Silica, Asbestos, Lead, Heavy Metals, and Dust Controls

Silica, Asbestos, Lead, Heavy Metals, and Dust Controls

Recognition in construction work

Respirable crystalline silica, asbestos fibers, lead, cadmium, hexavalent chromium, arsenic, and nuisance dusts are released by ordinary construction methods. A Construction Health and Safety Technician (CHST) thinks in terms of task, material, energy, and duration. Cutting concrete, drilling masonry, jackhammering, tuckpointing, abrasive blasting, sweeping settled dust, torch-cutting painted steel, demolishing pipe insulation, removing floor tile, and grinding coatings all create exposures that a brief job walk will miss.

Do not rely on appearance. Asbestos-containing material (ACM) can look like normal insulation, mastic, roofing, transite cement board, or floor products. Lead and metals hide in bridge paint, tank and marine coatings, solder, and primers. Silica is expected in concrete, mortar, brick, block, stone, tile, and sand.

Exact regulatory thresholds (memorize these)

The exam tests numbers, not vibes. Know these cold:

Lead has two more triggers worth memorizing: medical surveillance is required for workers above the 30 ug/m3 action level more than 30 days per year, blood-lead testing follows, and an employee removed for a blood lead level (BLL) at or above 50 ug/dL may return only when the BLL is at or below 40 ug/dL. Asbestos has no action level because the analytical method is unreliable below 0.1 f/cc.

Control sequence and the silica Table 1 shortcut

The strongest controls keep dust out of the air: wet methods, local exhaust ventilation (LEV), shrouded tools tied to a HEPA vacuum, enclosed cabs, isolation, negative-pressure containment, and substitution. Housekeeping matters because dried slurry becomes airborne later, so use HEPA vacuuming or wet cleanup. Dry sweeping and compressed-air blowdown are prohibited under the silica rule where they expose employees and a feasible alternative exists.

The silica standard, 29 CFR 1926.1153, gives a practical shortcut. Table 1 lists eighteen common tasks (e.g., handheld masonry saws, jackhammers, handheld grinders, walk-behind saws, drivable saws, rig-mounted drills). If the employer fully implements the engineering control, work practice, and respiratory protection specified for that task, it is not required to perform exposure monitoring or comply with the PEL for that task. If the task is not on Table 1, or the controls are not fully met, the employer must use the alternative exposure control method: assess exposure and keep it at or below the 50 ug/m3 PEL.

A worked example: a worker uses a handheld masonry saw with integrated water and runs it more than four hours per shift. Table 1 then requires at least a NIOSH-approved APF 10 respirator (a filtering facepiece or half mask); under four hours, no respirator is specified if water is used.

Worked example for lead: torch-cutting painted structural steel of unknown vintage. Treat the coating as lead-bearing until a coating survey or paint chip analysis says otherwise, perform an initial exposure determination, and provide change areas, hygiene facilities, and blood-lead surveillance if exposure can reach the action level.

Monitoring, documentation, and escalation

Exposure assessment links recognition to proof. Records should show the material disturbed, the task, the controls used, who was exposed, how long, and whether data was representative. Useful documents: bulk sample reports, safety data sheets (SDS), coating surveys, historical objective data, air sampling results, competent-person inspections, and respirator assignments. A CHST need not run every sample but must recognize triggers for monitoring: new tasks, changed tools, visible uncontrolled dust, worker complaints, no objective data, regulated materials, or conditions that differ from the written exposure control plan.

Escalate when suspect asbestos is disturbed, lead or metal coatings are heated or blasted without assessment, dust controls are missing, respirators are used without a written program, or cleanup spreads contamination. Route the issue to the competent person, site safety manager, certified industrial hygienist (CIH), environmental consultant, or owner. The goal is a defensible control decision before exposure becomes an injury, citation, or contamination event.

Common exam traps and field reasoning

The CHST exam frequently disguises these hazards in scenario questions, and several traps recur. First, candidates assume a dust mask or filtering facepiece satisfies the silica rule; it does not, because Table 1 specifies respirators only for certain tasks and durations, and a voluntary mask never replaces engineering controls or the written exposure control plan. Second, candidates treat a short task as automatically safe; duration matters, but a four-hour cutoff in Table 1 changes the required respirator, so the answer is task-specific, not just "it was quick." Third, candidates confuse general industry and construction standards: lead, silica, and asbestos each have a dedicated construction standard in Subpart of 1926, distinct from the 1910 versions, and the exam rewards knowing the 1926 citation.

A disciplined field reasoning sequence keeps answers correct. Identify the regulated material and its construction standard, determine whether the planned task appears on a prescribed-control list such as silica Table 1, verify the listed controls (water flow, HEPA vacuum filtration efficiency of 99.97% at 0.3 micrometers, enclosure integrity) are actually present, decide whether exposure assessment or objective data is still required, and confirm housekeeping uses HEPA or wet methods rather than dry sweeping.

Where any link in that chain is missing or uncertain, the defensible answer is to pause the task and obtain monitoring, objective data, or qualified review rather than to proceed and document later. This recognition-evaluation-control-escalation discipline is exactly what the certification is testing for a construction health technician.