Respirable crystalline silica

Where does it appear and what effects does it produce?

Crystalline silica is one of the most abundant minerals in the Earth’s crust and is present in most rocks and in construction and decorative materials. Exposure occurs in construction (cutting concrete, brick, and tile; demolition; drilling; blasting; and mortar grinding), in the quarrying and aggregates industries, in the manufacture and machining of quartz agglomerates for countertops, in ceramics, glass, foundries (molding sands), cement and precast concrete production, marble work, sandblasting, agriculture on sandy soils, and many other industrial processes. Visible dust is not a reliable indicator: the respirable fraction, just a few microns in size, is invisible and remains suspended in the air for hours.

Silicosis is the oldest known occupational disease and remains incurable: particles deposited in the lungs cause an inflammatory reaction and progressive fibrosis that reduces respiratory capacity and can continue to worsen even after exposure ceases. There is a chronic form, resulting from years of moderate exposure, and accelerated and acute forms with intense exposures, such as those observed in young workers machining quartz agglomerates, a material with a silica content exceeding 90 percent. The International Agency for Research on Cancer classifies inhaled crystalline silica in the form of quartz or cristobalite as carcinogenic to humans.

Directive (EU) 2017/2398 included work involving exposure to respirable crystalline silica dust generated in a work process in the Carcinogens Directive, and Royal Decree 1154/2020 transposed it into Royal Decree 665/1997 with a limit value of 0.05 milligrams per cubic meter. In the mining sector, Order TED/723/2021 approved the supplementary technical instruction on protection against respirable dust and crystalline silica. Silicosis is listed in the schedule of occupational diseases in Royal Decree 1299/2006 and is subject to specific health surveillance.

Obligations and preventive measures

• Carcinogen regime. Application of Royal Decree 665/1997: identification and evaluation, substitution where technically possible, closed systems and, if not, reduction of exposure to the lowest technically possible level and always below the limit value.
• Substitution. Materials with lower silica content or none at all (e.g., alternatives to high-silica quartz agglomerates, silica-free abrasives in blasting), and methods that avoid generating dust.
• Wet methods. Cutting, drilling, polishing and machining with water input, which drastically reduce the emission of respirable dust, with sludge management and subsequent cleaning.
• Localized extraction and enclosure. Tools with integrated dust collection, machine booths and enclosures, ventilation with high-efficiency filtration and recirculation control.
• Cleaning. Vacuuming with high-efficiency filters or wet methods; dry sweeping and blowing with compressed air are prohibited.
• Organization. Reduction of the number of exposed persons and exposure time, delimitation and signage of areas, prohibition of eating, drinking and smoking, and separate toilet and changing areas.
• Respiratory protection. As a complement when the above measures are not sufficient: FFP3 self-filtering masks or equipment with P3 filters, with fit testing and, in high exposure tasks, powered air-purifying respirators or supplied air equipment.
• Measurements. Personal sampling of the respirable fraction with particle selector and specific analysis of crystalline silica, according to standardized methods and with a representative strategy, and periodicity according to the results.
• Health surveillance and records. Specific examinations with silicosis and carcinogen protocols, list of exposed workers, records kept for at least 40 years and post-occupational surveillance.

Sectors of special attention

• Quartz agglomerates. Machining, cutting, polishing and installation of countertops with very high silica content; requires wet methods, extraction, respiratory protection and strict control, and has caused outbreaks of severe silicosis in young workers.
• Construction and demolition. Cutting of materials, drilling, sandblasting and demolition: water and vacuum tools, task planning and coordination of business activities.
• Extraction and aggregates. Drilling, blasting, crushing and screening: enclosures, irrigation, pressurized cabins and application of mining technical instruction.
• Foundries and ceramics. Molding sands, demolding and cleaning of parts, preparation of pastes and glazes: sand replacement, enclosures and extraction.
• Glass and cement. Handling of raw materials and cleaning of facilities with dust generation.
• Self-employed workers and small businesses. Particularly vulnerable due to lack of resources; the INSST and labor authorities’ campaigns target these groups with guides and simplified assessment tools.

Organizational application: how to manage the risk of respirable crystalline silica

1. Identify materials containing crystalline silica and tasks that generate respirable dust, and register exposed workers in accordance with Royal Decree 665/1997.
2. Apply the substitution of materials and methods whenever technically possible and document the justification when it is not.
3. Implement wet methods, localized extraction, enclosures and vacuum cleaning, and select equipment with integrated dust collection.
4. Evaluate exposure with personal measurements of the respirable fraction and analysis of crystalline silica, compare with the limit value and set the monitoring frequency.
5. Select additional respiratory protection with fit testing and training in its use.
6. Organize specific health surveillance with silicosis and cancer protocols, and keep histories and records for 40 years.
7. Train and inform workers, mark the areas and coordinate with contractors and self-employed workers who perform tasks with silica.

Preventive management software allows you to maintain the inventory of materials and tasks containing silica, the list of workers exposed to carcinogens, the results of measurements, the measures implemented, and the health surveillance records with the required retention periods.

Limits and common mistakes

1. Treat silica as a nuisance dust and not as a carcinogenic agent with a specific regime and binding limit value.
2. Cutting, polishing or dry drilling materials containing silica, especially quartz agglomerates.
3. Clean with a broom or compressed air, resuspending the respirable fraction.
4. Relying on masks without proper fit or class instead of applying technical measures.
5. Do not measure the respirable fraction or specifically analyze crystalline silica.
6. Omitting specific health surveillance, registration of exposed persons and retention of records for 40 years.

The requirements are detailed in Royal Decree 665/1997 and in the INSST technical guide on carcinogenic or mutagenic agents; this sheet is for informational purposes.

Regulatory and reference framework

• Royal Decree 665/1997, of May 12. Protection of workers against risks related to exposure to carcinogenic agents during work; Annex I with the work involving exposure to respirable crystalline silica and Annex III with its limit value.
• Royal Decree 1154/2020, of December 22. Amendment of Royal Decree 665/1997 which incorporates respirable crystalline silica and its limit value.
• Royal Decree 374/2001, of April 6. Protection against risks related to chemical agents during work.
• Order TED/723/2021, of July 1. Supplementary technical instruction 02.0.02 on the protection of workers against the risk of inhalation of respirable dust and crystalline silica in mining.
• Technical guide for the assessment and prevention of risks related to exposure to carcinogenic or mutagenic agents at work (INSST, 2022) . Criteria for the application of Royal Decree 665/1997, including respirable crystalline silica.
• INFOCARQUIM: Work involving exposure to respirable crystalline silica dust (INSST) . Information on the process, effects, and preventive measures.

Directive (EU) 2017/2398 incorporated respirable crystalline silica into Directive 2004/37/EC on carcinogens; Royal Decree 1299/2006 includes silicosis in the list of occupational diseases and the INSST publishes in BASEQUIM situations of exposure such as the machining of boards with silica content.