Particle release and control of worker exposure during laboratory-scale synthesis,handling and simulated spills of manufactured nanomaterials in fume hoods

Fume hoods are one of the most common types of equipment applied to reduce the potential of particle exposure in laboratory environments. A number of previous studies have shown particle release during work with nanomaterials under fume hoods. Here, we assessed laboratory workers’ inhalation exposure during synthesis and handling of CuO, TiO₂ and ZnO in a fume hood. In addition, we tested the capacity of a fume hood to prevent particle release to laboratory air during simulated spillage of different powders (silica fume, zirconia TZ-3Y and TiO₂). Airborne particle concentrations were measured in near field, far field, and in the breathing zone of the worker. Handling CuO nanoparticles increased the concentration of small particles (<?58 nm) inside the fume hood (up to 1?×?10⁵ cm^?3). Synthesis, handling and packaging of ZnO and TiO₂ nanoparticles did not result in detectable particle release to the laboratory air. Simulated powder spills showed a systematic increase in the particle concentrations inside the fume hood with increasing amount of material and drop height. Despite powder spills were sometimes observed to eject into the laboratory room, the spill events were rarely associated with notable release of particles from the fume hood. Overall, this study shows that a fume hood generally offers sufficient exposure control during synthesis and handling of nanomaterials. An appropriate fume hood with adequate sash height and face velocity prevents 98.3% of particles release into the surrounding environment. Care should still be made to consider spills and high cleanliness to prevent exposure via resuspension and inadvertent exposure by secondary routes.     

Generation of AuGe nanocomposites by co-sparking technique and their photoluminescence properties

Inhalation exposure to airborne nanoparticles (NPs) has been reported during manual activities using typical fume hoods. This research studied potential inhalation exposure associated with the manual handling of NPs using two new nanoparticle-handling enclosures and two biological safety cabinets, and discussed the ability to contain NPs in the hoods to reduce environmental release and exposure. Airborne concentrations of 5 nm to 20 μm diameter particles were measured while handling nanoalumina particles in various ventilated enclosures. Tests were conducted using two handling conditions and concentrations were measured using real-time particle counters, and particles were collected on transmission electron microscope grids to determine particle morphology and elemental composition. Airflow patterns were characterized visually using a laser-light sheet and fog. The average number concentration increase at breathing zone outside the enclosure was less than 1,400 particle/cm³ for each particle size at all tested conditions and the estimated overall mass concentration was about 83 μg/m³ which was less than the dosage of typical nanoparticle inhalation exposure studies. The typical front-to-back airflow was used in the studied hoods, which could potentially induce reverse turbulence in the wake region. However, containment of NPs using studied hoods was demonstrated with excellent performance. Smoke tests showed that worker’s hand motion could potentially cause nanoparticle escape. The challenge of front-to-back airflow can be partially overcome by gentle motion, low face velocity, and front exhaust to reduce nanoparticle escape.     

Editorial

An overview of the special issue of the Journal of Nanoparticle Research on Occupational and Environmental Health of nanotechnology is presented. Papers published in this special issue show considerable progress in understanding nanoparticle toxicity, monitoring, generation, dustiness, filtration, and applications of nanoparticles. More research is needed to ensure safe handling of nanomaterials as nanotechnology continues to develop at an incredible pace.

Exposure to nanoscale particles and fibers during machining of hybrid advanced composites containing carbon nanotubes

This study investigated airborne exposures to nanoscale particles and fibers generated during dry and wet abrasive machining of two three-phase advanced composite systems containing carbon nanotubes (CNTs), micron-diameter continuous fibers (carbon or alumina), and thermoset polymer matrices. Exposures were evaluated with a suite of complementary instruments, including real-time particle number concentration and size distribution (0.005–20 μm), electron microscopy, and integrated sampling for fibers and respirable particulate at the source and breathing zone of the operator. Wet cutting, the usual procedure for such composites, did not produce exposures significantly different than background whereas dry cutting, without any emissions controls, provided a worst-case exposure and this article focuses here. Overall particle release levels, peaks in the size distribution of the particles, and surface area of released particles (including size distribution) were not significantly different for composites with and without CNTs. The majority of released particle surface area originated from the respirable (1–10 μm) fraction, whereas the nano fraction contributed ~10% of the surface area. CNTs, either individual or in bundles, were not observed in extensive electron microscopy of collected samples. The mean number concentration of peaks for dry cutting was composite dependent and varied over an order of magnitude with highest values for thicker laminates at the source being >1 × 10⁶ particles cm⁻³. Concentration of respirable fibers for dry cutting at the source ranged from 2 to 4 fibers cm⁻³ depending on the composite type. Further investigation is required and underway to determine the effects of various exposure determinants, such as specimen and tool geometry, on particle release and effectiveness of controls.

