- Silica minerals
- Jobs and industries where exposure occurs
- Health hazards from crystalline silica
- How many people are harmed by RCS exposure?
- Legislation and good practice agreement
- Prevention and control
- Monitoring exposure
- Health surveillance
- Respirable dust
- Other serious diseases caused by exposure to RCS
- Lectures complémentaires
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Crystalline silica is the name for a group of naturally occurring minerals found in many types of rock. It can be released into the air when the rock or articles made from the rock are crushed, cut, or worked in some other way. It is the fine fraction of the dust, the respirable fraction, that is harmful to health when inhaled. Respirable Crystalline Silica is often abbreviated as RCS. Exposure to RCS over many years is harmful to health, causing silicosis and increasing the risk of lung cancer and other serious diseases amongst workers. Restricting exposure to very low levels (around 0.05 mg/m3 of RCS, averaged over each working day) will minimise the risk of harm. Methods of exposure control include eliminating crystalline silica from the process, adapting the process to reduce emission into the workroom, e.g. by using water to keep dust from becoming airborne, use of local ventilation and personal respiratory protection.
Key points: crystalline silica includes quartz and other related materials. Quartz is found in most rocks and consequently in many building materials. For example, building sand predominantly contains quartz.
The minerals quartz, cristobalite and tridymite are different forms of crystalline silica (The chemical name for silica is silicon dioxide and the chemical formula SiO2); they are crystalline silica polymorphs. In a crystalline mineral the atoms are arranged in a 3-dimensional repeating patterns, and it is this structure that gives the mineral many of its physical and chemical properties. Crystalline polymorphs differ in the crystalline structure although they all have the same composition, in this case SiO2. There are also many minerals made from silicon dioxide that are in a non-crystalline or amorphous form, for example diatomaceous earth, silica gel, and synthetic amorphous silica (or SAS). There are also a group of minerals known as silicates, which are composed of silicon, oxygen and at least one other chemical element. Silicates are the most abundant type of mineral on Earth and include olivine, micas, and clays. It’s important not to confuse amorphous silica or silicate minerals with crystalline silica, which is generally more hazardous than these other materials.
Quartz is found in most rocks, but particularly in sandstone (70- 90% crystalline silica) and granite (typically around 30% crystalline silica); quartz is just yellow sand. Some minerals contain only a small amount of quartz, for example limestone and marble both have around 2% crystalline silica content. Many building products contain crystalline quartz – bricks up to 30% and concrete and mortar between 25 and 70%.
Cristobalite and tridymite occur naturally in lava formations and these minerals can be formed when silica is heated to very high temperatures. For example, diatomaceous earth is a sedimentary mineral deposit of mostly amorphous silica diatom skeletons. For some industrial uses the materials is heated to around 1,000 oC, which converts the amorphous silica to crystalline silica, mostly as cristobalite. Diatomaceous earth is used in a variety of industrial applications, including filtration and in agriculture.
Key points: Exposure to RCS occurs in construction, foundries, steel production, potteries, and other industries. Daily average exposure to RCS is typically around 0.05 to 0.5 mg/m3.
Exposure to RCS can occur in many occupations, for example: abrasive blasting workers, bricklayers, concrete workers, construction workers cutting stone or drilling in stone, crushing and grinding operators, demolition workers, digger drivers, foundry workers, furnace men, glass manufacture workers, kiln operators, machinists, mining machine operators, moulding and casting operators, pottery workers, quarry workers, rock drillers, sandblasters, steelworkers, stonemasons, tunnel workers, welders, and workers grinding, abrading, buffing or polishing.
High levels of RCS exposure are found in particular in mining and quarrying, manufacture of coke and other fuels, manufacture of mineral products, manufacture of metals and machinery, electricity and gas supply, and in construction. Exposure also occurs in brickmaking, stonemasonry, potteries, quarrying and several other industries. Tasks that involve the use of power tools to cut or grind mortar, bricks or mineral products can produce very high airborne levels of dust and RCS.
Exposure to RCS is measured in units of mg/m3, with daily average exposures typically around 0.05 to 0.5 mg/m3 (the EU occupational exposure limit value (OEL) is 0.1 mg/m3 measured or calculated in relation to a reference period of eight hours; this OEL has been introduced in the European legislation based on an amendment of the Carcinogen and Mutagen Directive (directive 2017/2398/EU amending directive 2004/37/EC (see below Legislation and guidance)).
