The dangers of silica dust are becoming more and more widely known in the community – which is a positive – although it is knowledge dearly with people’s lives. Our goal here is to understand more about silica dust, its sources, and the dangers it poses. Crystalline silica is a very stable compound of silicon and oxygen. Silicon and oxygen are bound by silicon-oxygen bonds to form polymorphs. Its chemical structure is very organized with a framework pattern the arrangement of which sees oxygen and silicon atoms in three directions forming crystalline silica. Quartz is the most common form of crystalline silica in nature. Quartz is present in alpha and beta forms. Alpha quartz is the most common form and found in many rocks and soils. The mass of the Earth’s crust is 59% silica – so it is super abundant. Most dangerous human exposure to crystalline silica dust occurs in the workplace although recent news articles have shown that beyond the workplace the potential for exposure can also be very high. Quarries, construction and demolition site and tools like sandblasters generate dust clouds of fractured crystalline silica. Rock blasting and excavation suspends mineral dusts, which are harmful to human life via inhalation and deposition in the lungs. Exposure can also extend to communities close to silica dust generating activities. This article will unpack what silicosis is, its formation, and the contribution of silica dust generation. It will round off with why GRT says “crystalline silica dust control is non-negotiable.”
How is silicosis harmful to your health?
Unfortunately, silicosis is back in the news in Australia and New Zealand. Silicosis occurs because of exposure to silica dust from activities associated with quarries, mining, construction and stone masonry. Crystalline silica has very low solubility in human body fluids. Once deposited it can accumulate in the lungs. The main clearance mechanism is through macrophages. Inhalation of silica dust can result in cell membrane damage and macrophage death. This reduces the efficacy of the clearance mechanism. The cells ingest dust particles which leads to macrophage death. Free radical oxygen species generate on uptake of crystalline silica dust by cells. This leads to lipid peroxidation and membrane damage. It follows with release of lysosomal contents and lysis of the cell and its death. Silicosis happens as a result of breathing silica dust particles. It happens at high levels over a short period of time for acute silicosis. Chronic toxicity for low levels of exposure over long periods of time. The repetitive process of macrophage release and breakdown leads to formation of collagen by fibroblasts which scars the lung tissue. This leads to lung disease or pulmonary fibrosis. The scarring of the tissue leads to loss of alveolar airspace with high amounts of collagen fibers. Collagen fibers form wherever quartz particles have been deposited. The pattern of scarring is associated with silicosis. It is found in the upper lobes of the lung in a nodular pattern occupying alveolar air spaces.
The carcinogenic nature of silica is a matter of fact. Crystalline silica was classified as a Group 1 human carcinogen. This was by the International Agency for Research and Cancer in 2012. The designation based on epidemiological studies and experiments with laboratory rodents. Induction of DNA damage and reactive oxygen species contribute to cancerous cells. Exposure to silica dust leads to lung cancer. Review studies in 2020 showed damage to genetic material in crystalline silica workers. There are adverse health effects as a result of DNA instability. Exposure to crystalline silica causes formation of micronuclei and DNA breaks. Exposure to crystalline silica causes oxidative damage of DNA. The effects are on the base structure of DNA. Processes involving handling of rocks, concrete and quartz leads to crystalline silica exposure. Exposure to silica dust depends on specific scenarios. The health consequences caused by inhaling silica dust depend on particle size. Silicosis results from respirable dust particles in the range between 0.5 and 50 microns. Health effects of crystalline silica dust depends on the mode of deposition in the lungs. The amount of quartz in the rock contributes to what is released. Different occupations have different particle size ranges.
Are environmental regulations, health and safety concerns or potential profit loss a concern right now?
What are the industry regulations?
We recently penned a workplace health and safety article in the quarrying industry in Australia, although the learnings are transferrable worldwide. Growth in Australia’s population will also drive demand in public infrastructure. The Australian Bureau of Statistics projects high demand for heavy construction material. This means crystalline silica is always going to be present. We approached dust as a health and safety issue. Dust control measures at the source are key for health and safety of workers and communities. The risks associated with crystalline silica are discussed above. Mines situated in high silica rock content generate dust than those in less silica rock content areas. Drilling, blasting and crushing produce the most in quarrying mines in Australia. In Queensland, the Mining and Quarry Safety Health Act 1999 was updated in 2020. The new guidelines emphasize the need for effective and reliable dust control. Classification of reliable and effective is based on a hierarchy of controls. At the apex of the hierarchy is elimination of dust at its source.
Managing dust at the source – best practice WHS
Global Road Technology offers solutions at the apex of the hierarchy of control. It provides innovative solutions to completely eliminate exposure of quarry mine dust at its source before it can occur. Quarry mine roads generate a significant amount of dust. GRT Haul-Loc consisting of a formulated liquid polymer is added to the watering trucks. It binds fugitive dust particles preventing them from being airborne dust. Given the chemistries of mineral aggregates, it is key to use a product which exhibits both hydrophobic and hydrophilic properties. GRT Activate super activates hydrophilic water. This enables it to interact with hydrophobic surfaces of mineral aggregates. There is lowering in repulsion of fine dust particles relative to water use alone. Workplace Health and Safety in Australia’s quarrying industry can be achieved through robust legislative approaches. Most importantly the solutions employed should target the apex of the hierarchy of controls. GRT says “crystalline silica dust control is non-negotiable.” Crystalline silica dust must be eliminated at its source.
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REFERENCES
- Fleck et al. 2020. Parallel personal measurements of diesel engine exhaust and crystalline silica using dual sampling port. International Journal of Mining Science and Technology. 30. 313-319.
- Southard et al. 2014. Silica, Crystalline. Encyclopedia of Toxicology. 4. 1-4.
- Wultsch et al. 2021. Induction of DNA damage as a consequence of occupational exposure o crystalline silica: A review and meta-analysis. Mutation Research/Reviews in Mutation Research. 787:108349. 1-11.
