Atmospheric particulates *
Bev-Lorraine True, Robert H. Dreisbach in Dreisbach’s HANDBOOK of POISONING, 2001
Dust containing silica is produced during rock cutting, drilling, crushing, grinding, mining, abrasive manufacture, pottery making, processing of diatomaceous earth, and volcanic eruptions. Talcum powder contains magnesium silicate. Many substances containing silica are capable of causing silicosis; particles less than 5 μm in diameter appear to be the most important in causing silicosis. The exposure limit for dusts containing crystalline quartz, such as tripoli, is 0.1 mg of respirable particles of quartz per cubic meter of air. Cristobalite and tridymite have an exposure limit of 0.05 mg/m3. For diatomaceous earth and silica gel, the total respirable mass should not exceed 10 mg/m3 of air; for precipitated silica, the respirable mass should not exceed 5 mg/m3.
Occupational and Environmental Lung Diseases
James M. Rippe in Lifestyle Medicine, 2019
Asbestos-related lung disease is a group of lung diseases caused by exposure to naturally occurring asbestos fibers comprised of magnesium silicate minerals. These fibers have desirable physical properties for industrial use, such as high tensile strength, flexibility, and resistance to chemical and thermal degradation, hence their prior extensive use in the construction, automotive, and textile industries.23 Chrysotile (also known as white asbestos) is the most common and only type of asbestos currently used in manufacturing in the United States, while the more toxic amphibole fibers, including crocidolite, amosite, and tremolite are still used in parts of sub-Saharan Africa, South America, and Asia.24 Asbestos fibers are highly carcinogenic and are known to cause lung cancer and malignant mesothelioma. Asbestos is considered one of the most important occupational carcinogens.24
Antiperspirant/Deodorant Rheology
Laba Dennis in Rheological Proper ties of Cosmetics and Toiletries, 2017
The rheological additives in aqueous roll-ons are used mainly to build viscosity into the system. The main additives fall into two categories: clays and surfactants. Aluminum magnesium silicate (trademarked as Veegum by R. T. Vanderbilt) is often used, as is glyceryl stearate and PEG 100 stearate (trademarked as Arlacel 165 by ICI Americas). Changing the rheology of this system often means merely increasing the viscosity. This can be accomplished by either increasing the concentration of the rheological additive or increasing the concentration of the internal oil phase. The formulator must keep in mind that the system must be thin enough to allow easy passage through the small clearance between the roll-on ball and the container itself, yet not be so thin as to cause dripping off the ball or running down the axilla.
Correlative polarizing light and scanning electron microscopy for the assessment of talc in pelvic region lymph nodes
Published in Ultrastructural Pathology, 2019
Sandra A. McDonald, Yuwei Fan, William R. Welch, Daniel W. Cramer, Rebecca C. Stearns, Liam Sheedy, Marshall Katler, John J. Godleski
Figure 4 shows correlative polarizing light microscopy, in situ SEM, and EDX on case 9C from Table 4. Going clockwise from lower left, panel A shows numerous birefringent particles under polarized light microscopy (H&E, 400x) within the macrophages of a left external iliac lymph node. Panel B shows low-power backscattered electron imaging under SEM with several positive particles. Panel C shows an enlarged (cropped) view of the lower right-hand part of panel B. Three particles are labeled – 44, 45, and 46. Panel D shows the spectrum for particle 45, which showed an Mg-Si ratio of 0.643. Particle 44 was also within the 5% of the theoretical value of 0.649 and so was considered talc as well. Particle 46 had an Mg-Si ratio of 0.610, which falls just outside the 0.649 ± 5% range for talc, and so it was considered a nonspecific magnesium silicate.
Thermal energy and tableting effects in benznidazole product: the impacts of industrial processing
Published in Drug Development and Industrial Pharmacy, 2023
Maria Betânia de Freitas-Marques, Talita Santos do Valle, Bárbara Caroline Rodrigues de Araujo, Rita de Cássia de Oliveira Sebastião, Wagner da Nova Mussel, Maria Irene Yoshida, Christian Fernandes
However, the physical mixture did not exhibit the same behavior. Up to 600 °C, 92% of the tablet and 63% of the physical mixture were decomposed, suggesting higher heat propagation in the tablet and thermal degradation. Particle packing is one of the factors influencing the thermal behavior of pharmaceutical solids, as observed for the powder and compared to the single crystal of antimalarial lumefantrine, data described by Freitas-Marques [7]. For BZN: MS 1:1 w/w (Figure 8(B)), BZN: ST 1:1 w/w (Figure 8(C)), and BZN: LA 1:1 w/w (Figure 8(D)), the thermal behavior indicates the formation of systems with their fingerprints, whose temperatures at the beginning of the decomposition process and fragmentation mechanisms of the molecules follow different kinetics when compared to those of the individual components. This phenomenon was observed unequivocally in the presence of MS (Figure 8(B)), whose binary mixture decomposed after 185 °C, and in LA (Figure 8(D)), with modification of the mass loss profile. In practice, starch does not influence the thermal behavior of BZN (Figure 8(C)) because the physical mixture presents an intermediate thermal behavior for the individual components. The TG curve of TA (Figure 8(E), thin solid line) indicates the high thermal stability of this excipient because there was no mass loss within the range analyzed up to 600 °C. Magnesium silicate (talc component) exhibits a ‘refractory’ effect in the binary mixture, reducing heat propagation and consequent thermal decomposition of BZN (Figure 8(E), dashed line), as previously described for azathioprine, an immunosuppressant drug [6].
The role of lysosomal ion channels in lysosome dysfunction
Published in Inhalation Toxicology, 2021
Rebekah L. Kendall, Andrij Holian
Lysosomal dysfunction and NLRP3 inflammasome activity are both implicated in pneumoconiosis such as silicosis. Silicosis is a progressive respiratory disease marked by inflammation and fibrosis and is nearly always fatal (Barnes et al. 2019; Leso et al. 2019 ). The development of silicosis is largely dependent on the cumulative dose of cSiO2 exposure and exposure duration, making it a chronic disease typically requiring years to manifest. Because silica is an exceedingly abundant mineral and found in a wide-variety of rock types, it is pervasive in a variety of industries. Silica occurs in both crystalline and non-crystalline (amorphous) forms, with the crystalline form considered the most cytotoxic. Quartz, the most common cSiO2 polymorph, is comprised of a tetrahedral lattice of one silicon bound to four oxygen atoms in a repeating array that gives it a three-dimensional structure similar to diamond. Silica can also be found in combination with other elements to form silicates such as asbestos, talc or kaolinite or as a mineral contaminant of coal, each of which can contribute to pneumoconiosis (Hoy and Chambers 2020; Castranova and Vallythan 2000). In industrial settings respirable cSiO2 can be formed during sandblasting, including the use of sand for distressing denim jeans; coal and gold mining; drilling and cutting concrete; polishing semi-precious stones; and artificial stone benchtop fabricators (Mossman and Glenn 2013; Gottesfeld et al. 2015; Barnes et al. 2019). This wide range of occupational uses, results in millions of workers exposed to respirable cSiO2 worldwide (less than 10 µm in diameter; capable of reaching distal airways and alveoli of the lungs) (Leso et al. 2019).
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