We investigated the suitability of the graphitic carbon (GC) content of diesel particulate matter (DPM), measured using Raman spectroscopy, as a surrogate measure of elemental carbon (EC) determined by thermal optical analysis. The Raman spectra in the range of 800-1800 cm-1 (including the D mode at ∼1322 cm-1 and the G mode at ∼1595 cm-1) were used for GC identification and quantification. Comparison of the Raman spectra for two certified DPM standards (NIST SRM 1650 and SRM 2975), two types of diesel engine exhaust soot, and three types of DPM-enriched workplace aerosols show that the uncertainty of GC quantification based on the D peak height, G peak height, and the total peak area below D and G peaks was about 6.0, 6.7, and 6.9%, respectively. The low uncertainty for different aerosol types suggested possible use of GC as a surrogate measure of EC in workplace atmospheres. A calibration curve was constructed using two laboratory-aerosolized DPM standards to describe the relationship between GC measured by a portable Raman spectrometer and the EC concentration determined by NIOSH Method 5040. The calibration curve was then applied to determine GC-based estimates of the EC contents of diesel engine exhaust samples from two vehicles and seven air samples collected at a hydraulic fracturing worksite. The GC-EC estimates obtained through Raman measurements agreed well with those found by NIOSH Method 5040 for the same samples at EC filter loadings below 2.86 μg/cm2. The study shows that using an appropriate sample collection method that avoids high filter mass loadings, onsite measurement of GC by a portable or hand-held Raman spectrometer can provide a useful indicator of EC in workplace aerosol.

Background Carbon nanotubes and nanofibers (CNT/F) have known toxicity but simultaneous comparative studies of the broad material class, especially those with a larger diameter, with computational analyses linking toxicity to their fundamental material characteristics was lacking. It was unclear if all CNT/F confer similar toxicity, in particular, genotoxicity. Nine CNT/F (MW #1–7 and CNF #1–2), commonly found in exposure assessment studies of U.S. facilities, were evaluated with reported diameters ranging from 6 to 150 nm. All materials were extensively characterized to include distributions of physical dimensions and prevalence of bundled agglomerates. Human bronchial epithelial cells were exposed to the nine CNT/F (0–24 μg/ml) to determine cell viability, inflammation, cellular oxidative stress, micronuclei formation, and DNA double-strand breakage. Computational modeling was used to understand various permutations of physicochemical characteristics and toxicity outcomes. Results Analyses of the CNT/F physicochemical characteristics illustrate that using detailed distributions of physical dimensions provided a more consistent grouping of CNT/F compared to using particle dimension means alone. In fact, analysis of binning of nominal tube physical dimensions alone produced a similar grouping as all characterization parameters together. All materials induced epithelial cell toxicity and micronuclei formation within the dose range tested. Cellular oxidative stress, DNA double strand breaks, and micronuclei formation consistently clustered together and with larger physical CNT/F dimensions and agglomerate characteristics but were distinct from inflammatory protein changes. Larger nominal tube diameters, greater lengths, and bundled agglomerate characteristics were associated with greater severity of effect. The portion of tubes with greater nominal length and larger diameters within a sample was not the majority in number, meaning a smaller percentage of tubes with these characteristics was sufficient to increase toxicity. Many of the traditional physicochemical characteristics including surface area, density, impurities, and dustiness did not cluster with the toxicity outcomes. Conclusion Distributions of physical dimensions provided more consistent grouping of CNT/F with respect to toxicity outcomes compared to means only. All CNT/F induced some level of genotoxicity in human epithelial cells. The severity of toxicity was dependent on the sample containing a proportion of tubes with greater nominal lengths and diameters.

