6. RESULTS OF SUBSYSTEM 3: HEALTH CONSEQUENCES AND HARMFUL EFFECTS OF NOISE

6.1 Organization of the monitoring activities

Noise as a risk factor differs from other monitored factors in its specific spatial distribution. The subsystem is operated in 21 localities including three districts of Prague (Tab. 3.1). It contains the physical measuring of noise levels as well as a health survey with the aid of a separate questionnaire. In each city where monitoring is implemented two basic localities are selected, one of which represents a noisy site and the other a quiet one. The instrumentation of all collaborating Public Health Centers is the same and the monitoring is conducted according to a unified methodology.

The selection of basic noisy and quiet localities was carried out so as to be able to follow up the exposure of its inhabitants to noise with an accuracy greater than 2 dB LAeq. It is thus possible to register changes in the intensity of traffic because in expressing noisiness by an equivalent level a shift of 3 dB occurs at a 50 % drop in noisy events or in traffic intensity or by the doubling of them. The meeting of this criterion was verified at several sites of each locality. Other criteria for selection were:

6.2 Measurement of noise

The noise level is measured for 24 hours to record its development throughout the whole day. The accuracy of the measurement is guaranteed by the use of top equipment (modulation sound level meter 2231 Brüel & Kjaer). The detailed installation of the microphone is in accordance with the requirements of a unified methodology for measuring noise (Guidelines No. 43, Hygiene regulations, Ministry of Health, Czech Socialist Republic, Vol. 37, 1977). This means that the microphone is installed at a distance of two meters from the facade of a dwelling house usually in the level of a window in the first above-ground floor and at least three meters above ground when the measurement is conducted from a measuring vehicle or when the microphone is installed otherwise than from the window. The measurements are carried out alternately in a noisy locality and in a quiet one once a month, preferably from Wednesday through Thursday.

From the results it is apparent that noisiness in the individual localities is evenly distributed within the whole range of noise levels coming into consideration. The values found in the equivalent level of acoustic pressure A, on the one hand reach 75 dB in the day and 69 dB at night time in the noisiest localities, and on the other hand in quiet localities they drop to 45 dB in the day and to 37 dB at night. The equivalent levels of acoustic pressure A - LAeq found, express the noisiness corresponding to the still valid Public Notice No. 13/1977 Dig. and from the technical point of view mean the expression in terms of energy, of the state of noisiness at individual sites. The 90% probability levels of noise describe a piece of information on the permanent noisiness at each site. From the results presented there is apparent great nighttime noisiness in the localities of Prague, Plzeň, Ostrava and Olomouc. As regards the comparison of the results with requirements set in Public Notice No. 13/77 Dig., it is apparent that the basic requirement for quiet in residential areas is met in only a small portion of the localities.

From the differences in noisiness found for the monitoring periods of 1998 and 1999 it is apparent that changes in noise exceeding the tolerated limits of measuring precision, i.e. 1 dB, occurred in only a small portion of the localities. At the same time it does not matter whether such localities are situated in large cities or in small towns. These changes are most probably caused by local modifications in the traffic system. From an analysis of the dynamics of the noise levels in the course of one year in the individual localities it can be stated that in most localities no changes exceeding 2 dB LAeq occur. The individual seasons of the year have practically no influence on noise levels in the localities under monitoring. As far as changes of nighttime equivalent levels are concerned, there were changes in quiet localities rather than in noisy ones, namely in the evaluation in LAeq. However, this is a small difference easily explainable by that in the quiet localities changes in the detected equivalent level can occur more easily. In a formerly small traffic burden it can easily double.

Further, there was evaluated the trend in noisiness in each locality over the past six years of operation of the Monitoring System (Fig. 6.1, 6.2). From the figures it is apparent that in most localities no significant changes in noisiness occurred. The significant correlations registered, including repeated ones in Jablonec n/N and in Žďár n/S, were caused by local changes in traffic or in building activities. No generally overall tendency in an increase or decrease in noisiness was demonstrated in the majority of the individual localities under follow-up.

