Silica dust starts at the grinder

The hazard

Concrete is made from sand, gravel, and cement, and those aggregates carry crystalline silica. Cured concrete holds it. Cutting, grinding, chipping, drilling, or dry sweeping a cured panel breaks that silica into particles small enough to travel deep into a lung and stay there.

The particles that do the damage are not the ones you can see hanging in a sunbeam. They are far smaller than that. A bay can look clear and still be over the limit.

What they cause is silicosis, which scars lung tissue permanently and does not reverse. Exposure is also linked to lung cancer, chronic obstructive pulmonary disease, and kidney disease. None of it shows up the day of the exposure. It shows up years later, which is exactly why it is easy to skip the control today.

Which standard covers us

A precast plant is general industry, so the standard that applies here is the general industry silica standard, 29 CFR 1910.1053. The same work done on a construction site falls under 1926.1153 instead, and that one carries a table of specified control methods by tool and task. The general industry standard does not have that table. It relies on an exposure assessment for the tasks in this plant, which is why our own written exposure control plan is the document that tells you what to do on each job.

If you have never read that plan, that is worth fixing this week. It names the tasks, the controls, and who is in medical surveillance.

The controls, in order

Engineering controls come first because they take the dust out of the air instead of filtering it at your face.

Water at the point of cut. A wet saw or a water-fed grinder keeps most of the dust out of the air, and it needs enough water to stay wet through the cut rather than a trickle that dries out halfway.

On-tool local exhaust. A shroud on the grinder connected to a vacuum rated for this work, with the filter maintained. A shroud with a full vacuum bag is not a control.

Work practice. Do the cutting where the plant wants it done, keep other people out of the area while it runs, and clean up as you go so the dust does not get re-entrained by the next person walking through it.

Respirators come last, and only under the written program: medical evaluation, fit test, training, and the right cartridge or filter. A respirator that has not been fit tested to the person wearing it is not protecting them.

Cleanup

This is the part crews get wrong most often. Do not dry sweep concrete dust and do not blow it off with an air hose. The silica standard restricts both where they add to exposure and a safer method is available, and in this plant a HEPA vacuum or wetting the surface is available. All the air hose does is put a settled hazard back into the breathing zone.

Medical surveillance

If our exposure assessment puts you in surveillance, the exam is not optional paperwork and it is not a judgement on you. Early lung changes are found on a chest image long before a person feels anything. Keeping the appointment is the only way anybody finds out early.