Sheet 17Domain 3 of 5 · Health Hazards and Basic Industrial Hygiene
Lifting, vibration and noise exposure in STSC Domain 3
Construction noise is limited to 90 dBA averaged over an 8-hour shift under 29 CFR 1926.52, the federal construction standard, and the allowed time halves for every 5 dB above that. Ergonomics has no construction standard at all, so the cards on this sheet about lifting, posture and vibration turn on judgment about what each task does to the body.
Construction noise: sound level against allowed hours
Allowed daily duration by sound level under 29 CFR 1926.52, Table D-2. Impact noise has its own ceiling of 140 dB peak.scroll →Talking point 02
Practice: lifting, vibration and hearing
Cement bags, block, breakers, rebar, tile and drywall: most cards start from a trade task you would recognize.
Card 1 of 16 · 0 right
Card 1
A crew hand-carries 94-lb bags of portland cement from a pallet on the ground to a mixer all morning. Which ergonomic risk factor should the supervisor treat as the PRIMARY concern?
Pick an answer. A short note for each option, A to D, appears here.
AWorkers carrying bags are not holding the running mixer, so hand-arm vibration is not a major exposure here.
BGripping the bag corners adds some hand strain, but it is minor next to repeated heavy lifts from the ground.
CBag edges can press on the forearms, but this contact stress is secondary to the load on the back.
DCorrect: Repeated 94-lb lifts from floor level with a bent back combine high force with poor posture, the main back-injury risk.
Card 2
A crew is exposed to 100 dBA from a jackhammer. Using OSHA's Appendix B method, how should the supervisor apply the earplugs' labeled NRR to estimate the protected level?
Pick an answer. A short note for each option, A to D, appears here.
AThe NRR is a reduction, not an exposure level, so it cannot be compared directly with the 90 dBA limit.
BCorrect: Because the NRR comes from C-weighted lab testing, Appendix B subtracts 7 dB before applying it to a dBA reading.
CAdding 7 to the NRR reverses the correction and overstates the protection the earplugs give.
DSubtracting the full labeled NRR skips the C-to-A weighting correction and overstates real protection.
Card 3
Masons repeatedly pick up concrete block stacked directly on the ground. Which intervention BEST reduces their risk of back injury?
Pick an answer. A short note for each option, A to D, appears here.
ACorrect: Raising the block to about waist height removes the bend-over lift, an engineering fix that lowers back load on every lift.
BLifting-technique training is administrative and does not change the low starting point that drives the back strain.
CStretching programs have little evidence of preventing back injury and leave the floor-level lifting unchanged.
DBack belts have not been shown to prevent back injuries and may give workers false confidence.
Card 4
Which of the following would be considered an administrative control for reducing noise exposure?
Pick an answer. A short note for each option, A to D, appears here.
AChoosing quieter equipment reduces noise at the source, which is a substitution or engineering control.
BSound-absorbing materials change the work environment to lower noise, so they are an engineering control.
CEarplugs and earmuffs are personal protective equipment, the last line of the hierarchy.
DCorrect: Job rotation limits how long each worker spends in noise by changing work practices, which is an administrative control.
Card 5
A crew breaks concrete with pneumatic breakers on winter mornings. Which work practice BEST reduces their risk of hand-arm vibration syndrome?
Pick an answer. A short note for each option, A to D, appears here.
APushing hard on the handles increases the vibration transmitted into the hands and arms.
BLong uninterrupted exposures are worse than shorter periods with regular breaks spread through the shift.
CA firm grip transmits more vibration, and thick padded gloves give little real protection.
DCorrect: Cold and a tight grip both increase vibration injury, so warm, dry hands and a light, secure grip reduce the risk.
Card 6
Two workers on a demolition crew report hand symptoms after months of jackhammer use. Which control should the supervisor pursue FIRST under the hierarchy of controls?
Pick an answer. A short note for each option, A to D, appears here.
