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Carbon nanotubes (CNTs) are increasingly being used in industrial applications, but their toxicological data in animals and humans are still sparse. To assess the toxicological dose-response of CNTs and to evaluate their pulmonary biopersistence, their quantification in tissues, especially lungs, is crucial. There are currently no reference methods or reference materials for low levels of CNTs in organic matter. Among existing analytical methods, few have been fully and properly validated. To remedy this, we undertook an inter-laboratory comparison on samples of freeze-dried pig lung, ground and doped with CNTs. Eight laboratories were enrolled to analyze 3 types of CNTs at 2 concentration levels each in this organic matrix. Associated with the different analysis techniques used (specific to each laboratory), sample preparation may or may not have involved prior digestion of the matrix, depending on the analysis technique and the material being analyzed. Overall, even challenging, laboratories' ability to quantify CNT levels in organic matter is demonstrated. However, CNT quantification is often overestimated. Trueness analysis identified effective methods, but systematic errors persisted for some. Choosing the assigned value proved complex. Indirect analysis methods, despite added steps, outperform direct methods. The study emphasizes the need for reference materials, enhanced precision, and organized comparisons. [ABSTRACT FROM AUTHOR]

The recent revision of OECD inhalation toxicology test guidelines 412 and 413 presents new challenges for both the study director (SD) and quality assurance (QA) personnel when conducting GLP (good laboratory practice) studies. In the case of nanomaterial inhalation exposure studies, GLP has rarely been applied, yet the new revisions are applicable to soluble and insoluble nanomaterials, as well as conventional chemicals. For example, the new guidelines require an additional bronchoalveolar lavage (BAL) fluid assay and lung burden measurement during the post-exposure observation (PEO) period, plus nanomaterial physicochemical characterization before and after nano-aerosol generation when exposing experimental animals. Implementing these revised guidelines will prove especially challenging for QA measures related to the physicochemical characterization and aerosolization of test nanomaterials. Therefore, this review examines the key elements involved in nanomaterial inhalation GLP testing under the revised OECD guidelines, suggests an alternative to the increased animal numbers, in consideration of animal welfare and with scientific merits, and discusses the limitation of toxicokinetic estimation using the new testing guidelines. [ABSTRACT FROM AUTHOR]

Lung deposition and retention measurements are now required by the newly revised OECD inhalation toxicity testing guidelines 412 and 413 when evaluating the clearance and biopersistence of poorly soluble nanomaterials, such as multi-walled carbon nanotubes (MWCNTs). However, evaluating the lung deposition concentration is challenging with certain nanomaterials, such as carbon-based and iron-based nanomaterials, as it is difficult to differentiate them from endogenous elements. Therefore, the current 28-day inhalation toxicity study investigated the lung retention kinetics of tangled MWCNTs. Male Sprague Dawley rats were exposed to MWCNTs at 0, 0.257, 1.439, and 4.253 mg/m3 for 28 days (6 h/day, 5 days/week, 4 weeks). Thereafter, the rats were sacrificed at day 1, 7, and 28 post-exposure and the pulmonary inflammatory response evaluated by analyzing the bronchoalveolar lavage fluid. Plus, the blood biochemistry, hematology, and histopathology of the lungs were also examined. The lung deposition and retention of MWCNTs were determined based on the elemental carbon content in the lungs after tissue digestion. The number of polymorphonuclear cells and LDH concentration were both found to be significantly higher with the medium and high concentrations (1.439 and 4.253 mg/m3) and dose dependent. The estimated retention half-life for the high concentration (4.253 mg/m3) was about 35 days. The results of this study indicate that tangled MWCNTs seem to have a relatively shorter retention half-life when compared to previous reports on rigid MWCNTs, and the no-observed adverse effect level (NOAEL) for the tested tangled MWCNTs was 0.257 mg/m3 in a previous rat 28-day subacute inhalation toxicity study. [ABSTRACT FROM AUTHOR]

This paper introduces a new standardized testing procedure for nanomaterial environmental toxicity (International Organization for Standardization/Technical Specification (ISO/TS) 20787): 'aquatic toxicity assessment of manufactured nanomaterials in saltwater lakes using Artemia sp. Nauplii' intended to generate more reliable and repeatable aquatic toxicity data testing manufactured nanomaterials, using Artemia sp., to evaluate their possible ecotoxicity in saltwater lake ecosystems. The principles behind testing with Artemia sp. are reviewed and the paper gives an overview of research published between 2009 and 2018 in which manufactured nanomaterials were tested using Artemia sp. [ABSTRACT FROM AUTHOR]

Graphene oxides possess unique physicochemical properties with important potential applications in electronics, pharmaceuticals, and medicine. However, the toxicity following inhalation exposure to graphene oxide has not yet been clarified. Therefore, this study conducted a short-term graphene oxide inhalation toxicity analysis using a nose-only inhalation exposure system and male Sprague-Dawley rats. A total of four groups (15 rats per group) were exposed: (1) control (fresh air), (2) low concentration (0.76 ± 0.16 mg/m3), (3) moderate concentration (2.60 ± 0.19 mg/m3), and (4) high concentration (9.78 ± 0.29 mg/m3). The rats were exposed to graphene oxide for 6 h/day for 5 days, followed by recovery for 1, 3, and 21 days. No significant body or organ weight changes were noted after the short-term exposure or during the recovery period. Similarly, no significant systemic effects of toxicological importance were noted in the hematological assays, bronchoalveolar lavage fluid (BAL) inflammatory markers, BAL fluid cytokines, or blood biochemical assays following the graphene oxide exposure or during the post-exposure observation period. Moreover, no significant differences were observed in the BAL cell differentials, such as lymphocytes, macrophages, or polymorphonuclear cells. Graphene oxide-ingested alveolar macrophages as a spontaneous clearance reaction were observed in the lungs of all the concentration groups from post 1 day to post 21 days. Histopathological examination of the liver and kidneys did not reveal any significant test-article-relevant histopathological lesions. Importantly, similar to previously reported graphene inhalation data, this short-term nose-only inhalation study found only minimal or unnoticeable graphene oxide toxicity in the lungs and other organs. [ABSTRACT FROM AUTHOR]

