Ceramic and tile manufacture repeatedly handles, dries, presses, fires and finishes silica-containing materials. Firing changes which form of silica is present, which changes what must be analysed.
Ceramic and tile manufacture involves repeated handling, drying, pressing, firing and finishing of silica-containing materials. Exposure can arise during both routine production and less predictable activities such as cleaning, breakdown response and maintenance.
RAK Ceramics was founded in Ras Al Khaimah in 1989. The company operates ceramic tile and sanitaryware manufacturing at significant scale, with plants in several countries and a large workforce.
Ceramic bodies are produced from combinations of clays, feldspars, silica, sand and other mineral ingredients selected to achieve the required strength, colour and firing behaviour. Quartz may be deliberately added or may occur naturally within clay and other raw materials.
Dry powders can release respirable particles during bag opening, tipping, transfer and mixing.
Raw-material silica content can vary between suppliers, mineral seams and product formulations.
Material described simply as clay or ceramic powder should not automatically be assumed to have a low crystalline silica content.
Safety data, formulation information and representative bulk analysis can help identify potential sources but do not replace air monitoring.
Finished products may have a different crystalline composition from the unfired body because mineral phases can change during firing.
Body preparation converts mineral raw materials into a controlled feed suitable for pressing or forming. Although many stages use wet slurry, exposure can still arise during dry charging, spray-dryer operation, powder transfer and the handling of collected material.
Bag and bulk-material tipping can release quartz-containing dust at the point of charge.
Spray-dried granules may generate a respirable fraction when conveyed, screened, dropped or reclaimed.
Leaks from elevators, silos, flexible connectors and transfer chutes can create persistent deposits around the process.
Cleaning powder from floors, structures and machinery can produce greater exposure than normal enclosed production.
Maintenance inside spray dryers, ducts, cyclones and filters may disturb large quantities of accumulated fine material.
Pressing systems are commonly enclosed and automated, but powders can escape from mould filling, excess-powder recovery and damaged seals. Unfired or "green" ceramic material remains relatively friable and can release dust when trimmed, broken or mechanically handled.
Powder feed systems can leak at flexible connections, dosing points and press hoppers.
Trimming, scraping and dry fettling of unfired material may create fine quartz-containing dust.
Broken green tiles can generate dust when dropped into waste containers or mechanically crushed for recycling.
Operators may be exposed when opening guards, inspecting moulds or clearing powder build-up.
Compressed-air cleaning can disperse material across a much wider area and should be avoided where safer methods are practicable.
Glazes and colours contain mixtures of frits, minerals, pigments and other ingredients. Not every glaze contains crystalline silica in the same form or quantity, so the composition of each formulation should be understood before exposure risk is characterised.
Dry glaze ingredients may release dust during weighing, tipping and blending.
Spray application can create inhalable aerosol and fine overspray even when the original glaze is supplied as a liquid suspension.
Dried deposits inside booths, ducts and filters can become airborne when scraped or brushed.
Maintenance workers may be exposed while changing filters, cleaning nozzles or opening extraction systems.
Other substances in pigments and glazes may require assessment alongside silica rather than being treated as part of a single generic dust risk.
Cristobalite is a high-temperature crystalline form of silica with the same chemical formula as quartz but a different crystal structure. It can form when silica-containing ceramic materials are exposed to sufficiently high temperatures, although the quantity produced depends on the body composition, firing temperature, duration and presence of fluxes.
Quartz is generally the principal silica concern during raw-material and unfired-body handling.
Firing can alter the crystalline phases in the ceramic body and may produce cristobalite in certain products or kiln materials.
Cristobalite has historically been regarded as more biologically active than quartz, although modern toxicology also recognises that particle surface condition, impurities and thermal history influence reactivity.
Dust created after firing should therefore be analysed for both quartz and cristobalite where the process or product indicates that either may be present.
Cristobalite exposure is most relevant during polishing, grinding, cutting, kiln maintenance and handling of fired ceramic waste.
Mechanical finishing removes small amounts of fired ceramic material at high speed. These operations can generate fine particles directly from the finished tile and may therefore involve quartz, cristobalite or both.
Dry polishing and rectification can create concentrated airborne dust close to the grinding head.
