Pulmonary Toxicity of Silica Linked to Its Micro- or Nanometric Particle Size and Crystal Structure: A Review

Abstract

Silicon dioxide (SiO2) is a mineral compound present in the Earth’s crust in two mineral forms: crystalline and amorphous. Based on epidemiological and/or biological evidence, the pulmonary effects of crystalline silica are considered well understood, with the development of silicosis, emphysema, chronic bronchitis, or chronic obstructive pulmonary disease. The structure and capacity to trigger oxidative stress are recognized as relevant determinants in crystalline silica’s toxicity. In contrast, natural amorphous silica was long considered nontoxic, and was often used as a negative control in experimental studies. However, as manufactured amorphous silica nanoparticles (or nanosilica or SiNP) are becoming widely used in industrial applications, these paradigms must now be reconsidered at the nanoscale (<100 nm). Indeed, recent experimental studies appear to point towards significant toxicity of manufactured amorphous silica nanoparticles similar to that of micrometric crystalline silica. In this article, we present an extensive review of the nontumoral pulmonary effects of silica based on in vitro and in vivo experimental studies. The findings of this review are presented both for micro- and nanoscale particles, but also based on the crystalline structure of the silica particles.

The role of mitochondrial dysfunction in macrophages on SiO2‐induced pulmonary fibrosis: A review

“…Data derived from animal or cell experiments show that most of crystalline silica particles have a size of 0.5–10 μm (Marques Da Silva et al, 2022). They cause mitochondrial swelling and mitochondrial membrane rupture (Guo et al, 2018) and cause the apoptosis of mitochondria, leading to a decrease in mitochondria number (Fu et al, 2018).…”

Toward targeted treatments for silicosis

“…<100 nm) also disrupt normal autophagy processes, leading to lysosomal dysfunction and negative consequences. Artificial stone dust contains a high concentration of ultrafine or nano-silica particles, which may also contribute to silicosis and other silica-associated diseases [78].…”

Crystalline Silica-Induced Proinflammatory Interstitial Macrophage Recruitment through Notch3 Signaling Promotes the Pathogenesis of Silicosis

“…Silica is an abundant and versatile natural substance in the Earth’s crust that is used for multiple applications . Human exposure to silica occurs in industries such as agriculture, biomedicine, cosmetics, manufacturing, and construction and increases the risk of malignancies such as pneumoconiosis, pulmonary fibrosis, and lung cancer. , Respirable crystalline silica (CS) refers to particulates with a diameter of <10 μm, the size most likely to reach the lung alveolus while escaping retention in the upper respiratory airways such as the nose or throat. , CS particles have unique physical and chemical properties that make it difficult for their clearance via the mucociliary escalator, and they are consequently deposited in the lungs, causing tissue damage and an inflammatory response that subsequently stimulates fibroblast proliferation and collagen production, eventually causing silicosis . Silicosis is a progressive, incurable respiratory disease that rapidly progresses and is globally widespread .…”

“…2,3 Respirable crystalline silica (CS) refers to particulates with a diameter of <10 μm, the size most likely to reach the lung alveolus while escaping retention in the upper respiratory airways such as the nose or throat. 2,4 CS particles have unique physical and chemical properties that make it difficult for their clearance via the mucociliary escalator, and they are consequently deposited in the lungs, causing tissue damage and an inflammatory response that subsequently stimulates fibroblast proliferation and collagen production, eventually causing silicosis. 5 Silicosis is a progressive, incurable respiratory disease that rapidly pro-gresses and is globally widespread.…”