Synthetic amorphous silica nanoparticles (SiNPs) are one of the most applied nanomaterials and are widely used in a broad variety of industrial and biomedical fields. However, no recent long-term inhalation studies evaluating the toxicity of SiNPs are available and results of acute studies are limited. Thus, we conducted a subacute inhalation toxicity study of SiNPs in Sprague-Dawley rats using a nose-only inhalation system. Rats were separated into four groups and target concentrations selected in this study were as follows: control (fresh air), low- (0.407 ± 0.066 mg/m3), middle- (1.439 ± 0.177 mg/m3) and high-concentration group (5.386 ± 0.729 mg/m3), respectively. The rats were exposed to SiNPs for four consecutive weeks (6 hr/day, 5 days/week) except for control group of rats which received filtered fresh air. After 28-days of inhalation exposure to SiNPs, rats were sacrificed after recovery periods of one, seven and 28 days. Although there were minimal toxic changes such as temporary decrease of body weight after exposure, increased levels of red blood cells (RBCs) and hemoglobin (Hb) concentration, the lung histopathological findings and inflammatory markers in bronchoalveolar lavage (BAL) fluid including polymorphonuclear (PMN) leukocyte, lactate dehydrogenase (LDH), albumin and protein did not show significant changes at any recovery period. The results of this study suggest that the subacute inhalation of SiNPs had no toxic effects on the lung of rats at the concentrations and selected time points used in this study. [ABSTRACT FROM AUTHOR]

With the increased production and widespread commercial use of silver nanoparticles (AgNPs), human and environmental exposures to silver nanoparticles are inevitably increasing. In particular, persons manufacturing and handling silver nanoparticles and silver nanoparticle containing products are at risk of exposure, potentially resulting in health hazards. While silver dusts, consisting of micro-sized particles and soluble compounds have established occupational exposure limits (OELs), silver nanoparticles exhibit different physicochemical properties from bulk materials. Therefore, we assessed silver nanoparticle exposure and related health hazards in order to determine whether an additional OEL may be needed. Dosimetric evaluations in our study identified the liver as the most sensitive target organ following inhalation exposure, and as such serves as the critical target organ for setting an occupational exposure standard for airborne silver nanoparticles. This study proposes an OEL of 0.19 &#956:g/m³ for silver nanoparticles derived from benchmark concentrations (BMCs) from subchronic rat inhalation toxicity assessments and the human equivalent concentration (HEC) with kinetic considerations and additional uncertainty factors. It is anticipated that this level will protect workers from potential health hazards, including lung, liver, and skin damage. [ABSTRACT FROM AUTHOR]

Graphene, a two-dimensional engineered nanomaterial, is now being used in many applications, such as electronics, biological engineering, filtration, lightweight and strong nanocomposite materials, and energy storage. However, there is a lack of information on the potential health effects of graphene in humans based on inhalation, the primary engineered nanomaterial exposure pathway in workplaces. Thus, an inhalation toxicology study of graphene was conducted using a nose-only inhalation system for 28 days (6 h/day and 5 days/week) with male Sprague-Dawley rats that were then allowed to recover for 1-, 28-, and 90-day post-exposure period. Animals were separated into 4 groups (control, low, moderate, and high) with 15 male rats (5 rats per time point) in each group. The measured mass concentrations for the low, moderate, and high exposure groups were 0.12, 0.47, and 1.88 mg/m³, respectively, very close to target concentrations of 0.125, 0.5, and 2 mg/m³. Airborne graphene exposure was monitored using several real-time instrumentation over 10nm to 20 μ for size distribution and number concentration. The total and respirable elemental carbon concentrations were also measured using filter sampling. Graphene in the air and biological media was traced using transmission electron microscopy. In addition to mortality and clinical observations, the body weights and food consumption were recorded weekly. At the end of the study, the rats were subjected to a full necropsy, blood samples were collected for blood biochemical tests, and the organ weights were measured. No dose-dependent effects were recorded for the body weights, organ weights, bronchoalveolar lavage fluid inflammatory markers, and blood biochemical parameters at 1-day post-exposure and 28-day post-exposure. The inhaled graphenes were mostly ingested by macrophages. No distinct lung pathology was observed at the 1-, 28- and 90-day post-exposure. The inhaled graphene was translocated to lung lymph nodes. The results of this 28-day graphene inhalation study suggest low toxicity and a NOAEL of no less than 1.88 mg/m³. [ABSTRACT FROM AUTHOR]

Graphenes have emerged as a highly promising, two-dimensional engineered nanomaterial that can possibly substitute carbon nanotubes. They are being explored in numerous R&D and industrial applications in laboratories across the globe, leading to possible human and environmental exposures to them. Yet, there are no published data on graphene exposures in occupational settings and no readily available methods for their detection and quantitation exist. This study investigates for the first time the potential exposure of workers and research personnel to graphenes in two research facilities and evaluates the status of the control measures. One facility manufactures graphene using graphite exfoliation and chemical vapor deposition (CVD), while the other facility grows graphene on a copper plate using CVD, which is then transferred to a polyethylene terephthalate (PET) sheet. Graphene exposures and process emissions were investigated for three tasks – CVD growth, exfoliation, and transfer – using a multi-metric approach, which utilizes several direct reading instruments, integrated sampling, and chemical and morphological analysis. Real-time instruments included a dust monitor, condensation particle counter (CPC), nanoparticle surface area monitor, scanning mobility particle sizer, and an aethalometer. Morphologically, graphenes and other nanostructures released from the work process were investigated using a transmission electron microscope (TEM). Graphenes were quantified in airborne respirable samples as elemental carbon via thermo-optical analysis. The mass concentrations of total suspended particulate at Workplaces A and B were very low, and elemental carbon concentrations were mostly below the detection limit, indicating very low exposure to graphene or any other particles. The real-time monitoring, especially the aethalometer, showed a good response to the released black carbon, providing a signature of the graphene released during the opening of the CVD reactor at Workplace A. The TEM observation of the samples obtained from Workplaces A and B showed graphene-like structures and aggregated/agglomerated carbon structures. Taken together, the current findings on common scenarios (exfoliation, CVD growth, and transfer), while not inclusive of all graphene manufacturing processes, indicate very minimal graphene or particle exposure at facilities manufacturing graphenes with good manufacturing practices. [ABSTRACT FROM PUBLISHER]