Edge grinding, bevelling, slotting and cutting can expose operators when equipment is open or extraction is inadequate.
Recirculating water systems can reduce airborne dust but may create dried sludge deposits if leaks and overspray are not managed.
Tool changes and enclosure cleaning can disturb dust captured inside the machine.
Reject tiles and broken fired products may release further dust during crushing, recycling and waste handling.
A ceramics monitoring programme should distinguish between unfired-material processes, fired-product finishing and maintenance work. Samples collected only during stable automated production can miss the highest exposures if cleaning and interventions are excluded.
Personal breathing-zone samples should be collected from workers carrying out representative tasks and wearing the sampler throughout the defined period.
A calibrated pump and cyclone are used to collect the respirable fraction onto a suitable pre-weighed filter.
Gravimetric analysis can determine respirable dust mass, while X-ray diffraction or an appropriate infrared method determines the crystalline silica fraction.
The analytical request should identify quartz and cristobalite separately where fired materials are being ground, polished or disturbed.
Context records should include product type, formulation, firing status, wet or dry operation, extraction condition, cleaning methods and time spent on maintenance.
The strongest controls keep powders contained, apply water where it is compatible with the product and capture dust at the point of generation. Controls should be designed for foreseeable cleaning and maintenance activities as well as normal automated production.
Enclose weighing, dosing, mixing, pressing, grinding and waste-return systems wherever access is not required.
Use local exhaust ventilation at bag tipping, powder transfer, trimming, polishing and edge-grinding points.
Maintain wet polishing, cutting and grinding systems with sufficient water flow directed to the point of contact.
Clean using industrial vacuum systems fitted with suitable high-efficiency filtration or carefully managed wet methods instead of dry sweeping.
Provide suitable respiratory protection for residual risk, non-routine entry and maintenance where engineering controls cannot adequately control exposure.
Cristobalite can form at high temperature, so dust from fired material differs from the raw ingredients.
Spray-dryer entry, filter changes and dry cleaning can exceed normal enclosed production.
Unfired material releases dust when trimmed, broken or recycled.
Analysis should identify quartz and cristobalite separately wherever fired material is disturbed.
Abu Dhabi's Occupational Standards and Guideline Values document (2016), Schedule A, lists crystalline silica as alpha-quartz and cristobalite, with a time-weighted average of 0.025 mg/m³ for the respirable fraction, classified A2. Both forms are named, which matters in ceramics because firing can change which is present. Its status needs stating precisely. Section 3.2 of that document says the Schedule A values shall be adopted as maximum allowable limits, while the document's own introductory note describes its standards and guideline values as non-mandatory requirements — and it sits in the Standards and Guideline Values class, not among the Codes of Practice, which the Abu Dhabi Public Health Centre describes as mandatory for all entities. The framework has since been renamed ADOSH-SF under that Centre, which now records the Standards and Guideline Values document as suspended and directs entities to comply with relevant local or federal standards in force. The value is therefore a published reference point, not an enforceable UAE limit.
Abu Dhabi Occupational Standards and Guideline Values (2016), Schedule A — recorded as suspended by ADPHC
No. Firing changes the ceramic body but does not necessarily eliminate crystalline silica. Some quartz may remain, while cristobalite may form under particular firing conditions. The silica forms present in dust from fired material can therefore differ from those in the original raw ingredients.
Not necessarily. Its formation depends on mineral composition, peak temperature, time at temperature, cooling history and the behaviour of other ingredients in the body. A product-specific conclusion should be based on formulation knowledge, mineralogical analysis or air-sample results rather than an assumption that all fired ceramic contains the same cristobalite percentage.
Wet processing generally reduces airborne mineral dust, but it does not eliminate all exposure. Aerosol may be produced by spraying, and dried slurry or sludge can become airborne after leakage, evaporation or poor housekeeping. Workers may also move between wet and dry areas during the same shift.
Priority commonly falls on dry raw-material charging, spray-dried powder handling, dry fettling, glaze-powder preparation, fired-product polishing, edge grinding, kiln maintenance and dry cleaning. Short-duration but intense maintenance tasks may require task-based samples in addition to longer full-shift measurements.