HomeMy WebLinkAbout031 Noise Exposure and Public HealthNoise Exposure and Public Health
Willy Passchier-Vermeer1 and Wim F.Passchier2
1TNO Prevention and Health,Leiden,The Netherlands;2Department of Health Risk Analysis and Toxicology,Universiteit Maastricht,
Maastricht,The Netherlands
Exposure to noise constitutes a health risk.There is sufficient scientific evidence that noise
exposure can induce hearing impairment,hypertension and ischemic heart disease,annoyance,
sleep disturbance,and decreased school performance.For other effects such as changes in the
immune system and birth defects,the evidence is limited.Most public health impacts of noise
were already identified in the 1 960s and noise abatement is less of a scientific but primarily a policy
problem.A subject for further research is the elucidation of the mechanisms underlying noise-
induced cardiovascular disorders and the relationship of noise with annoyance and nonacoustical
factors modifying health outcomes.A high priority study subject is the effects of noise on children,
including cognitive effects and their reversibility.Noise exposure is on the increase,especially in the
general living environment,both in industrialized nations and in developing world regions.This
implies that in the twenty-first century noise exposure will still be a major public health problem.
Key words:annoyance,cardiovascular effects,children's health,environmental health,
environmental noise,hearing impairment,noise exposure,noise metrics,occupational noise,
performance.-Environ Health Perspect 1 08(suppl 1):1 23-131 (2000).
http.//ehpnetl.niehs.nih.gov/docs/2000/suppl-1/123-131passchier-vermeer/abstract.html
Noise Exposure and Health
Assessment of the human health risk
associated with the presence of a xenobiotic
substance in the environment usually follows
the relatively simple scheme depicted in
Figure 1.The substance occurs in environ-
mental media at certain concentrations,
depending on,among other factors,lifestyle,
residence time,and dietary habits,that people
may be exposed to this xenobiotic.Any sub-
sequent harm depends on the level of expo-
sure.The modifying impact of exogenous
determinants and personal characteristics on
the level of exposure and sensitivity with
respect to the toxic action usually are not
taken into account or are only considered in a
standardized way,at least for risk assessment
and standard-setting purposes.The data
available,often derived from animal experi-
ments and surveys of population behavior,do
not allow a more refined analysis.
In the case of the assessment of the health
effects of noise exposure,the scheme in
Figure 1 is too simple.With the exception of
damage to the hearing organ,the exposed
organism's reaction to the perception of
sound is strongly dependent on the context
of the exposure.The effects of noise exposure
cannot be understood only by taking mecha-
nisms of toxic action into account.For
example,the sounds in a discotheque are
music to the dancers but noise to the neigh-
bors.In the first case,the exposure would
not be annoying but is expected to con-
tribute to hearing loss;for the neighbors,
hearing loss would be improbable,but
annoyance would certainly occur.A concep-
tual model to address the health effects of
noise exposure is presented in Figure 2.
The model considers effects on health
and quality of life as the outcome of a pro-
cessing of exogenous determinants or envi-
ronmental factors-in this case,noise
exposure.Exposure,processing,and effect
take place within economic and social envi-
ronments and all are modified by societal fac-
tors.Furthermore,lifestyle and concurrent
exposure to other factors play a role.An
example of the former was given above.An
example of the latter is the finding that the
perceived presence of the risk of an aircraft
crash has been found to augment annoyance
(and vice versa)(1).This processing of
sounds is influenced by the genetic and
acquired characteristics of the organism.For
example,some people have a specific sensitiv-
ity to noise and will be more susceptible to
one or all of its effects than other people.
Examples of societal factors that determine
the adverse effects associated with noise
exposure are insulation of houses,noise level-
related depreciation of house prices,and
individual and societal appreciation of the
activities generating the noise.
These insights,as depicted in the model in
Figure 2,are not new.On the contrary,it is
striking that in the 1960s most of the effects of
sound on health and quality of life were
already known or at least hypothesized,indud-
ing the variety of modifying factors referred to
above (2).In the 1970s the research results
were sufficiently reviewed to allow science-
based recommendations to be made for policy
measures to protect public health (3-5).In the
last three decades new data have confirmed the
earlier insights and,as reviewed here in our
present paper,have made more precise assess-
ments of exposure-response relationships and
observation thresholds possible.Many of the
newer data stem from epidemiologic studies.
If politicians had taken a more protective
stance in the 1970s-which would have been
legitimate on the basis of the then-available
data-this review probably would have been
superfluous,as new data would not have
been published,but also harm would have
been avoided.
In this review we emphasize development
of insights into the effects of noise exposure
on health and quality of life.In accordance
with the relevant literature,we use the term
noise to represent sounds generated by
sources in the environment (indoors,out-
doors,at work,etc.);noise is often appreci-
ated negatively.Because several reviews on
this subject have been published recently-
some by international groups of scientists
(6)-we refer to original research papers
only when necessary for our argument.
Furthermore,given our background in envi-
ronmental health sciences,we also discuss
policy instruments for health protection.
Characterization of Noise
Exposure
Sound Pressure Level and Sound Level
Sound is a physical phenomenon consisting
of alternating compression and expansion of
air that propagate in all directions from a
source.These alternating compressions and
expansions can be described as small
changes in pressure around atmospheric
pressure.The frequency of the alternations
determines the pitch of a sound:a high-
pitched tone (e.g.,4,000 Hz)has a squeak-
ing sound;a low-pitched tone (e.g.,200
Hz),a humming sound.The environmental
noise sources discussed in this review usu-
ally generate sounds within a broad fre-
quency range.Sound pressures,relative to
the atmospheric pressure,range from <20
micropascal to >200 pascal,a range of
1-10 million.Therefore,in acoustics,the
logarithm of sound pressure relative to a ref-
erence sound pressure is used as a basis for a
sound (and noise)exposure measure:the
physical quantity sound pressure level
expressed in decibel (dB).
Address correspondence to W.Passchier-Vermeer,
TNO Prevention and Health,PO Box 2215,2301 CE,
Leiden,The Netherlands.Telephone:31 71 518 1786.