6.3 Health consequences and the disturbing effects of noise

Monitoring the effects of noise on the population was conducted in the past six years of operation of the Monitoring System through a health questionnaire in the periods of 1994 through 1995 and 1996 through 1997. Followed up were namely the occurrence of so-called “civilization” diseases (myocardial infarction, gastric and duodenal ulcers, gall and kidney stones, diabetes mellitus, hypertension, tumor diseases), sleep disturbances and manifestations of psychic well being eventually information on the occurrence of signs of neurosis in the population as indicators of the state of health in relation to noisiness at the site of residence.

In 1999 there was carried out a consequent processing of data from the last questionnaire survey, whose treatment was aimed at assessing the relationship between the degree of noise annoyance and morbidity. The objective was to find:

The evaluation was carried out by logistic regression analysis with the following findings:

In the evaluation of the influence of demographic and social factors on the incidence of the feeling of being disturbed by noise from the outdoor environment it was found that among inhabitants with a higher educational status there is significantly less people feeling annoyance than among inhabitants with elementary education, and that significantly more married persons feel the annoyance. Other factors of this kind do not assert themselves to any significant degree in the evaluation of the feeling of being disturbed by noise and of morbidity (Summary Reports 1997 and 1998).

In the evaluation of noisiness in adjacent localities there has been applied a model of estimating the relative risk of injury by noise on the basis of the correlation between noise levels and the incidence rate of civilization diseases in the basic localities. It was determined that in the period 1994 - 1995, 12.7 % of the population lived under risk of injury to health, and in the periods under monitoring in 1996 - 1997 and 1998 - 1999 only 4.7 %. The former estimate (1994 - 1995) for Prague localities was 14.7 % and in the other cities 11.5 %. In the latter periods (1996 - 1997 and 1998 - 1999) there were registered values of 6.3 % and 6.6 % for Prague, and 3.9 % and 3.7 % for the other localities, respectively. The decrease in those injured by noise (decrease in the negative action of noise on the population) in some cities could have taken place probably due to the moving of people out of central down-town areas. Results from the last period of monitoring, which had practically not changed when compared to the period 1996 - 1997 do not rule that out.

6.4 Partial conclusions

The measuring of noise levels takes place regularly at 42 localities. In 1999 noise in those localities was found to be in a continuous range of from 75 dB in the day and 69 dB at night in the noisiest localities down to 45 dB in the day and 37 dB at night in the quiet ones. From the evaluation of the development of noisiness in the individual localities over the past six years it is apparent that in most of them there did not take place any significant change in noise levels, nor can there be demonstrated any significant general rising or declining trend.

The part pertaining to health is based on a questionnaire survey of demographic, sociological and health data on the population of the localities under monitoring. In the so-called civilization diseases there was repeatedly found a positive correlation between their occurrence and the degree of noisiness (taking into account only the sum of all diseases under follow-up). Individual diseases, exceptions to which belong hypertension and inflammations of the upper respiratory tract, do not show this in the set of all the respondents. Comparisons of this correlation between noisiness and health since 1985 (that campaign was conducted outside the activities of the present Monitoring System) to 1997, after three completed investigations show that the correlation is similar. Through further processing of the original database of results on health there arises the basic finding that the effect of noise is permanent and just as permanent also remains its significance in relation to the effect of other contaminants on population health.

Fig. 6.1a   Equivalent level of acoustic pressure A (LAeq), 1994 - 1999, measurements in day
Fig. 6.1b   Equivalent level of acoustic pressure A (LAeq), 1994 - 1999, measurements at night
Fig. 6.2a   90% level of acoustic pressure A (L90), 1994 - 1999, measurements in day
Fig. 6.2b   90% level of acoustic pressure A (L90), 1994 - 1999, measurements at night

Main page

CONTENTS