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In this study, molybdenum(IV) sulfide (MoS2) nanoparticles (97 ± 32 nm) and microparticles (1.92 ± 0.64 μm) stabilized with poly (vinylpolypyrrolidone) (PVP) were administered intratracheally to male and female rats (dose of 1.5 or 5 mg/kg bw), every 14 days for 90 days (seven administrations in total). Blood parameters were assessed during and at the end of the study (hematology, biochemistry including glucose, albumins, uric acid, urea, high density lipoprotein HDL, total cholesterol, triglycerides, aspartate transaminase, and alanine transaminase ALT). Bronchoalveolar lavage fluid (BALF) analyses included cell viability, biochemistry (total protein concentration, lactate dehydrogenase, and glutathione peroxidase activity), and cytokine levels (tumor necrosis factor α, TNF‐α, macrophage inflammatory protein 2‐alpha, MIP‐2, and cytokine‐induced neutrophil chemoattractant‐2, CINC‐2). Tissues were subjected to routine histopathological and electron microscopy (STEM) examinations. No overt signs of chronic toxicity were observed. Differential cell counts in BALF revealed no significant differences between the animal groups. An increase in MIP‐2 and a decrease in TNF‐α were observed in BALF in the exposed males. The histopathological changes in the lung evaluated according to a developed classification system (based on severity of inflammation, range 0–4, with 4 indicating the most severe changes) showed average histopathological score of 1.33 for animals exposed to nanoparticles and microparticles at the lower dose, 1.72 after exposure to nanoparticles at the higher dose, and 2.83 for animals exposed to microparticles at the higher dose. In summary, it was shown that nanosized and microsized MoS2 can trigger dose‐dependent inflammatory reactions in the lungs of rats after multiple intratracheal instillation irrespective of the animal sex. Some evidence indicates a higher lung pro‐inflammatory potential of the microform. Molybdenum(IV) sulfide (MoS2) nanoparticles and microparticles administered intratracheally to rats (1.5 or 5 mg/kg bw), every 14 days for 90 days, induced no overt signs of systemic chronic toxicity. An increase in MIP‐2 and a decrease in TNF‐α were observed in BALF in the exposed males. Based on histopathological examination, nanosized and microsized MoS2 can trigger dose‐dependent inflammatory reactions in the lungs of rats after multiple intratracheal instillations, with a slightly higher lung pro‐inflammatory potential of the microform. [ABSTRACT FROM AUTHOR]

New materials require the use of advanced technology in manufacturing parts of complex shape. One of the modern nonconventional technology of manufacturing difficult to cut materials is the wire electrical discharge machining (WEDM). The article presents the results of theoretical and experimental research in the influence of the WEDM conditions and parameters on the shape deviation during a rough cut. A numerical model of the dielectric flow in the gap (ANSYS) was developed. The influence of the dielectric velocity field in the gap on the debris evacuation and stability of WEDM process was discussed. Furthermore, response surface methodology (RSM) was used to build empirical models for influence of the wire speed Vd, wire tension force Fn, the volume flow rate of the dielectric Qv on the flatness deviation after the WEDM. [ABSTRACT FROM AUTHOR]

The vulnerability of the nervous system to toxic insult is particularly high during foetal life and early childhood. Exposures during this period, via maternal blood and/or milk, may result in neurobehavioural disorders, some of which may not become apparent before in adulthood. Methylmercury (MeHg) and polychlorinated biphenyls (PCB) are persistent environmental pollutants and may be present in some food products. Both are neurotoxic. It is suspected that MeHg and PCBs may act synergistically in inducing neurotoxic effects. Some data suggest that catecholaminergic systems, especially the dopaminergic one, are particularly vulnerable to the harmful action of MeHg and PCBs. This study aimed to assess the influence of separate or combined perinatal exposure to MeHg and PCB 153 on brain catecholamine contents in maturity. The subjects were adult (90-94 days of age) rats, progeny of mothers exposed to methylmercury (MeHg, CH3HgCl) or 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153), or MeHg and PCB 153, from day 7 of gestation to day 21 post partum. MeHg was administered with drinking water at daily doses of 0.5 mg/kg b.w./day. PCB 153 was administered by gavage at daily doses of 5 mg/kg b.w./day. The concentrations of adrenaline (A), noradrenaline (NA), dopamine (DA) and 3,4-dihydroxyphenylacetic acid (DOPAC) were determined by HPLC in homogenates of the following brain regions: olfactory bulb, hippocampus, striatum, occipito-temporal cortex, diencephalon, mesencephalon and cerebellum. The results suggest some exposure-related alterations in amine contents and point to the significant role of gender in their development. In the female MeHg-exposed progeny, the content of NA, DA and DOPAC in the mesencephalon was significanrtly elevated (by 43.1, 68.9 and 65.1%, respectively) while in the male progeny no differences were noted in any region of the brain. On the other hand, in the progeny exposed to PCB 153, some differences, i.e. increased NA concentration in the olfactory bulb (by 59.9%) and hippocampus (by 124.5%) and increased DA (by 75.0%) in the striatum were found in males, whereas in females significant differences were not found. In the case of combined exposure, the data suggest some effects in the female progeny only: a decreased concentration of A in the hippocampus (by 40.9%) but increased in the stratum (by 53.1%) and an increased DA concentration in the mesencephalon (by 78.9%). Summing up, the results confirm that gender may be an important determinant of the rat's vulnerability to MeHg and PCB153. They provide no evidence, however, of a synergism in the action of these neurotoxicants when given perinatally on the brain catecholaminergic systems in adulthood. A rough analysis of the obtained data allows one to suspect an antagonistic rather than synergistic type of interaction. [ABSTRACT FROM AUTHOR]