Fax:31 71 518 1920.E-mail:w.passchier@pg.tno.nl
Received 4 August 1999;accepted 30 November
1999.
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PASSCHIER-VERMEER AND PASSCHIER
Cause-effect sequence
Environmental Exposure Harmagent
Figure 1.Simple cause-effect chain for the assessment
of the health effects of an environmental agent,such as
a xenobiotic substance.
The human hearing organ is not equally
sensitive to sounds of different frequencies.
Therefore,a spectral sensitivity factor is used
that rates sound pressure levels at different fre-
quencies in a way comparable to that of the
human hearing organ;this is called A-weight-
ing.The biophysical quantity A-weighted
sound pressure level (L)is expressed as dB(A)
and is referred to as sound level.Examples of
sound levels in some common situations are
falling leaves (very quiet),10-20 dB(A);vac-
uum cleaner,55-65 dB(A);location close to a
main road or highway,70-80 dB(A);pop
music concerts,1 00-1 1 0 dB (A).
Equivalent Sound Level
and Day-Night Level
Sound level is the basic metric from which
other biophysical metrics to specify long-term
exposure to noise are derived.Usually a noise
metric is assessed on an annual basis.In envi-
ronmental and occupational situations,sound
levels fluctuate with time.From these fluctuat-
ing sound levels,the equivalent sound level
(LAeq,T)over a period of time,T,is determined
from [see (7)]:
1 L(t)
LAeq,T =10log -1 0 10 dtTT
Common exposure periods T are 24 hr
(full day)and 8 hr (work day).
For some environmental health assessment
purposes,the day-night level (Ld")is used.
This metric is the equivalent sound level over
24 hr with the sound levels during the night
(11 PM-7 AM)increased by 10 dB(A).Also a
day-evening-night level (L1,is used,which is
constructed similarly,such that the sound lev-
els during the evening (7 PM-1 1 PM)are
increased by 5 dB(A)and those during the
night (1 1 PM-7 AM)by 10 dB(A).These
adjustment factors of 10 or 5 dB(A)take into
account that night-time and evening-time
noise are more annoying than day-time noise
with the same equivalent sound level.
Because of road,railway,and aircraft traf-
fic noise,most of the urban population in
industrialized countries are exposed to out-
door Ld,levels of >50 dB(A).Rural popula-
tions usually are exposed to outdoor traffic
Ld,values of <50 dB(A).Rough estimates of
the percentage of people in Europe living in
locations with Ld,,values >60 dB(A)vary from
2 to 8%,depending on the country in which
Figure 2.Conceptual model of the interaction of sound with the organism and the occurrence of effects on health
and quality of life.
they live.For the Netherlands population this
percentage is 4%.It is further estimated that
0.6%of the Netherlands population is
exposed to traffic noise with Ld,,values of
>70 dB(A)(8,9).
Both in research and in policy,Ld,,or Ld,,is
applied in a specific way:the metrics are used as
location-specific quantities to be measured in
front of the facade of residential buildings.
Sound Exposure Level
A single noise event is characterized by its
sound exposure level.The sound exposure
level (SEL)of a noise event,such as the over-
flight of an airplane or the passage of a truck,
is the equivalent sound level during the event
normalized to a period of 1 sec (10).
Exposure Settngs
In this review we discuss the health effects of
occupational and environmental noise expo-
sure.Even though noise sources at work are
quite divergent,the exposure setting is well
defined;i.e.,exposure during the execution of
occupational tasks.In the living environment
not only the sources but also the exposure set-
tings are quite diverse.As mentioned above,a
common environmental noise source is traffic.
In addition,in industrialized regions indus-
trial noise may affect environmental quality.
Another type of noise is neighbor noise,a fac-
tor frequently mentioned in surveys on resi-
dential satisfaction.Increasingly,people are
exposed to noise during recreational activities
such as pop music concerts,motor races,and
arcade activities;often these types of exposures
are undergone consciously or at least taken for
granted.In this review emphasis is on chronic
environmental noise exposures,particularly
those due to traffic and industrial noises.If
other sources of noise or exposure settings are
meant,this will be mentioned explicitly.
Assessment of Health Effects
The Committee on Noise and Health,an
international committee of the Health
Council of the Netherlands,in 1994 assessed
the health effects of environmental and occu-
pational noise exposure (6).It rated the evi-
dence in terms of categories used by the
International Agency on the Research of
Cancer (11)as "sufficient,""limited,""inade-
quate,"or "lacking".The report also presents
observation thresholds for those adverse
health effects for which sufficient evidence
was considered available.The observation
threshold for an effect was defined in the
report as the lowest noise exposure value at
which on average the effect was observed in
well-designed epidemiologic studies (12).
This definition implies that in the course of
time the observation threshold of an effect
may have to be lowered if supported by new
information from epidemiologic studies.
In this review,the 1994 Health Council
report (6)is considered a starting point.
More recent reviews (13-19)and papers pre-
sented at the November 1998 meeting in
Sydney,Australia,of the International
Commission on the Biological Effects of
Noise (20)were used to extend the 1994
evaluation.In general,the more recent
reviews and papers (13-20)concur well with
the conclusions of the Health Council if we
take a rating of "inconclusive"(15,16)to be
equivalent to the Health Council's "limited."
With respect to some effects such as ischemic
heart disease,hypertension,and congenital
defects,there appear to be differences of
opinion.This will be further discussed below
("Noise-Induced Stress-Related Health
Effects").
In Table 1 information is presented about
the adverse effects related to environmental
and occupational noise exposure that have
been examined in epidemiologic studies.The
table is adapted from Table 1 of the 1994
Health Council report (6).Changes concern
the noise metric in which the observation
thresholds for hypertension and ischemic
heart disease were originally given (21).Also
the observation threshold for being awakened
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NOISE EXPOSURE AND PUBUC HEALTH
by a single noise event was lowered by
5 dB(A).Finally,we have added that the
observation threshold for sleep pattern changes
is <60 dB(A)(expressed in outdoors LAeq,nigh).Several health end points are not specific
to noise exposure.In fact,in accordance with
the conceptual model of Figure 2,factors that
apparently modify the effects of noise expo-
sure may also affect health in ways similar to
those for noise exposure.Situations exist in
which it is difficult to identify primary and
modifying factors.