Potential inhalation of fibrous carbon nanomaterials depends on the manufacturing/handling process and their tendency for air dispersion. Because of the large variety of carbon nanotube and nanofiber (CNT and CNF) products, with varying physical and chemical properties, characterization of these materials and their associated exposure risks is challenging. In this study, we aerosolized different types of CNT and CNF materials using an acoustic generator (AG) and characterized their aerodynamic and physical properties. The generation characteristics of the AG for the different CNT and CNF materials were investigated by measuring aerosol number concentrations and its decay properties with time. Airborne particle properties such as mobility and aerodynamic diameters were measured using mobility and aerodynamic particle sizers. The bulk and effective densities of the powder and aerosol were obtained by measuring the mass and volume of the bulk material and aerosol particles, where effective density was calculated by a tandem mobility-mass technique. The relationship between the aerosol properties (i.e., particle size, concentration, and dustiness) and bulk density of the material was also investigated to understand the potential for dispersion in air. The results showed that the aerosol concentration decay for each nanomaterial has a unique time constant, and that the rate of decay is positively correlated with the bulk density of the powder: the lower the bulk density, the slower the concentration decay. The aerodynamic diameter increased with increasing bulk density, while the mobility diameter showed the opposite trend. In general, bulk density is smaller than the particle effective density, and the effective density tends to approach the bulk density as particle size increases. Also, the bulk density of the fibrous nanomaterials tested in this study showed a reasonable correlation with dustiness data obtained from both our measurements and the literature, which was relatively weak for non-fibrous powders. This study indicates that more loosely agglomerated CNT powders, with lower bulk densities, would be more readily dispersed, and the dispersed particles remain airborne for longer periods. Depending on particle size, such materials can pose higher exposure risks due to their ease of dispersion and longer residence times.

Respirable crystalline silica (RCS) produced in mining and construction industries can cause life-threatening diseases such as silicosis, lung cancer, and chronic obstructive pulmonary disease (COPD). These diseases could be more effectively treated and prevented if RCS-related biomarkers were identified and measured at an early stage of disease progression, which makes development of a point of care test (POCT) platform extremely desirable for early diagnosis. In this work, a new, highly sensitive lab on a chip (LOC) immunoassay has been designed, developed, and characterized for tumor necrosis factor α (TNF-α), a protein biomarker that causes lung inflammation due to RCS exposure. The designed LOC device is composed of four reservoirs for sample, enzyme conjugated detection antibody, wash buffer, and chemiluminescence substrate in liquid form, along with three spiral reaction chambers for test, positive control, and negative control. All reservoirs and spiral microchannels were connected in series and designed to perform sequential delivery of immunoassay reagents with minimal user intervention. The developed LOC measured TNF-α concentrations as low as 16 pg/mL in plasma from RCS-exposed rats and also had a limit of detection (LOD) of 0.5 pg/mL in spiked artificial serum. In addition, the analysis time was drastically reduced to about 30 min, as opposed to hours in conventional methods. Successful implementation of a highly sensitive, chemiluminescence-based immunoassay on a preloaded LOC with proper quality control, as reported in this work, can pave the way toward developing a new rapid POCT platform for in-field clinical diagnosis.

A Raman spectroscopy based method has been developed for measurement of trace airborne concentrations of respirable crystalline silica (RCS) using various aerosol sampling and analysis techniques. Three aerosol microconcentration techniques were investigated for effective coupling of collected particulate samples with micro-Raman spectroscopy: (i) direct analysis on a particulate filter after focused aerosol collection using a converging nozzle; (ii) analysis of dried particulate deposit on a filter obtained directly from the aerosol phase using the Spotsampler device; and (iii) analysis of a dried spot (∼1-3 mm diameter) obtained by redepositing the particulate sample, after low-temperature plasma ashing of the filter sample. The deposition characteristics (i.e., spot diameter, shape, and deposit uniformity) of each technique were investigated. Calibration curves were constructed and detection limits were estimated for α-quartz using the A1 Raman Si-O-Si stretching-bending phonon mode at 465 cm-1. The measurement sensitivity could be substantially improved by increasing the signal integration time and by reducing the particle deposition area. Detection limits in the range of 8-55 ng could be achieved by microconcentrating the aerosol sample over a spot measuring 400-1000 μm in diameter. These detection limits were two to three orders of magnitude lower compared to those attainable using current standardized X-ray diffraction and infrared spectroscopy methods. The low detection limits suggest that near real-time measurements of RCS could be achieved with limits of quantification ranging from 2 to 18.5 μg/m3 (at 10 min collection time and 1.2 L/min sampling flow rate), depending on microconcentration technique used. The method was successfully extended to the measurement of α-quartz air concentration in representative workplace aerosol samples. This study demonstrates the potential of portable micro-Raman spectroscopy for near-real time measurement of trace RCS in air.