The aim of our study was to explore the tissue distribution of 3,5-dimethylbenzene acid (3,5-DMBA) and its excretion with urine of rats and to evaluate toxicokinetics of mesitylene in blood of rats after single and repeated inhalation exposure to mesitylene vapours. Experiments were performed on male outbred IMP:WIST rats. The animals were exposed to mesitylene vapours at the target concentration of 25, 100, and 250 ppm in dynamic inhalation chambers for 6 h at single exposure and for 4 weeks (6 h/day for 5day/week) at repeated exposure. The study revealed in rats, after inhalation exposure to mesitylene, exposure-dependent increases in 3,5-DMBA tissue concentration and urinary excretion as well as enhanced mesitylene concentration in tissues and blood. After termination of exposure, mesitylene was rapidly eliminated from blood of rats. Mesitylene retention reduced in rat lungs after repeated exposure, as compared to a single exposure, was most likely the reason for its lower concentration in lungs and blood. Compared with single exposure, 3,5-DMBA concentration increased in rat lungs after repeated inhalation exposure to mesitylene at 100 and 250 ppm, and in the liver at 250 ppm, which may be associated with the induction of mesitylene-metabolizing enzymes. Mesitylene metabolism in the lungs of the rats after repeated exposure to its low concentrations probably had a significant impact on the increased urinary excretion of 3,5-DMBA. [ABSTRACT FROM AUTHOR]

The objective of our study was to estimate metabolites of pseudocumene in the lung, liver, kidney and urine of rats after single and repeated inhalation exposure. Male Wistar rats were exposed to pseudocumene vapors at nominal concentrations of 25, 100 or 250 ppm in the dynamic inhalation chambers for 6 h or 4 weeks (6h/day; 5 days/week). Following exposure, three metabolites were measured in biologic material after hydrolysis: 3,4-dimethylbenzoic acid (3,4-DMBA), 2,4-dimethylbenzoic acid (2,4-DMBA) and 2,5-dimethylbenzoic acid (2,5-DMBA). The metabolites were analyzed by gas chromatography with a flame ionization detector. The study showed no significant increase in concentrations of the analyzed DMBA metabolites in the liver and lungs of rats exposed to repeated inhalation exposures to pseudocumene as compared to a single exposure. It was found that metabolic transformation of pseudocumene, leading to the production of 3,4-DMBA in the rats kidneys, are more pronounced after repeated inhalation exposure. [ABSTRACT FROM AUTHOR]

Methylmercury (MeHg) and polychlorinated biphenyls (PCBs) are ubiquitous and persistent environmental pollutants and known neurotoxicants. It has been recognized that dietary exposure to neurotoxic substances during pregnancy and breast feeding may affect the development of the child's nervous system and result in various neurological and neurobehavioural alterations later in life. One of the suspected consequences of such exposure may be an increased propensity to psychostimulant abuse and psychostimulant addiction. Data from animal studies indicate that behavioural sensitivity to psychostimulants is a good predictor of the propensity to psychostimulant self-administration - an animal model of drug abuse in humans. The aim of this study was to find out whether and how perinatal exposure to MeHg and/or PCB153 determines behavioural sensitivity and sensitizability to the psychostimulant amphetamine (AMPH) in adulthood. The subjects were adult rats, Wistars, born to mothers exposed, via drinking water, to MeHg (CH3HgCl) at 0.5 mg/kg/day; or PCB153 (2,2',4,4',5,5'-hexachlorobiphenyl) at 5.0 mg/kg/day by gavage, or jointly MeHg (0.5 mg/kg/day, and PCB153 (5.0 mg/kg/day), from day 7 of pregnancy to day 21 post partum. The testing started at the age of 3 months. It consisted in measuring the behavioural response to a test dose of AMPH (0.5 mg/kg. i.p.) twice: 1) before a sensitization treatment in order to assess the rat's "normal" sensitivity to the psychostimulant, and 2) three weeks after the sensitizing treatment. The sensitization treatment consisted in a repeated (once a day for five consecutive days) administration of AMPH at 2.5 mg/kg. Results: 1) Before the sensitization treatment there were no differences between the exposed and the control rats in the response to the psychostimulant. 2) Three weeks after the sensitizing treatment the response to an AMPH challenge was increased in all rats. However, in males exposed perinatally to MeHg alone, this increase was significantly more pronounced than in males of the control group. A similar effect was not present in MeHg-exposed females as well as males or females exposed to PCB153 alone or in combination with MeHg. Perinatal exposure to MeHg may result in an increased susceptibility to psychostimulant sensitization in the male progeny. Co- exposure to PCB153 may compromise this effect of MeHg-exposure. [ABSTRACT FROM AUTHOR]