You cannot rely on visualising airborne dust to assess the extent of the crystalline silica risk because the fine respirable size particles are not easily seen. If dust containing crystalline silica is visible in the air, or the workplace is heavily contaminated with settled dust, then the airborne dust concentration is likely to be greater than any of the existing occupational exposure limits for RCS in the European Union and is potentially harmful to health.
Key points: Exposure to RCS over many years can cause silicosis and increase the risk of lung cancer amongst workers.
Exposure to RCS at work can cause silicosis, an irreversible chronic respiratory illness, lung cancer and a number of other serious diseases (see below Other serious diseases caused by exposure to RCS). It is one of the most important causes of occupational disease around the world.
Crystalline silica particles can be inhaled and deposit in the narrow lung airways and air sacs (alveoli) where oxygen is taken up into the body. The particles are persistent in the lungs and are toxic to their natural defence cells (macrophages) causing an inflammatory response and subsequent deposition of fibrotic or scar tissue in the lung. As this scarring gets worse it becomes more and more difficult for the worker to breathe, and this worsening can continue after the exposure to RCS stops. The early stages of the disease are described as simple or nodular silicosis, but if there is sufficient exposure the disease may go to what is called ‘progressive massive fibrosis’ (PMF), where the fibrotic nodules (lumps) combine into larger lumps of 1 cm or more in diameter. Silicosis can be fatal if the lungs stop working effectively (respiratory failure), or there are serious complications such as pneumonia, tuberculosis or other infections.
The symptoms of silicosis are likely to occur after many years of exposure, and can include:
- Shortness of breath when walking or doing other physical activities;
- Severe persistent cough;
However, many people can have the early stages of silicosis without obvious symptoms. Health surveillance is therefore an important part of preventing serious disease. In Europe the number of fatal cases of silicosis has been decreasing steadily for at least the last 40 years and there are now around 1 in 100,000 of the population who die from this cause each year.
Lung cancer is more common amongst people diagnosed with silicosis than amongst other worker exposure to RCS. However, epidemiological studies, mostly in the diatomaceous earth industry, industrial sand production, pottery, granite production and mining, have also shown that there is a clear increased risk of lung cancer amongst those workers who have prolonged exposure to RCS, regardless of whether they do or do not have silicosis.
The overall relative risk of lung cancer from cohort studies of RCS exposed workers is around 1.3, i.e. around a 30% increase in risk, and in case-control studies the odds ratio is around 1.4, i.e. 40% increase. In cohort studies of silicotics the relative risk is 1.7. In a number of studies where exposure measurements were available it has been possible to investigate the exposure-response relationship for RCS and lung cancer. In pooled analyses of data from the key informative studies there is considerable heterogeneity, but there is an overall statistically significant relationship that shows increased risks down to the equivalent of 0.04 mg/m3 exposure to RCS over a working lifetime (45-years). It has been suggested that differences between the dusts, such as the freshness of the particle cleavage surfaces and the presence of contaminant coating on the RCS surface could explain some of the differences in outcome between studies. Although the lung cancer risk is apparently greater for silicotics than for non-silicotic workers there is evidence from a large epidemiological study carried out in China and another in the USA that having silicosis is not a perquisite for a lung cancer risk. So, preventing silicosis by health surveillance will not necessarily prevent workers from lung cancer from RCS exposure.
When the RCS has been recently produced by high-energy work processes such as blasting, drilling or chipping the toxicity is greatest. As particles “age" in the air, the surface reactivity and the toxicity decrease. In addition, if there are other particles present and these adhere to the surface of the RCS the toxicity may also be reduced. For example, controlled toxicological experiments have demonstrated decreased toxicity of RCS when aluminium or aluminosilicate clay particles coat the RCS particles. There is little evidence that exposure to RCS in desert regions of the world, where the particles are “aged", results in silicosis in the general population.
In a number of epidemiological studies exposure to RCS has also been associated with chronic renal disease resulting in premature death, with the risk increasing as cumulative RCS exposure increases. Epidemiological data also supports an association between RCS exposure and autoimmune diseases such as scleroderma, rheumatoid arthritis and systemic lupus erythematosus. Although, there was no clear exposure-response relationship evident for these diseases. The biological mechanisms linking RCS exposure to kidney or autoimmune diseases are unclear.
