1634 Chapter 47
Unfortunately, OSHA’s regulations are among the
least protective of any developed nation’s hearing
protections standards. Scientists and OSHA itself have
known for more than a quarter-century that between 20
and 30% of the population exposed to OSHA-permitted
noise levels over their lifetime will suffer substantial
hearing loss, see Table 47-2. As a result, the National
Institute of Occupational Safety and Health (NIOSH), a
branch of the Centers for Disease Control and Preven-
tion (CDC), has recommended an 85 dB standard as
shown in Table 47-3. Nevertheless, NIOSH recognizes
that approximately 10% of the population exposed to the
lower recommended level will still develop hearing loss.
Table 47-3 compares the permissible or recom-
mended daily exposure times for noises of various
levels. The table is complicated but instructive. The first
three columns represent the recommendations of the
Environmental Protection Agency (EPA) and World
Health Organization (WHO) and starts with the recom-
mendation that the 8-hour average of noise exposure not
exceed 75 dBA. The time of exposure is reduced by half
for each 3 dBA that is added; a 4-hour exposure is
78 dBA, and a 2-hour exposure is 81 dBA. This is
called a 3 dB exchange rate, and is justified on the prin-
ciple that a 3 dB increase is a doubling of the energy
received by the ear, and therefore exposure time ought
to be cut in half. The EPA and WHO recommendations
can be thought of as safe exposure levels. The NIOSH
recommendations in the next three columns represent an
increased level of risk of hearing loss and are not
protective for approximately 10% of the population.
NIOSH uses a 3 dB exchange rate, but the 8-hour expo-
sure is 10 dB higher than EPA—that is, 85 dBA.
Finally, the OSHA limits are in the last two columns.
OSHA uses a 5 dB exchange rate, which results in
much longer exposure times at higher noise levels, and
the 8-hour exposure is 90 dBA. Between 20 and 30% of
people exposed to OSHA-permitted levels will experi-
ence significant hearing loss over a lifetime of expo-
Table 47-2. NIOSH’s 1997 Study of Estimating
Excess Risk of Material Hearing Impairment
Average Exposure
Level–dBARisk of Hearing Loss Depending on
the Definition of Hearing Loss Used90 (OSHA) 25–32%
85 (NIOSH) 8–14%
80 1–5%
While 25–30% of the population will suffer substantial hearing
loss at OSHA permitted levels, everyone would suffer some hear-
ing damage.Table 47-3. EPA, WHO, NIOSH, and OSHA Recom-
mended Decibel StandardsEPA and WHO NIOSH OSHA
dBA Hours Min s Hours Min s Hours Min75 8
76
77
78 4
79
80
81 2
82
83
84 1
85 8
86
87 30
88 4
89
90 15 8
91 2
92
93 7 30
94 1
95 4
96 3 45
97 30
98
99 1 53
100 15 2
101
102 56
103 7 30
104
105 28 1 60
106 3 45
107
108 14
109 1 53
110 0.5 30
111 7
112 56
113
114 4
115 28 0.25 15