Electrical discharge machining (EDM) is a rapidly evolving method in modern industry that manufactures highly complex components. The physical properties of a tool electrode material are significant factors in determining the effectiveness of the process, as well as the characteristics of the machined surfaces. The current trend of implementing graphite tool electrodes in manufacturing processes is observed. Innovative material engineering solutions enable graphite production with miniaturized grain size. However, the correlation between the graphite electrode grain size and the mechanism of the process removal in the EDM is a challenge for its widespread implementation in the industry. This research introduces a new method to evaluate the impact of the graphite electrode grain size and machining parameters on the material removal effectiveness, relative tool wear rate, and surface roughness ( Ra ) of Hastelloy C-22 following EDM with negative polarity. The study utilized new graphite materials with a grain size of 1 µm (POCO AF-5) and 10 µm (POCO EDM-180). An assessment of the impact of the EDM process parameters on the technological parameters and the development of the surface roughness was carried out. Electrical discharge machining with fine-grained graphite electrodes increases process efficiency and reduces tool wear. Graphite grains detached from the tool electrode affect the stability of electrical discharges and the efficiency of the process. Based on the experimental results, mathematical models were developed, enabling the prediction of machining effects to advance state-of-the-art manufacturing processes. The obtained mathematical models can be implemented in modern industrial EDM machines as guidelines for selecting adequate machining parameters depending on the desired process efficiency, tool wear rate, and surface roughness for advanced materials.

Additive manufacturing has garnered significant interest in various industries due to its flexibility and capability to produce parts with complex shapes. However, issues related to surface quality, such as roughness and microstructural defects, necessitate the use of post-processing techniques to achieve the desired properties. Ti6Al4V alloy, produced additively, was finished using low-energy discharges, and the new surface integrity properties resulting from the induced heat energy were investigated. To further understand the influence of discharge energy on the formation of the new layer, roughness parameters and power spectral density were used to characterize the surface topography. SEM and EDS analyses were performed to examine the morphology and microstructural defects such as microcracks. The results indicate that the heat energy induced by the discharge improved the properties of the surface. SEM analysis revealed that the new layer was characterized by a reduction in defects such as unmelted particles, the balling effect, and microcracks. At the lowest investigated discharge energy of E = 0.21 mJ, surface roughness, Sa , was reduced by about 69%, which is equal to about 2 μm, accompanied by a significant decrease in microcracks. EDS analysis indicated that the diffusion of copper and zinc from the electrode to the top surface was related to the discharge energy. Furthermore, prediction models of the influence of wire electrical discharge polishing parameters, including discharge energy, wire speed, and time interval, on the surface roughness and material removal rate ( MRR ) were developed using the response surface methodology.

The Selective laser melting (SLM) technology of recent years allows for building complex-shaped parts with difficult-to-cut materials such as Ti6Al4V alloy. Nevertheless, the surface integrity after SLM is characterized by surface roughness and defects in the microstructure. The use of additional finishing technology, such as machining, laser polishing, or mechanical polishing, is used to achieve desired surface properties. In this study, improving SLM Ti6Al4V alloy surface integrity using wire electrical discharge machining (WEDM) is proposed. The influence of finishing WEDM cuts and the discharge energy on the surface roughness parameters Sa, Svk, Spk, and Sk and the composition of the recast layer were investigated. The proposed finishing technology allows for significant improvement of the surface roughness by up to 88% (from Sa = 6.74 µm to Sa = 0.8 µm). Furthermore, the SEM analyses of surface morphology indicate improving surface integrity properties by removing the balling effect, unmelted particles, and the presence of microcracks. EDS analysis of the recast layer indicated a significant influence of discharge energy and the polarization of the electrode on its composition and thickness. Depending on the used discharge energy and the number of finishing cuts, changes in the composition of the material in the range of 2 to 10 µm were observed.

Finishing operations are one of the most challenging tasks during a manufacturing process, and are responsible for achieving dimensional accuracy of the manufactured parts and the desired surface topography properties. One of the most advanced finishing technologies is grinding. However, typical grinding processes have limitations in the acquired surface topography properties, especially in finishing difficult to cut materials such as Inconel 625. To overcome this limitation, a new type of grinding wheel is proposed. The tool is made up of grains of different sizes, which results in less damage to the work surface and an enhancement in the manufacturing process. In this article, the results of an experimental study of the surface grinding process of Inconel 625 with single-granular and multi-granular wheels are presented. The influence of various input parameters on the roughness parameter (Sa) and surface topography was investigated. Statistical models of the grinding process were developed based on our research. Studies showed that with an increase in the cutting speed, the surface roughness values of the machined samples decreased (Sa = 0.9 μm for a Vc of 33 m/s for a multigranular wheel). Observation of the grinding process showed an unfavorable effect of a low grinding wheel speed on the machined surface. For both conventional and multigranular wheels, the highest value for the Sa parameter was obtained for Vc = 13 m/s. Regarding the surface topography, the observed surfaces did not show defects over large areas in the cases of both wheels. However, a smaller portion of single traces of active abrasive grains was observed in the case of the multi-granular wheel, indicating that this tool performs better finishing operations.