Graphene has recently been attracting increasing attention due to its unique electronic and chemical properties and many potential applications in such fields as semiconductors, energy storage, flexible electronics, biosensors and medical imaging. However, the toxicity of graphene in the case of human exposure has not yet been clarified. Thus, a 5-day repeated inhalation toxicity study of graphene was conducted using a nose-only inhalation system for male Sprague-Dawley rats. A total of three groups (20 rats per group) were compared: (1) control (ambient air), (2) low concentration (0.68 ± 0.14 mg/m3graphene) and (3) high concentration (3.86 ± 0.94 mg/m3graphene). The rats were exposed to graphene for 6 h/day for 5 days, followed by recovery for 1, 3, 7 or 28 days. The bioaccumulation and macrophage ingestion of the graphene were evaluated in the rat lungs. The exposure to graphene did not change the body weights or organ weights of the rats after the 5-day exposure and during the recovery period. No statistically significant difference was observed in the levels of lactate dehydrogenase, protein and albumin between the exposed and control groups. However, graphene ingestion by alveolar macrophages was observed in the exposed groups. Therefore, these results suggest that the 5-day repeated exposure to graphene only had a minimal toxic effect at the concentrations and time points used in this study. [ABSTRACT FROM PUBLISHER]

While manyin vivoandin vitrotoxicology studies of multi-walled carbon nanotubes (MWCNTs) have already indicated that exposure to MWCNTs can potentially induce health effects in humans, the actual health effects of MWCNTs among exposed workers are not yet known. Moreover, the levels of exposure and internal doses of MWCNTs are becoming more and more important for estimating the health effects resulting from exposure to MWCNTs. However, information on biomonitoring and exposure to MWCNTs remains limited. Therefore, the authors conducted a health surveillance study in a workplace that manufactures MWCNTs, including assessment of the personal and area exposure levels to MWCNTs, a walk-through evaluation of the manufacturing process, and collection of blood and exhaled breath condensates (EBCs) from the MWCNT manufacturing and office workers. In addition, a pulmonary function test was also conducted on the MWCNT manufacturing workers (9) and office workers (4). The worker exposure to elemental carbon was found to be 6.2–9.3 μg/m3in the personal samplings and 5.5–7.3 μg/m3in the area samplings. Notwithstanding, the workers exhibited a normal range of hematology and blood biochemistry values and normal lung function parameters. When analyzing the EBCs, the malondialdehyde (MDA), 4-hydroxy-2-hexenal (4-HHE) and n-hexanal levels in the MWCNT manufacturing workers were significantly higher than those in the office workers. The MDA and n-hexanal levels were also significantly correlated with the blood molybdenum concentration, suggesting MDA, n-hexanal and molybdenum as useful biomarkers of MWCNT exposure. [ABSTRACT FROM PUBLISHER]

Single-wall carbon nanotubes (SWCNT) possess a small size, large surface area, and high reactivity, which enable them to permeate the cytoplasmic or nuclear membrane and attach to biological molecules. During medical applications, SWNCT are usually administered intravenously, which enhances interaction with blood components. Yet despite this exposure potential, safety evaluation studies of SWCNTs focused on human blood cells are still lacking. Therefore, this study was undertaken to examine cytotoxicity, genotoxicity, and proinflammatory responses following SWCNT treatment of phytohemagglutinin (PHA)-stimulated male human peripheral blood lymphocytes (PBL). SWCNT were found to inhibit cell growth, as well as to induce DNA breakage, and micronuclei (MN) formation via reactive oxygen species (ROS) generation. The addition ofN-acetylcysteine (NAC) a cell-permeable antioxidant, decreased ROS generation, cytotoxicity, and genotoxicity produced by SWCNT treatment. In addition, SWCNT induced tumor necrosis factor (TNF)-α release after 24 h, yet this phenomenon was not related to ROS generation, as antioxidant NAC treatment did not affect increased proinflammatory cytokine levels in the phytohemagglutinin (PHA)-stimulated male human PBL. [ABSTRACT FROM AUTHOR]

Despite their useful physico-chemical properties, carbon nanotubes (CNTs) continue to cause concern over occupational and human health due to their structural similarity to asbestos. Thus, to evaluate the toxic and genotoxic effect of multi-wall carbon nanotubes (MWCNTs) on lung cells in vivo, eight-week-old rats were divided into four groups (each group = 25 animals), a fresh air control (0 mg/m3), low (0.17 mg/m3), middle (0.49 mg/m3), and high (0.96 mg/m3) dose group, and exposed to MWCNTs via nose-only inhalation 6 h per day, 5 days per week for 28 days. The count median length and geometric standard deviation for the MWCNTs determined by TEM were 330.18 and 1.72 nm, respectively, and the MWCNT diameters ranged from 10 to 15 nm. Lung cells were isolated from five male and five female rats in each group on day 0, day 28 (only from males) and day 90 following the 28-day exposure. The total number of animals used was 15 male and 10 female rats for each concentration group. To determine the genotoxicity of the MWCNTs, a single cell gel electrophoresis assay (Comet assay) was conducted on the rat lung cells. As a result of the exposure, the olive tail moments were found to be significantly higher ( p < 0.05) in the male and female rats from all the exposed groups when compared with the fresh air control. In addition, the high-dose exposed male and middle and high-dose exposed female rats retained DNA damage, even 90 days post-exposure ( p < 0.05). To investigate the mode of genotoxicity, the intracellular reactive oxygen species (ROS) levels and inflammatory cytokine levels (TNF-α, TGF- β, IL-1, IL-2, IL-4, IL-5, IL-10, IL-12 and IFN-γ) were also measured. For the male rats, the H2O2 levels were significantly higher in the middle (0 days post-exposure) and high- (0 days and 28 days post-exposure) dose groups ( p < 0.05). Conversely, the female rats showed no changes in the H2O2 levels. The inflammatory cytokine levels in the bronchoalveolar lavage (BAL) fluid did not show any statistically significant difference. Interestingly, the short-length MWCNTs deposited in the lung cells were persistent at 90 days post-exposure. Thus, exposing lung cells to MWCNTs with a short tube length may induce genotoxicity. [ABSTRACT FROM AUTHOR]

To define the relationship between the brain concentration of manganese and neurological signs, such as locomotion, after prolonged welding-fume exposure, cynomolgus monkeys were acclimated for 1 month and then divided into three concentration groups: unexposed, low concentration (31 mg/m3 total suspended particulate (TSP), 0.9 mg/m3 of Mn), and high concentration (62 mg/m3 TSP, 1.95 mg/m3 of Mn) of TSP. The monkeys were exposed to manual metal-arc stainless steel (MMA-SS) welding fumes for 2 h per day over 8 months in an inhalation chamber system equipped with an automatic fume generator. The home cage locomotor activity and patterns were determined using a camera system over 2-4 consecutive days. After 25 and 32 weeks of exposure, the home cage locomotor activity of the high-concentration primates was found to be 5-6 times higher than that of the unexposed primates, and this increased locomotor activity was maintained for 7 weeks after ceasing the welding-fume exposure, eventually subsiding to three times higher after 13 weeks of recovery. Therefore, the present results, along with our previous observations of a high magnetic resonance imaging (MRI) T1 signal in the globus pallidus and increased blood Mn concentration, indicate that prolonged welding-fume exposure can cause neurobehavioral changes in cynomolgus monkeys. [ABSTRACT FROM AUTHOR]