Introduction Respirable crystalline silica (RCS) exposure is considered as one of the most significant occupational health problems in the United States. Recent National Institute for Occupational Safety and Health (NIOSH) field studies identified overexposure to RCS in oil and gas extraction workers, with exposures exceeding occupational RCS exposure levels by factors of 20 or more in sand moving and transfer belt operations. To facilitate on-site screening of workers to identify early (i.e., preclinical) biological responses to RCS exposure, there is a strong need for field-portable diagnostic instruments and methods, particularly for workers in mining, oil and gas extraction, and construction industries. Methods A portable analyzer for on-site biomonitoring using a lab-on-a-chip (LOC) device was developed, and its performance in measurement of an inflammatory biomarker for inhalation of RCS aerosol was evaluated. Results The overall performance of the portable analyzer with the LOC device had accuracy and precision comparable to laboratory testing results. It runs on a LabView-based program that controls variable parameters: on/off sequence, reagent flow speed, pump run time and optical detection. The pump input to the LOC and a portable analyzer are coupled to the LOC device with PEEK tubing, for automated ELISA testing in the field. Conclusion This is the first field-portable analyzer capable of on-site screening of workers to identify early (i.e., preclinical) biological responses to RCS exposure. Our work supports application of the analyzer together with the developed LOC as a portable monitor for on-site detection of lung inflammation in workers exposed to RCS, with minimum user intervention. Development of a device for detecting exposure-related biomarkers of biological processes (e.g., inflammation) that are predictive of the pathogenicity of exposure to RCS and other airborne toxicants would offer an important new approach for silicosis prevention.

The increasing prevalence of carbon nanotubes (CNTs) in manufacturing and research environments, together with the potential exposure risks, necessitates development of reliable and accurate monitoring methods for these materials. We examined quantification of CNTs by two distinct methods based on Raman spectroscopy. First, as measured by the Raman peak intensity of aqueous CNT suspensions, and second, by Raman mapping of air filter surfaces onto which CNTs were collected as aerosols or applied as small-area (0.05 cm2) deposits. Correlation (R2 = 0.97) between CNT concentration and Raman scattering intensity for suspensions in cuvettes was found over a concentration range from about 2 to 10 µg/ml, but measurement variance precludes practical determination of a calibration curve. Raman mapping of aerosol sample filter surfaces shows correlation with CNT mass when the surface density is relatively high (R2 = 0.83 and 0.95 above about 5 µg total mass on filter), while heterogeneity of CNT deposition makes obtaining representative maps of lower density samples difficult. This difficulty can be mitigated by increasing the area mapped relative to the total sample area, improving both precision and the limit of detection (LOD). For small-area deposits, detection of low masses relevant to occupational monitoring can be achieved, with an estimated LOD of about 50 ng.

Background Commercial use of carbon nanotubes and nanofibers (CNT/F) in composites and electronics is increasing; however, little is known about health effects among workers. We conducted a cross-sectional study among 108 workers at 12 U.S. CNT/F facilities. We evaluated chest symptoms or respiratory allergies since starting work with CNT/F, lung function, resting blood pressure (BP), resting heart rate (RHR), and complete blood count (CBC) components. Methods We conducted multi-day, full-shift sampling to measure background-corrected elemental carbon (EC) and CNT/F structure count concentrations, and collected induced sputum to measure CNT/F in the respiratory tract. We measured (nonspecific) fine and ultrafine particulate matter mass and count concentrations. Concurrently, we conducted physical examinations, BP measurement, and spirometry, and collected whole blood. We evaluated associations between exposures and health measures, adjusting for confounders related to lifestyle and other occupational exposures. Results CNT/F air concentrations were generally low, while 18% of participants had evidence of CNT/F in sputum. Respiratory allergy development was positively associated with inhalable EC ( p =0.040) and number of years worked with CNT/F ( p =0.008). No exposures were associated with spirometry-based metrics or pulmonary symptoms, nor were CNT/F-specific metrics related to BP or most CBC components. Systolic BP was positively associated with fine particulate matter ( p -values: 0.015-0.054). RHR was positively associated with EC, at both the respirable ( p =0.0074) and inhalable ( p =0.0026) size fractions. Hematocrit was positively associated with the log of CNT/F structure counts ( p =0.043). Conclusions Most health measures were not associated with CNT/F. The positive associations between CNT/F exposure and respiratory allergies, RHR, and hematocrit counts may not be causal and require examination in other studies.

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.