The following sections highlight the main
aspects of the data presented in Table 1.
Noise-Induced Hearing Impairment
Hearing impairment is an increase in the
hearing threshold level.In the International
Standard ISO 1999 (22),a hearing handicap
is defined as the disadvantage imposed by
hearing impairment sufficiently severe to
affect one's personal efficiency in the activities
of daily living,usually expressed in terms of
understanding conventional speech in low
levels of background noise.Hearing impair-
ment is also associated with aging as well as as
certain diseases,exposure to some industrial
chemicals,ototoxic drugs,head injuries,acci-
dents,or factors that are of hereditary origin.
ISO 1999 (6)gives a method to estimate
noise-induced hearing impairment in popu-
lations exposed to continuous,intermittent,
or impulse noises during working hours.
Noise exposure is characterized by the equiv-
alent sound level over an 8-hr work day
(LAeq,8h).Relations are given (for exposure
times up to 40 years)between LAeq,8h and
noise-induced hearing impairment at fre-
quencies between 500 and 6,000 Hz.These
relations show that noise-induced hearing
impairment occurs predominantly in the
higher frequency range of 3,000-6,000 Hz,
with largest effects observed at 4,000 Hz.
With increasing LAeq,8h and increasing expo-
sure time,noise-induced hearing impair-
ment can also occur at lower frequencies,
more specifically at 2,000 Hz.Even with
prolonged occupational noise exposure,
however,according to ISO 1999 noise-
induced hearing impairment does not occur
at LAq,8h levels of 75 dB(A)and lower.This
value is equal to the value specified in 1980
by the World Health Organization (23).
Since the method specified in ISO 1999 is
the only universally adopted method to esti-
mate occupational noise-induced hearing
impairment,attempts have been made to
assess whether this method also applies to
hearing impairment due to environmental
noise,including leisure-time noise.The
results of various studies strongly suggest that
the ISO 1999 procedure can also be accepted
for environmental and leisure-time noise
exposures of adults and older children
Table 1.long-term effects related to exposure to noise and classification of the evidence for a causal relationshipbetweennoiseandeffect.The last three columns contain information on the observation threshold of an effect forwhichthecausalrelationshipwithnoiseexposure(second column)is judged to be sufficient.a
Observation threshold
Classification Exposure Indoors/Effect of evidenceb situation Metric Value (dB(A)outdoorsc
Hearing impairment Sufficient Occ LAeq8h 75 Indoors
Env LAeq,24h 70 Indoors
Occ unb LAeq,8h <85 Indoors
Hypertension Sufficient Occ ind LAeq8h <85 Indoors
Env Ldn 70 Outdoors
Ischemic heart disease Sufficient Env Ldn 70 Outdoors
Biochemical effects Limited Occ
Env
Immune effects Limited Occ
Env
Birth weight Limited Occ
Env air
Congenital effects Lacking Occ
Env
Psychiatric disorders Limited Env air
Annoyance Sufficient Occ office LAeq,8h <55 Indoors
Occ ind LAeq8h <85 Indoors
Env Ldn'42d Outdoors
Absentee rate Limited Occ ind
Occ office
Psychosocial well-being Limited Env
Performance Limited Occ env
Sufficient School LAeqschool 70 Outdoors
Sleep disturbance,changes in
Sleep pattern Sufficient Sleep LAegnight <60 OutdoorsAwakeningSufficientSleepSEL55IndoorsSleepstagesSufficientSleepSEL35IndoorsSubjectivesleepqualitySufficientSleepLAepgnight40OutdoorsHeartrateSufficientSleepSEL40IndoorsHormonelevelsLimitedSleep
Immune system Inadequate Sleep
Mood next day Sufficient Sleep LAegnight <60 OutdoorsPerformancenextdayLimitedSleep
Abbreviations:env,living environment;ind,industrial;occ,occupational situation;school,exposure of children at school;unb,unborn:
exposure of pregnant mother.°The table is adapted from Table 1 of the 1994 Health Council report (6 ).bClassification of evidence of
causal relationship between noise and health.'Value relates to indoor or outdoor noise assessment.dthe observation threshold for
percentage of highly annoyed persons is about 12 dB(A)lower for environmental impulse noise.
provided the exposures are not too extreme
and the exposures are expressed in LAeq,24h
(because exposure during the full 24-hr day is
important in this case)instead of LAeq,8h
(6,23-31).This implies that exposure to
environmental and leisure-time noise with
LAeq,24h values <70 dB(A)does not cause
hearing impairment in the large majority of
people (>95%),even in the case of life-time
exposure (32).It should be considered,how-
ever,that there are no large-scale epidemio-
logic studies that investigated noise-induced
hearing impairment in the general population
that support this proposition.Also,data from
animal experiments indicate that young chil-
dren may be more vulnerable to noise-
induced hearing impairments than adults
(31).For impulsive (shooting)noises with
LAeq,24h>80 dB(A)studies on temporarythresholdshifts(26)suggest the possibility of
an increased risk for impulse noise-induced
hearing impairment in adults.
At high instantaneous sound levels,
mechanical damage to the outer and the inner
ear may occur.Occupational limits for such
types of exposures have been set equal to the
observation threshold for this effect at a peak
sound pressure level of 140 dB (33).For
adults,it is reasonable to assume that a similar
threshold applies with respect to exposure to
environmental and leisure-time noise.In the
case of children,however,taking into account
their habits of playing with noisy toys,peak
sound pressure levels >120 dB may cause
mechanical damage to the hearing organ (31).
Noise exposure may also result in tinnitus
(ringing in the ears).This effect has been
observed among teenagers attending pop
music concerts and discotheques (34).Noise-
induced tinnitus may be temporary,lasting up
to 24 hr after exposure,or it may have a more
permanent character,such as after prolonged
occupational noise exposure.Approximately
25%of workers with both noise-induced
Environmental Health Perspectives *Vol 108,Supplement *March 2000 125
PASSCHIER-VERMEER AND PASSCHIER
hearing impairment and tinnitus consider
tinnitus the more disturbing effect (35).