The industrial application of electrical discharge machining (EDM) for manufacturing injection molding, in many cases, requires forming depth cavities with high length-to-width ratios, which is quite challenging. During slot EDM with thin-walled electrodes, short-circuits and arcing discharges occur, as a result of low efficiency in removing debris and bubble gas from the gap. Furthermore, unstable discharges can cause increases in tool wear and shape deviation of the machined parts. In order to characterize the influence of the type of electrode material and EDM parameters on the deep slot machining of high-thermal-conductivity tool steel (HTCS), experimental studies were conducted. An analytical and experimental investigation is carried out on the influence of EDM parameters on discharge current and pulse-on-time on the tool wear (TW), surface roughness (Ra), slot width (S)-dimension of the cavity, and material removal rate (MRR). The analyses of the EDS spectrum of the electrode indicate the occurrence of the additional carbon layer on the electrode. Carbon deposition on the anode surface can provide an additional thermal barrier that reduces electrode wear in the case of the copper electrode but for graphite electrodes, uneven deposition of carbon on the electrode leads to unstable discharges and leads to increase tool wear. The response surface methodology (RSM) was used to build empirical models of the influence of the discharge current I and pulse-on-time t on on Ra, S, TW, and MRR. Analysis of variance (ANOVA) was used to establish the statistical significance parameters. The calculated contribution indicated that the discharge current had the most influence (over 70%) on the Ra, S, TW, and MRR, followed by the discharge time. Multicriteria optimization with Derringer's function was then used to minimize the surface roughness, slot width, and TW, while maximizing MRR. A validation test confirms that the maximal error between the predicted and obtained values did not exceed 7%.

Objectives: 1-Methylnaphthalene (1-MN) is composed of 2 benzene rings and belongs to polycyclic aromatic hydrocarbons. The metabolism of 1-MN in laboratory animals and bacteria leads to the formation of 1-naphthoic acid (1-NA)., Material and Methods: In this study the distribution of 1-NA in lung, liver, spleen, kidney and urinary excretion of 1-NA in rats after single and repeated inhalation exposure to 1-MN vapors were investigated. The activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and cytochrome were measured of the rats. Genotoxic effects were evaluated with the in vitro micronucleus test on V79 hamster fibroblasts., Results: The concentrations of 1-NA in the tissues of rats after single and repeated exposure to 1-MN were dependent on the exposure dose. High levels of 1-NA were found in kidneys of animals after the single and repeated exposure to 1-MN. With an increase of 1-MN dose, an increase in the activity of cytochrome P450 (CYP1A1 and CYP1A2) was observed in the liver of rats. Compared to control animals, significantly higher ALT activity was noted in serum of rats exposed to 1-MN. The micronuclei frequency in V79 cells exposed to 1-MN (in the range of analyzable concentrations; i.e., 5-25 μg/ml) did not differ significantly from the vehicle control, whereas urine extracts from rats exposed to 1-MN induced a significant increase in the frequency of micronuclei compared to urine extracts from the group of control animals., Conclusions: Metabolism of 1-MN in rats after the inhalation exposure leading to 1-NA was mainly observed during the first day after the end of exposure. It is likely that 1-MN metabolites present in rat urine can induce the increased micronuclei frequency as was shown in V79 cells. Int J Occup Med Environ Health. 2022;35(6):731-46., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

Precise machining of micro parts from difficult-to-cut materials requires using advanced technology such as wire electrical discharge machining (WEDM). In order to enhance the productivity of micro WEDM, the key role is understanding the influence of process parameters on the surface topography and the material's removal rate ( MRR ). Furthermore, effective models which allow us to predict the influence of the parameters of micro-WEDM on the qualitative effects of the process are required. This paper influences the discharge energy, time interval, and wire speed on the surface topography's properties, namely Sa , Sk , Spk , Svk , and MRR , after micro-WEDM of Inconel 718 were described. Developed RSM and ANN model of the micro-WEDM process, showing that the discharge energy had the main influence (over 70%) on the surface topography's parameters. However, for MRR , the time interval was also significant. Furthermore, a reduction in wire speed can lead to a decrease in the cost process and have a positive influence on the environment and sustainability of the process. Evaluation of developed prediction models of micro-WEDM of Inconel 718 indicates that ANN had a lower value for the relative error compared with the RSM models and did not exceed 4%.