Rapid synthesis and size control of CuInS2 semi-conductor nanoparticles using microwave irradiation

The properties of CuInS₂ semi-conductor nanoparticles make them attractive materials for use in next-generation photovoltaics. We have prepared CuInS₂ nanoparticles from single source precursors via microwave irradiation. Microwave irradiation methods have allowed us to increase the efficiency of preparation of these materials by providing uniform heating and rapid reaction times. The synergistic effect of varying thiol capping ligand concentrations as well as reaction temperatures and times resulted in fine control of nanoparticle growth in the 3–5 nm size range. Investigation of the photophysical properties of the colloidal nanoparticles were performed using electronic absorption and luminescence emission spectroscopy. Qualitative nanoparticles sizes were determined from the photoluminescence (PLE) data and compared to HRTEM images.

A theoretical study on calculation of absolute hydration enthalpies for some univalent ions

Using the total radius of alkaline fluorides and sodium halides and their experimental total enthalpy values, absolute hydration enthalpies of sodium and fluoride ions ( and ) were previously calculated. Also, by the help of data of sodium and fluoride ions for all alkaline metal ions and halides absolute hydration enthalpies were determined.

Size distributions of aerosols in an indoor environment with engineered nanoparticle synthesis reactors operating under different scenarios

Size distributions of nanoparticles in the vicinity of synthesis reactors will provide guidelines for safe operation and protection of workers. Nanoparticle concentrations and size distributions were measured in a research academic laboratory environment with two different types of gas-phase synthesis reactors under a variety of operating conditions. The variation of total particle number concentration and size distribution at different distances from the reactor, off-design state of the fume hood, powder handling during recovery, and maintenance of reactors are established. Significant increases in number concentration were observed at all the locations during off-design conditions (i.e., failure of the exhaust system). Clearance of nanoparticles from the work environment was longer under off-design conditions (20 min) compared to that under normal hood operating conditions (4–6 min). While lower particle number concentrations are observed during operation of furnace aerosol reactors in comparison to flame aerosol reactors, the handling, processing, and maintenance operations result in elevated concentrations in the work area.     

Public perception of nanotechnology

While several studies on the public opinion of nanotechnology have pointed to a rather enthusiastic U.S. public, the public uptake of nanotechnology in Europe is more contained. The results of the Swiss publifocus on nanotechnology reveal a pragmatic attitude of citizens toward the emerging technologies, thus confirming what has been identified as a “balanced approach” in the NanoJury UK.

General model for the functional dependence of defect concentration on oxygen potential in mixed conducting oxides

To understand and engineer applications for mixed conducting oxides, it is desirable to have explicit, analytical expressions for the functional dependence of defect concentration and transport properties on the partial pressure of the external gas phase. To fulfill this need, general expressions are derived for the functional dependence of defect concentration on the oxygen partial pressure () for the mixed ionic electronic conductors. The model presented in this paper differs from expressions obtained using the popular Brouwer approach because they are continuous across multiple Brouwer regions.

Sonochemical syntheses and characterization of nano-sized lead(II) coordination polymer with ligand 1H-1,2,4-triazole-3-carboxylate

Nanoparticles of a two-dimensional coordination polymer, {[Pb(L)(μ_1,1-NCS)(H₂O)]}_n (1), (L⁻ = 1H-1,2,4-triazole-3-carboxylate), have been synthesized by a sonochemical process and characterized by scanning electron microscopy, X-ray powder diffraction, IR spectroscopy and elemental analyses. The thermal stability of compound 1 both its bulk and nano-size has been studied by thermal gravimetric (TG) and differential thermal (DTA) analyses and compared each other. Concentration of initial reagents effects and the role of power ultrasound irradiation on size and morphology of nano-structured compound 1, have been studied. Calcination of the single crystals and nano-sized compound 1 at 400 °C under air atmosphere yields mixture of PbS and Pb₂(SO₄)O nanoparticles. Results show that the size and morphology of the PbS and Pb₂(SO₄)O nanoparticles are dependent upon the particles size of compound 1. A decrease in the particles size of compound 1 leads to a decrease in the particles size of the PbS and Pb₂(SO₄)O.     

Expert opinion on nanotechnology: risks,benefits, and regulation

A survey of American (US) nanotechnology researchers (N = 177) suggests a diversity of views about what areas are most important to the burgeoning field, as well as perceptions about the overall benefits and risks of such research. On average, respondents saw a range of technologies as key and viewed public health and environmental issues as areas where both risks and the need for regulation are greatest. These areas were also where respondents said current regulations were least adequate. Factor analyses of the survey questions suggest that, when considering both risks and regulations, respondents make a distinction between health and environmental risks, and what might be termed “social risks” (e.g., invasion of privacy, use of nanotechnology in weapons, and economic impacts).

