“Unnecessary noise is the most cruel absence of care that can be inflicted on the sick or the well.” — Florence Nightingale
I grew up in an age of loud rock ‘n roll. I, like one in six people of my generation, suffer some hearing loss. To save the hearing that I still have, I wear ear plugs whenever I do something in a loud environment like mowing the yard, using a chainsaw, or going to a rock ‘n roll performance. They’re cheap and easy to use, not particularly uncomfortable, and even at clubs, people don’t give me a hard time about it.
I like being able to hear. So, I voluntarily wear earplugs.
Hearing Protection
OSHA’s requirements for occupational noise include adequate hearing protection “sufficient to reduce employee exposure to a time-weighted average of 85 dB.” With an exposure of up to 120 dB for no more than 4 hours in a day (for me, usually a Saturday), my earplugs, with a noise reduction rating—an NRR—of 30 dB provide adequate hearing protection. That is, assuming that I’ve worn them correctly. Because I take care to completely insert the earplug into my ears, I can count on them working every time I use them.
That’s not something we can generally say about PPE.
Risk Reduction from Earplugs
Most LOPA procedures allow credit for PPE as an independent layer of protection. Generally, PPE is treated as a specific form of administrative control, with an average probability of failure on demand (PFDavg) of 0.1 and therefore, a risk reduction factor (RRF) of 10. That means that we can expect earplugs to fail to provide the protection we are expecting about one time out of ten. Why? As is the case with all PPE, there is often resistance to wearing earplugs, or wearing them properly.
How much risk reduction do we need? Noise hazards can result in hearing loss — a permanent disabling injury. Most organizations have risk tolerance criteria that consider a permanent disabling injury as one of the most severe categories of consequence. It is typical for a risk assessment of a hazard that causes a permanent disabling injury on an annual basis to require three or more orders of magnitude, or levels, of risk reduction.
Earplugs only provide one order of magnitude, or level, of risk reduction.
When the exposure is constant, earplugs are not enough.
The Hierarchy of Controls
The National Institute for Occupational Safety and Health (NIOSH), which is not part of OSHA, has addressed the issue of occupational noise by using the familiar concept of the hierarchy of controls.
At the top is elimination—removing the source of the noise. The PFDavg of elimination is zero.
If that cannot be done, then we consider substitution—replacing the source of noise with something that is quieter. Substitution does not reduce the likelihood of exposure, but it does reduce the consequence severity. The PFDavg could be as low as zero, but it might be more.
Then there are engineering controls—putting a sound barrier between the worker and the source of noise. Depending on the engineering control and the care with which it is designed, installed, operated, and maintained, the PFDavg could be as low as 0.001 to as much as 0.1. NIOSH suggests three approaches:
- Isolating the noise source in an insulated room or enclosure
- Placing the barrier between the noise source and the worker
- Isolating the worker from the noise source in a room or booth
Lower on the hierarchy are administrative controls—all of which reduce the amount of time that a worker is exposed to noise sources. The PFDavg of an administrative control is typically taken to be 0.1, although a well-designed administrative control might provide a PFDavg as low as 0.01. Again, NIOSH suggest three approaches:
- Scheduling loud work when fewer workers are around
- Giving workers shifts doing quieter tasks and breaks from loud work
- Providing quiet and convenient break areas.
At the very bottom of the hierarchy of controls, the risk reduction measure of last resort, is PPE—earplugs and earmuffs. The best PFDavg we can plan for from PPE is 0.1.
Risk Reduction, Not Just Noise Reduction
Noisy work environments are a hazard with an intolerably high risk. They can, and do, result in hearing loss, a permanent disabling injury. PPE for hearing protection, such as earplugs and earmuffs, can reduce the noise exposure to acceptable levels, but by themselves cannot reduce the risk to tolerable levels. A hearing conservation program that relies exclusively on earplugs for hearing protection can be in compliance with the requirements of OSHA’s Occupational Noise Exposure standard, 29 CFR 1910.95, but not be in compliance with your own Risk Tolerance Criteria.
Still, earplugs are better than nothing.
It may be time to reconsider your approach to hearing protection, not just from the perspective of noise reduction, but from the perspective of risk reduction.
