Workplace dust: total dust, respirable fraction, and silicon dioxide

Why workplace dust must be assessed professionally

Dust arises during cutting, grinding, drilling, crushing, mixing, transfer, handling of bulk materials, processing of wood, stone, concrete, ceramics, or building materials. At first glance it may appear as an ordinary operational problem, but from the perspective of employee health protection it is often a significant risk factor.

Important is that "dustiness" is not one universal parameter. Dust can have different particle sizes, different chemical composition, and different health effects. From a practical point of view it is therefore not enough to say that "it gets a bit dusty there" or that "dust is not very visible". For job categorisation, regional public health authority inspection, or assessment of the work environment it is necessary to determine what the worker actually breathes.

Dust visible to the eye may not be the most risky. Fine particles may be less noticeable but more significant from the perspective of penetration into the respiratory tract.

Total dust does not mean the whole risk

In practice people often speak of "total dust". In legal regulations and professional terminology the term total concentration, or the inhalable fraction of dust, is used in particular. These are particles that can be inhaled through the nose or mouth.

Total dust is important, for example, where ordinary mineral, construction, wood, metal, or technological dust arises. It can serve as a basic indicator of load on workplace air.

On its own, however, it may not be enough. The same concentration of total dust can mean different health risk depending on whether it is, for example:

Total dust is therefore an important indicator, but it does not always answer the question of whether the work environment is safe for health.

Respirable fraction: fine dust that penetrates deep into the lungs

The respirable fraction is the part of inhaled dust that can penetrate into deeper parts of the respiratory tract and as far as the alveoli. That is why it is essential for some types of dust.

While coarser particles may be captured in the upper respiratory tract, finer respirable particles can get much deeper. For dusts with a fibrogenic effect this is important because long-term exposure can lead to serious lung damage.

The respirable fraction is addressed especially when working with materials such as:

• concrete,
• stone,
• ceramics,
• bricks and fireclay,
• sand and aggregate,
• some building materials,
• materials containing quartz,
• dust from grinding, cutting, drilling, or crushing mineral materials.

In practical terms: for construction, ceramic, or stonemasonry dust it is often not enough to measure only total dustiness. It is necessary to assess whether the respirable fraction and content of crystalline silicon dioxide should also be measured.

Crystalline silicon dioxide: why SiO₂ matters

Silicon dioxide occurs in nature in various forms. From the work environment perspective crystalline silicon dioxide is especially important, for example quartz. It may be present in a range of construction, ceramic, stonemasonry, or mineral materials.

The risk does not arise because the material contains SiO₂ as such, but especially because fine respirable dust arises during its mechanical processing. It can be inhaled by the employee and deposited in deep parts of the lungs.

Typical activities with possible risk of exposure to respirable crystalline SiO₂:

1. cutting concrete, bricks, stone, or ceramic products,
2. grinding and milling of building materials,
3. drilling into concrete, masonry, or natural stone,
4. crushing and sorting of construction waste,
5. handling dry bulk mineral materials,
6. blasting, cleaning, and surface treatment,
7. production and processing of building materials.

For materials such as concrete, ceramics, stone, bricks, aerated concrete, Ytong, or building mixes it is advisable always to verify whether dust with respirable crystalline SiO₂ content can arise. The trade name of the material is not decisive, but its actual composition and method of processing.

Why "dust by eye" is not enough

Visual estimation of dustiness can be useful for basic orientation but is not a reliable basis for assessing employee exposure. Dust can behave very differently according to particle size, humidity, air flow, extraction, method of work, and distance of the worker from the source.

Some situations can be deceptive:

• the workplace looks clean but fine respirable fraction arises,
• dust is visible only briefly during cutting but exposure repeats every day,
• coarse dust settles quickly but fine fraction remains in the air longer,
• the worker does not stand directly at the source but moves in a dusty space,
• technology changes according to order and dustiness varies,
• extraction is installed but may not capture dust in the worker's breathing zone.

Therefore for assessment of the work environment sampling under conditions corresponding to actual work activity is important. Measurement should capture not only that dust arises, but also what quantity and what type of dust the employee inhales.

When to measure total dust and when the respirable fraction

The scope of measurement depends on material, technology, and purpose of assessment. Sometimes measurement of total dust concentration is sufficient. Sometimes the respirable fraction and possibly crystalline SiO₂ content must also be measured.

The correct design of measurement therefore does not start with the question "how much does dust measurement cost", but with what material is processed, in what way, and who is exposed.

Typical operations where dust is addressed

Workplace dust is often addressed in construction, industry, maintenance, production of building materials, and waste management. Sometimes it is a one-off requirement of the regional public health authority, sometimes documentation for job categorisation or internal verification of extraction effectiveness.

