (such as willingness to baby-sit). These remained non-significant after co-varying for level of personal income (higher among homosexual men), psychological gender, and interest in children. Overall, little support was found for the kin selection theory in a community sample.

Effect of cage design on growth of transplanted Asian clams: implications for assessing bivalve responses in streams.

This study was designed to determine whether survivorship and growth of Asian clams (Corbicula fluminea [Müller]) differed significantly between two types of field enclosures. Enclosures were either flexible mesh bags or rigid cages (hereto after referred as bioboxes) designed to homogenize substrate among study sites and accommodate Asian clam feeding mechanisms. For 96d, cages remained at 12 Clinch River (CR), Hurricane Fork (HF), and Dump's Creek (DC) sites upstream and downstream of a coal-fired power plant discharge, coal mining effluent, and coal combustion-related disposal facilities in Carbo, Virginia. Although survivorship was not significantly different between cage types, mean growth of clams in bioboxes was significantly greater overall (p = 0.0157). Despite the difference in growth between the two cage types, both confirmed significant reductions of survivorship and growth directly below the power plant discharge. Additionally, coefficient of variance values for biobox growth data were reduced at most study sites (averages of 16% for bioboxes versus 19% for mesh bags). Our results have implications toward strengthening weight-of-evidence approaches used to link impairment of transplanted bivalves to environmental contaminants. More importantly, these results suggest that ecotoxicological impairment of bivalves transplanted downstream of the coal-fired power plant discharge functioned independently of site-specific substrate provisions.