Relevance of aerosol dynamics and dustiness for personal exposure to manufactured nanoparticles

Production and handling of manufactured nanoparticles (MNP) may result in unwanted worker exposure. The size distribution and structure of MNP in the breathing zone of workers will differ from the primary MNP produced. Homogeneous coagulation, scavenging by background aerosols, and surface deposition losses are determinants of this change during transport from source to the breathing zone, and to a degree depending on the relative time scale of these processes. Modeling and experimental studies suggest that in MNP production scenarios, workers are most likely exposed to MNP agglomerates or MNP attached to other particles. Surfaces can become contaminated by MNP, which constitute potential secondary sources of airborne MNP-containing particles. Dustiness testing can provide insight into the state of agglomeration of particles released during handling of bulk MNP powder. Test results, supported by field data, suggest that the particles released from powder handling occur in distinct size modes and that the smallest mode can be expected to have a geometric mean diameter >100 nm. The dominating presence of MNP agglomerates or MNP attached to background particles in the air during production and use of MNP implies that size alone cannot, in general, be used to demonstrate presence or absence of MNP in the breathing zone of workers. The entire respirable size fraction should be assessed for risk from inhalation exposure to MNP.     

Refining search terms for nanotechnology

The ability to delineate the boundaries of an emerging technology is central to obtaining an understanding of the technology’s research paths and commercialization prospects. Nowhere is this more relevant than in the case of nanotechnology (hereafter identified as “nano”) given its current rapid growth and multidisciplinary nature. (Under the rubric of nanotechnology, we also include nanoscience and nanoengineering.) Past efforts have utilized several strategies, including simple term search for the prefix nano, complex lexical and citation-based approaches, and bootstrapping techniques. This research introduces a modularized Boolean approach to defining nanotechnology which has been applied to several research and patenting databases. We explain our approach to downloading and cleaning data, and report initial results. Comparisons of this approach with other nanotechnology search formulations are presented. Implications for search strategy development and profiling of the nanotechnology field are discussed.

Nanotoxicology: characterizing the scientific literature, 2000–2007

Understanding the toxicity of nanomaterials and nano-enabled products is important for human and environmental health and safety as well as public acceptance. Assessing the state of knowledge about nanotoxicology is an important step in promoting comprehensive understanding of the health and environmental implications of these new materials. To this end, we employed bibliometric techniques to characterize the prevalence and distribution of the current scientific literature. We found that the nano-toxicological literature is dispersed across a range of disciplines and sub-fields; focused on in vitro testing; often does not specify an exposure pathway; and tends to emphasize acute toxicity and mortality rather than chronic exposure and morbidity. Finally, there is very little research on consumer products, particularly on their environmental fate, and most research is on the toxicity of basic nanomaterials. The implications for toxicologists, regulators and social scientists studying nanotechnology and society are discussed.

The Millimeter Wave Radiation of a Traveling Wave Sinusoidal Wire Antenna

In this paper, investigation of radiation properties of the traveling-wave sinusoidal wire antennas is extended to the millimeter-wave frequencies (Ka-band) for the antennas whose geometrical dimensions vary in a wide range. Far-field patterns and S-parameters of composed three antenna sets were measured. A mathematical model was constructed for the structure and a MATLAB code based on this theoretical approach was written to calculate patterns, phase and attenuation constants of all investigated antennas. Frequency characteristics and the relation of antenna dimensions with wave parameters were investigated. Measured and calculated patterns were also compared with the constructed far-field patterns obtained by MoM (method of moments) and the MoM current distributions were used to explain the loss mechanisms of antennas. A directive, undistorted and smooth radiation can be achieved only choosing small undulated antennas whose peak-to-peak amplitude to period ratio κ is smaller than 0.4 (κ < 0.4). It is shown that wavelength of broadside radiation is not equal to antenna period for all antennas, except for very small undulated antennas (κ < 0.2). This antenna type can be used as a frequency-scan antenna for millimeter wave radars.

