Noise In the Workplace:
How Much Is Too Much?
OSHA’s
regulations for noise control (1910.95)
were introduced in 1972 and underwent a major revision in 1983.
Recently, however, there has been concern that current regulations are
insufficient to prevent hearing loss among employees.
The
National Institute for Occupational Safety and Health (NIOSH) lent
credence to this concern with the publication of “Criteria for a
Recommended Standard: Occupational Noise Exposure: Revised Criteria
1998” — a document that recommends a number of changes in OSHA’s
standard.
It
was, in fact, a NIOSH document published in 1972 — “Criteria for a
Recommended Standard: Occupational Exposure to Noise” — that
provided the basis for the agency’s earliest regulations. The 1972
standard called for employers not to allow noise levels to exceed 90 dB
TWA (time weighted average for an eight-hour day).
This
regulation prompted employers to focus largely on engineering controls
(e.g.: machine enclosures) and administrative controls (e.g.: reducing
the time employees spent in high noise areas) to achieve compliance.
The
1983 Amendment
The
1983 amendment created an “action level” of 85 dB for a TWA of eight
hours. This “action level” is the noise level at which employers
must take action to protect hearing. Noise levels above 85 dB may be
allowed when the allowable exposure time (called the “time/intensity
tradeoff”) decreases. One example of this is that a noise level of 115
dB is acceptable for up to 15 minutes per eight-hour shift.
The
amendment states that, if employees are exposed to between 85 and 90 dB
TWA, employers must implement an occupational hearing conservation
program (OHCP) for these employees. Under such a program, employers
must:
-
Survey
their workplaces at least once every two years to determine if
hazards exist and where
-
Train
employees in the areas of noise hazard awareness, hearing
protection, instructions in how to use the hearing protection, and
motivation to do so
-
Monitor
program effectiveness by testing workers’ hearing at least
once a year and making sure they are wearing appropriate hearing
protection on a regular basis
-
Record
hearing shifts (25 dB or greater average hearing loss shift in
either ear of an employee) in the OSHA log
The
amendment did nothing to change requirements for employers with noise
levels exceeding 90 dB. That is, employers were still required to use
engineering and administrative controls as their first lines of defense
if noise levels exceeded 90 dB to actually reduce levels to 90 dB or
lower.
What
the amendment focused on was the area between 85 dB and 90 dB. That is,
if noise levels were within this range, employers were encouraged to
implement engineering and administrative controls, but could instead
implement an OCHP.
Assessment
of the 1983 Amendment
Not
everyone agrees that the amendment has achieved the desired results,
however. One area of contention focuses on damage associated with
hearing loss, as identified by annual audiograms.
“The
1983 amendment played an interesting game,” says Mark Stephenson,
Ph.D., a research audiologist with NIOSH (Cincinnati, OH). “It’s
based on the assumption that, if you use the 90 dB criterion, about 20
percent of workers will experience hearing damage, while 80 percent will
not.”
The
idea behind the amendment was to find an inexpensive way to protect the
hearing of the most sensitive workers — the 20 percent. Thus was born
the OHCP, including the annual audiogram testing. “The problem is that
once you determine a person has been overexposed, that person has
already had significant damage,” says Stephenson.
Another
concern is that the amendment has allowed employers to shift their focus
from reducing noise levels via engineering controls to placing the
burden of responsibility on employees to wear hearing protection devices
properly and continuously.
Prior
to 1983, employers spent their time reducing noise levels. With the 1983
amendment, they began to focus on hearing conservation programs and
backed off on noise control activities.
However,
it wasn’t the 1983 amendment per se that shifted the emphasis
from engineering controls to the OCHP. Rather, it was an OSHA compliance
directive that same year that said:
●
If noise levels exceed 100 dB TWA, employers must implement
engineering controls if technically feasible, regardless of cost.
●
If noise levels are between 85 dB and 90 dB TWA, employers must
implement an OHCP (as outlined by the 1983 amendment).
●
If noise levels are between 90 dB and 100 dB TWA, employers
should implement engineering controls if technically and
economically feasible. Economic feasibility is defined as the cost of a
hearing conservation program for the affected employees.
NIOSH
Weighs In
While
there are numerous recommendations for revisions to OSHA’s standard in
NIOSH’s 1998 document, three are of particular interest:
1.
Noise Exposure Levels.
NIOSH recommends replacing OSHA’s current two-tiered program (85 dB
for an OHCP and 90 dB for noise controls) with a single program kicking
in at 85 dB. In other words, if a site has noise levels of 85 dB or
greater, employers must either reduce noise levels below 85 dB or
implement a mandatory hearing protection program.
2.
Exchange Rate. NIOSH recommends that the current 5 dB exchange rate
used to calculate the TWA exposures to noise be lowered to 3 dB.
(Exchange rates account for the intermittency of noise levels over the
course of a workday.)
“Most
of the world and even parts of the U.S. government use the 3 dB exchange
rate,” says Stephenson. “Granted, there is no perfect exchange rate
that will be the best method for managing all noise exposures. For
example, one exchange rate when employees are exposed to continuous
noise may be better than another rate, which may be more appropriate
when employees are exposed to intermittent noise. However, overall, we
believe that 3 dB is the best exchange rate for predicting overall
risk.”
3.
Derating. Another recommended change relates to the derating of
hearing protection. Under current OSHA regs, employers are expected to
assume a 50 percent noise reduction rating (NRR) when assessing the
adequacy of hearing protectors (muffs, plugs, etc.). In other words,
employers should assume that any given protector will actually provide
only half of its rated value in field use. For example, if a protector
is rated at 30 dB of protection, employers should assume it will only
provide 15 dB of protection.
However,
since the level of protection is believed to depend on a number of
things, including the type of protector being used, NIOSH is proposing a
variable derating process. NIOSH recommends that earmuffs will provide
75 percent protection of their labeled NRR; that formable foam earplugs
will provide 50 percent of their labeled NRR; and all other earplugs
will provide 30 percent of their labeled NRR.
Another
variable is how employees wear their protection devices. If they wear
them properly, they will obviously provide more protection than if they
wear them improperly. For this reason, NIOSH recommends that OSHA
utilize a recent ANSI standard that recommends a subject fit.
“This
is a lab method in which subjects fit hearing protectors themselves,
instead of having the experimenter fit the devices,” explains
Stephenson. “In fact, some manufacturers are already switching to this
approach, which seems to yield results that correspond well with the
protection one would expect a user to receive as the devices are worn in
the real world. If consumers can see subject fit data as well as NRR
data, they will have better information on which to make their
decisions,”
A
Final Thought. Whether
or not OSHA adopts all or part of NIOSH’s recommendations, employers
should still take notice. The courts will likely consider NIOSH’s
recommendations as best practices when considering challenges filed by
employees.
For
more information:
Criteria
for a Recommended Standard: Occupational Noise Exposure (revised 1998)
-- PDF file
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