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 spatial distribution. In question are namely considerable gradients of changes in the intensity of noisiness at one site. The subsystem is operated in 21 localities including three districts of Prague, and 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. 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 noise level of the whole locality through the repeated measuring of noise and thereby form a description of 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 of the 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 10:00 a.m. Wednesday through Thursday for a period of 24 hours.

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 70 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 39 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 2 and Plzeò. 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 present monitoring period (1997 and 1998) 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 follows 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 rather changes in quiet localities than in noisy ones, namely in the evaluation in LAeq. However, that is a small difference easily explainable by that in the quiet localities there can occur changes in the detected equivalent level more easily. In a formerly small traffic burden it can be double.

Further, there was evaluated the trend in noisiness in each locality over the past five years of the run of the Monitoring System (Fig. 6.1a, 6.1b, 6.2a, 6.2b). From the figures it is apparent that in most localities there did not take place any significant changes in noisiness. The correlation registered were caused by local changes in traffic or in building activities, and there was demonstrated no generally overall tendency in an increase or decrease of noisiness 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 five years of the run 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, 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 both questionnaire campaigns, there was recorded a significant increase in the occurrence of “civilization” diseases as a whole, in connection with noisiness in the localities. In the last questionnaire survey the correlation was only at the 10% level of significance, i.e. with a 90% probability (such a correlation is usually considered as “weak”). All in all, from a comparison with results from preceding years it is apparent that noise continues to exert its effect on the health of the population.

Data from both questionnaire surveys were classified for further continuous statistical evaluation. In question was namely the evaluation of marital status, occupation, sources of heat for cooking, orientation of the windows, insulation capacity of doors and windows, sources of noise in the building, mode of transportation to work, smoking characteristics of the respondent, passive smoking, as well as sum values combining civilization, allergic and respiratory diseases. The classification of the set of respondents for processing was carried out by gender (3 335 males, 4 408 females) and by age groups. Further classification was based on the intensity of acoustic pressure A (LAeq), i.e. values of daytime or nighttime noise levels, and the original set of all respondents was divided according to so-called quiet and noisy localities.

Some further significant relationships were revealed by a complex analysis applying methods of factor analysis, distribution analysis and logistic regression analysis. These are namely, in older age groups, a positive correlation (with increasing noisiness the indicator evaluated also increases significantly) between daytime noisiness and lithiasis (in females) and hypertension and ulcer disease of the gastrointestinal tract (in males). The subjective assessment of one’s own health correlates to daytime noisiness very significantly (p < 0.01). Analysis further confirmed that the majority of the other indicators in which there has been demonstrated a statistically significant dependence on the noise level, or on localities designated either as noisy or quiet, belong to the group characterizing the environment of the houses or homes of the respondents. The structural and noise characteristics of the building and namely of the home environment in most instances correlates positively with the data of probands characterizing their relation to noisiness.

Furthermore, there correlates positively the information that “noise is disturbing” with incommensurate vegetative reactions to stress, which in fact reflect the so-called neurotization of the organism. The whole field of the relationship of human psychics and communal noise (bad temper, annoying noise, disturbing by noise, incommensurate fatigue during the day, headache, etc.) reflects itself in the state of health of the respondents, i.e. in manifestations lying in insufficient rest, sleep and in difficulties in falling asleep. However, there has not been confirmed any correlation between the duration of the living of probands in the home in the locality under monitoring. On the contrary, there has been confirmed a statistically significant correlation of airing and recreation away from the residence in relation to the noise levels in the localities. It goes to show that the inhabitants themselves regulate the degree of their exposure to noise by closing the windows, i.e. by the mode of ventilation. An analogous relationship was found from recreational stays (utilizing them or not). These conclusions are supported by the assessment of indicators dealing with window orientation in the homes and their noise-proofing characteristics. No significant results were found that are not in line with the logic and expectations of present knowledge and this complex analysis.

6.4 Partial conclusions

The measuring of noise levels takes place regularly at 42 localities. In 1998 noise in those localities was found to be in a continuous range of from 75 dB in the day and 70 dB at night in the noisiest localities down to 45 dB in the day and 39 dB at night in the quiet ones. From the evaluation of the development of noisiness in the individual localities over the past five years it is apparent that in most of them there did not take place any significant change in noise levels and that there cannot 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. This result is valid only in noise and the sum of all diseases under follow-up. Individual diseases, with exception hypertension and inflammations of the upper respiratory tract, do not show this in the set of all the respondents. Comparisons of these correlation between noisiness and health since 1985 (that the campaign was conducted outside the activities of the present Monitoring System) to 1997, after three completed investigations show that the correlation is similar. From that it the basic finding arises 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), measurements in day, 1994 - 1998
Fig. 6.1b Equivalent level of acoustic pressure A (LAeq), measurements in night, 1994 - 1998
Fig. 6.2a 90% level of acoustic pressure A (L90), measurements in day, 1994 - 1998
Fig. 6.2b 90% level of acoustic pressure A (L90), measurements in night, 1994 - 1998

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