ACorrect: Low-vibration tools reduce the hazard at the source, an engineering control that ranks above administrative steps and PPE.
BSymptom reporting helps catch cases early, but it does not reduce the vibration reaching the hands.
CCapping trigger time is an administrative control, ranked below changing the tool itself.
DAnti-vibration gloves are PPE, the last resort, and often do little against the low-frequency vibration of breakers.
Card 7
Ironworkers tying rebar on a bridge deck spend hours bent at the waist. Which control BEST addresses the main ergonomic risk?
Pick an answer. A short note for each option, A to D, appears here.
ABack belts do not reduce the load of prolonged stooping and have not been shown to prevent injury.
BStretching does not change the bent-over posture held for hours while tying.
CKneeling trades back strain for knee strain and contact stress, moving the hazard rather than removing it.
DCorrect: Extension-handled tying tools let workers stand upright, which eliminates the prolonged stooped posture at the source.
Card 8
An excavator operator on a rough, rutted site reports low-back pain at the end of each day. Which ergonomic factor is the MOST likely contributor?
Pick an answer. A short note for each option, A to D, appears here.
AResting forearms on padded armrests causes little contact stress and does not explain low-back pain.
BTwisting to watch the bucket strains the neck, but it is not the main cause of low-back pain.
CCorrect: Rough ground sends whole-body vibration and jolts through the seat into the spine, a known cause of low-back pain in operators.
DHand-arm vibration from the controls affects the hands and arms, not the lower back.
Card 9
A long-time concrete chipper says the fingertips turn white and numb on cold mornings after using a chipping hammer. What should the supervisor do?
Pick an answer. A short note for each option, A to D, appears here.
AWarm gloves may ease symptoms, but keeping the same exposure lets hand-arm vibration syndrome progress.
BCorrect: White fingers in the cold suggest vibration white finger, so the worker needs a medical evaluation and the tool exposure must be reduced.
CLonger breaks alone do not address a possible occupational illness, and recordability depends on the medical findings.
DWaiting for warm weather allows nerve and blood vessel damage to keep developing.
Card 10
A tile setter routinely strikes tiles with the heel of the hand to seat them. Which ergonomic risk factor does this practice MAINLY create?
Pick an answer. A short note for each option, A to D, appears here.
AStatic loading comes from holding a posture or grip for long periods, not from repeated striking.
BLong reaches can bend the wrist, but the main problem here is the repeated blow to the palm.
CHand-arm vibration comes from powered tools, not from striking with the hand.
DCorrect: Using the hand as a hammer concentrates force on the palm, causing contact stress that can injure nerves and blood vessels.
Card 11
A rebar fabrication crew stands in one spot on a concrete slab all shift at a bending table. Which control BEST reduces the strain from this static standing?
Pick an answer. A short note for each option, A to D, appears here.
AStretching once before the shift does not relieve hours of standing on concrete.
BCorrect: Anti-fatigue mats and a foot rail or sit-stand stool allow posture changes and reduce leg and back fatigue from standing.
CStiffer soles transmit more of the hard slab's impact; cushioned footwear helps more.
DA longer lunch does not change the standing demands for the rest of the shift.
Card 12
A drywall finisher reports numbness and tingling in the thumb, index and middle fingers that is often worse at night. Which condition do these symptoms MOST suggest?
Pick an answer. A short note for each option, A to D, appears here.
ACorrect: Numbness in the thumb, index and middle fingers that worsens at night follows the median nerve, the pattern of carpal tunnel syndrome.
BHand-arm vibration syndrome is tied to powered tools and often shows finger blanching rather than this nerve pattern.
CTrigger finger makes a finger catch or lock when it bends; it does not cause numbness and tingling.
DLateral epicondylitis, or tennis elbow, causes pain at the outer elbow, not numbness in the fingers.
