6. HEALTH CONSEQUENCES AND HARMFUL EFFECTS OF NOISE

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:

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
Fig. 6.1b Equivalent level of acoustic pressure A (LAeq), night, 1994–2004
Fig. 6.2a Equivalent level of acoustic pressure A (LAeq), noisy localities – day and night, 2004
Fig. 6.2b Equivalent level of acoustic pressure A (LAeq), quiet localities – day and night, 2004
Fig. 6.3a 90th level of acoustic pressure A (L90), day, 1994–2004
Fig. 6.3b 90th level of acoustic pressure A (L90), night, 1994–2004
Fig. 6.4a 90th level of acoustic pressure A (L90), noisy localities – day and night, 2004
Fig. 6.4b 90th level of acoustic pressure A (L90), quiet localities – day and night, 2004

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