Modern industry is focused on looking for new and effective technologies to manufacture complex shapes from alloys based on nickel and chromium. One of the materials widely used in the chemical and aerospace industry is Hastelloy C-22. This material is difficult to machine by conventional methods, and in many cases, unconventional methods are used to manufacture it, such as electrical discharge machining (EDM). In the EDM process, the material is removed by electrical discharges between a workpiece and a tool electrode. The physical and mechanical properties of the tool electrodes have a direct impact on the process efficiency, machining accuracy, and surface roughness. Currently, there has been a significant increase in the use of graphite as a material for tool electrodes due to the low purchase cost of the raw material, good machinability, and high sublimation temperature. In this work, an experimental investigation of the influence of the grain size of the graphite tool electrode on material removal rate (MRR), tool wear rate (TWR), and surface roughness ( Ra ) of Hastelloy C-22 was carried out. Two POCO graphite tool electrodes with a grain size of 1 µm (AF-5) and 10 µm (S-180) were used. Based on the experimental studies, empirical models describing the influence of machining parameters on technological indicators and the condition of the surface texture were determined. The research indicates that graphite with a larger grain provides higher process efficiency with high relative wear of the tool electrode. The lowest surface roughness was obtained for graphite with a smaller grain size (AF-5). The analysis of the machining parameters proves that the discharge current and pulse duration are the main factors determining the MRR and Ra values for both AF-5 and S-180 graphite. The time interval is the dominant parameter with regard to the relative wear of the graphite electrode.

Background: The article presents a review of the literature on the chemical composition of smoke generated from a standard cigarette and the aerosol generated after heating tobacco and chemical compounds formed in the aerosol of electronic cigarettes., Methods: The literature review was carried out on the PubMed online bibliographic database, Google search engine, Google Scholar based on science articles published in recent 20 years., Results: The bibliographic analysis shows that: replacing smoking in the traditional way by heating tobacco modifies significantly the content of chemical substances found in aerosol, the substances found in aerosols generated by e-cigarettes have proven toxic effects, e.g. pro-inflammatory effect on lung epithelial cells (e.g. crotonaldehyde) or a mutagenic effect (e.g. NNK), using e-cigarette aerosol does not rule out a health risk for people, which is not fully recognized at present., Conclusions: Replacing smoking in the traditional way by heating tobacco modifies significantly the content of chemical substances found in aerosol. Using e-cigarette aerosol does not rule out a health risk for people, because the substances found in aerosols generated by e-cigarettes have proven toxic effects.

Purpose: Nail technicians (NTs) are exposed to a low-level mixture of volatile organic solvents (VOCs), yet the health hazards related to such exposure are unknown. This study thus aimed to compare the blood plasma levels of selected biomarkers related to liver status and lipid profile among occupationally exposed NTs and unexposed controls. Associations between out-of-normal-range levels of such biomarkers and occupational exposure to VOCs mixture have also been investigated., Methods: The study enrolled 145 female NTs and 152 unexposed controls. Biochemical analyses were performed using spectrophotometric assays and obtained data were analyzed using general linear model and Poisson regression modelling adjusted to multiple confounders., Results: Compared to controls, NTs presented significantly increased plasma activities of ALT (2.04 ± 0.63 ln-U/l vs. 1.25 ± 0.71 ln-U/l; p < 0.0001) and AST (2.73 ± 0.25 ln-U/l vs. 2.08 ± 0.95 ln-U/l; p < 0.0001), and significantly increased plasma levels of TG (4.38 ± 0.53 ln-mg/dl vs. 4.21 ± 0.42 ln-mg/dl; p < 0.05) and TC/HDL ratio (1.18 ± 0.36 vs. 1.02 ± 0.27; p < 0.0005). Plasma levels of HDL were significantly lower among NTs (4.02 ± 0.29 ln-mg/dl vs. 4.21 ± 0.26 ln-mg/dl; p < 0.0001). Moreover, NTs were found to present significantly increased risk of occurrence of clinically relevant plasma HDL levels below 3.91 ln-mg/dl (i.e., 50 mg/dl; RR = 1.58, 95% CI 1.07-2.32, p < 0.05), as well as increased risk of clinically relevant TC/HDL ratio above the normal range limit of 3.5 (RR = 1.68, 95% CI 1.19-2.35, p < 0.005), as compared to unexposed controls., Conclusion: Nail technicians are subject to adverse changes in selected plasma biomarkers related to liver functions, some of which may be of clinical relevance.

Objectives: This paper reports on the trend of the stressogenic stimulus caused by a repeated exposure to 1-methylnaphthalene (1-MN) vapors at the nominal concentrations of 0 mg/m 3 (the control restrainer), 50 mg/m 3 or 200 mg/m 3 in the nose-only inhalation system, by analyzing the serum corticosterone (CORT) levels in rats., Material and Methods: Three groups of rats were exposed in restrainers to 1-MN vapors at the nominal concentrations of 0 mg/m 3 , 50 mg/m 3 or 200 mg/m 3 for 5 days. One control group of animals spent all the time during the experiment in an individually ventilated plastic cage. The serum CORT concentrations were determined in all 4 groups of the rats. The blood samples drawn from the tail vein were collected every day after termination of the 6-h exposure. On the fifth day, blood samples were collected 15 min, 30 min, 45 min, 1 h, and 3 h after termination of the 6-h exposure., Results: On the fifth day of the study, no statistically significant changes in body weights between all groups of animals were found. After 5 days of the observation, increased food intake in the control groups was noted. Significantly higher CORT concentrations in the rats exposed to 1-MN at 200 mg/m 3 and in the animals from the control restrainer were found, comparing to the animals exposed to 1-MN at 50 mg/m 3 and the animals from the control cage., Conclusions: The application of 6-h restraining induced high concentrations of the stress hormone, CORT, in the blood of rats. The short-term exposure of rats to 1-MN non-linearly reduced the restraint stress measured with CORT concentration. Int J Occup Med Environ Health. 2020;33(5):691-9., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