The main social consequence of hearing
impairment is the inability to understand
speech in daily living conditions-a severe
social handicap.Even small values of hearing
impairment (10 dB averaged over 2,000 and
4,000 Hz and over both ears)may have an
effect on the understanding of speech.When
the hearing impairment exceeds 30 dB (again
averaged over 2,000 and 4,000 Hz and both
ears),a social hearing handicap is noticeable.
Psychosocial Effects
Psychosocial effects due to exposure to
environmental noise that have been studied in
epidemiologic investigations include annoy-
ance,psychosocial well-being,and psychiatric
hospitalization.The main psychosocial effect
from exposure to occupational noise observed
in epidemiologic investigations is annoyance.
Noise annoyance is a feeling of resent-
ment,displeasure,discomfort,dissatisfaction,
or offense when noise interferes with some-
one's thoughts,feelings,or actual activities.It
is not yet possible to predict noise annoyance
on an individual basis because of the large
variety of (partly unknown)endogeneous and
exogeneous characteristics that affect annoy-
ance (Figure 2).However,relationships
between noise annoyance and noise exposure
have been elucidated on a population level
together with several effect-modifying factors.
Annoyance in populations is evaluated using
questionnaires.Exposure-effect relationships
have been derived for exposure to the three
main types of traffic noise:road,railway,and
aircraft.The most recent and comprehensive
relationships are shown in Figure 3 (36).
These relationships pertain to populations
chronically exposed to noise at specified levels
for periods of more than a year.The effect is
given as the percentage of the population
highly annoyed by a specific environmental
noise."Highly annoyed"persons are those
Be 80-
-0 --Air
.Road60Rail
>.40 -
20-
Co
=40 50 60 70
CL Ldn in dB(A)
Figure 3.Relationships between the percentage of
highly annoyed persons and Ldn for air,road,and railway
traffic noise.Each curve has been derived by a multilevel
analysis of all studies for which original data were avail-
able.The vertical bars at 60 and 70 dB(A)represent 95%
confidence intervals [bar at 60 dB(A)for road has been
displaced by 0.5 dB(A)for clarity].
who respond to a question about the degree
of annoyance in the worst 25%range of
answer categories (37).The noise exposure is
expressed in LdA,assessed in front of
dwellings.The relationships depicted in
Figure 3 demonstrate that annoyance
induced by the different modes of trans-
port-air,road,and rail-differs at higher
exposure levels.Taking into account the sta-
tistical variations within and between the
various studies,Miedema and Vos showed
that aircraft noise is statistically significantly
more annoying and railway noise is less
annoying than road traffic noise (36).
Environmental noise exposure is only one
of the factors that contributes to noise
annoyance,albeit a significant one.The
degree of annoyance experienced by an indi-
vidual as well as that on a population level in
practice can differ considerably from the
exposure-response relationships presented in
Figure 3 because of the influence of so-
called nonacoustical factors.Important
nonacoustical effect-modifying factors are
anxiety,fear of the noise source,and a feel-
ing that the noise could be avoided.These
effect-modifying factors have been identi-
fied in multivariate analyses of population
data (19,38-41).However,general quanti-
tative multifactorial exposure-response
relationships have not yet been published.
Much attention has been paid in laboratory
experiments to the effects of uncontrollable
noise exposure on such things as task perfor-
mance and annoyance.No relationships have
been assessed between general noise annoy-
ance experienced during working hours and
noise exposure.Epidemiologic studies show
that annoyance in offices is considerable at
equivalent sound levels >55 dB(A).A few
studies show that 35-40%of office workers
are highly annoyed at noise levels from 55 to
60 dB(A).If the noise source is more or less
constant,such as the noise produced by ven-
tilation systems (e.g.,fans in computers),the
observation threshold for annoyance in offices
is lower than a LAeq,8h value of 55 dB(A).In
industrial situations,similar percentages of
highly annoyed workers occur at equivalent
sound levels >85 dB(A).
Also at the workplace,nonacoustical
factors have a large effect on the actual noise
annoyance on an individual and on a popula-
tion level.These factors include the meaning
and information contents of the noise (tele-
phone conversations and discussions between
colleagues score high),predictability,avoid-
ability,controllability,task demands,and
attitudes toward the noise source.
Noise-related annoyance is widespread in
present-day society.Even though annoyance
as such is not directly invalidating,there are
indications that for sensitive individuals or
in cases of concurrent exposure to other
environmental agents or socially distressing
situations,more serious health effects can
occur [see Figure 2 and a recent report of
another International Health Council
committee (42)].
Noise-Induced Stress-Related
Health Effcs
Reactions to a stressor can be psychologic
(feelings of fear,depression,sorrow),behav-
ioral (social isolation,aggression,excessive use
of alcohol,tobacco,food,drugs),and somatic
(cardiovascular,gastrointestinal,respiratory
illnesses)in nature.A large number of labora-
tory experiments [reviewed by Passchier-
Vermeer (24)]have shown noise-induced
temporal changes in the cardiovascular system.
These findings led to several investigations
into possible long-term effects associated with
noise exposure,e.g.,stress-related cardiovascu-
lar disorders.In addition,some research has
been conducted on the effects of noise expo-
sure on the hormone and immune systems.
Effects from occupational or environmental
noise on reproduction and development were
also studied.High-frequency hearing impair-
ment in babies of mothers exposed to high
levels of occupational noise during pregnancy
is also considered to be a consequence of a
mother's stress induced by exposure to noise
during pregnancy (43).
Research into the chronic effects of long-
term exposure to noise is complicated
because cardiovascular and biochemical
changes are nonspecific and a number of
other factors may also cause these changes;
these factors must be controlled for in
research projects.In cross-sectional studies it
is difficult to obtain appropriate information
about past noise exposure,and longitudinal
studies are time-consuming and financially
draining.Furthermore there are large indi-
vidual differences in susceptibility.Also,peo-
ple intervene in their own situations,e.g.,by
changing jobs [thus contributing to the
"healthy worker effect"(44)]or by moving
from noisier surroundings to quieter places.
