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 area distribution, especially in considerable changes of noise intensity in individual places under measurement and different times of day. This subsystem has been in operation for the past eight years in 21 sites including three Prague districts. It comprises the physical 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. All participating Public Health Service teams are identically equipped and measurements are carried out according to a unified methodology. The noisy and quiet areas under observation were selected to enable 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:

6.2 Noise measurement

Noise levels are measured for a period of 24 hours to record their development throughout the day. The required accuracy of measurements is achieved through the use of top technology (2231 Brüel & Kjaer modulation sound meter) and strict compliance with a unified methodology. It means, among others, that the microphone is installed at a distance of two metres from the facade of the target dwelling, most frequently at the height of the first floor window. If the measurements are taken from a truck – measuring car or by a microphone not attached to a window, the microphone is installed at least three metres above ground level. Measurements are taken once per month, alternately in noisy and quiet areas, preferably from Wednesday to Thursday.

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 reach 75 dB by day and 69 dB by night in the noisy areas, and drop below 49 dB by day and 39 dB by night in the quiet areas. Equivalent levels of acoustic pressure A – LAeq express noise as stipulated by  Governmental Resolution No. 502/2000 Coll. and from a technical point of view describe noise as energy levels at different sites (Fig. 6.1a, b and Fig. 6.2a, b). The 90%-probability noise levels L90 describe permanent noise at each site (Fig. 6.3a, b and Fig. 6.4a, b). The results presented are suggestive of high night-time noise levels in Prague, Plzeň, Ostrava and Olomouc. Comparison of these results with the requirements set by Governmental Resolution No. 502/2000 Coll. shows that only a few areas meet basic requirements in residential areas.

Comparison of data obtained in 2000 and 2001 has revealed that changes in noise levels exceeding the tolerated limits of measuring accuracy, i.e. 1 dB, have occurred in a minority of areas, irrespective of whether in large or small cities. These changes are most probably caused by local modifications of the traffic system. Analysis of noise levels recorded in each of the areas during a twelve-month period revealed that fluctuations in excess of 2 dB LAeq are rare in most cases. Greater fluctuations occurred only in those areas subject to traffic system changes or other noisy activities.

Seasonal change has virtually no effect on noise levels in the monitored areas. In terms of nocturnal equivalent levels there was a greater increase in the quiet, rather than in noisy areas. This is, however, a minor difference, explainable by the fact that in quiet areas traffic burden may easily be doubled.

Temporal trends for the past eight years of monitoring in separate areas were evaluated using linear regression. After all of these values were transformed into logarithms the reliability interval was calculated at a significance level of 5 % to yield a standard for linear dependence of noise on time.

Noisy areas with a decreasing trend of noise are Prague 10 (day and night), České Budějovice, Hradec Králové and Brno (day) and Prague 3 (night). Increasing noise trends were registered in Havlíčkův Brod (day and night), Olomouc, Znojmo and Kladno (night) and Ostrava (day). Of the quiet areas there was a decrease in day-time noise in Prague 2 and Hradec Králové and increase in Ústí nad Labem and Ostrava. Night-time noise is on the increase in Příbram and Kladno and decreasing in Znojmo. Other areas have complex non-linear trends with no general tendency towards either higher or lower noise levels.

6.3 Health consequences and disturbing effects of noise

Monitoring the effects of noise on population health was conducted by questionnaire in 1994–1995 and 1996–1997. Questionnaires were employed again in 2000–2001 with results due in 2003. The questionnaires focussed on so-called non-communicable diseases, sleep disorders and mental well-being (incidence of neurotic symptoms as an indicator of health status). The health specifics of respondents were correlated with measured noise levels. The relationship between noise disturbance and non-communicable diseases was researched. A more detailed description is published in the Subsystem 3 Special report for 1998 and 1999.

Selected non-communicable diseases comprise hypertension, myocardial infarction, high blood pressure, gastric and duodenal ulcers, kidney and gall stones, diabetes mellitus, cancer, frequent catarrh of the upper respiratory tract and allergies. Other monitored factors were insomnia, sleep disorders and excessive fatigue during and after work. Besides monitoring the relationship of single selected non-communicable diseases and noise, the relationship of noise and the sum of these diseases (excluding allergies) was likewise followed.

