What dust does grinding the floor make?

The material the machine meets

Concrete is a crystalline silica substance, and the rule that matters comes from a definition rather than a product. Safe Work Australia’s silica pages state that people conducting a business have specific duties when they work with any material containing 1 per cent or more crystalline silica, and the model Code of Practice gives that material its legal name: a crystalline silica substance is a material with at least 1 per cent crystalline silica in it, measured by weight. Safe Work Australia names concrete among the common crystalline silica substances.

Where the silica sits in concrete is well documented. Safe Work Australia records that sand, stone, concrete and mortar all carry crystalline silica, and that it also goes into products from benchtops to bricks and tiles. SafeWork NSW lists most rocks, sand and clay as sources, and concrete among the manufactured products that carry it. That figure is an example, not a specification: WorkSafe WA’s table of indicative levels puts concrete at less than 30 per cent crystalline silica, beside granite at 25 to 60 per cent and marble at 2 per cent.

What the machine does

The agencies write the trade down in the same verbs. Safe Work Australia’s page on the exposure standard gathers the acts into one sentence: the dust is produced by mechanical processes at work, and the list runs from crushing through cutting, drilling and grinding to sawing and polishing, on natural stone or on manufactured products holding silica. The particles can penetrate deep into the lungs and can cause irreversible lung damage. NT WorkSafe’s page names the same acts and adds the detail a floor makes vivid: some particles can be too small to see, and these are commonly called respirable particles.

Workplace Health and Safety Queensland’s ban page describes the acts at bench scale, and its sentence is about material with silica in it rather than any one product: cutting, polishing, grinding, sanding and trimming release very fine particles, the ones the rules call respirable crystalline silica. NT WorkSafe has the fuller version for anyone who wants the physical path: the particles these processes generate are small enough to reach deep into the lungs, and they can cause illness or disease.

None of these sentences is an instruction for how to grind a floor. They are the reason the law treats the pass as processing, and the duty attached to processing is written on the business. Under the model Code of Practice, processing a crystalline silica substance must be controlled, and no business may carry out, direct or allow it otherwise.

Three numbers on one slab

One per cent is the threshold for the specific silica duties. From 1 September 2024, Safe Work Australia says, amendments to the model WHS Regulations provide for stronger regulation of work with all materials containing at least 1 per cent crystalline silica, including permitted work with engineered stone, across all industries.

Less than 30 per cent is what WorkSafe WA’s examples give for concrete, in a table the page presents as an indication of the levels different products carry rather than a measurement of any particular slab. A second state page gives a different kind of figure to the same reader: SafeWork NSW says construction materials such as sandstone, concrete and bricks can contain up to 90 per cent silica dust. The two are not measuring the same thing, and each figure stands with its own source rather than blended.

0.05 mg/m³ is the number the air is held to. Safe Work Australia’s workplace exposure standard for respirable crystalline silica is 0.05 mg/m³ as an eight-hour time weighted average, and the page is unambiguous that it must not be exceeded. Safe Work Australia defines the standard as the level in a worker’s breathing zone that ought not to cause adverse health effects or undue harm. The model Code of Practice makes the same figure a duty: exposure to RCS at a workplace is not to go above 0.05 mg/m³ averaged over eight hours. From 1 December 2026, the model Code of Practice says, workplace exposure standards will be known as workplace exposure limits, and a PCBU will have to make sure nobody at the workplace is exposed above the limit.

The dust you can see, and the dust you cannot

Two regulators describe the same scene from opposite ends. Safe Work Australia says the particles are so small you cannot see them, and that they can stay in the air for a long time. WorkSafe WA says the very fine particles can be hard to see in the air, and that assessing the risk they carry calls for monitoring.

The same state page then allows for the times when the air is not quiet. Where the air is visibly clouding with dust off high-silica material, it gives dry concrete cutting as its own example, the risk can be clear without monitoring. The two sentences are not in conflict: one says a visible cloud is already an answer, and the other says an invisible one is the reason the rules do not rely on looking. NT WorkSafe closes the loop with the health half: particles small enough to reach deep into the lungs can cause irreversible damage there.

What the engineered stone ban is about

One distinction belongs in a floor guide, because it is asked so often. The ban that applies in all Australian jurisdictions covers the manufacture, supply, processing and installation of engineered stone benchtops, panels and slabs, and it applies to those products only. A cast concrete floor is none of those three things. It is a crystalline silica substance by the same body’s definition, and it falls under the crystalline silica substance rules rather than the engineered stone prohibition.

What the agencies say about exposure

This is general information from the regulators, not medical advice. NT WorkSafe sets out what a worker exposed to and breathing in silica dust could develop: acute silicosis, after a short exposure to very high levels, within weeks or years, with severe inflammation and protein pouring into the lung; accelerated silicosis, after 3 to 10 years of moderate to high exposure, with inflammation, protein in the lung and scarring; and chronic silicosis, after long-term exposure to lower levels, bringing fibrotic nodules and shortness of breath.

Safe Work Australia adds the two facts that shape everything else: ongoing exposure can lead to grave illness, lasting disability and death, from diseases that include silicosis and lung cancer, and the symptoms can take many years to appear, and can keep progressing even after exposure stops. Its health pages carry the counterpart: all silica-related diseases are preventable by using controls that eliminate or effectively minimise exposure. For a reader with a health worry, the pages that answer it are the regulators’ own, and they are linked at the foot of this page.

Where this goes next

Under the model Code of Practice, the duty to keep the processing controlled is written on the business, and the guide that follows that duty through a house is the house guide. If the covering above the slab may still be there when the work begins, the asbestos side starts at what is under the old floor.