To clarify the health risks related to silver nanoparticles (Ag-NPs), we evaluated the genotoxicity, acute oral and dermal toxicity, eye irritation, dermal irritation and corrosion and skin sensitisation of commercially manufactured Ag-NPs according to the OECD test guidelines and GLP. The Ag-NPs were not found to induce genotoxicity in a bacterial reverse mutation test and chromosomal aberration test, although some cytotoxicity was observed. In acute oral and dermal toxicity tests using rats, none of the rats showed any abnormal signs or mortality at a dose level of ∼ 2000 mg/kg. Similarly, acute eye and dermal irritation and corrosion tests using rabbits revealed no significant clinical signs or mortality and no acute irritation or corrosion reaction for the eyes and skin. In a skin sensitisation test using guinea pigs, one animal (1/20) showed discrete or patchy erythema, thus Ag-NPs can be classified as a weak skin sensitiser. [ABSTRACT FROM AUTHOR]

Printed electronics uses converging technologies, such as printing, fine mechanics, nanotechnology, electronics and other new technologies. Consequently, printed electronics raises additional health and safety concerns to those experienced in the traditional printing industry. This study investigated two printed electronics workplaces based on a walk-through survey and personal and area sampling. All the printed electronics operations were conducted in a cleanroom. No indication of exposure to excess silver nanoparticles or carbon nanotubes (CNTs) was found. While the organic solvents were lower than current occupational exposure limits, there was a lack of engineering controls, such as local exhaust ventilation, correct enclosure and duct connections. There was also an insufficient quantity of personal protective equipment, and some organic solvents not described in the safety data sheets (SDSs) were detected in the air samples. Plus, the cleaning work, a major emissions operation, was not conducted within a hood, and the cleaning waste was not properly disposed of. Therefore, the present exposure assessment results from two printed electronics workplaces suggest that the printed electronics industry needs to take note of the occupational safety and health risks and hazards already established by the traditional printing industry, along with new risks and hazards originating from converging technologies such as nanotechnology. [ABSTRACT FROM AUTHOR]

The specific properties of silver nanoparticles (AgNPs), such as antimicrobial activity and electrical conductivity, allow them to be used in many fields. However, their expanding application is also raising health, environmental and safety concerns. Previous in vivo AgNP toxicity studies have indicated a gender-different accumulation of silver in the kidneys, with 2-3 times more silver in female kidneys compared to male kidneys. However, no other studies have further addressed this gender difference. Accordingly, the current study investigated the gender-dependent effect of AgNPs on the kidney gene level based on toxicogenomic studies of kidneys obtained from rats exposed to AgNPs via inhalation for 12 weeks. When compared with the fresh air control, the silver nanoparticle-exposed kidneys included 104 genes with a more than 1.3-fold expression increase. For the male rat kidneys exposed to a low or high dose of silver nanoparticles, 96 genes exhibited expression changes, where six genes changed with both the low and high dose; four increased and two decreased. Meanwhile, for the female rat kidneys exposed to a low or high dose of silver nanoparticles, 66 genes exhibited expression changes, where 11 genes changed with both the low and high dose; nine increased and two decreased. Gender-dependent gene expression changes of more than 2-fold were linked to 163 genes, with 79 genes in the male kidneys and 84 genes in the female kidneys, plus gender-dependent gene expression changes of more than 5-fold were linked to 21 genes. However, no genes involved in apoptosis or the cell cycle were activated by the 12-week silver nanoparticle inhalation exposure. Overall, the male rat kidneys showed a higher expression of genes involved in xenobiotic metabolism, while the female rat kidneys showed a higher expression of genes involved in extracellular signaling. [ABSTRACT FROM AUTHOR]

Safety data sheets (SDS5) and labelling are the basic hazard communication tools for hazardous chemicals as regards their manufacture, storage, transport and other handling activities. Thus, in the context of the growing use of nanomaterials and nanomaterial-containing materials, this study evaluated the information provided in 97 nanomaterial-related SDSs according to the criteria set by the GHS (Globally Harmonized System of Classification and Labelling of Chemicals) and found that most of the SDSs did not include sufficient information on the safety of nanomaterials, such as their toxicity and physicochemical properties. The reasons for this lack of information in the nanomaterial SDSs can mainly be attributed to (1) a lack of toxicity and physicochemical property information on nanomaterials, (2) unawareness of the effectiveness of conventional exposure controls, such as local exhaust ventilation and encapsulation, and personal protective equipment (PPE), in protecting against nanomaterial exposure, (3) a lack of information on emergency and firefighting measures and (4) a lack of knowledge on how existing regulations apply to nanomaterials. Therefore, to create a consistent standard for the information provided on safety, health and environmental matters for manufactured nanomaterial-containing products, guidance for the preparation of nanomaterial-specific SDSs, including both nanomaterials and mixtures of nanomaterials with conventional non-nanoscale materials, was recently initiated by the ISO TC 229. Their guidance, in the form of a technical report, recommends that nanomaterial-related SDSs should be prepared based on a precautionary approach in terms of the toxicity and other risks associated with the nanomaterial contents within the mixture in question. One of the key recommendations in the technical report is to include additional physicochemical properties, including the particle size (average and range), size distribution aggregation/agglomeration state, shape and aspect ratio, crystallinity, specific surface area, dispersibility and dustiness, which help to distinguish the characteristics of nanomaterials from those of non-nanoscale materials. The technical report also recommends the preparation of SDSs for all nanomaterials and mixtures that meet the GHS criteria for physical, health or environmental hazards, and for all mixtures containing nanomaterials that meet the criteria for carcinogenic, toxic to reproduction or specific target organ toxicity in concentrations exceeding the cut-off limits for an SDS specified by the criteria for mixtures. Finally, the technical report recommends that SDSs be prepared for all nanomaterials, unless there is evidence that they are not hazardous. [ABSTRACT FROM AUTHOR]