Background: Recent animal studies have suggested the potential for wide-ranging health effects resulting from exposure to carbon nanotubes and nanofibers (CNT/F). To date, no studies in the US have directly examined the relationship between occupational exposure and potential human health effects. Objectives: Our goal was to measure CNT/F exposures among US workers with representative job types, from non-exposed to highly exposed, for an epidemiologic study relating exposure to early biologic effects. Methods: 108 participants were enrolled from 12 facilities across the US. Personal, full-shift exposures were assessed based on the mass of elemental carbon (EC) at the respirable and inhalable aerosol particle size fractions, along with quantitatively characterizing CNT/F and estimating particle size via transmission electron microscopy (TEM). Additionally, sputum and dermal samples were collected and analyzed to determine internal exposures and exposures to the hands/wrists. Results: The mean exposure to EC was 1.00 mu g/m(3) at the respirable size fraction and 6.22 mu g/m(3) at the inhalable fraction. Analysis by TEM found a mean exposure of 0.1275 CNT/F structures/cm(3), generally to agglomerated materials between 2 and 10 pm. Internal exposures to CNT/F via sputum analysis were confirmed in 18% of participants while similar to 70% had positive dermal exposures. Conclusions: We demonstrated the occurrence of a broad range of exposures to CNT/F within 12 facilities across the US. Analysis of collected sputum indicated internal exposures are currently occurring within the workplace. This is an important first step in determining if exposures in the workforce have any acute or lasting health effects.

Adverse human health impacts due to occupational and environmental exposures to manufactured nanoparticles are of concern and pose a potential threat to the continued industrial use and integration of nanomaterials into commercial products. This chapter addresses the inter-relationship between dose and response and will elucidate on how the dynamic chemical and physical transformation and breakdown of the nanoparticles at the cellular and subcellular levels can lead to the in vivo formation of new reaction products. The dose-response relationship is complicated by the continuous physicochemical transformations in the nanoparticles induced by the dynamics of the biological system, where dose, bio-processing, and response are related in a non-linear manner. Nanoscale alterations are monitored using high-resolution imaging combined with in situ elemental analysis and emphasis is placed on the importance of the precision of characterization. The result is an in-depth understanding of the starting particles, the particle transformation in a biological environment, and the physiological response.

The bioprocessing of CeO2 nanoparticles after uptake in lung tissues is compared with the formation of nanoparticles after inhalation of CeCl3 aerosols. In both cases, high-resolution TEM/STEM analyses indicate that cerium phosphate nanoparticles (NPs) had precipitated in phagolysosomal regions within macrophages. Importantly, the primary particle size, morphology, and agglomeration tendencies of the NPs were strikingly similar. Formation of cerium phosphate NPs after bioprocessing of inhaled CeO2 crystals proceeds via dissolution, ion transport, followed by nucleation and growth [1]. Application of 2D and 3D elemental maps of the NP bioprocessing stages and corresponding tissue interactions provide insights on the breakdown mechanisms, formation of new precipitates, size, and morphology changes of the original delivered NPs, and ion transport phenomena that result in secondary particle formation. Particle size and morphology are very similar for all of the cerium phosphate NPs, suggesting a common underlying precipitation mechanism independent of whether the metal ions are derived from dissolution of nanoparticles (CeO2) or from instilled metal ions (CeCl3).

Efficient microconcentration of aerosols to a substrate is essential for effectively coupling the collected particles to microscale optical spectroscopies such as laser-induced or spark microplasma, or micro-Raman or infrared spectroscopies. In this study, we present detailed characterization of a corona-based aerosol microconcentration technique developed previously (Diwakar & Kulkarni, 2012). The method involves two coaxial electrodes separated by a few millimeters, one held at a high electrical potential and the other grounded. The particles are collected on the collection (i. e., ground) electrode from a coaxial aerosol flow in a one-step charge-and-collect scheme using corona discharge and electrical precipitation between the two electrodes. Performance of the corona microconcentration method was determined experimentally by measuring collection efficiency, wall losses, and particle deposition density. An intrinsic spectroscopic sensitivity was experimentally determined for the aerosol microconcentrator. Using this sensitivity, we show that corona-based microconcentration is much superior to alternative methods, including filtration, focused impaction using aerodynamic lens, and spot collection using condensational growth. The method offers unique advantages for compact, hand-held aerosol analytical instrumentation.

