6. HEALTH CONSEQUENCES AND HARMFUL EFFECTS OF NOISE
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6.1 Organization of monitoring activities
This subsystem has been operating for the past eleven years in 19 cities.
Monitoring comprises the measurement of noise levels and a health questionnaire
survey. In each monitored city two areas are selected: one defined as noisy
and the other as quiet. The noisy and quiet areas were selected to enable
monitoring of total population noise exposure following repeated measurements
to an accuracy in excess of 2 dB LAeq. This enables changes in traffic intensity
to be recorded because a 3 dB shift occurs (when expressing noise as equivalent
acoustic pressure levels) in the event of a 50 % decrease, or doubling, of
the amount of noisy events or traffic intensity. Compliance with this criterion
of accuracy was tested at several sites in each area. Other criteria for
site selection were as follows:
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The number of people inhabiting the monitored areas – selected areas must
have a minimum of 300 inhabitants for valid statistical evaluation of results.
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Absence of any other significant negative factors such as frequent atmospheric
inversions or industrial exhalations.
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Similarity to the general population of the Czech Republic in social,
demographic and occupational features.
Noise levels are measured for a period of 24 hours. Measurements are taken
once per month, alternately in noisy and quiet areas. The required accuracy
is obtained by application of the same technique in all areas, as well as
by observing procedures as defined by the unified measurement methodology for
Subsystem III, in accordance with the Methodological Guideline of the Chief
Public Health Officer, 2001.
The health-related effects of noise have been studied via health questionnaire
surveys in the monitored areas a total of three times (in 1995, 1997 and
2002) over the past 11 years. The next questionnaire survey is due in 2007.
6.2 Noise measurement
Existing legislation in the Czech Republic for evaluation of public health
limits is based on the noise descriptor LAeq (equivalent level of acoustic
pressure A). Recorded values of equivalent levels of acoustic pressure A - LAeq
comprise an energetic expression of noise in specific places. Another
noise descriptor commonly used for describing noise since the inception
of monitoring in the areas studied is the so-called 90% probability noise
level – L90 – which describes constant noise in specific places, or the background
noise present in 90 % of the period of measurement. In 2004, the mean annual values
of equivalent levels A and 90% levels of noise formed a continuous sequence.
The results show that noise in different areas is evenly distributed throughout
the whole range of noise levels monitored. Noise levels detected as equivalent
acoustic pressure A reached up to 75 dB by day and 69 dB by night in the most
noisy areas, and dropped to 50 dB by day and 40 dB by night in the quiet areas.
The highest noise levels have traditionally been measured in the noisy
areas of Plzeň, Prague districts 3 and 10, Ostrava and Olomouc. The lowest
noise levels are repeatedly recorded in the quiet areas of Kolín, Příbram
and České Budějovice. Noise levels expressed by the equivalent level during
day and night measurements in specific areas are presented in Fig. 6.1a,
6.1b and 6.2a, 6.2b;
90% noise levels are depicted in Fig. 6.3a, 6.3b
and 6.4a, 6.4b.
Since 2004, noise values have also been expressed by a new noise descriptor
which correlates with guideline 2002/49/ES of the European Parliament and
Council, concerning the evaluation and management of noise in the outdoor
environment. This guideline is to be incorporated in the legislation of
the Czech Republic under the heading Statute on the evaluation and minimisation
of noise. The main reason for its inclusion is the opportunity of comparing
the noise situation in EC member states. The noise descriptor Lden
or Lday + evening + night describes noise in the environment from the position of
so-called all-day all-night noise disturbance. The new ‘European noise descriptor’
differs from the currently used and, under Czech legislation, valid noise
descriptor LAeq in that it also describes noise in the evening from 18.00
to 22.00 hours, and in the morning from 06.00 to 18.00; night time measurements
remain the same as when expressing noise with equivalent levels of acoustic
pressure A. When describing noise in monitored areas using the noise descriptor Lden
the values in noisy areas largely fluctuated at 70 to almost 81 dB in Plzeň.
Of the quiet areas, the highest noise level was registered in Olomouc
(70 dB) and in one half of the quiet areas the noise levels ranged from 60 dB
to 70 dB.
6.3 Health consequences of noise
Noise is one of the most widespread harmful factors in the occupational
and general environment. Noise is each unwanted sound which has a disturbing
or irritating character, or which has harmful effects on human health. The
hearing analyser functions as an alarm mechanism. The vast majority of warning
signals from the environment are transmitted via the hearing mechanism.
The organism is unable to deactivate the hearing function; the CNS processes
all sound stimuli even in sleep. Alarming noise on a daily basis is identified
as dangerous even during sleep and unconsciously activates a stress reaction.
The effects of noise on human beings are both specific, with direct effects
on the hearing apparatus, and systemic, affecting the organism as a whole.
The effects that act on the hearing apparatus tend to occur following long-term
occupational exposure to excessive noise. Excessive noise is proven to affect the
central nervous, hormonal, immune and cardiovascular systems; this is known
to contribute to the development of so-called civilization diseases, mental
problems etc. Even at levels of 55 dB(A) a so-called primary vegetative reaction
to noise is known to occur (e.g. a reaction that cannot be controlled by
the will). It causes increased sympathetic nervous system activity which in
turn results in increased heart frequency, increased blood pressure, decreased
blood flow to the peripheral organs; furthermore, muscular tension and digestive
system motility increase. By fixing these reactions to during long-term
noise exposure, noise acts as a so-called chronic stressor and contributes
to the inception of cardiovascular and other civilization diseases that
have a confirmed stress aetiology. Other proven negative effects of noise
are overall metabolic changes, such as elevated blood sugar (glucose), insulin,
blood lipid levels and cholesterol. Noise also causes increased release of
magnesium from cells. The widespread deficiency of Mg in the diet and concurrent
effects of noise or other chronic stress factor leads to a permanent decrease of cellular
Mg levels, which in turn may result in the proliferation of fibrous tissue
in cardiac muscle. Deterioration of reactions to all (not just noise-based)
stress stimuli has been described during Mg deficiency. Simultaneous exposure
to excessive noise and other load (occupational, for instance) leads to increased
release of the so-called stress hormones adrenalin and noradrenalin into
the peripheral blood circulation. The long-term effects of excessive noise
cause changes in blood vessels, caused by released stress hormones, with
subsequent elevation of blood pressure.