Release potential of single-wall carbon nanotubes produced by super-growth method during manufacturing and handling

We investigated the release potential of single-wall carbon nanotubes (CNTs) produced by the super-growth method during their manufacturing and handling processes at a research facility. We generally sampled air at points both outside and inside of protective enclosures such as a glove box and fume hood. Sampling the air outside of the enclosures was intended to evaluate the actual exposure of workers to CNTs, while sampling the air inside the enclosures was performed to quantify the release of CNTs to the air in order to estimate the potential exposure of workers without protection. The results revealed that airborne CNTs were generated when (1) CNTs were separated from the substrates using a spatula and placed in a container in a glove box; (2) an air gun was used to clean the air filters (containing dust that included CNTs) of a vacuum cleaner; (3) a vacuum cleaner was used to collect CNTs (emission with exhaust air from the cleaner); (4) the container of CNTs was opened; and (5) CNTs in the bin of the cleaner were transferred to a container. In these processes, airborne CNTs were only found inside the enclosures, except for a small amount of CNTs released from the glove box when it was opened. Electron microscopic observations of aerosol particles found CNT clusters, which were fragments of CNT forests, with sizes ranging from submicrometers to tens of micrometers.     

Frequency Domain Fluorescence Lifetime Study of Crude Petroleum Oils

Frequency domain (FD) fluorescence lifetime data was collected for a series of 20 crude petroleum oils using a 405 nm excitation source and over a spectral range of ~426 to ~650 nm. Average fluorescence lifetimes were calculated using three different models: discrete multi-exponential, Gaussian distribution, and Lorentzian distribution. Fitting the data to extract accurate average lifetimes using the various models proved easier and less time consuming for the FD data than with Time Correlated Single Photon Counting (TCSPC) methods however the analysis of confidence intervals to the computed average lifetimes proved cumbersome for both methods. The uncertainty in the average lifetime was generally larger for the discrete lifetime multi-exponential model when compared to the distribution-based models. For the lifetime distributions, the data from the light crude oils with long lifetimes generally fit to a single decay term. Heavier oils with shorter lifetimes required multiple decay terms. The actual value for the average lifetime is more dependant on the specific fitting model employed than the data acquisition method used. Correlations between average fluorescence lifetimes and physical and chemical parameters of the crude oils were made with a view to developing a quantitative model for predicting the gross chemical composition of crude oils. It was found that there was no significant benefit gained by using FD over TCSPC other than more rapid data analysis in the FD case. For the FD data the Gaussian distribution model for fluorescence lifetime gave the best correlations with chemical composition allowing a qualitative correlation to some bulk oil parameters.

Some consequences of the conformally invariant generalization of Einstein’s equations

New possibilities in the solution to the general relativity problems appearing in the conformally invariant generalization of Einsteins equations are addressed. The conformally invariant equations and their solutions possess the following properties:

Magnetic Resonance in Gadolinium Nanoparticles near the Curie Point

The Influence of temperature in the range from 275 to 320 K on ESR spectra and magnetization m of ensembles of spherical gadolinium nanoparticles with the diameter from 89 to 18 nm was studied. The particles with d = 18 nm had a cubic face centered structure and no magnetic transition. At T > T_C all particles were paramagnetic, and their g factors were g = 1.98 ± 0.02 irrespective of their size and structure. At T = T_C the particles having 28 to 89 nm in size experienced a magnetic and orientation transition; at T < T_C their m(H) dependences were described by the Langevin function, and the FMR lines broadened and shifted towards H = 0. FMR lines of the Gd particle ensembles showed a hysteresis behavior during magnetization reversal, which did not correlate with the coercivity of the particles. Dependences of the Gd nanoparticles FMR linewidth ΔH(T) changed proportionally to |T–T_C|.     

A Simple Spectrofluorometric Assay to Measure Total Intracellular Magnesium by a Hydroxyquinoline Derivative

The intracellular behaviour of diaza-18-crown-6 appended with two H-substituted hydroxyquinoline groups (DCHQ1) was investigated to explore its application as a new sensor for the evaluation of cell magnesium content and distribution. We used five cells lines characterised by different contents of magnesium and different intracellular membrane-defined compartments. The main result is the definition of the appropriate experimental conditions to quantitatively assess the total cell magnesium by fluorescence spectroscopy. We showed that disrupting cells by sonication, DCHQ1 was capable to assess total cell magnesium in all cell types examined, obtaining overlapping results with atomic absorption spectroscopy (AAS). This new analytical approach requires very small cell samples and a simple fluorimetric technique, and can be a valid alternative to AAS. The fluorescent properties of DCHQ1 in living cells are: (a) it consistently stains live cells, (b) it discriminates small variations of cell Mg contents, (c) cell staining is stable for at least 30 min. We also investigated the role of lipophilic environment on DCHQ1 fluorescence by mimicking cell membranes and described how the composition and structure of lipid vesicles affect Mg-DCHQ1 fluorescence. Thus, DCHQ1 may offer important information also on magnesium distribution in living cells, providing a novel strategy to map the intracellular compartmentalization of this cation.