This may result in "noise proof'populations
exposed to the higher noise levels (45).Not
withstanding these complications,conclu-
sions on the relationship between noise expo-
sure and cardiovascular disease appear
possible from meta-analyses of the available
epidemiologic data (6).
Cardiovascular effects in adults.
Epidemiologic environmental noise studies
on changes in blood pressure and increased
risk for ischemic heart disease in adults are
limited mainly to the effects of road traffic
noise,with the exception of a Dutch study on
the effects of aircraft noise (46,47).In general
these studies demonstrate no obvious effects
from noise exposure on mean diastolic and
mean systolic blood pressure,but some effects
Environmental Health Perspectives *Vol 108,Supplement 1 *March 2000126
NOISE EXPOSURE AND PUBUC HEALTH
were observed in terms of an increase in the
percentage of people with hypertension
(including those who use medication for
hypertension).The observation threshold for
hypertension is estimated to correspond to an
Ldn value of 70 dB(A)for environmental
noise exposure.The Health Council of the
Netherlands in 1994 (6)suggested the same
observation threshold for ischemic heart dis-
ease (Table 1).The relative risks (compared
to populations with low environmental noise
exposure)for both hypertension and ischemic
heart disease for exposure levels above the
observation thresholds are estimated to be
about 1.5 (48).
In 1997 a Chinese study (49)was
conducted among a large sample of more
than 20,000 residents in rural communities.
The results show that self-reported exposure
to noise (unfortunately,exposure was not
assessed objectively)is an important determi-
nant of systolic and diastolic blood pressure.
Of special interest is the outcome of the
recent,unique longitudinal study (50)on the
effect of road traffic noise exposure on the
incidence of ischemic heart disease.In this
Caerphilly and Speedwell study,two cohorts
of about 2,500 middle-aged men in the
United Kingdom were recruited for a study
of the predictive power of already-known and
new risk factors for ischemic heart disease.
Noise measurements were performed in each
of the streets where subjects lived.Even in the
highest noise exposure class,Ldn did not
exceed 70 dB(A).Statistical analysis on the
relationships between incidence of ischemic
heart disease (classified in a standardized way)
and environmental noise exposure was con-
trolled for potentially confounding factors.
The average annual incidence rate of ischemic
heart disease appeared to be 1.4%during the
second phase of the study (6 year follow-up;
mean age of the men,57 years).If orientation
of the living room and the bedroom,window
opening habits,and years of residence over 15
years were taken into account,the relative
risk for incidence of ischemic heart disease of
the highest exposed group relative to the
group exposed to levels between 50 and 55
dB(A)was 1.6,which statistically is not sig-
nificantly different from 1 at the 5%level
(p <0.10).This study fits in with the earlier
evaluation that above levels of 70 dB(A)there
is sufficient evidence for a noise exposure-
related effect,and provides no support for
lowering the observation level of 70 dB(A)for
ischemic heart disease.
Through analysis of twelve studies on the
risk of hypertension among occupational
noise-exposed workers,the observation
threshold for industrial noise exposure was
determined to be at most equal to an LAC 8h
value of 85 dB(A)(24).No data are availatle
for noise exposure in offices.If annoyance
and stress-related health effects are associated,
and taking into account that the observation
threshold for annoyance in offices is much
lower than that for industrial situations,we
hypothesize that the observation threshold
for noise-induced risk for hypertension in
office workers is about 30 dB(A)lower than
that for hypertension in blue-collar workers.
The data in more recent publications on car-
diovascular effects from exposure to noise are
not in disagreement with the previous find-
ings (51-53).However,one must be careful
interpreting the results of these studies,as
either noise measurements or proper control
groups are lacking or the size of populations
studied is small.
Only few epidemiologic studies considered
biochemical and immunologic effects
(54,55).More recently,overnight resting lev-
els of epinephrine and norepinephrine levels
were assessed in a study of middle-aged
women living in Berlin (56).Significantly
elevated levels of norepinephrine were found
in women whose bedrooms faced busy streets
(>20,000 vehicles a day)and epinephrine
levels were also higher in women reporting
high disturbances of communication and
sleep under closed window conditions.Some
smaller studies in industrial settings showed
the effects of wearing personal hearing protec-
tion on urinary excretion of catecholamines
(epinephrine and norepinephrine)and corti-
sol (57,58).On the days hearing protectors
were worn,urinary catecholamine levels were
statistically significantly lower than on days
protectors were not worn.
Cardiovascular effects in children.Two
early studies (59,60)showed an increase in
systolic and diastolic blood pressure in chil-
dren exposed to very high road traffic noise
levels or aircraft noise levels.The increases
were assumed to be of a transient nature.
Recently,Slovakian researchers studied 1,542
children 3-7 years of age in kindergartens
(61).The authors observed significantly
higher systolic and diastolic blood pressures
among children in noisy environments [>60
dB(A)]compared to those among children in
quieter environments.Although the study is
carefully designed,the possibility that social
class has confounded the results cannot be
excluded [see also Lercher et al.(62)].In the
Munich airport study (63,64),schoolchildren
were examined during the years Munich air-
port moved from one location to another.
One study location was close to the old air-
port and another was close to the new airport.
The cross-sectional part of the study showed a
marginally significant higher systolic blood
pressure in children highly exposed at school.
Children were matched on socioeconomic
characteristics.In the study,neuroendocrine
indices of chronic stress (urinary cortisol levels
and levels of epinephrine and norepinephrine)
were also examined.Overnight resting levels
of epinephrine and norepinephrine levels were
significantly higher in children exposed to air-
craft noise at the old Munich airport com-
pared to control groups.There were no
differences in cortisol levels.After the airport
was moved,overnight resting levels of epi-
nephrine and norepinephrine rose signifi-
cantly among children living under the flight
paths of the new airport.Again,no effects
were observed on urinary cortisol levels.We
propose that this subject be studied further.