In a previous study, the lung function, as indicated by the tidal volume, minute volume, and peak inspiration flow, decreased during 90 days of exposure to silver nanoparticles and was accompanied by inflammatory lesions in the lung morphology. Therefore, this study investigated the recovery from such lung function changes in rats following the cessation of 12 weeks of nanoparticle exposure. Male and female rats were exposed to silver nanoparticles (14-15 nm diameter) at concentrations of 0.66 × 106 particles/cm3 (49 μg/m3, low dose), 1.41 × 106 particles/cm3 (117 μg/m3, middle dose), and 3.24 × 106 particles/cm3 (381 μg/m3, high dose) for 6 h/day in an inhalation chamber for 12 weeks. The rats were then allowed to recover. The lung function was measured every week during the exposure period and after the cessation of exposure, plus animals were sacrificed after the 12-week exposure period, and 4 weeks and 12 weeks after the exposure cessation. An exposure-related lung function decrease was measured in the male rats after the 12-week exposure period and 12 weeks after the exposure cessation. In contrast, the female rats did not show a consistent lung function decrease either during the exposure period or following the exposure cessation. The histopathology showed a gradual recovery from the lung inflammation in the female rats, whereas the male rats in the high-dose group exhibited persistent inflammation throughout the 12-week recovery period. Therefore, the present results suggest a potential persistence of lung function changes and inflammation induced by silver nanoparticle exposure above the no observed adverse effect level. [ABSTRACT FROM AUTHOR]

In this study, a direct-flow-type nose-only exposure chamber developed for inhalation toxicity experiments using a numerical analysis and experiments is evaluated. Maintaining a uniform flow rate and test article concentration are the critical factors when designing an inhalation exposure chamber. Therefore, this study evaluated whether the flow rate and particle size distribution at the injection nozzles at each port could be maintained with a deviation below 10%. To achieve this requirement, a nose-only exposure chamber flow field was simulated using a numerical analysis method, i.e. computational fluid dynamics (CFD) code FLUENT 6.3.26. Based on the simulation results, a test chamber was built and tested. The flow velocity was measured at the injection nozzle of the chamber and the aerosol particle size distribution was also measured at each port while inserting the test material into the exposure chamber. The results indicated that a uniform flow field distribution at each stage and port, the deviation of the flow velocity, and particle size distribution were all within 10%. Thus, the resulting nose-only exposure chamber could be described as well-designed. [ABSTRACT FROM AUTHOR]

With the increased production and widespread use of nanomaterials, human and environmental exposure to nanomaterials is inevitably increasing. Therefore, this study monitored the possible exposure to nanoparticles at workplaces that manufacture nano-TiO2 and nano-silver. To estimate the potential exposure of workers, personal sampling, area monitoring, and real-time monitoring using a scanning mobility particle sizer (SMPS) and dust monitor were conducted at workplaces where the workers handle nanomaterials. The gravimetric concentrations of TiO2 ranged from 0.10 to 4.99 mg/m3, which were lower than the occupational exposure limit 10 mg/m3 set by the Korean Ministry of Labor or American Conference of Governmental Industrial Hygienists (ACGIH). Meanwhile, the silver metal concentrations ranged from 0.00002 to 0.00118 mg/m3, which were also lower than the silver dust 0.1 mg/m3 and silver soluble compound 0.01 mg/m3 occupational exposure limits set by the ACGIH. The particle number concentrations at the nano-TiO2 manufacturing workplaces ranged from 11,418 to 45,889 particles/cm3 with a size range of 15--710.5 nm during the reaction, although the concentration decreased to 14,000 particles/cm3 when the reaction was stopped. The particle concentrations at the TiO2 manufacturing workplaces increased during the reactor and vacuum pump operations, and during the collection of the synthesized TiO2 particles. Similarly, the particle concentrations at the silver nanoparticle manufacturing workplaces increased when the sodium citrates were weighed or reacted with the silver nitrates, and during the cleaning of the workplace. The number of silver nanoparticles in the samples obtained from the workplace manufacturing silver nanoparticles using induced coupled plasma ranged from 57,789 to 2,373,309 particles/cm3 inside the reactor with an average size of 20--30 nm and 535--25,022 particles/cm3 with a wide range of particle sizes due to agglomeration or aggregation after the release of nanoparticles into the workplace air. In contrast, the silver nanoparticles manufactured by the wet method ranged from 393 to 3526 particle/cm3 with an average size of 50 nm. Thus, when taken together, the TiO2 and silver nanoparticle concentrations were relatively lower than existing occupational exposure limits. [ABSTRACT FROM AUTHOR]

Seven CNT (carbon nanotube) handling workplaces were investigated for exposure assessment. Personal sampling, area sampling, and real-time monitoring using an SMPS (scanning mobility particle sizer), dust monitor, and aethalometer were performed to characterize the mass exposure, particle size distribution, and particle number exposure. No workplace was found to exceed the current ACGIH (American Conference of Governmental Industrial Hygienists) TLVs (threshold limit values) and OELs (occupational exposure levels) set by the Korean Ministry of Labor for carbon black (3.5 mg/m3), PNOS (particles not otherwise specified; 3 mg/m3), and asbestos (0.1 fiber/cc). Nanoparticles and fine particles were most frequently released after opening the CVD (chemical vapor deposition) cover, followed by catalyst preparation. Other work processes that prompted nanoparticle release included spraying, CNT preparation, ultrasonic dispersion, wafer heating, and opening the water bath cover. All these operation processes could be effectively controlled with the implementation of exposure mitigation, such as engineering control, except at one workplace where only natural ventilation was used. [ABSTRACT FROM AUTHOR]

