Using an alternative saw blade designed to reduce noise can help lower the risk of hearing loss.
Hazard Analysis — Noise
Problem:
Workers who cut boards and panels may be exposed to noise.
Risk Description:
Noise-induced hearing loss (NIHL). A worker who is repeatedly exposed to noise at 85 decibels or above without hearing protection is at risk for serious hearing loss. Noise-induced hearing loss is 100 percent preventable but once acquired, hearing loss is permanent and irreversible.
Hearing loss is a gradual and irreversible process; without regular testing, few workers will realize that they are losing their hearing until it is too late. Therefore, prevention measures must be taken by employers and workers to ensure the protection of workers' hearing since working near noisy equipment may be enough to damage hearing.
How do we hear?
Hearing is a series of events in which the ear converts sound waves into electrical signals that are sent to the brain and interpreted as sound. The ear has three main parts: the outer, middle, and inner ear. Sound waves enter through the outer ear and reach the middle ear where they cause the eardrum to vibrate. The vibrations are transmitted through three tiny bones in the middle ear, called the ossicles. These three bones are named the malleus, incus, and stapes (and are also known as the hammer, anvil, and stirrup). The eardrum and ossicles amplify the vibrations and carry them to the inner ear. The stirrup transmits the amplified vibrations through the oval window and into the fluid that fills the inner ear. The vibrations move through fluid in the snail-shaped hearing part of the inner ear (cochlea) that contains the hair cells. The fluid in the cochlea moves the top portion of the hair cells, called the hair bundle, which initiates the changes that lead to the production of nerve impulses. These nerve impulses are carried to the brain, where they are interpreted as sound. Different sounds move the hair bundles in different ways, thus allowing the brain to distinguish one sound from another, such as vowels from consonants. Continuous exposure to loud noise can damage the structure of the hair cells, resulting in hearing loss and tinnitus (ringing in the ears).
NIHL can be caused by a one-time exposure to loud sound as well as by repeated exposure to sounds at various loudness levels over an extended period of time. The loudness of sound is measured in units called decibels. For example, normal conversation is approximately 60 decibels, the humming of a refrigerator is 40 decibels, and heavy city traffic noise can be 85 decibels. Examples of sources of loud noises that cause NIHL are motorcycles, firecrackers, and firearms, which emit sounds over 120 decibels. Sounds of less than 80 decibels, even after long exposure, are unlikely to cause hearing loss.
People with hearing loss often become socially isolated because they cannot communicate easily with others. They also may not be able to hear warning signals, and so may have an injury.
For more information, please see:
NIOSH Noise Topics
Noise and Hearing Damage in Construction Apprentices
Assessment Info:
To see if you may be in an environment that could cause hearing loss, ask yourself the following questions:
- Is the noise at my workplace so loud that I have to raise my voice signficantly for someone an arm's length away to hear me?
- When I leave work to a quieter environment, do my ears feel plugged?
- Or do I hear a mild ringing or whooshing noise that goes away after an hour or two?
If you answer yes to any of these questions, your workplace is too noisy.
At the NIOSH site for occupational noise exposure you can find information on assessing noise exposure at work.
Detailed information on measurement of noise exposure can be found in this NIOSH document http://www.cdc.gov/niosh/topics/noise/default.html.
For information on NIOSH noise measurements on your specific power tools, see http://wwwn.cdc.gov/niosh-sound-vibration/.
OSHA does not require hearing testing for construction workers, but construction employers are required to comply with the OSHA noise standard; the standard also contains details on noise measurement. OSHA Noise page. Consensus standards applicable to noise in the construction industry can be purchased from the American National Standards Institute (ANSI).
Regulations & Standards:
OSHA standard 1926.52 sets the permissible noise exposure at 90 dBA for an 8 hour day in construction. As the noise level increases, the permissible exposure time decreases:
TABLE D-2 - PERMISSIBLE NOISE EXPOSURES
| Duration per day (hours) | Sound level (dBA slow response) |
|---|---|
| 8 | 90 |
| 6 | 92 |
| 4 | 95 |
| 3 | 97 |
| 2 | 100 |
| 1 1/2 | 102 |
| 1 | 105 |
| 1/2 | 110 |
| 1/4 or less | 115 |
The standard does not require audiometry. OSHA has issued a notice of proposed rule making which would update the standard to include a hearing conservation program, as is required for general industry, but a revised standard has not yet been issued. Details on the standard and the proposed revision can be found here http://www.osha.gov/SLTC/noisehearingconservation/index.html
Both ACGIH and NIOSH consider 8 hr exposures to noise at 85dBA to be hazardous. At the noise levels of most power tools (100-110 dbA) the OSHA allowable exposure times are eight to ten times greater than the NIOSH hazard-based limits (http://www.cdc.gov/niosh/docs/98-126/pdfs/98-126.pdf).
Regulations adopted by a state must be at least as protective as the corresponding federal standard. Work may also be subject to rules of other federal, state and local agencies. Even where there is no hazard specific standard, OSHA provides a general duty for the employer to provide a work site free from recognized hazards.
Federal OSHA Standards are enforced by the U.S. Department of Labor in 26 states. There are currently 22 states and jurisdictions operating complete State plans (covering both the private sector and state and local government employees) and 5 - Connecticut, Illinois, New Jersey, New York and the Virgin Islands - which cover public employees only. If you are working in one of those states or jurisdictions you should ensure that you are complying with their requirements.
