The health hazard posed by asbestos exposure may also concern other minerals with an asbestos-like crystalline habit. One of these potentially hazardous minerals is fibrous glaucophane which can occur with a fibrous habit similar to regulated amphibole asbestos minerals. Fibrous glaucophane is an important component of the blueschist rocks of the Franciscan Complex (USA) that are commonly mined for construction purposes in northern and central California (e.g., the Calaveras Dam Replacement Project). Dust generated by excavation activities involving blueschist rocks could potentially expose workers and the general public to health risks. For this reason, it was considered to represent a potential health hazard as naturally occurring asbestos (NOA) by the dam owner, the San Francisco Public Utilities Commission, though an evaluation of the potential health hazard of this mineral fibre was not mandatory per local state and federal regulations. In this work, in vitro tests on glaucophane from the Franciscan complex were performed to assess the actual potential toxicity/pathogenicity of fibrous glaucophane (Gla). Biological responses of cultured human monocytes and lung mesothelial cells (THP-1 and Met-5A) following 24 and 48h of exposure to different doses of Gla (25, 50 and 100 µg/mL), have been determined by Alamar Blue viability, extracellular lactate dehydrogenase (LDH) and Comet assays. Generation of reactive oxygen species (ROS) has been evaluated performing a luminescent assay. Crocidolite UICC asbestos (100 µg/mL) was also tested for comparison. Results of in vitro tests showed that Gla may induce a decrease in cell viability and an increase in LDH release in tested cell cultures in a concentration dependent mode. Overall, the rank of the investigated fibres in increasing order of cytotoxicity is: Gla (25 μg/mL) < Gla (50 μg/mL) < crocidolite (50 μg/mL) < Gla (100 μg/mL). For both the cells lines, Gla was able to induce DNA damage. Moreover, it was found that Gla can induce the formation of ROS. The biological reactivity of Gla observed in this study confirms that this mineral fibre is a cytotoxic agent. Although Gla induced lower toxic effects compared to the carcinogenic crocidolite, the inhalation of its fibres may be hypothetically responsible for the onset of lung diseases. For a conclusive understanding of the toxicity and carcinogenicity mechanisms of fibrous glaucophane, in vivo animal tests should be performed to stimulate a critical evaluation and a classification by the International Agency for Research on Cancer (IARC).
In vitro assessment of the potential toxicity of fibrous glaucophane
Scarfì S.;Mirata S.;
2022-01-01
Abstract
The health hazard posed by asbestos exposure may also concern other minerals with an asbestos-like crystalline habit. One of these potentially hazardous minerals is fibrous glaucophane which can occur with a fibrous habit similar to regulated amphibole asbestos minerals. Fibrous glaucophane is an important component of the blueschist rocks of the Franciscan Complex (USA) that are commonly mined for construction purposes in northern and central California (e.g., the Calaveras Dam Replacement Project). Dust generated by excavation activities involving blueschist rocks could potentially expose workers and the general public to health risks. For this reason, it was considered to represent a potential health hazard as naturally occurring asbestos (NOA) by the dam owner, the San Francisco Public Utilities Commission, though an evaluation of the potential health hazard of this mineral fibre was not mandatory per local state and federal regulations. In this work, in vitro tests on glaucophane from the Franciscan complex were performed to assess the actual potential toxicity/pathogenicity of fibrous glaucophane (Gla). Biological responses of cultured human monocytes and lung mesothelial cells (THP-1 and Met-5A) following 24 and 48h of exposure to different doses of Gla (25, 50 and 100 µg/mL), have been determined by Alamar Blue viability, extracellular lactate dehydrogenase (LDH) and Comet assays. Generation of reactive oxygen species (ROS) has been evaluated performing a luminescent assay. Crocidolite UICC asbestos (100 µg/mL) was also tested for comparison. Results of in vitro tests showed that Gla may induce a decrease in cell viability and an increase in LDH release in tested cell cultures in a concentration dependent mode. Overall, the rank of the investigated fibres in increasing order of cytotoxicity is: Gla (25 μg/mL) < Gla (50 μg/mL) < crocidolite (50 μg/mL) < Gla (100 μg/mL). For both the cells lines, Gla was able to induce DNA damage. Moreover, it was found that Gla can induce the formation of ROS. The biological reactivity of Gla observed in this study confirms that this mineral fibre is a cytotoxic agent. Although Gla induced lower toxic effects compared to the carcinogenic crocidolite, the inhalation of its fibres may be hypothetically responsible for the onset of lung diseases. For a conclusive understanding of the toxicity and carcinogenicity mechanisms of fibrous glaucophane, in vivo animal tests should be performed to stimulate a critical evaluation and a classification by the International Agency for Research on Cancer (IARC).
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