Previous studies on welding-fume-induced lung fibrosis have indicated that recovery is possible when the degree of exposure is short-term and moderate. However, this study investigated the recovery after recurrent exposure to welding fumes, as welders are invariably re-exposed to welding fumes after recovering from radiographic pneumoconiosis. Thus, to investigate the disease and recovery processes of welding-fume-induced pneumoconiosis in the case of recurrent welding-fume exposure, rats were exposed to manual metal arc-stainless steel (MMA-SS) welding fumes with a total suspended particulate (TSP) concentration of 51.4 ± 2.8 mg/m3 (low dose) or 84.6 ± 2.9 mg/m3 (high dose) for 2 h/day in an inhalation chamber for 1 mo and then allowed to recover from the inflammation for 1 mo. Thereafter, the rats were exposed again to MMA-SS with a TSP concentration of 44.1 ± 8.8 mg/m3 (low dose) or 80.1 ± 9.8 mg/m3 (high dose) for another 30 d and then allowed to recover from the inflammation for 1 mo. The recovery from the first exposure was then compared with that from the second exposure. The first and second exposures to MMA-SS welding fumes were found to produce significant increases in the lung weights and inflammatory parameters, including total cell numbers, alveolar macrophages (AMs), polymorphonuclear cells (PMNs), lymphocytes, and lactate dehydrogenase (LDH) in the bronchoalveolar lavage fluid (BALF) when compared with the unexposed controls. Following the first and second recovery, a significant reduction in inflammatory parameters of BALF was observed between the exposure and recovery groups. Histopathological observations showed foamy or pigmented macrophage accumulation, cellular debris, or pigment from burst macrophages after the first or second exposure. Following the first or second recovery, cellular debris or pigment from burst macrophages was cleared away from the lungs and accumulation of foamy or pigmented macrophages was decreased when compared to previous exposure. Reactive hyperplasia was noticed after second exposure or either recovery. However, significant differences were observed between the first and second exposure or the first and second recovery. In particular, the number of PMNs was significantly higher after the second exposure than after the first exposure. Also, all cell types in the BALF were significantly elevated in the high-dose second recovery group than in the first recovery group, indicating an incomplete recovery from second exposure. In conclusion, these results indicated that the lung damage caused by the second welding-fume exposure was more difficult to recover from than the first exposure. [ABSTRACT FROM AUTHOR]

With the increased production and widespread use of multiwalled carbon nanotubes (MWCNTs), human and environmental exposure to MWCNTs is inevitably increasing. Therefore, this study monitored the possible exposure to MWCNT release in a carbon nanotube research laboratory. To estimate the potential exposure of researchers and evaluate the improvement of the workplace environment after the implementation of protective control measures, personal and area monitoring were conducted in an MWCNT research facility where the researchers handled unrefined materials. The number, composition, and aspect ratio of MWCNTs were measured using scanning transmission electron microscopy with an energy-dispersive x-ray analyzer. The gravimetric concentrations of total dust before any control measures ranged from 0.21 to 0.43 mg/m3, then decreased to a nondetectable level after implementing the control measures. The number of MWCNTs in the samples obtained from the MWCNT blending laboratory ranged from 172.9 to 193.6 MWCNTs/cc before the control measures, and decreased to 0.018-0.05 MWCNTs/cc after the protective improvements. The real-time monitoring of aerosol particles provided a signature of the MWCNTs released from the blending equipment in laboratory C. In particular, the number size response of an aerodynamic particle sizer with a relatively high concentration in the range of 2 to 3 μ m in aerodynamic diameter revealed the evidence of MWCNT exposure. The black carbon mass concentration also increased significantly during the MWCNT release process. Therefore, the present study suggests that the conventional industrial hygiene measures can significantly reduce exposure to airborne MWCNTs and other particulate materials in a nano research facility. [ABSTRACT FROM AUTHOR]

The antimicrobial activity of silver nanoparticles has resulted in their widespread use in many consumer products. However, despite the continuing increase in the population exposed to silver nanoparticles, the effects of prolonged exposure to silver nanoparticles have not been thoroughly determined. Accordingly, this study attempted to investigate the inflammatory responses and pulmonary function changes in rats during 90 days of inhalation exposure to silver nanoparticles. The rats were exposed to silver nanoparticles (18 nm diameter) at concentrations of 0.7 × 106 particles/cm3 (low dose), 1.4 × 106 particles /cm3 (middle dose), and 2.9 × 106 particles /cm3 (high dose) for 6 h/day in an inhalation chamber for 90 days. The lung function was measured every week after the daily exposure, and the animals sacrificed after the 90-day exposure period. Cellular differential counts and inflammatory measurements, such as albumin, lactate dehydrogenase (LDH), and total protein, were also monitored in the acellular bronchoalveolar lavage (BAL) fluid of the rats exposed to the silver nanoparticles for 90 days. Among the lung function test measurements, the tidal volume and minute volume showed a statistically significant decrease during the 90 days of silver nanoparticle exposure. Although no statistically significant differences were found in the cellular differential counts, the inflammation measurements increased in the high-dose female rats. Meanwhile, histopathological examinations indicated dose-dependent increases in lesions related to silver nanoparticle exposure, such as infiltrate mixed cell and chronic alveolar inflammation, including thickened alveolar walls and small granulomatous lesions. Therefore, when taken together, the decreases in the tidal volume and minute volume and other inflammatory responses after prolonged exposure to silver nanoparticles would seem to indicate that nanosized particle inhalation exposure can induce lung function changes, along with inflammation, at much lower mass dose concentrations when compared to submicrometer particles. [ABSTRACT FROM AUTHOR]

The antibacterial effect of silver nanoparticles has resulted in their extensive application in health, electronic, and home products. However, while the population exposed to silver nanoparticles continues to increase with ever new applications, silver nanoparticles remain a controversial research area as regards their toxicity to biological systems. In particular, the oral toxicity of silver nanoparticles is of particular concern to ensure public and consumer health. Accordingly, this study tested the oral toxicity of silver nanoparticles (60 nm) over a period of 28 days in Sprague-Dawley rats following Organization for Economic Cooperation and Development (OECD) test guideline 407 with Good Laboratory Practice (GLP) application. Eight-week-old rats, weighing about 283 g for the males and 192 g for the females, were divided into four 4 groups (10 rats in each group): vehicle control, low-dose group (30 mg/kg), middle-dose group (300 mg/kg), and high-dose group (1000 mg/kg). After 28 days of exposure, the blood biochemistry and hematology were investigated, along with a histopathological examination and silver distribution study. The male and female rats did not show any significant changes in body weight relative to the doses of silver nanoparticles during the 28-day experiment. However, some significant dose-dependent changes were found in the alkaline phsophatase and cholesterol values in either the male or female rats, seeming to indicate that exposure to over more than 300 mg of silver nanoparticles may result in slight liver damage. There were no statistically significant differences in the micronucleated polychromatic erythrocytes (MN PCEs) or ratio of polychromatic erythrocytes among the total erythrocytes after silver nanoparticle exposure when compared with the control. Therefore, the present results suggest that silver nanoparticles do not induce genetic toxicity in male and female rat bone marrow in vivo. Nonetheless, the tissue distribution of silver nanopaticles did show a dose-dependent accumulation of silver content in all the tissues examined. In particular, a gender-related difference in the accumulation of silver was noted in the kidneys, with a twofold increase in the female kidneys when compared with the male kidneys. [ABSTRACT FROM AUTHOR]