Effects on the unborn child.Data from
older studies suggest that it is possible that
when pregnant women are exposed to high
levels of aircraft noise [Ldn >62 dB(A)],small
reductions in birthweight occur.In a more
recent study of 200 Taiwanese women,noise
exposure was measured by personal noise
dosimeters on three occasions during preg-
nancy (65).Noise exposure was not related to
birthweight after adjustment for social class,
smoking and alcohol use,maternal weight
gain in pregnancy,gender of the child,and
duration of pregnancy.Older and more
recent investigations do not show statistically
significant effects of occupational or environ-
mental exposure of pregnant women to noise
in the course of pregnancy and congenital
defects of babies,with the exception of high-
frequency hearing damage mentioned at the
beginning of this section.
Absences due to accident and sickness.
Epidemiologic studies suggest that the absen-
tee rate of industrial workers increases when
they are exposed to equivalent sound levels
during working hours of over 75 dB(A)
[CORDIS study,(66)]or over 90 dB(A)
(67).The CORDIS study also showed that
the number of accidents increases with rises
in equivalent sound levels during working
hours.Mortality from injury was studied in
more than 20,000 steelworkers (68).On the
basis of job and workplace information,
industrial hygienists estimated noise exposure
as high [LAq,8h >95 dB(A)],medium [LAeq8h
90-95 dB(A)],low [LAeq,8h 85-90 dB(A)],
and minor.Hearing damage and noise expo-
sure in the high and medium noise classes
appeared to be factors that contributed statis-
tically significantly to mortality.The study
did not identify the mechanisms behind
these findings.Moreover the impact of using
personal hearing protectors is unclear.
Wearing of hearing protection by workers
with substantial noise-induced hearing
impairment reduces the possibility of hearing
moving sound sources,warning signals,or
colleagues shouting and hampers localization
of moving sound sources because of reduced
capacities to determine the direction of a
sound source.Therefore,we hesitate to con-
sider stress as the underlying mechanism for
the increase in mortality.
Environmental Health Perspectives *Vol 108,Supplement 1 *March 2000 127
PASSCHIER-VERMEER AND PASSCHIER
Sleep Disturbance
Sleep is a recovery process essential for
humans to function properly.In addition,
people like to sleep and usually consider a
good night's sleep to be an important aspect
of an individual's quality of life.Deleterious
health effects are expected from chronic noise-
induced interference with sleep,as it impairs
the functions of sleep such as brain restoration
and provision of a period of respite for the
cardiovascular system (69,70).In addition to
the physiologic aspects of a noise-induced
reduction of sleep quality,night-time noise
exposure of sufficient intensity (Table 1)is
also related to subjectively experienced sleep
quality (71).Reduced sleep quality also inter-
feres with daytime functioning and can have
adverse effects on mood next day and possibly
on vigilance and cognitive performance.
Sleep quality can be quantified by subjec-
tive and objective methods.The most com-
monly applied subjective methods are
self-reporting using sleep logs or diaries and,
to a lesser extent,behavioral observations.
The most commonly used objective methods
are electroencephalograph (EEG)recordings
and actimetry.In field studies on noise-
induced sleep disturbance subjects usually
wear watchlike actimeters for movement
detection at their wrist.Sleep quality may be
adversely affected by
*changes in the cardiovascular system;
*changes in sleep pattern such as increased
sleep latency time and reduced sleep time
because of premature awakening;
*changes in sleep stages from deeper to
less-deep sleep;
*increases in motility during the sleep
period;
*increases in number of awakenings during
the sleep period;
*changes in subjectively experienced sleep
quality;and
*changes in the hormonal and immune
systems.
Present knowledge about the relationships
between awakening and exposure to single
noise events indicates that habituation or
adaptation occurs.This insight is not new.
Cohen stated in 1968 [in Ward and Fricke
(2)]that
Aspects of adaptation to noise with regard
to sleep disturbance also need to be evalu-
ated.Common experience has found that
the city dweller,frequently encountering
significant levels of outdoor and indoor
noise,becomes accustomed to such expo-
sures and can sleep in their presence.The
same individual vacationing in the quiet
atmosphere of the country finds it difficult
to sleep because of the background of
cricket noise.The degree of familiarity or
meaningfulness of the noise has a consider-
able effect on its disturbing quality.
From the epidemiologic studies there
appears to be sufficient evidence for a causal
relationship between exposure to night-time
noise and changes in sleep pattern,sleep
stages,awakenings,subjective sleep quality,heart rate,and mood the next day (6).
Observation thresholds for these effects are
given in Table 1.Evidence for other effects is
limited (hormone levels and performance the
next day)or inadequate (immune system).
Exposure-response functions have been
derived from field studies for only some of
these effects,among others or reduction of
subjective sleep quality and increase in num-
ber of awakenings during sleep period time.
The relationship between the risk of awaken-
ing and exposure to night-time environmen-
tal noise is established only for single noise
events,with exposure specified by the indoor
SEL values of the events.
An international group of experts who
were convened in 1997 by the Health
Council of the Netherlands assessed the
observation threshold for awakening due to
single noise events at the lower indoor SEL
value of 55 dB(A)(Table 1)instead of 60
dB(A)(8).This change reflected improved
knowledge of the transfer functions of SEL
values measured outdoors compared to those
measured indoors in some of the underlying
studies.Using the relationship between
indoor SEL value and the risk of awakening
due to single noise events,the expected maxi-
mal number of awakenings per year in an
adult habituated to night-time noise expo-
sure was estimated as a function of the equiv-
alent sound level during the night.The latter
quantity was calculated from the number of
single noise events during the night and their
indoor SEL values (8).The result,which
represents a worst-case situation,is depicted
in Figure 4.
Apart from the direct effects of night-time
noise on sleep,various authors point to the
importance of the impact of sleep disturbance
on quality of life,including such factors as
somatic health and annoyance.Such observa-
tions had already been made in the 1950s.
Cohen,referring to a paper of Borsky from
1958,states
Field studies have shown that much greater
annoyance results when sleep and rest are
disturbed than when only talking or listen-
ing activities are interrupted.This finding
plus the health significance attributed to rest
and sleep suggest that criteria for annoyance
be based on noise-induced disturbances to
sleep.[in Ward and Fricke (2)]
Babisch et al.reported larger overnight
changes in epinephrine levels in subjects
reporting high disturbance of sleep than in
those without severe complaints (56).