It is important for people to be aware of the potential symptoms of lung cancer, especially if they are or have been a smoker or have worked with RCS. The key things to look out for are:
- Having a persistent cough for more than a few weeks or a change in a cough you have had for some time;
- Coughing up phlegm with spots of blood in it;
- Shortness of breath;
- A pain in the chest or shoulder that won’t go away;
- Loss of appetite;
- Loss of weight.
Key points: Around 5.5 million workers in the EU are regularly exposed to RCS, and each year around 7,000 die from past exposure to RCS. With stringent controls in the future we could reduce the number of deaths in Europe from silica-related lung cancer to around 400 per year.
In the EU there are probably around approximately 5.5 million workers potentially exposed to RCS, with around three-quarters of them employed in the construction industry; most of the exposed workers are employed by SMEs. Average exposures across all industries have most probably been decreasing over the last 20 or more years – perhaps by between around 5 and 15% per annum, although clearly in specific worksites or industry sectors the trends may differ (and the trend is less strong at times over the period). Using the available epidemiological data and details of the work activities it has been estimated that each year in the EU there are about 7,000 deaths from lung cancer and 8,000 new cases of the disease attributable to past exposure to RCS. This corresponds to about 2.5% of all lung cancer deaths amongst the exposed workers.
If no new initiatives are taken to reduce exposure to RCS, based on the assumption that current trends in employment and reductions in exposure are maintained, the predicted numbers of lung cancer deaths in 2070 attributable to RCS would be slightly lower than today at around 6,000 per annum. The lung cancers attributable to RCS would have reduced to 1.3% of all lung cancer deaths in the exposed population.
With stringent efforts to control RCS exposures in the future the number of predicted lung cancer deaths in 2070 could drop to under 400 per year, which over the next 50 years there might be more than 100,000 lives saved. The majority of the companies that would be affected by efforts to control RCS exposure are SMEs, and the costs of achieving stringent control may be very high for a large proportion of the affected organisations, and could adversely affect their financial viability. However, for society as a whole the human costs of inaction are very large and overall monetised benefits to society outweigh the financial costs of tighter control.
Key points: RCS is regulated Europe under the provisions of the Chemical Agents Directive and the Carcinogen and Mutagen Directive 2004/37/EC which sets a binding occupational limit value for RCS.
RCS in the form or either quartz or cristobalite is classified by the International Agency for Research on Cancer (IARC) as a human carcinogen (Group 1). Crystalline silica is not regulated under the REACH Regulations in Europe.
Exposure to RCS is regulated under the provisions of the Chemical Agents Directive (Directive 98/24/EC - CAD) and the Carcinogen and Mutagen Directive 2004/37/EC (CMD). In 2017 an amendment of the CMD has been published (directive 2017/2398). This amendment introduced Work involving exposure to respirable crystalline silica dust generated by a work process in annex I of the directive and a Binding Occupational Exposure Limit (BOEL) Value has been established of 0.1 mg/m3 in annex III. The amendment entered into force on the 16th of January 2018 and member states had until the 17th January 2020 to transpose the amendment into national legislation.
An important development in Europe to try to raise standards of control in many industries where RCS exposure is present is the social partner agreement between fifteen trade associations and the European trade unions – this is the European Network on Silica or NEPSi. The agreement aims to protect the health of employees in the industries covered by the agreement, by minimizing exposure to RCS through the application of good practice guidance, which is freely available on the organisation website. However, it is notable that the construction industry is not currently a party to the NEPSi agreement (although the SLIC guidance provides a valuable alternative). A key part of the initiative is to regularly monitor RCS exposure, and to provide worker training plus health surveillance for silicosis.
Research in Finland has shown that the introduction of the NEPSi good practice agreement coincided with a strong decrease in the exposure to RCS. In the years following the agreement there was more than a 10-fold decrease in the average exposures to RCS. Before the NEPSI agreement, more than half of Finnish workplace had exposures above 0.2 mg/m3, but by 2013 only around 10% of the measurements were above the Finish occupational exposure limit (0.05 mg/m3). Data from the rest of Europe shows a steady decline in exposure in sites covered by the NEPSi agreement, with the average exposure around 0.02 mg/m3 and most measurements less than 0.1 mg/m3.
To complement the NEPSI good practice guide, IMA-Europe, the sector organisation of industrial minerals, issued in 2018 NEPSI 2.0 guidelines following the introduction of the OEL for silica in the Carcinogen and Mutagen Directive. These guidelines explain how to integrate the NEPSI principles into a company's health and safety management system. The NEPSI 2.0 guidelines are inspired on ISO 45001 but also offer a framework for companies that do not have a formal safety management system.