Typical operations and activities:

• cutting of concrete, ceramic, and aerated concrete products,
• cutting of materials such as Ytong, bricks, blocks, paving, or cladding,
• stone processing and stonemasonry operations,
• grinding of concrete floors and building structures,
• drilling and sawing into building materials,
• crushing and sorting of construction waste,
• recycling centres,
• production of building materials,
• cement plants, lime works, and operations with bulk materials,
• wood-processing operations,
• welding shops and workplaces with metal grinding,
• foundries and grinding shops,
• operations with powder raw materials.

Example: cutting building blocks

When cutting building blocks a mixture of coarser and fine particles may arise. Coarse dust is clearly visible, settles quickly, and contaminates the area around the machine. Finer particles, however, may remain in the air longer and can enter the worker's breathing zone.

For such activity it is advisable to address not only total quantity of dust but also the possibility of respirable fraction and content of mineral components, especially crystalline SiO₂, if that corresponds to material composition.

Example: recycling of construction waste

At recycling centres the situation is often more complex because input material is not always the same. Concrete, brick, asphalt mix, ceramics, plasters, or mixed construction waste may have different dustiness and composition. Dustiness is also influenced by material moisture, crushing method, sorting, transfers, transport around the site, and effectiveness of sprinkling.

In such an operation measurement should be designed to cover the main sources of employee exposure and typical operating regime.

How dust measurement is prepared

Before measurement it is necessary to find out what materials are processed, how dust arises, and how employees are exposed to dust. Without this information measurement may be formal but may not answer the operator's or regional public health authority's actual question.

Before measurement it is advisable to prepare:

1. description of technology and work activities,
2. list of processed materials,
3. safety data sheets or technical data sheets of materials,
4. information on work shifts and exposure time,
5. description of extraction, ventilation, or sprinkling,
6. data on respirators and other PPE used,
7. existing job categorisation, if any,
8. requirement of the regional public health authority, if issued.

For well-prepared measurement it is clear whether total dust, respirable fraction, crystalline SiO₂ content, or a combination of these indicators will be assessed.

Most common mistakes when assessing dustiness

Dustiness is often underestimated because it is perceived as an ordinary accompaniment of production or construction activity. Problems arise especially where mineral materials are worked with long-term and fine dust arises every day.

Common mistakes:

• only visible dust is assessed,
• only total dust is measured even when respirable fraction is relevant,
• crystalline SiO₂ content is not addressed,
• measurement takes place outside typical operation,
• actual working time is not taken into account,
• differences between work positions are not reflected,
• reliance is placed only on a respirator without verifying exposure,
• effectiveness of local extraction or sprinkling is not verified.

Particular caution is needed for activities where material with possible quartz content is cut, ground, drilled, or crushed. There the difference between visible mess and actual health load can be very significant.

How measurement can help the operator

Dust measurement is not just documentation for the authority. Well-carried-out measurement helps determine whether measures in operation are sufficient and whether it makes sense to adjust technology, ventilation, extraction, or organisation of work.

Results can be used, for example, for:

• job categorisation,
• documentation of regional public health authority requirement,
• assessment of extraction effectiveness,
• comparison of operating regimes,
• proposal of technical measures,
• verification of exposure with new technology,
• internal check of work environment,
• setting use of personal protective equipment.

In practice it is often not just a matter of "measuring dust", but of correctly deciding what exactly should be measured and why.

Summary

Workplace dust must be assessed according to its quantity, particle size, and composition. Total dust provides important information on inhalable dustiness, but for many operations it is not enough. When working with concrete, stone, ceramics, bricks, Ytong, building materials, or recycled materials, respirable fraction and content of crystalline silicon dioxide may be essential.

Visual estimation of dustiness is not a sufficient basis for professional assessment. What is most visible may not be the most risky. Conversely, fine respirable fraction may be less noticeable but significant from the perspective of employee health protection.

Send us a description of operation, processed materials, safety or technical data sheets, a regional public health authority requirement, or existing job categorisation. We will propose a suitable scope of dust measurement, respirable fraction, and possibly crystalline silicon dioxide as documentation for assessment of the work environment.

Factual basis of the article

The article is based mainly on these regulations and professional sources:

• Government Regulation No. 361/2007 Coll., setting conditions for health protection at work,
• Decree No. 432/2003 Coll., on job categorisation,
• terminology of workplace air used in the field of dust exposure measurement, especially distinction between inhalable and respirable fraction,
• common professional practice in measurement of dustiness, respirable fraction, and crystalline SiO₂ in the work environment.

Government Regulation No. 361/2007 Coll. distinguishes permissible exposure limit for total dust concentration, designated as PELc, and permissible exposure limit for respirable fraction of dust, designated as PELr. For dust with a fibrogenic component the respirable fraction and concentration of the fibrogenic component are assessed. Decree No. 432/2003 Coll. sets criteria for classifying jobs into categories, including assessment of dust exposure in relation to PEL values.