Electrical discharge machining (EDM) is an advanced technology used to manufacture difficult-to-cut conductive materials. However, the surface layer properties after EDM require additional finishing operations in many cases. Therefore, new methods implemented in EDM are being developed to improve surface characteristics and the material removal rate. This paper presents new research about improving the surface integrity of 55NiCrMoV7 tool steel by using reduced graphene oxide (RGO) flakes in the dielectric. The main goal of the research was to investigate the influence of RGO flakes in the dielectric on electrical discharge propagation and heat dissipation in the gap. The investigation of the influence of discharge current I and pulse time t on during EDM with RGO flakes in the dielectric was carried out using response surface methodology. Furthermore, the surface texture properties and metallographic structure after EDM with RGO in the dielectric and conventional EDM were investigated and described. The obtained results indicate that using RGO flakes in the dielectric leads to a decreased surface roughness and recast layer thickness with an increased material removal rate (MRR). The presence of RGO flakes in the dielectric reduced the breakdown voltage and allowed several discharges to occur during one pulse. The dispersion of the discharge caused a decrease in the energy delivered to the workpiece. In terms of the finishing EDM parameters, there was a 460% reduction in roughness Ra with a uniform distribution of the recast layer on the surface, and a slight increase in MRR (12%) was obtained.

Electrical discharge machining (EDM) is a nonconventional technology that is frequently used in manufacturing for difficult-to-cut conductive materials. Drawbacks to using EDM include the resulting surface roughness and integrity. One of the recent innovations for improving surface integrity with EDM is the use of a powder mixed dielectric. The aim of this study is to analyze the influence of having reduced graphene oxide (RGO) in the dielectric on the ionization of the plasma channel and the dispersion of electrical discharges. The main goal is to improve the surface integrity of the tool steel 55NiCrMoV7 during finishing machining. To achieve this goal, an experimental investigation was carried out to establish the smallest possible values of discharge current and pulse time at which it is possible to initiate an electric discharge, which causes material removal. Next, the effect of the direction of the electric discharges (electrode polarity) and the concentration (percentage) of RGO in the dielectric on surface integrity was investigated. The results of this experiment indicate that during EDM with RGO, the discharges are dispersed on the RGO flakes. This leads to a multiplication of the discharges during a single pulse, and this strongly affects the surface integrity. The obtained results indicate that it is possible to reduce surface roughness and thickness of the recast layer by approximately 2.5 times compared with conventional EDM.

Electrical discharge machining (EDM) is a modern technology that is widely used in the production of difficult to cut conductive materials. The basic problem of EDM is the stochastic nature of electrical discharges. The optimal selection of machining parameters to achieve micron surface roughness and the recast layer with the maximal possible value of the material removal rate (MRR) is quite challenging. In this paper, we performed an analytical and experimental investigation of the influence of the EDM parameters: Surface integrity and MRR. Response surface methodology (RSM) was used to build empirical models on the influence of the discharge current I, pulse time t on, and the time interval t off , on the surface roughness ( Sa ), the thickness of the white layer (WL), and the MRR, during the machining of tool steel 55NiCrMoV7. The surface and subsurface integrity were evaluated using an optical microscope and a scanning profilometer. Analysis of variance (ANOVA) was used to establish the statistical significance parameters. The calculated contribution indicated that the discharge current had the most influence (over the 50%) on the Sa, WL, and MRR, followed by the discharge time. The multi-response optimization was carried out using the desirability function for the three cases of EDM: Finishing, semi-finishing, and roughing. The confirmation test showed that maximal errors between the predicted and the obtained values did not exceed 6%.

Objectives: 1-Methylnaphthalene (1-MN) is a constituent of polycyclic aromatic hydrocarbons, the chemicals that have become ubiquitous in the environment as result of natural and industrial process. This paper reports a study on the distribution and excretion of 1-MN in rats after single and repeated inhalation exposure to 1-MN vapor., Material and Methods: Male Wistar rats were exposed to 1-MN vapor at nominal concentrations of 50 mg/m3 or 200 mg/m3 in the dynamic inhalation chambers (TSE Systems Head Nose Only Exposure) for 6 h (single exposure) or 5 days (6 h/day, repeated exposure). Blood, urine and tissue samples were collected during and after the exposure. Blood, urine and tissue concentrations of 1-MN were estimated by gas chromatography using the headspace technique., Results: The elimination of 1-MN from blood followed an open 2-compartment model. The concentration in rat tissues was dependent on the magnitude and time of exposure. After repeated exposure, the concentration 1-MN in tissue decreased in comparison to single exposure. The elimination of 1-MN with urine after single and repeated exposure to 1-MN occurred mainly in the samples collected during the first day of collection., Conclusions: 1-Methylnaphthalene was rapidly eliminated from the blood and tissues of animals exposed by inhalation to 1-MN. In repeated exposure, there was probably a significant increase of 1-MN metabolism in rats exposed to low and high 1-MN doses. Under conditions of repeated 1-MN exposure, no significant systemic 1-MN accumulation could be observed. Int J Occup Med Environ Health 2018;31(6):763-770., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