Another study showed that psychosocial
well-being of subjects exposed to high levels
of road traffic noise was not related to day-time noise exposure but to night-time equiva-lent sound level in the bedroom and to
subjectively experienced sleep quality (71).Although in the 1990s several field studies
were started (72)or completed (73-76),there still is an urgent need for a tested model
on sleep disturbance,environmental noise
exposure,and secondary effects,in which
causal and modifying factors and their
mutual relations are assessed.
Efects on Performance
There is overwhelming evidence from
laboratory experiments that the presence of
uncontrollable noise can significantly impaircognitiveperformance.Noise can induce
learned helplessness,increase arousal,alter
the choice of task strategy,and decrease
attention to the task.Noise may also affect
social performance,mask speech and other
sound signals,impair communication,and
distract attention from relevant social clues.
Adverse acute effects already have been
assessed at low levels.Performance of a task
involving motor and monotonous activities is
sometimes not only is not decreased,but on
the contrary,is enhanced.
Two older epidemiologic studies have
shown that schoolchildren when exposed to
high levels of traffic noise show impairments
in performing cognitive tasks (59,60).The
observation threshold derived from these data
is 70 dB(A)(expressed in LAeq,schoolour).More
recently this subject has received renewed
attention (64,77-78).In the Munich airportstudymentionedpreviously,reading compre-hension and long-term memory were
impaired in children attending schools
located around the old Munich airport and
reading comprehension improved after the
closing of the airport.However,reading com-
prehension deteriorated in children subjected
to aircraft noise exposure near the new
Munich airport.Recently,in the United
Kingdom a field study with tests repeated
annually was conducted to assess whether the
association between aircraft noise exposure
and reading comprehension was mediated
-300-
0am>
._C
"o 200-
C
E=c
=CB
CD
0 30 35 40 45 50
LAeq,23-07h in dB(A)
55 60
Figure 4.The maximum number of awakenings per year
as a function of the outdoors night-time equivalent
sound level (8).
Environmental Health Perspectives *Vol 108,Supplement *March 2000
T-r..
128
NOISE EXPOSURE AND PUBLIC HEALTH
through sustained attention and whether it
was confounded by social deprivation and
language spoken at home.The 340 children
who participated were about 9 to 10 years of
age.They attended a school classified either
as a high-noise school [LA ,I6h >66 dB(A)]
or as a low-noise school [Aeq,16 h <57
dB(A)].There appeared to be a high correla-
tion between the noise at school and the air-
craft noise exposure at home.Results show
that the average reading comprehension of
children attending the high-noise schools was
poorer at both measuring times compared
with that of children from the low-noise
schools.Sustained attention,measured only
at follow-up,was poorer in children at the
high-noise schools than in children at the
low-noise schools.Sustained attention did
not play a significant role in explaining the
relation between reading comprehension and
aircraft noise exposure.However,if adjust-
ments are made for age,main language spo-
ken at home,and social deprivation,the
differences in reading comprehension failed
to be significant.These results are not in dis-
agreement with the 1994 evaluation (6)lead-
ing to an observation threshold of 70 dB(A)
(expressed in LAeq,schoolhours),but setting the
threshold at a lower level does not appear to
be warranted.Given the possible long-term
consequences of cognitive effects in children,
we feel that further research into mechanisms
and contributing factors is urgently needed.
Noise Metrics and Noise
Limits for Health Protection
Several biophysical quantities to represent
noise exposure were introduced in the sec-
tion "Characterization of Noise Exposure."
Exposure quantities are not only of scientific
interest,i.e.,for recording data and commu-
nicating research results;policymakers and
risk managers need exposure quantities to
judge the necessity of taking protection or
mitigation measures and to evaluate the
effectiveness of such measures.Criteria for
noise exposure metrics to be used in health
and environmental policy (8)are that they
should be a)relatively simple to determine
or measure;b)transparent with respect to
exposure-response relationships;c)corre-
lated with health effects on a population
level;d)applicable to all outdoors noise
sources;e)universal;and J)communicative.
In practice it appears almost impossible to
derive a single metric and at the same time
fulfill all these criteria because noise sources,
noise characteristics,and exposure situations
differ extensively.
One application of noise metrics is to set
exposure limits.Because such limits are
intended for health protection it is essential
that the science policy decisions made to derive
the metrics be known to the policymaker.
Noise-Induced Hearing Impainment
Sound exposure measures were already being
proposed in the 1960s and 1970s that would
apply to a variety of settings and,if an expo-
sure-response relationship were known,would
be a good predictor of effects to be expected
for any case at the population level.A good
example is the equivalent sound level over an
8-hr work period (LAeq,8h),which correlates
well on a population level with noise-induced
hearing impairment.Confidence in the expo-
sure-response relationships is such that they
have been standardized by ISO (22).This is
reflected in policy debates;such debates focus
on the measures to be taken if certain exposure
levels are exceeded,and not on the validity of
the exposure-response relationships.
A value of LAeq,8h of 85 dB(A)(some-
times lower)has been almost universally
adopted as a limit for unprotected occupa-
tional noise exposure,with additional
requirements for personal hearing protection
above this value (79).However,among
workers exposed to an LA 8 hr value of 85
dB(A),some noise-induced'hearing impair-
ment will occur.Given such exposure over a
lifetime in a job,a hearing impairment at
4,000 Hz of about 5-10 dB is estimated for
most workers,although for those persons
highly sensitive to noise,noise-induced
impairment is considerably greater.This
implies that a lifetime of exposure to 85
dB(A)of occupational noise will slightly
increase the risk for a hearing handicap in a
small proportion of exposed persons.
We concur with the suggestion to use the
equivalent noise level over a period of 24 hr,
to set targets for the exposure during the full
24-hr day for protecting the hearing of the
general population (80).Setting such targets
appears to be warranted,given the increasing
number of noisy activities and exposure dura-
tion,such as loud music in cars,the use of
portable music cassette and CD players,and
the playing of loud computer games at home
and in arcades.
