ELASTOMERIC COMPOSITIONS WITH A HIGH CONTENT OF CHRYSOTILE ASBESTOS

The studies have shown the possibility of increasing the safety level of chrysotile asbestos (AX) in the technological process of its use in elastomeric compositions. This is achieved by dispersing ACh in a lactam-containing melt. As a result, dispersed ACh almost completely eliminates dusting, which is the main essence of increasing its safety level and allows solving the problem of its maximum content in elastomeric compositions, which in turn provides the necessary level of swelling of the elastomeric composition as a whole upon its contact with working fluids. drilling wells.

Nephrite of Bazhenovskoye Chrysotile–Asbestos Deposit, Middle Urals: Localization, Mineral Composition and Color

In the Bazhenovskoye chrysotile–asbestos deposit (Middle Urals), nephrite bodies of the serpentinite type were found on the contact of after gabbro rodingites and serpentinites. The color is uniform to non-uniform, green to light green, bluish green, greyish green, and whitish. Spots, streaks, lenticules of bright bluish-green or, on the contrary, light green color are sometimes noted. The nephrite is mostly comprised of tremolite. Chromite decreases the quality of the ornamental stone, but it is replaced by chrome grossular, which gives the nephrite a brighter bluish-green color locally. Crushed grains of chromite contain increased concentrations of Zn and Mn. The quality of the nephrite is decreased by serpentine and talc, as well as by fractures due to drilling and blasting works. The specific feature of the nephrite in the Bazhenovskoye deposit is the formation of nickeline, maucherite, and uvarovite. The green color is associated with Fe2+ ions. The nephrite of the Bazhenovskoye deposit meets the requirements for an ornamental stone. The origin of this nephrite includes a combination of metasomatic and metamorphic processes.

Scots Pine (Pinus sylvestrisL.) Undergrowth on the Dumps of the Chrysotile Asbestos Deposit

The studies were carried out on the dumps of overburden rocks and tailings of poor ores of the chrysotile asbestos deposit. According to the scheme of forest site zoning, the studying area belongs to the pre-forest steppe district of pine and birch forests of the Zabaikal’ye plain province of the West Siberian plain forest site area. The survey sites were laid out on the terraces of the dump along the running lines. Undergrowth was counted at each survey site. It was classified by viability, size (small, medium, large), and life form (tree, bush, scrub). The provision with undergrowth of the indicated type of disturbed soils was defined and recommendations for measures aimed at accelerating the process of reforestation were given. Undergrowth on the dumps is represented by Scots pine (Pinus sylvestris L.), silver birch (Betula pendula Roth.), aspen (Populus tremula L.), and goat willow (Salix caprea L.). Scots pine and silver birch are the dominant species in the undergrowth composition. Large share of Scots pine of scrub and bush form is the specific feature of the developing young growth. These specimens were found among small- and medium-sized undergrowth. It is the undergrowth of these heights that becomes an annual attrition without passing into the large-sized category. The latter is the main reason for faster conversion of the dumps into forest-covered area, for increasing the share of clay particles in the upper 50 cm thick dump layer, or for coating the dump surface by non-traditional fertilizers, in particular sewage sludge. It was noted that silvicultural trend in the dump reclamation on the chrysotile asbestos deposit is the most preferable. Scots pine should be preferred as the primary species for reclamation planning. For citation: Zaripov Yu.V., Zalesov S.V., Zalesova E.S., Popov A.S., Platonov E.P., Starodubtseva N.I. Scots Pine (Pinus sylvestris L.) Undergrowth on the Dumps of the Chrysotile Asbestos Deposit. Lesnoy Zhurnal [Russian Forestry Journal], 2021, no. 5, pp. 22–33. DOI: 10.37482/0536-1036-2021-5-22-33

Trends in Airborne Chrysotile Asbestos Fibre Concentrations in Asbestos Cement Manufacturing Factories in Zimbabwe from 1996 to 2016

Zimbabwe has two major factories that have been manufacturing chrysotile asbestos cement products since the 1940s. Exposure monitoring of airborne fibres has been ongoing since the early 1990s. This study examines trends in personal exposure chrysotile asbestos fibre concentrations for the period 1996–2016. Close to 3000 historical personal exposure measurements extracted from paper records in the two factories were analysed for trends in exposure. Exposure over time was characterised according to three time periods and calendar years. Mean personal exposure chrysotile asbestos fibre concentrations generally showed a downward trend over the years in both factories. Exposure data showed that over the observed period 57% and 50% of mean personal exposure chrysotile asbestos fibre concentrations in the Harare and Bulawayo factories, respectively, were above the OEL, with overexposure being exhibited before 2008. Overall, personal exposure asbestos fibre concentrations in the factories dropped from 0.15 f/mL in 1996 to 0.05–0.06 f/mL in 2016—a decrease of 60–67%. These results can be used in future epidemiological studies, and in predicting the occurrence of asbestos-related diseases in Zimbabwe.