Key points: Effective techniques to control RCS exposure are available, e.g. elimination of crystalline silica from some processes, process modification to reduce emission into the workplace, local ventilation and respiratory protection. Well-designed systems can reduce exposure by more than a factor of ten.
Hierarchy of control
Control of exposure to dusts containing crystalline silica requires a coordinated strategy to reduce dust emission, to minimise spread around the workroom and to protect the worker, where appropriate. See, for example, SLIC guidance on RCS on construction sites. It should involve:
- Design and operation of work processes to minimise emission of RCS into the air;
- Control exposure by measures that are proportionate to the health risk, i.e. taking dust control very seriously;
- Choose the most effective and reliable control options that minimise the escape and spread of RCS;
- Use a combination of engineering and other control measures, along with suitable respiratory protection;
- Regularly check that control measures continue to be effective;
- Inform and train all employees on the hazards and risks from RCS, and how to use the available control measures;
- Ensure that the introduction of new control measures does not increase the overall risk to worker health and safety.
The Chemical Agents Directive, establishes a hierarchy of control, with elimination of hazards at the top of the list and use of personal protective equipment at the bottom. Elimination would involve completely removing the source of crystalline silica from the process; for example, in an abrasive blasting process it is possible to choose an alternative to crystalline silica from a wide range of alternative materials such as slags or glass beads. The hierarchy of control is also reflected in the 10 Golden Rules to reduce workers´ exposure to dust. These rules are an initiative from the German Fachausschuss Glas-Keramik but are also made available in English on the NEPSI website https://www.nepsi.eu/dont-give-dust-chance. The use of silica containing abrasive blast material is forbidden in most European countries or its use requires specific permission from the authorities. In making efforts to eliminate or substitute materials it is always important to ensure that the risk is reduced, i.e. that the hazard is less and the level of exposure is not increased.
Dust protection must begin in an early stage. Preparation and storage in closed systems (e.g. silos, drums or closed raw material bunkers) must be pursued. Stacked material or material stored openly must be covered or at least kept moist. It is possible to adapt the process to reduce the emission of RCS into the workroom, e.g. by using a closed system for processing materials (encapsulation, enclosure), by reducing the amount of energy being dissipated into the crystalline silica material or by using water or controlling the moisture content of powders. For example, when cutting kerbstones and paving it is recommended that the work is done with water suppression using a hose directly attached to the tool delivering at least 0.5 litres per minute of water onto the cutting surface. In addition, for this type of work it is necessary for the workers involved to wear a respirator, either a disposable respirator certified to FFP3 or similar. Healy and colleagues (2014) in their research on Irish stonemasons showed that wet cutting resulted in exposure to RCS that was about 35 times lower than during dry cutting, which underlines the potential impact that can come from relatively simple changes to working methods.
Control of airborne dust is often achieved through the use of local ventilation, particularly in fixed worksites such as factories. On mobile work sites the use of on-tool local extraction may be an attractive alternative to the use of water. Research in the USA has shown that the use of local ventilation in grinding may have a greater impact on worker exposure to RCS in such situations than wet working, with the water reducing exposure on average between 7 and about 50 times, depending on the grinding equipment used. However, the use of local on-tool ventilation was more effective, reducing average exposures by between 50 and around 150 times. A second study investigated the impact of local ventilation on concrete-cutting hammer drills. In this study the local ventilation reduced respirable dust levels from around 0.3 mg/m3 to less than 0.03 mg/m3.
The main issue is that engineering controls, such as local ventilation, are not as widely used as they should be and where there are such controls they are often not fully effective or properly maintained.
Tools and cleaning methods
By using adequate tools, the formation of dust can be limited. Examples of such equipment include saws with integrated water delivery systems that continuously feed water to the blade or grinders with dust collection systems. The tools have to be correctly maintained and used according the manufacturer's instructions.
Cleaning up dust should never be done by using a broom or by blowing off dust deposits but by using suitable industrial vacuum cleaners. Industrial vacuum cleaners, dedusters and brushing vacuum cleaners are divided into three dust categories according to standard IEC 60335-2-69. For carcinogenic dusts the use of dust-eliminating equipment of the category "H" is prescribed according to this standard.