Journal Article In vivo formation of Ce-phosphate Nanoparticles following Intratracheal Instillation of CeCl3: Subcellular sites, Nanostructures, Precipitation Mechanisms and Nanoparticle 3D-Alignment Get access Uschi M Graham, Uschi M Graham National Institute for Occupational Safety and Health, Cincinnati, OH, USA Search for other works by this author on: Oxford Academic Google Scholar Chen Wang, Chen Wang National Institute for Occupational Safety and Health, Cincinnati, OH, USA Search for other works by this author on: Oxford Academic Google Scholar Joseph Fernback, Joseph Fernback National Institute for Occupational Safety and Health, Cincinnati, OH, USA Search for other works by this author on: Oxford Academic Google Scholar Alan K Dozier, Alan K Dozier National Institute for Occupational Safety and Health, Cincinnati, OH, USA Search for other works by this author on: Oxford Academic Google Scholar Lawrence Drummy, Lawrence Drummy Air Force Research Laboratory, Dayton, OH Search for other works by this author on: Oxford Academic Google Scholar Krishnamurthy Mahalingam, Krishnamurthy Mahalingam Air Force Research Laboratory, Dayton, OH Search for other works by this author on: Oxford Academic Google Scholar Ramon M Molina, Ramon M Molina Harvard T.H. Chan School of Public Health, Boston, MA, USA Search for other works by this author on: Oxford Academic Google Scholar Nagarjun V Konduru, Nagarjun V Konduru Harvard T.H. Chan School of Public Health, Boston, MA, USA Search for other works by this author on: Oxford Academic Google Scholar M Eileen Birch, M Eileen Birch National Institute for Occupational Safety and Health, Cincinnati, OH, USA Search for other works by this author on: Oxford Academic Google Scholar Joseph D Brain Joseph D Brain Harvard T.H. Chan School of Public Health, Boston, MA, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 23, Issue S1, 1 July 2017, Pages 1342–1343, https://doi.org/10.1017/S1431927617007371 Published: 04 August 2017

Background: Carbon nanotubes and nanofibers (CNT/F) are increasingly used for diverse applications. Although animal studies suggest CNT/F exposure may cause deleterious health effects, human epidemiological studies have typically been small, confined to single workplaces, and limited in exposure assessment. Objectives: We conducted an industrywide cross-sectional epidemiological study of 108 workers from 12 U.S. sites to evaluate associations between occupational CNT/F exposure and sputum and blood biomarkers of early effect. Methods: We assessed CNT/F exposure via personal breathing zone, filter-based air sampling to measure background-corrected elemental carbon (EC) (a CNT/F marker) mass and microscopy-based CNT/F structure count concentrations. We measured 36 sputum and 37 blood biomarkers. We used factor analyses with varimax rotation to derive factors among sputum and blood biomarkers separately. We used linear, Tobit, and unconditional logistic regression models to adjust for potential confounders and evaluate associations between CNT/F exposure and individual biomarkers and derived factors. Results: We derived three sputum and nine blood biomarker factors that explained 78% and 67%, respectively, of the variation. After adjusting for potential confounders, inhalable EC and total inhalable CNT/F structures were associated with the most sputum and blood biomarkers, respectively. Biomarkers associated with at least three CNT/F metrics were 72 kDa type IV collagenase/matrix metalloproteinase-2 (MMP-2), interleukin-18, glutathione peroxidase (GPx), myeloperoxidase, and superoxide dismutase (SOD) in sputum and MMP-2, matrix metalloproteinase-9, metalloproteinase inhibitor 1/tissue inhibitor of metalloproteinases 1, 8-hydroxy-2'-deoxyguanosine, GPx, SOD, endothelin-1, fibrinogen, intercellular adhesion molecule 1, vascular cell adhesion protein 1, and von Willebrand factor in blood, although directions of associations were not always as expected. Conclusions: Inhalable rather than respirable CNT/F was more consistently associated with fibrosis, inflammation, oxidative stress, and cardiovascular biomarkers.

Pulmonary toxicity studies on carbon nanotubes focus primarily on as-produced materials and rarely are guided by a life cycle perspective or integration with exposure assessment. Understanding toxicity beyond the as-produced, or pure native material, is critical, due to modifications needed to overcome barriers to commercialization of applications. In the first series of studies, the toxicity of as-produced carbon nanotubes and their polymer-coated counterparts was evaluated in reference to exposure assessment, material characterization, and stability of the polymer coating in biological fluids. The second series of studies examined the toxicity of aerosols generated from sanding polymer-coated carbon-nanotube-embedded or neat composites. Postproduction modification by polymer coating did not enhance pulmonary injury, inflammation, and pathology or in vitro genotoxicity of as-produced carbon nanotubes, and for a particular coating, toxicity was significantly attenuated. The aerosols generated from sanding composites embedded with polymer-coated carbon nanotubes contained no evidence of free nanotubes. The percent weight incorporation of polymer-coated carbon nanotubes, 0.15% or 3% by mass, and composite matrix utilized altered the particle size distribution and, in certain circumstances, influenced acute in vivo toxicity. Our study provides perspective that, while the number of workers and consumers increases along the life cycle, toxicity and/or potential for exposure to the as-produced material may greatly diminish.