POTENTIAL SOURCES OF AIR POLLUTION BY INDUSTRIAL FIBERS

Resume. Currently almost no attention is paid to the potential possibility of air pollution of premises for various purposes by industrial fibers (natural (asbestos) and man-made mineral fibers) in the Russian Federation while there is increasing use of materials containing such fibers in industrial and civil construction. Purpose. To conduct a survey of premises for various purposes to identify materials containing industrial fibers and assess the potential possibility of releasing fibers from them using research methods adopted in modern world practice. Materials and methods. A visual and instrumental survey of premises was carried out; 169 materials samples, 57 dust samples and 45 air samples were sampled and analyzed. Results. The numerical fiber concentrations in air samples did not exceed the standarts for working area air (0.2 f/ml for man-made mineral fibers (MMMF) and 0.01 f/ml for asbestos fibers), used in modern world practice. MMMF were detected in half of the dust samples, chrysotile asbestos fibers (CAF) were detected in 3 dust samples, MMMF together with CAF were detected in 9 dust samples. CAF were presented in 85 of 169 materials samples, MMVF were presented in 34 materials samples, organic fiber were presented in 18 materials samples, no fibers were presented in 32 materials samples. When using the algorithm for estimating the probability of fiber releasing, 43 materials containing CAF had a very low chance of fiber releasing, 18 – low, 21 – medium, and 3 – high chance, and 15 materials containing MMVF had a very low chance of fiber releasing, 11 – low, 7 – medium, 1 – high. Conclusion. Materials containing industrial fibers are widely used in premises for various purposes. Visual and instrumental survey allows detecting such materials and assessing their condition for the development of measures set to control working area air pollution. The detection of fibers in dust samples makes it possible to establish the presence of sources of air pollution, as well as to identify them in most cases.

COMPARATIVE EVALUATION OF THE CAUSES OF DEATH IN A COHORT OF WORKERS IN THE MINING AND ENRICHMENT OF CHRYSOTILE ASBESTOS

A retrospective cohort study was carried out to investigate the mortality of workers occupationally exposed to dust containing chrysotile asbestos fibers. In its chemical and physical properties, it differs from the fibers of other types of asbestos and is the only type of asbestos that is currently approved for use in many countries of the world. The members of the cohort are current and former employees who have worked for at least one year at the production sites of the complex of enterprises for the mining and enrichment of chrysotile asbestos (JSC «Uralasbest», Asbest, Sverdlovsk region) in the period from 01.01.1975 to 31.12.2010. Of the 35837 members of the cohort, 12729 (35.5%) people died (2373 of them were malignant neoplasms of various localizations, including 10 mesotheliomas), 18799 (52.5%) were alive at the end of the observation period (2015), and 4309 people (12.0%) were censored by the end of 2015. The mean follow-up period was 21.7 years for men and 25.9 years for women. The average age at death was 59.4 years for men and 66.5 years for women. This paper presents a general comparative evaluation of the causes of death of cohort members. Further processing of data obtained is currently underway.

Comparative characteristics of various fibrous materials in in vitro experiments

Aim. Comparative assessment of the effect of fibrous materials on cell cultures RAW264.7 and BEAS-2B. Methods. The effects of various fibrous materials single-walled carbon nanotubes of two types (SWCNT-1 and SWCNT-2), differing in morphological characteristics, and chrysotile asbestos as a positive control was assessed on two cell lines macrophages RAW 264.7 and human bronchial epithelium BEAS-2B cells. The studied materials concentration range for experiments on cells was selected taking into account the SWCNT content in the air of the working area and the subsequent modeling of SWCNT deposition in the human respiratory tract. Suspensions of the studied materials were prepared based on cell culture media by ultrasonication. Cytotoxicity assessment after 48 hours of incubation was performed by using the MTS colorimetric assay. The expression level of apoptosis markers was assessed by immunoblotting using the corresponding monoclonal antibodies. Visualization of SWCNT-1, SWCNT-2 and chrysotile asbestos in BEAS-2B cell cultures was carried out by improved dark-field microscopy. Results. According to dark-field microscopy, all the studied fibrous materials were found on the surface or cytoplasm of the cells. SWCNT and chrysotile asbestos did not have a direct cytotoxic effect in the MTS assay and did not induce apoptosis according to the results of Western blotting in cell cultures of RAW264.7 macrophages and BEAS-2B bronchial epithelium. In the cells of the bronchial epithelium (BEAS-2B) that showed greater sensitivity, a slight increase in the expression of pro-apoptotic protein PARP, which was more pronounced for shorter SWCNT-2, was revealed. Conclusion. Both types of SWCNTs, despite the differences in morphological characteristics, demonstrated similar effects in in vitro experiments; this result, with its further verification, can have an important practical application in justifying approaches to determining the safety criteria for single-walled carbon nanotubes as a class of nanomaterials of the same type.