Personal respiratory protection
If it is not possible to adequately control airborne RCS using engineering solutions it is necessary to protect workers using personal respiratory protection. Respirators are designed to cover the nose and mouth, and filter the air to remove specific contaminants before they can enter the lungs. When the worker inhales, the air will mostly either pass through the filter or through leaks in the seal between the respirator and the face. The overall effectiveness of a respirator depends on the “total inward leakage" of RCS. We express the effectiveness of respirators as the ratio of the concentration in the workers breathing zone outside the mask and the concentration inside the facepiece; this is the protection factor or PF. A protection factor of 10 means that the respirator reduces the concentration by ten times, i.e. only 10% of the original challenge would “leak" into the facepiece. A protection factor of 100 means only 1% of a contaminant should leak into the mask.
There are several different designs of respirator, from a half-mask that just covers the nose and mouth through to full-face respirators. Many half-masks are now designed to be disposable and these are often referred to as filtering facepiece respirators because these are designed so that the whole of the mask is made from the filter material. Respiratory protection is tested and certified to European Standards (European Norms – EN), for example filtering facepiece respirators are certified to EN 149 - Respiratory protective devices - Filtering half masks to protect against particles - Requirements, testing, marking.
When selecting a respirator it is important to ensure it is both adequate and suitable. A device will be adequate if it can provide sufficient reduction in exposure to protect the workers’ health and it will be suitable if it is right for the wearer, for example in terms of fit to the face and comfort. In many countries respirators are given an Assigned Protection Factor (APF), a numerical rating that indicates how much exposure should be reduced when the device is properly work. For example, if a device has an APF of 10 then the exposure should be reduced by at least ten times in use, i.e. if the worker would have been exposed to 0.5 mg/m3 of RCS if they had not worn the mask then when wearing it their exposure should be less than 0.05 mg/m3.
There are three types of filtering facepiece respirator identified in the standard: FFP1 are the simplest types of device and they offer an APF of 4, FFP2 are of slightly more sophisticated design offering an APF of 10, while FFP3 masks offer the greatest level of protection with an APF of 20.
All respirator wearers should have a “fit test" to ensure the mask they are being asked to wear is suitable and the device will protect them. Ideally the fit tests should be carried out by a trained and experienced technician. There are a number of sources of guidance on respiratory protection. 
Key points: Air sampling to measure exposure to RCS can be undertaken using established occupational hygiene methods with specialist laboratory analysis. High volume sampling may be required to measure low exposure levels.
RCS exposure can be measured using conventional occupational hygiene sampling gear using a battery operated sampling pump, with a cyclone sampling head or similar to select the respirable fraction of the aerosol. The dust sample is collected on pre-weighed PVC filters and the crystalline silica can be analysed by x-ray diffractometry or infrared spectrophotometry. There are standard methods published by many national competent authorities, e.g. UK: HSE; France: AFNOR; International: ISO.
General guidance on sampling airborne dust in the workplace is available:
- EN 689: Workplace exposure - Measurement of exposure by inhalation to chemical agents - Strategy for testing compliance with occupational exposure limit values
- EN 481: Workplace atmospheres - Size fraction definitions for measurement of airborne particles.
- EN-ISO 13137: Workplace atmospheres - Pumps for personal sampling of chemical and biological agents - Requirements and test methods
Personal samples should be collected throughout the working shift with the sampling head located close to the worker’s nose/mouth in the breathing zone. The filters need to be sent to a specialist laboratory for analysis for crystalline silica. The final result is expressed as a concentration – milligrams of RCS per cubic metre of air sampled (mg/m3). The filter can also be reweighed to allow a calculation of the respirable dust concentration and the percentage of RCS on the sample. The data can then be compared with the relevant OELV.
Measurement of low level exposure, i.e. <0.1 mg/m3, or exposure during tasks within a work day may require specialised high-volume sampling systems.
It is necessary to have appropriate competency to undertake this type of occupational hygiene monitoring work.
Key points: Health surveillance to protect workers from silicosis should be undertaken for all workers exposed to RCS. Health surveillance cannot replace control measures to prevent exposure but provides a means of monitoring their adequacy.
Where there is a chance that workers may develop silicosis it is appropriate for an employer to consider introducing health surveillance. When and how health surveillance is organised depends on national legislation and varies between member states. The SLIC guideline provides the following guidance.
Risk assessment, undertaken by the employer (taking into account any exposure monitoring), should demonstrate when and where there is a need to introduce health surveillance for employees.