To investigate the effects of welding fumes on the glycoconjugates in nasal respiratory mucosa, male Sprague-Dawley rats were exposed to manual metal arc stainless steel (MMA-SS) welding fumes at a concentration of 56-76 mg/m3 total suspended particulate for 2 h/day in an inhalation chamber for 90 days. During the exposure period, the experimental animals were sacrificed after 2 h and 15, 30, 60, and 90 days of exposure; then sections were examined using lectin histochemistry. Some remarkable changes, such as destroyed cilia, desquamation and mucification of epithelial cells, and destruction of nasal septal glands, were seen in the welding fume-exposed groups. Specific changes in the lectin binding patterns were also observed in the welding fume-exposed rats. The Ricinus communis agglutinin-I (RCA-I) staining of the cilia and columnar cells increased slightly when compared with the unexposed rats. The RCA-I and Ulex europaeus agglutinin-I (UEA-I) staining of the goblet cells also increased as the exposure continued. The mucigenous epithelial cells reacted with Bandeiraea simplicifolia lectin-I (BSL-I), RCA-I, and succinylated wheat germ agglutinin A (sWGA) after 15 days of exposure, which was not visible in the control group. The dorsal septal glands exhibited an affinity with peanut agglutinin (PNA), BSL-I, and RCA-I, which was also not visible in the control group. The affinity for Dolichos biflorus agglutinin (DBA), soybean agglutinin (SBA), PNA, sWGA, BSL-I, and UEA-I in the ventral septal glands of the welding fume-exposed groups tended to increase, whereas the concanavalin A (Con A) reactivity in the dorsal septal glands decreased slightly. In conclusion, it was assumed that the changes in the glycoconjugate residues in the nasal respiratory mucosa of the welding fume-exposed rats represented important components of defense mechanisms against the toxicants in the welding fumes. [ABSTRACT FROM AUTHOR]

Several pharmacokinetic studies on inhalation exposure to manganese (Mn) have already demonstrated that Mn readily accumulates in the olfactory and brain regions. However, a shortening of the magnetic resonance imaging (MRI) T1 relaxation time or high T1 signal intensity in specific sites of the brain, including the globus pallidus and subcortical frontal white matter, as indicative of tissue manganese accumulation has not yet been clearly established for certain durations of known doses of welding-fume exposure in experimental animals. Accordingly, to investigate the movement of manganese after welding-fume exposure, six cynomolgus monkeys were acclimated and assigned to three dose groups: unexposed, low dose (31 mg/m3 total suspended particulate [TSP], 0.9 mg/m3 of Mn), and high dose (62 mg/m3 TSP, 1.95 mg/m3 of Mn) of total suspended particulate. The primates were exposed to manual metal arc stainless steel (MMA-SS) welding fumes for 2 h per day in an inhalation chamber system equipped with an automatic fume generator. Magnetic resonance imaging (MRI) studies were conducted before the initiation of exposure and thereafter every month. The tissue Mn concentrations were then measured after a plateau was reached regarding the shortening of the MRI T1 relaxation time. A dose-dependent increase in the Mn concentration was found in the lungs, while noticeable increases in the Mn concentrations were found in certain tissues, such as the liver, kidneys, and testes. Slight increases in the Mn concentrations were found in the caudate, putamen, frontal lobe, and substantia nigra, while a dose-dependent noticeable increase was only found in the globus pallidus. Therefore, the present results indicated that a shortening of the MRI T1 relaxation time corresponded well with the Mn concentration in the globus pallidus after prolonged welding-fume exposure. [ABSTRACT FROM AUTHOR]

The antibacterial effect of silver nanoparticles has resulted in their extensive application in health, electronic, and home products. Thus, the exposed population continues to increase as the applications expand. Although previous studies on silver dust, fumes, and silver compounds have revealed some insights, little is yet known about the toxicity of nano-sized silver particles, where the size and surface area are recognized as important determinants for toxicity. Thus, the inhalation toxicity of silver nanoparticles is of particular concern to ensure the health of workers and consumers. However, the dispersion of inhalable ambient nano-sized particles has been an obstacle in evaluating the effect of the inhalation of nano-sized particles on the respiratory system. Accordingly, the present study used a device that generates silver nanoparticles by evaporation/condensation using a small ceramic heater. As such, the generator was able to distribute the desired concentrations of silver nanoparticles to chambers containing experimental animals. The concentrations and distribution of the nanoparticles with respect to size were also measured directly using a differential mobility analyzer and ultrafine condensation particle counter. [ABSTRACT FROM AUTHOR]

The use of silver nanoparticles is rapidly growing in various industries. However, exposure to nano-sized silver particles generated during production, use, and disposal in ambient air or the workplace remains an important concern for public and occupational health. There are currently no specific methods for measuring the inhalation toxicity of nanoparticles or specific nanoparticle generation methods. In a previous study, silver nanoparticles were generated using a small ceramic heater with a local heating area that allowed direct heating of the bulk silver source, thereby eliminating any space between the heating unit and the source material such that the volume of the nanoparticle generator and power consumption are both remarkably reduced. Therefore, to evaluate the efficacy of this nanoparticle generator for inhalation toxicity studies, the long-term particle generation characteristics were investigated, and the results confirmed a very stable continuous operation over 20-30 h. The geometric mean diameter and total number concentration of nanoparticles remained stable for about 24 h when the initial loaded mass of bulk silver on the heater surface was 160 mg. The particle size distribution after a long operating time was then estimated when changing the initial mass of bulk silver on the heater surface. It took about 36 h for the loaded silver mass to decrease from 160 mg to 100 mg, during which time the geometric mean diameter of the nanoparticles only decreased 6%, from 14 nm to 13.2 nm. [ABSTRACT FROM AUTHOR]

