Often found in Quartz, Respirable Crystalline Silica is among one of the most toxic non-fibrous mineral dusts known to us. Inhalation of this substance can lead to fatal lung conditions including cancer. Diseases can be both chronic and acute and controlling exposures is vitally important for any business.
The Effects of Exposure
Acute effects can show just months after exposure to Respirable Crystalline Silica. Contrastly, the latency period between exposure and chronic conditions appearing in humans can be decades.
Particles enter the airways via inhalation during processes like cutting, surfacing, sanding and polishing natural stone or concrete based products. The respirable fractions become airborne during the processes and are inhaled. Inhaling Crystalline Silica deep into the lungs triggers a physiological response from the body which sees the body attempt to remove the contaminant from the lungs. However, insoluble and inert particles of quartz can damage specific cells within the lungs, known as cytotoxicity, with the release of lipases and proteases, activation of oxidant production by pulmonary macrophages, activation of mediator release from alveolar macrophages leading to the production of cytokines and reactive species and secretion of growth factors from alveolar macrophages.
Acute Silicosis (Silicotic Alveolar Proteinosis or Silicotic Alveolar Lipoproteinosis)
High-level exposure to active dusts may cause immediate damage to the Alveolus. Subsequently, alveolar lining cells die as well as the macrophages (cells which actively remove foreign bodies from the body). It is known that protein fluid and inflamed cells leak from the capillaries into the alveoli. The alveoli tissues become fibrous. As a result, lung function reduces significantly leading to severe pulmonary dysfunction and incapacity which can see the affected individuals incur life-changing disease, and which can often be fatal.
Chronic Silicosis
Symptoms of Chronic Silicosis can appear many years after a single exposure to Respirable Crystalline Silica. Symptoms can be a late manifestation of the disease and often by the time breathlessness is noticed, the disease has already advanced significantly.
Scar tissue develops in a similar way to that seen with Acute Silicosis with lung capacity further reduced by Hilar node enlargement and lesions in the lungs to which dense collagen tissue containing quartz particles. Lymph nodes within the lungs and pleura may also calcify and harden.
Cancer - The Known Carcinogenicity of Respirable Crystalline Silica
Significant increases in the incidence of adenocarcinomas and squamous cell carcinomas of the lung were found in experimental studies performed when reviewing the carcinogenicity of Respirable Crystalline Silica.
The International Association for Research on Cancer (IARC) classified inhaled crystalline silica (quartz or cristobalite) from occupational sources as a Group 1 carcinogen based on sufficient evidence of carcinogenicity in humans and experimental animals.
Main Activities in Which Workers May be Exposed to Crystalline Silica
Exposures to Respirable Crystalline Silica can be found in a variety of industrial settings and often specific processes which involve working with or generating dust from quartz containing materials, leading to exposure. Common industries or processes are mentioned in the IARC Monograph for Respirable Crystalline Silica which can be found below.
The HSE released an updated copy of the EH40: Workplace Exposure Limits which had revised limits for specific hazardous substances.
This latest version of EH40/2005 ‘Workplace exposure limits’ has been updated to include the new and revised workplace exposure limits (WELs) as introduced by the Carcinogens and Mutagens Directive (EU) 2017/2398 amending Directive (2004/37/EC) of which Respirable Crystalline Silica had a revised entry.
Controlling Exposures
There are many ways of controlling silica dust emitted from specific processes. The preferred method often involves water suppression techniques whereby particulates can be dampened down or rinsed away using on-tool water discharge units or background mister systems. Although, controlling the source of emission should be a priority.
Extraction systems can also be applied to a process to remove the contaminants and prevent exposure. An on-tool extraction system is an option for many, but it's often difficult to fully remove at source, particularly where the particulates are forced into the air at speed when grinding, cutting or milling for example. That said, often such processes are carried out within a fully enclosed booth with the operator wearing suitable respiratory protective equipment as a secondary control measure.
A great publication for informing of how to control airborne contaminants is the HSG258 of which is provided in the link below.
Respiratory Protective Equipment (RPE) should be the last line of defence to protect against exposures. We typically advise that RPE is worn in conjunction with other forms of control systems, such as local exhaust ventilation. The RPE offers to protect the worker should any airborne contaminants become fugitive either accidentally, or due to primary control failure. Combining multiple levels of control will effectively help reduce exposures to as low as reasonably practicable. In general, the hierarchy of control should be followed.
Creating an Awareness
It's vitally important that suitable and sufficient training is provided to highlight the seriousness of needing to control respirable crystalline silica and prevent exposure. Organisations should design, implement and continually review safe systems of work and ensure best available techniques are followed by staff members. These techniques should be clearly communicated by a means of implementing suitable and sufficient training programs. Along with training, the provision of information and instruction should be provided as a means of encouraging clear and concise communication.
It is hoped that this article goes some way to providing a brief overview of Respirable Crystalline Silica. If you wish to know more on this subject or need support with your COSHH assessments, exposure monitoring or the testing of your LEV systems, RPE Fit Testing then please feel free to get in touch with us through social media or our website (www.workplacescientifics.com), by email at support@workplacescientifics.com or simply give us a call on 01709 931299.
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