For example, a health surveillance programme for workers should be established:
- when there is still a risk to health from RCS exposure, even after the implementation of all reasonable precautions;
- where there is reliance on RPE/PPE as a control measure.
A health surveillance programme for those exposed to RCS would include the following measures:
- Baseline assessment includes questionnaires, lung function tests and consideration of chest x-rays for comparison with future chest x-rays.
- The on-going health surveillance programme would include periodic chest x-rays as well as questionnaires and lung function tests. As chest x-rays carry some risks associated with the use of ionising radiation, their use always needs to be justified on health grounds, even though the actual dose of radiation required to carry out a single chest x-ray is very low. The competent person (e.g. occupational physician) should advise on the frequency of chest x-rays.
The competent person must explain the test results to the individual and report to the employer on the worker’s fitness to work. Workers with early silicosis are often able to work normally, but they should be assigned to different tasks, with no exposure to silica dust. The competent person also needs to interpret any health trends in workers under health surveillance. This may drive a need to revise the risk assessment and implement improvements in control measures.
Particles from less than around 0.1mm (100 μm) can be inhaled into the nose or mouth. However, as the air passes down into the lungs the larger particles are progressively deposited in the upper airways and it is only the smallest particles (<10 μm) that can reach the gas-exchange region of the lung where they can contribute to the risk of disease.
The size, shape and density of a particle determines how it behaves in air. We use the particle’s aerodynamic diameter to account for the effects of all of these variables, where aerodynamic diameter is the diameter of a spherical particle of density 1000kg/m3 that has the same falling speed in air as the particle in question. The aerodynamic diameter of a particle is critical in determining how it will behave when it inhaled.
Airborne dust concentration can be measured by drawing a sample of contaminated air through a filter and then weighing the amount of dust collected. Inhalable dust represents the size fraction of the aerosol that can be inhaled into the nose or mouth and thoracic dust the fraction that those materials that are hazardous when deposited anywhere within the lung airways including the gas-exchange region. For dusts like crystalline silica, which mainly have their effect in the deepest parts of the lung, i.e. the alveoli, we measure the respirable fraction, which is defined in relation to the aerodynamic diameter of the dust, see Figure 1.
In addition to causing silicosis and lung cancer, exposure to RCS can also cause the following:
- Infections, usually in addition to silicosis, such as tuberculosis (pulmonary and extra-pulmonary) or other mycobacterial, fungal, and bacterial lung infections;
- Chronic obstructive pulmonary disease (COPD);
- Autoimmune disease such as scleroderma and rheumatoid arthritis;
- Chronic kidney disease.
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EU-OSHA - European Agency for Safety and Health at Work, Infosheet: Carcinogens at Work. Available at: https://osha.europa.eu/en/publications/infosheet-carcinogens-work/view
EU-OSHA - European Agency for Safety and Health at Work, Summary - Exposure to carcinogens and work-related cancer. A review of assessment measures. Available at: https://osha.europa.eu/en/publications/summary-exposure-carcinogens-and-work-related-cancer-review-assessment-measures/view
SLIC Guidance for National Labour Inspectors on addressing risks from worker exposure to respirable crystalline silica (RCS) on construction sites https://osha.europa.eu/en/guidance-national-labour-inspectors-on-addressing-risks-from-worker-exposure-to-respirable-crystalline-silica
NEPSI The Good Practice Guide https://www.nepsi.eu/good-practice-guide
ILO - Occupational Health: Silicosis http://www.ilo.org/safework/areasofwork/occupational-health/WCMS_108566/lang--en/index.htm
IARC - Arsenic, Metals, Fibres, and Dusts. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans Volume 100C https://publications.iarc.fr/Book-And-Report-Series/Iarc-Monographs-On-The-Identification-Of-Carcinogenic-Hazards-To-Humans/Arsenic-Metals-Fibres-And-Dusts-2012
US OSHA Topic page on Cristalline Silica https://www.osha.gov/dsg/topics/silicacrystalline/
The British HSE has a range of guidance and resources relevant to silica and its health risks:
- A general guide to silica and cancer http://www.hse.gov.uk/aboutus/occupational-disease/cancer/silica.htm
- A guide for employees https://www.hse.gov.uk/pubns/indg463.pdf
- Using cut-off saws. A guide to protecting your lungs https://www.hse.gov.uk/pubns/indg461.htm