Welders can be exposed to high levels of manganese through welding fumes. Although it has already been suggested that excessive manganese exposure causes neurotoxicity, called manganism, the pathway of manganese transport to the brain with welding-fume exposure remains unclear. Iron is an essential metal that maintains a homeostasis in the body. The divalent metal transporter 1 (DMT1) transports iron and other divalent metals, such as manganese, and the depletion of iron is known to upregulate DMT1 expression. Accordingly, this study investigated the tissue distribution of manganese in iron-sufficient and iron-deficient rats after welding-fume exposure. The feeding of an iron-deficient diet for 4 wk produced a depletion of body iron, such as decreased iron levels in the serum and tissues, and upregulated the DMT1 expression in the rat duodenum. The iron-sufficient and iron-deficient rats were then exposed to welding fumes generated from manual metal arc stainless steel at a concentration of 63.5 ± 2.3 mg/m3 for 2 h per day over a 30-day period. Animals were sacrificed on days 1, 15, and 30. The level of body iron in the iron-deficient rats was restored to the control level after the welding-fume exposure. However, the tissue distributions of manganese after the welding-fume exposure showed similar patterns in both the iron-sufficient and iron-deficient groups. The concentration of manganese increased in the lungs and liver on days 15 and 30, and increased in the olfactory bulb on day 30. Slight and heterogeneous increases of manganese were observed in different brain regions. Consequently, these findings suggest that the presence of Fe in the inhaled welding fumes may not have a significant effect on the uptake of Mn into the brain. Thus, the condition of iron deficiency did not seem to have any apparent effect on the transport of Mn into the brain after the inhalation of welding fumes. [ABSTRACT FROM AUTHOR]

Welders are at risk of being exposed to high concentrations of welding fumes and developing pneumoconiosis or other welding-fume exposure-related diseases. Among such diseases, manganism resulting from welding-fume exposure remains a controversial issue, as although the movement of manganese into specific brain regions has been established, the similar movement of manganese presented with other metals, such as welding fumes, has not been clearly demonstrated as being similar to that of manganese alone. Meanwhile, the competition between Mn and iron for iron transporters, such as transferrin and DMT-1, to the brain has also been implicated in the welding-fume exposure. Thus, the increased signal intensities in the basal ganglia, including the globus pallidus and subcortical frontal white matter, based on T1-weighted magnetic resonances in welders, require further examination as regards the correspondence with an increased manganese concentration. Accordingly, to investigate the movement of manganese after welding-fume exposure, 6 cynomolgus monkeys were acclimated for 1 mo and assigned to 3 dose groups: unexposed, low dose of (total suspended particulate [TSP] 31 mg/m3, 0.9 mg/m3 of Mn), and high dose of total suspended particulate (62 mg/m3 TSP, 1.95 mg/m3 of Mn). The primates were exposed to manual metal-arc stainless steel (MMA-SS) welding fumes for 2 h/day in an inhalation chamber system equipped with an automatic fume generator for 6 mo. Magnetic resonance imaging (MRI) studies of the basal ganglia were conducted before the initiation of exposure and thereafter every month. During the exposure, the blood chemistry was monitored every 2 wk and the concentrations of metal components in the blood were measured every 2 wk and compared with ambient manganese concentrations. The manganese concentrations in the blood did not show any significant increase until after 2 mo of exposure, and then reached a plateau after 90 days of exposure, showing that an exposure period of at least 60 days was required to build up the blood Mn concentration. Furthermore, as the blood Mn concentration continued to build, a continued decrease in the MRI T1 relaxation time in the basal ganglia was also detected. These data suggested that prolonged inhalation of welding fumes induces a high MRI T1 signal intensity with an elevation of the blood manganese level. The presence of a certain amount of iron or other metals, such as Cr and Ni, in the inhaled welding fumes via inhalation was not found to have a significant effect on the uptake of Mn into the brain or the induction of a high MRI T1 signal intensity. [ABSTRACT FROM AUTHOR]

In this report, the process of designating a GLP facility by the Korean Ministry of Environment (MOE) is described in detail using the case of the Center of Occupational Toxicology (COT). The COT, which had been prepared as a GLP facility, filed an application to the National Institute of Environmental Research (NIER) of the MOE. The GLP system of the COT was evaluated by a harmonized evaluation team that consisted of several authorities including the NIER, the National Institute of Agricultural Science and Technology (NIAST), and the National Institute of Toxicological Research (NITR). The evaluation was arranged for mutual acceptance of data among GLP authorities. The designation process, additional documents necessary for applying GLP facility, the process of test facility evaluation including reviewing the application and site inspection, and inspection results and submission of correction plans are explained by using the instance of the inspection process of the COT. COT was evaluated as a suitable GLP facility for acute oral and inhalation toxicity tests and the Ames test. [ABSTRACT FROM AUTHOR]

The Korean Society of Good Laboratory Practice (KSGLP) was established Dec. 10, 1998. The objectives of the KSGLP are to enhance the quality of domestic studies and the level of GLP compliance, in safety testing, and to promote information exchange among its members. The activities of KSGLP include: offering workshops and symposiums, linking with related governmental organizations, collecting GLP related information and providing the information to the related organizations, building international networks to collect information and to establish relationship, developing training materials and publishing periodicals, and other business necessary to achieve the objectives of the KSGLP. The KSGLP achieved its goals within a short period of time by offering workshops and symposia, and by providing important GLP related information in newspapers or via the KSGLP's internet homepage (www.ksglp.or.kr). The main role of the KSGLP will be to disseminate GLP technology nationwide. The KSGLP would like to help many labs that are preparing their facilities for GLP compliance. Further, the KSGLP is hoping to share GLP experiences with other members. [ABSTRACT FROM AUTHOR]

The levels of exposure and internal doses of nanomaterials are becoming more and more important for estimating the health effects resulting from exposure to nanomaterials. Health surveillance can be used as an indicator of whether exposure is occurring, rather than in determining if levels of exposure are safe. We have conducted a health surveillance study in a workplace which manufactures silver nanomaterials, including the assessment of personal exposure levels to silver nanoparticles, a walk-through evaluation of the manufacturing process and the collection of blood and urine samples from the exposed workers. Two male workers who had worked for 7 years in the business of manufacturing silver nanomaterial were exposed to silver concentrations of 0.35 and 1.35 μg/m3. The blood and urine levels of silver were 0.034 and 0.0135 μg/dl for blood and 0.043 μg/dl and not detected level for urine. The blood chemistry and haematology data were determined to be within a normal range. Taken together, the health surveillance indicated that the nanomaterial manufacturing workers were exposed to a much lower concentration of silver dust or soluble silver threshold limit values and showed no significant findings on their health status. [ABSTRACT FROM AUTHOR]

Examines the occupational exposure level (OEL) for 2-bromopropane established in Korea. Hematopoietic and reproductive toxic effects experienced by the workers operating the process of tactile switch assembling; Importance of establishing an OEL for 2BP; Documentation of the OEL for 2BP.