A correlation between levels of noise and non-communicable diseases was repeatedly apparent. Statistical significance was detected in cases of hypertension, frequent catarrh of upper respiratory tract, recurring bronchial complaints and skin diseases. The incidence of cancer was not confirmed. However, significant links were found between day-time noise and kidney and gall stones (females) and day-time noise and hypertension and gastric ulcers (males).

Increasing noise levels correlate with increased numbers of inhabitants suffering from excessive fatigue after work and sleep disorders. The consumption of sedative and hypnotic prescription medicines is significantly higher in noisy areas. Subjective assessment of personal health status significantly correlates with day-time noise, while for night-time noise the differences between areas were not apparent. A significant relationship was found between the number of inhabitants disturbed by noise and the incidence of non-communicable diseases, particularly hypertension.

6.3.1 Assessment of relative health risk posed by noise

The repeatedly found correlation between noise levels and incidence of non-communicable diseases was again used to assess the relative health risk posed by outdoor noise which is mostly caused by traffic (from almost 90 %). A programme called Noise M was developed for this purpose allowing estimation of the percentage of population whose health is impaired by night-time noise in different two-decibel bands from 40–72 dB, based on the number of inhabitants in each house and their noise exposure levels. In contrast to the last monitoring period there has been a 0.05 % decrease in the estimated number of inhabitants affected by noise to 4.6 % of the total monitored areas population (76 762 population) i.e. about 3500 persons, which is not a negligible figure. After dividing the results between Prague and the remaining areas there was a decline of 0.13 % in Prague to 6.4 % (comprising 28 146 population). Outside of Prague the decrease is 0.14 % to 3.5 % affected inhabitants (48 616 population). A slight decrease in numbers affected may therefore be claimed and viewed as a positive trend. Individual risk assessment of health damage from night-time noise exposure lasting a minimum of 10 years as shown in two-decibel bands is presented in Table 6.1.

6.4 Partial conclusions

Noise levels are being regularly measured in 42 areas. In 2001, the noise levels in these areas ranged continuously from 75 dB in day-time to 69 dB at night-time in the noisy areas and 49 dB in day-time and 39 dB at night-time in quiet areas.

Noise levels in noisy areas are increasing in Jablonec nad Nisou, Ostrava, Olomouc, Znojmo, Žďár nad Sázavou and Příbram, in the quiet areas in Příbram, Ústí nad Labem, Liberec, Žďár nad Sázavou, Havlíčkův Brod, Kladno and Ústí nad Orlicí. In quiet areas there is a decrease in noise levels in Znojmo, Jihlava, Prague 2, Prague 3 and Plzeň, in the noisy areas in Děčín, Prague 3, Brno, Hradec Králové, Ústí nad Orlicí, Prague 10, Liberec, České Budějovice and Prague 2.

The health-oriented section of this subsystem is based on questionnaire survey of demographic, sociological and medical data. Correlation between non-communicable diseases and noise levels has repeatedly been confirmed. However, these results are valid for the relationship of noise and the sum of all monitored health complaints. Individual diseases (except hypertension, catarrh of upper respiratory tract, bronchitis, lithiasis and skin complaints) do not correlate in the group of respondents. A significant link has been found between persons disturbed by outdoor noise and the incidence of neurotic symptoms (headache, accelerated heartbeat), sleep disorders and associated consumption of sedatives and hypnotics. A significant relationship has been identified between persons disturbed by noise and the incidence of non-communicable diseases, particularly hypertension.

Table 6.1 Relative risk assessment of health impairment by outdoor noise

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), noisy localities – day, 2001
Fig. 6.1b Equivalent level of acoustic pressure A (LAeq), noisy localities – night, 2001
Fig. 6.2a Equivalent level of acoustic pressure A (LAeq), quiet localities – day, 2001
Fig. 6.2b Equivalent level of acoustic pressure A (LAeq), quiet localities – night, 2001
Fig. 6.3a 90th level of acoustic pressure A (L90), noisy localities – day, 2001
Fig. 6.3b 90th level of acoustic pressure A (L90), noisy localities – night, 2001
Fig. 6.4a 90th level of acoustic pressure A (L90), quiet localities – day, 2001
Fig. 6.4b 90th level of acoustic pressure A (L90), quiet localities – night, 2001

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