Card 13
A NIOSH lifting-equation analysis of a block-handling task gives a Recommended Weight Limit (RWL) of 25 lb, and the blocks weigh 38 lb. How should the supervisor interpret the result?
Pick an answer. A short note for each option, A to D, appears here.
ADividing the RWL by the load inverts the ratio; the Lifting Index is the load divided by the RWL.
BCorrect: The Lifting Index is load divided by RWL, about 1.5 here, and any value above 1.0 signals increased risk and a need to redesign the task.
CThe index is a ratio, not the pound difference between the load and the recommended limit.
DFifty-one pounds is the equation's load constant for ideal conditions, not a safe limit, and an index above 1.0 is not acceptable.
Card 14
During a site walk-through, which observation is the STRONGEST early warning sign of an ergonomic problem with a task?
Pick an answer. A short note for each option, A to D, appears here.
AGroup stretching is a planned activity and says nothing about whether a task is causing strain.
BMore cuts from sheet metal point to sharp-edge hazards, not musculoskeletal strain.
CRequests for other glove sizes concern fit and cut protection, not ergonomic stress.
DCorrect: Improvised padding shows workers reacting to pressure, pain or awkward work, an early sign of an ergonomic problem.
Card 15
Which combination of task features presents the HIGHEST risk of work-related musculoskeletal disorders?
Pick an answer. A short note for each option, A to D, appears here.
ACorrect: Force, repetition and awkward posture together raise the risk far more than any single factor alone.
BOccasional lifts with a mechanical assist reduce both how often and how hard workers exert.
CLight loads with straight wrists keep force and posture risk low even when handled often.
DBrief standing on a cushioned mat is a low-risk condition.
Card 16
Which hand-tool design principle does the MOST to reduce wrist injury risk?
Pick an answer. A short note for each option, A to D, appears here.
ACorrect: A tool bent to fit the task lets the wrist stay neutral, which reduces strain on tendons and nerves.
BHandles that end in the middle of the palm press into it and create contact stress over the nerve.
CVery thin handles demand more grip force; a moderate diameter spreads the load better.
DDeep finger grooves fit only some hands and create pressure points for others.
Talking point 03
Ergonomic risk factors, by name
Force
How hard the muscles work: a heavy load, a stiff trigger, a pump hose dragged against resistance.
Repetition
The same motion again and again with little recovery, such as driving screws through metal decking all shift.
Awkward posture
Joints held away from neutral: drilling overhead into a ceiling, kneeling to set floor drains, twisting to throw material into a dumpster.
Contact stress
A hard or sharp edge pressing into soft tissue, such as knees on rebar mats or a narrow bucket handle across the fingers.
Hand-arm vibration
Vibration that enters through the hands from grinders, breakers or compactor handles. Years of it can damage the nerves and blood vessels of the fingers.
Talking point 04
Judgment where the rules give no number
OSHA has no ergonomics standard for construction and handles serious cases under the General Duty Clause. Choosing among fixes is a job for the hierarchy of controls.
Ask what the job makes the body do, then how often and for how long. The weights, hours and days in a scene tell you which risk factor you are looking at.
On noise, the 85 dBA figure that tends to sit next to 90 belongs to general industry; the construction noise limits sheet traces each figure to its rule.
Heat adds to physical strain too: a crew working hard on a hot deck tires sooner and handles loads less surely. The heat and cold stress sheet covers that side, and if you would rather take this topic in a mixed set, open the practice test.
Talking point 05
Noise limits on longer and louder days
Does the 90 dBA limit stretch to cover a 10-hour shift?
No. Table D-2 in 29 CFR 1926.52 allows 90 dBA for 8 hours a day, so ten hours at that level is over the limit and the crew needs controls or hearing protection for the extra time.
Is impact noise from nail guns or pile driving limited separately?
Yes. 29 CFR 1926.52(e) says exposure to impulsive or impact noise should not exceed 140 dB peak sound pressure level, on top of the 8-hour average.