Annoyance and Stress-Related Diorders
Metrics such as LAeq,24 ,Ldn,and Lde came
into use several decades ago (3,4)to regulate
general annoyance.Recently,an international
group of experts convened by the Health
Council of the Netherlands again studied
specification of a biophysical metric to express
noise-induced general annoyance for public
health purposes (8).The Health Council
committee agreed on adjustment factors to be
applied to the metrics to account for differ-
ences in annoyance related to the tonal and
impulse characteristics of noise.The commit-
tee extensively debated the choice between
Lden and Ld,.Analysis of available data indi-
cated that for road traffic noise,general
annoyance is estimated from Lde,with smaller
confidence intervals than those from the other
metrics.However,a decision based on statisti-
cal grounds could not be made (81).Because
from a policy viewpoint,using Lden would
result in somewhat more plausible protection
and mitigation measures,the committee
finally expressed its preference for this metric.
In Europe Ldn may become the future noise
metric to represent general noise-related
annoyance (82).
When using the adjusted Lden levels,the
exposure-response relationships are statisti-
cally significantly different for different modes
of transport.One might envisage performing
a further adjustment that would result in a
single relationship for all types of transporta-
tion noise and possibly industrial noise;in fact
recommendations for such a further integra-
tion were made in the Health Council report
(8).We strongly support such a development
that would require standardization of the
noise exposure-general annoyance relation-
ship;basic data for reaching that goal are
presently available (36).The final step to rep-
resenting general annoyance with a universal
noise metric would be a procedure to combine
concurrent noise exposures from different
sources.This step requires further research,as
limited data have been published on exposure
to two or more sources at the same time.
However,in most practical situations
exposure from one source will dominate.
A question arises about whether noise
abatement policies based on the adjusted Ld,are also effective in reducing the prevalence of
other noise-induced health effects such as
hypertension,ischemic heart disease,and
cognitive performance in schoolchildren.
Although this appears to be plausible,further
study is needed.
A cautionary remark is in order here.As
previously indicated,many other factors in
addition to noise exposure influence noise-
related health effects on a population level.
The exposure-response relationships
between,for example,the percentage of
highly annoyed persons and Lden should be
used for policy guidance rather than to obtain
accurate predictions of effects expected in
specific situations.However,the quantitative
relationships presented here are the best sci-
ence has to offer today and appear to be
rather robust.
Sleep Disturbance
There appears to be consensus that for
protection against sleep disturbance a separate
night-time noise exposure metric is required,
even though limiting exposure using Ld,or a
similar 24-hr metric would also provide some
limitation of night-time noise exposure.The
Health Council committee report (8)men-
tioned previously proposed the night-time
equivalent sound level (see Figure 4).A
Environmental Health Perspectives *Vol 108,Supplement 1 *March 2000 129
PASSCHIER-VERMEER AND PASSCHIER
science policy question arises about whether
the worst-case approach in converting SEL to
LAeq,23-07h is acceptable in policy situations.
In specific situations,for example,popula-
tions in the vicinity of large airports,eco-
nomic consequences of the noise abatement
measures may be severe,although from a
health protection viewpoint using the equiva-
lent sound level could be defended.
The Way Ahead
In addition to natural sounds,speech,and
music,noise is widespread and becoming
more so in our present day society.Major
factors are the increase in motorized traffic,
apparent preferences for noisy leisure and
recreational activities among large groups in
industrialized societies,and increasing
urbanization,particularly in the Third
World,resulting in megacities where high
noise levels 24 hr a day have become com-
monplace.Although at the beginning of the
1960s the major effects of noise exposure
were already known,at the beginning of the
21st century noise exposure still is a major
public health problem.Given our view that
knowledge about effective noise abatement
measures for public health protection has
been available for decades,solving the prob-
lem appears now to be primarily in the
hands of policymakers.In addition to regu-
latory measures,activities in the realm of
health education with respect to the impact
of noise exposure in everyday life appear to
be warranted.Concerns are increasing that
noise-induced hearing loss is not only an
occupational risk but may become an
environmental risk as well.
Science still has important contributions
to make.We mentioned in the previous sec-
tion the study of policy-relevant metrics,for
which more insight in the exposure-response
relationships for different types of noise and
exposure settings is required.The modifying
influence of nonacoustical factors is of
utmost importance,as these influences may
to a large degree determine the effectiveness
and efficiency of noise abatement measures
directed at reducing effects other than noise-
induced hearing impairment.This is obvious
in the case of environmental exposures,but it
may also be relevant for the workplace,for
example,the possible differences between
observation thresholds for cardiovascular
disorders in white and blue collar workers
mentioned previously.
We believe that two subjects should be
priorities in research:the study of cardiovascu-
lar effects and the underlying mechanisms and
the study of the effects of noise on children.
Attention to effects on children is particularly
urgent,as such effects in terms of years of life
with a reduced quality of life or a handicap are
greater for children than for adults.
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tionships of Figure 3 are based,various measuring scales were
used to assess the responses to annoyance questions.The pro-
cedures for converting the different measuring scales to a com-
mon one is discussed in Miedema and Vos (36).
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43.The American Academy of Pediatrics recently issued a state-
ment warning against the risks of high-frequency hearing loss
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equal to 1.5,this does not imply that the noise-induced
increases in persons with such disease are equal.For example,
in the Netherlands about 10%of the adult population is hyper-
tensive or is using medication for hypertension.There are no
data on the prevalence of ischemic heart disease in the
Netherlands,but data on the admission to hospitals (including
death)due to ischemic heart disease give 0.5%.This implies
that the noise-induced increase in hypertensives is 20 times as
large as the noise-induced increase in admission to hospitals
due to ischemic heart disease.
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80.It would be worthwhile to study whether metrics related to
annoyance,such as Lde,,might also be instrumental in prevent-
ing hearing impairment among the general population.The
problem here is that a metric like Lden is location specific (usu-
ally specified in front of the facade of a building),whereas met-
rics to prevent hearing impairment are person specific and
should give the noise exposure at the ear.
81.On average the differences between Lden and Ldn are only mar-
ginal.By analyzing over 60,000 situations with road,railway,or
aircraft noise,the average difference between Lden and Ldn
appeared to be less than 0.5 dB(A).In specific situations,how-
ever,the difference may be substantially larger.
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Environmental Health Perspectives *Vol 108,Supplement 1 *March 2000 131