Noise, Vibration, Radiation, and Impact Exposure Control

Noise, Vibration, Radiation, and Impact Exposure Control

Recognizing nonchemical exposures

Construction injures through energy as well as dust. Noise damages hearing, hand-arm vibration (HAV) contributes to vascular and nerve disorders such as hand-arm vibration syndrome (HAVS), whole-body vibration (WBV) aggravates the spine, ionizing and non-ionizing radiation injure tissue, and impact energy damages eyes, hands, and joints. High-noise tasks include pile driving, concrete chipping, powder-actuated tools, saw cutting, demolition, pneumatic tools, compressors, and earthmoving equipment. Vibration sources include breakers, grinders, rivet busters, rotary hammers, and mobile equipment.

The construction noise standard and the 5-dB exchange rate

The exam expects exact numbers. Under 29 CFR 1926.52 the construction noise PEL is 90 dBA as an 8-hour time-weighted average (TWA), measured on the A-scale, slow response. Construction uses a 5-dB exchange rate, meaning the allowable duration halves for every 5-dB increase. This is different from the 3-dB rate some other systems use, and it is a classic trap.

Note the trap: unlike general industry (29 CFR 1910.95), the construction standard does not have its own 85 dBA hearing-conservation action level written into 1926.52, although OSHA expects a continuing, effective hearing conservation program once the 90 dBA PEL is exceeded. A sound level meter (SLM) screens loud areas and tasks; a personal noise dosimeter worn during representative work is the better tool for full-shift dose because it accounts for changing tasks, distance, and duration.

Controls beat plugs: buy quieter equipment, maintain mufflers and bearings, use acoustic blankets, enclose generators, increase distance, schedule noisy work for off-hours, and reduce reverberation. Hearing protectors must be fitted and worn correctly; a common field failure is issuing earplugs no one inserts properly or that block needed communication.

Vibration and impact controls

Vibration control is part equipment selection, part work design: lower-vibration tools, sharp bits, damped accessories, preventive maintenance, and task rotation. Keep hands warm and dry because cold worsens HAVS circulation problems. Anti-vibration gloves have limited, task-dependent value and may reduce grip; they do not replace source reduction. For mobile equipment, maintain seats, suspension, tires, tracks, and haul roads to cut WBV. Impact control keeps energy contained: guards, deflectors, tool rests, face shields, ANSI Z87.1 safety glasses with side shields, screens, barricades, exclusion zones, and line-of-fire planning. Treat repeated impact to knees, wrists, and shoulders as an ergonomic exposure, not only an acute hazard.

Radiation field control: time, distance, shielding

Radiation work demands source-specific competence and follows the classic triad of time, distance, and shielding. Because dose from a point source falls with the inverse-square law, doubling distance cuts intensity to one-quarter, a powerful and cheap control. Lasers need class recognition (Class 3B and 4 are the dangerous ranges), controlled beam paths, warning signs, and proper eyewear. Welding arcs require correct shade selection and screens to control reflected ultraviolet exposure to bystanders. Nuclear density gauges, radiography sources, and thickness gauges are regulated radioactive sources requiring trained, licensed operators, secured storage and transport, restricted areas, survey instruments, dosimetry where required, and immediate reporting of a lost, damaged, or uncontrolled source. A CHST should never improvise radiation controls; if dose rate, boundary, or licensing is unclear, escalate to the radiation safety officer (RSO) or qualified operator.

Documentation and escalation

Document noise surveys, dosimetry, equipment substitutions, hearing-protector selection, audiometric referrals, radiation permits, laser classifications, and gauge logs. Escalate when workers report ringing ears, a temporary threshold shift, numbness or white fingers, burns, eye pain after arc exposure, a suspected damaged source, an uncontrolled laser path, or repeated impact injuries. These signs mean exposure is no longer theoretical and needs competent review.

Hearing protector ratings and field reality

Hearing protectors carry a Noise Reduction Rating (NRR) in decibels, set by the manufacturer under laboratory conditions. The exam expects candidates to know that real-world attenuation falls far short of the label. OSHA's common derating method subtracts 7 from the NRR, then takes 50% of the remainder for estimating field protection under a C-weighted measurement, and many hygienists apply a flat 50% derate for A-weighted noise. So a plug labeled NRR 29 may deliver only about 11 dB of useful protection in practice. The control lesson: do not chase a high NRR while ignoring fit, training, and engineering controls. Dual hearing protection (plugs plus muffs) does not add the two NRR values; it adds only about 5 dB above the higher-rated device. This is a frequent distractor on the test.

Worked scenario: pile-driving exposure

Consider a worker positioned near a diesel pile-driver measured at 100 dBA. Using the 90 dBA / 8-hour PEL and the 5-dB exchange rate, the permissible duration is 2 hours. If the foreman wants the worker there for the full 8-hour shift, the exposure is four times the allowable dose, so administrative controls (rotation out after 2 hours), distance (move support crew back, applying the inverse-square logic of energy falling with distance), and barriers must close the gap before hearing protection is even credited. The defensible CHST answer is engineering and administrative reduction first, dosimetry to confirm, then properly fitted protection - never plugs alone as the primary control. The same energy-source reasoning - reduce time, increase distance, add shielding or barriers - applies whether the energy is sound, vibration, or radiation, which is why the exam groups them together.