Objectives: Welding processes that generate fumes containing toxic metals, such as hexavalent chromium (Cr(VI)), manganese, and nickel (Ni), have been implicated in lung injury, inflammation, and lung tumor promotion in animal models. Bronchiolar epithelium Clara cells/club cells, coordinate these inflammatory responses. Clara cells secretory protein (CC16) with ant-inflammatory role., Material and Methods: The pulmonary toxicity of welding dust (WD) was assessed for Wistar rats exposed to 60 mg/m 3 of respirable-size welding dust (mean diameter 1.17 μm for 1 and 2 weeks (6 h/day, 5 days/week)) or the aerosols of soluble form (SWD) in the nose-only exposure chambers. Additionally the effect of antiinflammatory betaine supplementation was assessed. Clara cells secretory protein, differential cell counts, total protein concentrations and cellular enzyme (lactate dehydrogenase - LDH) activities were determined in bronchoalveolar lavage fluid, and corticosterone and thiobarbituric acid reactive substances (TBARS) and prolactin concentrations were assessed in serum. Histopathology examination of lung, brain, liver, kidney, spleen was done. Additionally slices of brain and lung were exanimated in laser ablation inductively coupled plasma mass spectrometry., Results: Both WD and SWD exposure evoked large bronchiolar infiltration shoved in histopathology examination. In this study, TBARS inversely correlated with a significant decrease of CC16 concentration that occurred after instillation of both WD and SWD indicating decreased anti- inflammatory potential in the lung. In WD exposed rats prolactin correlated with nuclear factor-kappa B (NF-κB), LDH, TBARS and serum levels Cr, Ni and inversely with c-Jun. In SWD exposed rats prolactin correlated with CC16 indicated effect of prolactin on the population of epithelial cells., Conclusions: In the current study, deleterious effects of repeated inhalation stainless steel welding dust form on club (Clara) cell secretory protein (CC16) were demonstrated. Clara cells secretory protein relation with prolactin in exposed rats to welding dust were shown and explored whether the NF-κB and c-Jun/activator protein 1 related pathway was involved. Int J Occup Med Environ Health 2018;31(5):613-632., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

Objectives: The study has aimed at investigating the subjective assessment of an individual's health status and comparing the prevalence of selected work-related symptoms among nail technicians occupationally exposed to volatile organic compounds (VOCs) to the one among control subjects. Associations between occupational exposure to VOCs and the incidence of adverse health effects were also analyzed., Material and Methods: The study involved 145 female nail technicians and 152 control subjects. Data on the prevalence of adverse health effects was collected using the researcher- made questionnaire and then analyzed by means of survival analysis methods., Results: Only 22% of nail technicians as compared to 45% of control subjects described their current health status as "excellent" or "very good" (odds ratio (OR) = 0.4, 95% confidence interval (CI): 0.2-0.6, p < 0.00005). In general, 61% of nail technicians confirmed to have experienced any out of all symptoms considered in the study since the commencement of the job, which was significantly higher as compared to 17% of control subjects (adjusted OR = 2.8, 95% CI: 2.1-3.7, p < 0.0001). Estimated median length of the employment period free of investigated symptoms was significantly shorter among nail technicians as compared to controls (12 years vs. 33 years, p < 0.0001), consistent with almost 4-times increased hazard of the occurrence of such symptoms among the technicians (hazard ratio (HR) = 3.9, 95% CI: 2.7-5.7, p < 0.0001). Cox proportional hazard regression modeling revealed almost 5-times increased hazard of the occurrence of any symptoms among nail technicians exposed to higher levels of the mixture of VOCs as compared to those exposed to lower levels (HR = 4.9, 95% CI: 1-24.1, p = 0.05)., Conclusions: All outcomes combined together indicate that nail technicians are subject to faster health deterioration, which may be assumed to be caused by occupational exposure to low levels of VOCs. Int J Occup Med Environ Health 2017;30(3):469-483., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

Background: In this study we tested whether the seasonal variations in levels of selected biomarkers of oxidative stress in female nail technicians occupationally exposed to low levels of volatile organic compounds (VOCs) differ significantly from those observed among healthy unexposed controls. Airborne levels of selected VOCs in nail salons were also analyzed and tested for associations with seasonal variations of the levels of biomarkers among nail technicians., Methods: The study enrolled 145 female nail technicians and 145 healthy unexposed female controls. The airborne VOCs and levels of biomarkers were assessed by GC-MS chromatography and absorption/fluorescence spectrophotometry, respectively., Results: Plasma levels of thiobarbituric acid reactive species, ceruloplasmin, the activity of glutathione peroxidase (GPx1) and the SOD1/GPx1 activity ratio presented significant differences between the so-called "hot" and "cold" seasons in the case of nail technicians as well as in unexposed controls (p < <0.0001 for all four biomarkers). The pattern of these variations among nail technicians was found to be significantly different compared to that of the control subjects (p < <0.0001). Although such differences might intuitively be attributed to occupational exposure of nail technicians to VOCs, which was found to be higher during the "cold" season compared to the "hot" one, our study provided only limited evidence in favor of the hypothesis, that the different pattern of seasonal variations of biomarkers among nail technicians might have resulted from seasonal fluctuations in their occupational exposure to VOCs., Conclusion: Further investigation is thus needed in order to elucidate the effect of low-level occupational exposure to VOCs on seasonal variations of biomarkers of oxidative stress.