A further significant damaging effect of noise is its influence on sleep
quality. Excessive noise increases the time taken to fall asleep, leads
to changes in the quality and duration of sleep and subsequent tiredness
and decreased efficiency. Long-term sleep deprivation may contribute to
weakened immune response and increased susceptibility to infectious disease.
The effects of long-term exposure to various levels of noise on health
are studied by regular questionnaire surveys of demographic, sociological
and medical data of the inhabitants of the areas monitored. The most recent
questionnaire survey was conducted in 2002, yielding data from 12,000 respondents
from 19 cities in the Czech Republic. These questionnaire studies repeatedly
confirmed the statistical significance between increasing values of daytime
noise and certain selected civilization diseases. The closest statistical
link involves increased noise levels and incidence of hypertension, stomach
and duodenal ulcers and catarrh in the upper respiratory tract. A statistically
significant relationship was revealed between local noise levels and the
number of people complaining of sleep disorders and quality. Likewise,
a significant connection was uncovered between the ratio of people disturbed
by noise in their environment and precisely measured noise levels in monitored
areas. Furthermore, a statistically significant relationship was revealed
between the increasing percentage of persons disturbed by noise and the
incidence of civilization diseases, particularly hypertension. Almost 65 %
of persons disturbed by noise suffered from a selected civilization disease,
and increasing noise levels are associated with an increasing average number
of these diseases per person.
6.3.1 Assessment of the health effects of noise in adjacent areas
The selected primary noisy and quiet areas represent a relatively small
population sample, and they are instruments for research on relations between
the noise levels and the health conditions. Therefore, for the assessment
of the health effects of noise in wider territories, so-called adjacent
areas were selected. One of the major criteria for selection of an adjacent
area was similarity to the monitored areas (the same type of buildings,
for instance). The number of inhabitants in separate homes in the adjacent
area is acquired from up-to-date voting registers. Capacity problems do
not enable 24-hour monitoring of noise levels in adjacent areas. Monitoring
in adjacent areas involves 60 minute measuring periods outside selected
houses during the day. These values are approximated to expected nighttime
values extrapolated from pertinent primary areas. Another input is the
updated resulting relationship between the noise level and the sum rate
of non-communicable diseases determined in questionnaire surveys (in 1995,
1997 and 2002) at a significance level of more than 5%. Based on this approach,
health risk from noise can be estimated for an even larger area, of course
with lower accuracy.
6.4 Partial conclusions
In 2004, the mean annual values of equivalent levels A and 90% noise levels,
as well as Lden noise descriptor levels, formed a continuous sequence. Noise
levels expressed by equivalent noise levels A reached 75 dB in the noisiest
areas during the day and 69 dB at night. In quiet areas these values reached
50 dB during the day and 40 dB at night. The highest noise levels are,
as previously, in the noisy areas of Plzeň, Prague districts 3 and 10, Ostrava
and Olomouc. The least noisy are again the quiet areas of Kolín, Příbram
and České Budějovice. Noise levels expressed in the main areas by the Lden
noise descriptor which characterises all day noise disturbance mostly ranged from
70 dB to 79 dB. In quiet areas the greatest noise levels were recorded
in Olomouc (70 dB), and in approx. one half of the quiet areas the noise
levels ranged from 60 dB to 70 dB.
Differences in past and present noise levels are minimal in individual
main areas. There is no obvious increase or decrease in city noise levels
since clear variations occurred in few areas and the significance of any
increase in certain areas is neutralised by decreased levels in others.
The effects of long-term exposure to varying noise levels are monitored
by regular questionnaire surveys of demographic, sociological and medical
data of inhabitants of the main areas monitored. The most recent questionnaire
survey was conducted in 2002. A significant relationship between so-called civilization
diseases, and individually for hypertension, and monitored noise levels
has been repeatedly confirmed. Likewise, an important relationship between
persons subjected to noise disturbance and precisely measured noise levels
in main areas has been revealed. A significant relationship exists between
noise levels and the number of persons suffering from sleep disorders.
Fig. 6.1a |
Equivalent level of acoustic pressure A (LAeq), day, 1994–2004
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Fig. 6.1b |
Equivalent level of acoustic pressure A (LAeq), night, 1994–2004
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Fig. 6.2a |
Equivalent level of acoustic pressure A (LAeq),
noisy localities – day and night, 2004
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Fig. 6.2b |
Equivalent level of acoustic pressure A (LAeq),
quiet localities – day and night, 2004
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Fig. 6.3a |
90th level of acoustic pressure A (L90), day, 1994–2004
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Fig. 6.3b |
90th level of acoustic pressure A (L90), night, 1994–2004
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Fig. 6.4a |
90th level of acoustic pressure A (L90),
noisy localities – day and night, 2004
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Fig. 6.4b |
90th level of acoustic pressure A (L90),
quiet localities – day and night, 2004
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