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

6.1 Organization of monitoring activities

Noise as a risk factor differs from other monitored factors in its specific areal distribution, especially in considerable changes of noise intensity. The subsystem has been in operation for seven years in 21 localities including three districts of Prague. It comprises the physical measuring of noise levels and a health questionnaire survey. In each monitored city, two representative localities are selected: one noisy and one quiet. All collaborating Public Health Service teams have been equally equipped and the measurements are performed according to a unified methodology. The noisy and quiet localities were selected to allow measuring the population exposure to noise with accuracy higher than 2 dB LAeq. Thus changes in traffic intensity can be recorded; using the equivalent level of acoustic pressure to express the noise level, a 3 dB shift occurs if the noisy events or traffic intensity either decrease by one half or by their doubling. Compliance with this criterion was tested at several sites of each locality. Other criteria for selection were as follows:

6.2 Noise measurement

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) and compliance with the standard measuring procedures given in Guideline No. 43, Hygiene Regulations of the Ministry of Health of the Czech Republic, vol. 37, 1977. For illustration, according to these requirements, the microphone is installed either at a distance of two metres from the facade of a dwelling house usually in the level with the window of the first above-ground floor or at least three metres above ground, if the measurement is conducted from a measuring vehicle or using a microphone installed otherwise than from the window. The measurements are carried out alternately in a noisy and a quiet localities, once a month, preferably from Wednesday through Thursday.

From the results it is apparent that noise in the individual localities is evenly distributed within the whole range of noise levels to be taken into consideration. The values found in the equivalent level of acoustic pressure A, on the one hand reach 75 dB in the day time and 69 dB in the night time in the noisiest localities, and on the other hand, drop to 45 dB in the day time and to 37 dB in the night time in quiet localities. The equivalent levels of acoustic pressure A - LAeq express noise in agreement with Regulation No. 13/1977 Coll., and from the technical point of view, express noise as energy levels at different sites. The 90 % probability noise levels describe permanent noise at each of the sites. The results presented are suggestive of high noise levels in the night time in the localities of Prague, Plzeò, Ostrava and Olomouc. Comparison of the results with the requirements set in Regulation No. 13/1977 Coll. shows that a few localities only meet the basic requirement for quiet in residential areas.

Comparison of the data obtained in 1999 and 2000 has shown changes in noise levels exceeding the tolerated limits of measuring accuracy, i.e. 1 dB, in a minority of the monitored localities irrespective of whether situated in large or small cities. These changes are most probably caused by local modifications in the traffic system. Analysis of the noise levels recorded for each of the localities within one year revealed that fluctuations exceeding 2 dB LAeq were rather rare in most localities. No seasonal effect on the noise levels was detected. The night time equivalent levels slightly increased rather in quiet than in noisy localities, which can be explained by the fact that in initially quiet localities with limited traffic the noise levels may have doubled easily.

Based on the 7-year monitoring of noise (Figures 6.1a, 6.1b, 6.3a, 6.3b), it can be stated that most localities remained without any significant changes. The significant linear increase or decrease recorded in some localities was caused by local changes in the traffic or building activities. No general tendency towards either lower or higher noise levels was identified for most of the monitored localities.

6.3 Health consequences and disturbing effects of noise

Noise effects on population health were monitored using a questionnaire in the periods of 1994 through 1995 and 1996 through 1997. The investigation has shown a significant correlation between noise levels and frequency of non-communicable diseases in general, hypertension and frequent upper airways morbidity as the indicator of compromised immunity.

The questionnaire survey was based on demographic, sociological and health data from the population of the monitored localities. A correlation has repeatedly been found between the incidence of non-communicable diseases and noise levels. This means that the effect of noise is permanent and so is its significance with reference to the effects of the other harmful factors on population health. Furthermore, a significant correlation was found between the percentage of the population who feel disturbed by the noise outdoors and the incidence of non-communicable morbidity, mainly hypertension and compromised immunity.

The repeatedly found correlation between the noise levels and the incidence of non-communicable diseases was indicative of the need for assessment of relative risk of damage to health from outdoor noise caused mostly by traffic (almost 90 %). A program called Noise M was created for this purpose allowing estimation of the percentage of population whose health would be damaged by night time noise in different two-decibel bands from 40 dB to 72 dB in LAeq, based on the data on population number in each house and their noise exposure. Individual risk assessment of damage to health from presumptive night time noise exposure for 10 years and more is given for the two-decibel bands in Table 6.1.

Phase three of the standard questionnaire monitoring of noise effects on population health will take place in 2002. The same questionnaire will be used as in the previous phases. The incidence of the health indicators such as selected non-communicable diseases, sleep disorders, mental discomfort, and neurotic symptoms will be monitored. Demographic, sociological and lifestyle factors will be monitored as well.

6.4 Partial conclusions

Noise levels have been regularly measured in 42 localities. In 2000, the noise levels ranged continuously from 75 dB in the day time and 69 dB in the night time in the noisy localities to 42 dB in the day time and 36 dB in the night time in the quiet localities. Based on the seven-year monitoring data, it can be stated that the noise levels in most localities have not shown either significant changes or a significant ascending or declining tendency.

Table 6.1 Relative risk assessment of health impairment by noise in environment

dB LAeq

Probability
of health
impairment risk
[%]

dB LAeq

Probability
of health
impairment risk
[%]

dB LAeq

Probability
of health
impairment risk
[%]

< 40

-

50–52

4.0

62–64

  8.3

40–42

0.4

52–54

4.7

64–66

  9.1

42–44

1.1

54–56

5.4

66–68

  9.8

44–46

1.8

56–58

6.2

68–70

10.5

46–48

2.5

58–60

6.9

70–72

11.2

48–50

3.3

60–62

7.6

 

 


Fig. 6.1a Equivalent level of acoustic pressure A (LAeq), day, 1994–2000
Fig. 6.1b Equivalent level of acoustic pressure A (LAeq), night, 1994–2000
Fig. 6.2a Equivalent level of acoustic pressure A (LAeq) in noisy localities, day and night, 2000
Fig. 6.2b Equivalent level of acoustic pressure A (LAeq) in quiet localities, day and night, 2000
Fig. 6.3a 90th level of acoustic pressure A (L90), day, 1994–2000
Fig. 6.3b 90th level of acoustic pressure A (L90), night, 1994–2000

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