Hearing impairment among workers occupationally exposed to excessive levels of noise

Pure tone audiometry screening and ear examinations were conducted among 138 males working as machine and equipment operators occupationally exposed to intermittent noise of 85 to 105 dBA. Hearing loss up to 30 dB (preserved socially adequate hearing) was found in 25 workers. The hearing impairment was confirmed by distortion products of otoacoustic emissions measurements. A sharp increase in the frequency of cases can be found among the workers with service length over 10 years. While the frequency of the cases among workers with service length below 10 years is 5.45%, it is 26.5% among the subjects with service length over 10 years, with a gradual increase as a result of the increase in exposure duration. A positive correlation (p < 0.05) was found between the frequency of hearing impairment among the workers and the years of exposure to excessive noise levels. Some measures for preventing occupational noise-induced hearing loss were suggested.     

Effect of antioxidants in women with increased risk of preeclampsia. The role of oxidative stress in preeclampsia

New frontiers have been opened lately in the understanding of the patho-phisiology of preeclampsia thus giving new directions in the process of therapy of this condition. Oxidative stress is a condition characterized by peroxidants predominating over antioxidants. Numerous intensive studies are carried out to reveal the role of oxidative stress in the pathogenesis of preeclampsia.     

Effect of Exchangeable Ions in Natural and Modified Zeolites on Ag Content,Ag Nanoparticle Formation and Their Antibacterial Activity

To broaden the application of silver nanoparticles (AgNPs), which are well-known antibacterial agents, they are supported on different substrates to prevent aggregation, increase their surface area and antibacterial efficiency, and to be separated from the system more effectively at the end of treatment. To produce nanocomposites that consist of silver nanoparticles on natural and modified zeolites, silver ions (Ag⁺) were loaded onto zeolite (natural, Na-modified, H-modified) and then thermally reduced to AgNPs. The effect of the exchangeable cations in zeolite on Ag⁺ uptake, AgNPs formation, size and morphology was investigated by the TEM, SEM, EDX, XPS, UV-vis, XRD and BET methods. The silver amount in the nanocomposites decreased in the following order Na-modified zeolite > natural zeolite > H-modified zeolite. Microscopic techniques showed formation of AgNPs of 1–14 nm on natural and Na-modified zeolite, while the diameter of metal particles on H-modified zeolite was 12–42 nm. Diffuse reflectance UV-vis and XPS methods revealed the presence of both silver ions and AgNPs in the materials indicating that partial reduction of Ag⁺ ions took place upon heating at 400 °C in air. Additionally, antibacterial properties of the nanocomposites were tested against Escherichia coli, and it was found that Ag–containing composites originating from the Na-modified zeolite demonstrated the highest activity.     

Green Synthesis of Stable Spherical Monodisperse Silver Nanoparticles Using a Cell-Free Extract of Trichoderma reesei

In the current study, a green method for the preparation of silver nanoparticles (AgNPs) is presented as an alternative to conventional chemical and physical approaches. A biomass of Trichoderma reesei (T. reesei) fungus was used as a green and renewable source of reductase enzymes and metabolites, which are capable of transforming Ag⁺ ions into AgNPs with a small size (mainly 2–6 nm) and narrow size distribution (2–25 nm). Moreover, extracellular biosynthesis was carried out with a cell-free water extract (CFE) of T. reesei, which allows for facile monitoring of the bioreduction process using UV–Vis spectroscopy and investigation of the effect of experimental conditions on the transformation of Ag⁺ ions into AgNPs, as well as the simple isolation of as-prepared AgNPs for the study of their size, morphology and antibacterial properties. In continuation to our previous results about the influence of media on T. reesei cultivation, the amount of biomass used for CFE preparation and the concentration of Ag⁺ ion solution, herein, we present the impact of temperature (4, 20, 30 and 40 °C), agitation and time duration on the biosynthesis of AgNPs and their properties. A high stability of AgNPs in aqueous colloids was observed and attributed to the capping effect of the biomolecules as shown by the zeta potential (−49.0/−51.4 mV) and confirmed by the hydrodynamic size of 190.8/116.8 nm of AgNPs.     

Serum neopterin in workers exposed to inorganic dust containing free crystalline silicon dioxide

The study was conducted among 92 male workers, divided into two groups depending on workplace and level of inorganic dust containing free crystalline SiO₂ in the work environment, and 43 healthy workers without exposure to dust aerosols. The measured inhalable and respirable dust concentrations, as well as the concentration of free crystalline silica (FCS) in the respirable fraction were different for the two groups, but the percentage of free crystalline silica in the respirable fraction was almost identical. Significantly higher neopterin levels were found in workers exposed to dust, compared to the control group: 12.72 nmol/L and 6.32 nmol/L respectively (p<0.05). No significant difference was found between serum neopterin levels in both groups of the exposed workers. Among the groups with different length of service, a statistically higher neopterin level was evident only in the workers with length of service less than 10 years (p<0.05). The correlation analysis did not find a significant dependence of neopterin levels on the age of the studied workers or on the duration of smoking in packet years. The difference between neopterin levels in smokers and non-smokers was nonsignificant. The results obtained show that increased neopterin levels in the exposed workers are not influenced by individual features, duration and level of exposure to inorganic dust, but mostly by the presence of FCS in the respirable fraction.     

Plasmapheresis in clinical practice

The authors presented their experience of the use of intermittent plasmapheresis in 220 children with bacterial-inflammatory and immune-mediated diseases characterized by extreme severity and refractoriness to common therapeutic methods. Its use against a background of adequate etiological and pathogenetic therapy was shown to improve therapeutic results. In virus hepatitis with liver insufficiency, bullous erythema and hemorrhagic vasculitis plasmapheresis can be used as an independent method. Differentiated programs of the use of plasmapheresis were proposed, its safety was shown.     

Monitoring of acid-base status of workers at a methyl methacrylate and polymethyl methacrylate production plant in Bulgaria

This study was carried out on 104 workers at three work operations and a control (nonproduction) area, within a methyl methacrylate (MMA)/polymethyl methacrylate (PMMA) production facility in Bulgaria. Airborne monitoring was conducted over a 10-year period for MMA and the reactant chemicals methanol and acetone cyanhydrine at the MMA operation, and MMA was monitored at the PMMA operation. Acid-base status of the workers was evaluated using traditional criteria (pH, pCO(2), pO(2), and HCO(3) in plasma). Data from retrospective monitoring of air levels of the chemicals were compared with the acid-base status of workers at the plant. In some cases air concentrations exceeded the threshold limit value, with the highest percentage of overexposure occurring with airborne MMA in the PMMA production operation. Acid-base disruption indicated by reductions in plasma pH and HCO(3) was found for all groups except the control population. The highest percentage reduction was associated with PMMA production workers. Additionally, respiratory acidosis, indicated by increased pCO(2), was noted in the MMA production and maintenance groups, implying that the response to MMA exposure may involve both the metabolic and respiratory acidosis component. This study was unique in that the combined exposure to MMA and the precursor chemical (methanol) were shown to produce the same effects in workers. It is suggested that when combined exposure occurs, disruption of acid-base status may occur. Enforcement of PPM requirements for coveralls and gloves should prevent skin contamination. Additionally, improvement of equipment in MMA and PMMA production areas is recommended: (1) automation of some manual operations; (2) use of respiratory protection during equipment cleaning; and (3) installation of local ventilation when applicable.