Objectives: The aim of the study has been to explore hemimellitene distribution in blood, liver, lung and kidney as well as toxicokinetics of its elimination from blood of rats after single and repeated inhalation exposure to this compound. Tissue distribution and excretion with urine of 2-dimethylbenzoic acids (2,3-DMBA and 2,6-DMBA) were also evaluated., Material and Methods: Male outbred IMP:WIST rats were used in the experiment. The animals were exposed to hemimellitene vapors at the nominal concentration of 25 ppm, 100 ppm, and 250 ppm in the dynamic inhalation chambers for 6 h for single exposure purpose and for 4 weeks (6 h/day for 5 day/week) for repeated exposure purposes., Results: Significantly lower concentrations of hemimellitene were detected in the blood and tissues of animals after repeated inhalation exposure of animals to hemimellitene vapors, which points to reduced retention of the chemical in the lungs of the experimental rats. The trend of hemimellitene elimination from the blood depended solely on exposure intensity, irrespective of exposure time, both after single and repeated exposure. As regards the 2 determined hemimellitene metabolites, the major trend of the metabolic transformation involved formation of 2,3-DMBA., Conclusions: The significantly higher urinary 2,3-DMBA concentration after repeated exposure shows that hemimellitene induces enzymatic processes in the rat., (This work is available in Open Access model and licensed under a CC BY-NC 3.0 PL license.)

Objectives: Diisocyanates (DIC) are highly reactive, low-molecular-weight chemicals which are the leading cause of occupational asthma (OA). The aim of the study was to analyze certain aspects of the pathogenesis of allergic inflammation in the airways induced by toluene diisocyanate (TDI) in an experimental model in mice., Materials and Methods: The experiment was carried out on 50 female BALB/cJ/Han/IMP mice, which were exposed by inhalation (intranasal and in the inhalation chamber) to toluene diisocyanate (2,4-TDI). After the experiment, the bronchoalveolar lavage fluid (BALF) was collected from the animals, and the composition of the induced inflammatory cells, and the concentrations of certain cytokines (IL-4, IL-5, TNF-α) were evaluated., Results: The total number of cells in BALF of the examined group of mice was significantly higher compared to the control mice. There was also a significant increase in neutrophils and eosinophils in the study group compared to the controls. The number of lymphocytes and macrophages did not differ significantly between the two groups. A statistically significant increase in the level of TNF-α was shown to occur in the group exposed to toluene diisocyanate in comparison to the control group. The concentration of IL-4 increased in the study group, compared to the control one, but the differences did not reach the level of significance, p > 0.05. Such difference was not observed for IL-5., Conclusions: We developed a murine model of TDI-induced asthma which caused the influx of inflammatory cells like eosinophils and neutrophils in the bronchoalveolar lavage fluid (BALF) in the TDI-treated mice. The increase of the concentration of some proinflammatory cytokines (TNF-α, IL-4) in BALF from the exposed mice was also observed.

Objectives: The solvent, dimethylene glycol monobutyl ether (DGBE), is a component of latex paints, inks; it is used as a degreasing agent, industrial detergent. The aim of the study was evaluating the effects of DGBE administered by gavage on the estrous cycle and given with drinking water on fertility in rats and early development of their progeny., Materials and Methods: Female rats were exposed to DGBE by gavage during 8 weeks at 250, 500 or 1000 mg/kg/day. Vaginal smears were collected during the exposure and 4 weeks after its cessation. Fertility studies were performed in male and female animals exposed to in drinking water. Males were exposed for 10 weeks and then mated with females exposed before mating, during pregnancy and lactation. Young animals were observed during 3 weeks after birth., Results: DGBE does not cause disturbances of the menstrual cycle in females. Parameters used to assess the general toxicity indicate that males receiving DGBE in drinking water are more sensitive to this compound than females: significantly greater, dose-dependent relative spleen weight, significant decrease in hematological parameters from 8% to 15% depending on the dose, were observed. Clinical chemistry parameters (HDL-cholesterol, BUN) and some markers of oxidative stress differ between the exposed groups and the control one, but without adverse health effect. The microscopic examination of internal organs did not reveal morphological changes in male and female rats., Conclusion: The results of our study on the impact of exposure to DGBE on fertility in rats indicate that the substance administered for 9-10 weeks to females and males at a limit dose of 1000 mg/kg did not impair fertility or viability of their offspring during the first three weeks of life.