6. HEALTH CONSEQUENCES AND HARMFUL EFFECTS OF NOISE |
6.1 Organization of monitoring activities
This subsystem has been operating for the past ten years in 19 cities and 2 Prague districts (Prague 3 and 10). In 2003, monitoring was concluded in Prague 2. 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 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:
In the main areas, the health effects of noise have been studied over the past ten years on three occasions (in 1995, 1997, and 2002) by means of a questionnaire.
6.2 Noise measurement
Noise levels are measured for a period of 24 hours to record their development throughout the day. 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 Project III, in accordance with the Methodological Guideline of the Chief Public Health Officer, 2001.
In 2003, the mean annual values of equivalent levels 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 reach 75 dB by day and 69 dB by night in the most noisy areas, and drop to 50 dB by day and 40 dB by night in the quiet areas. Equivalent levels of acoustic pressure A – LAeq express noise from the technical point of view describing noise as energy levels at different sites. The 90%-probability noise levels L90 describe permanent noise at each site. As previously, the highest noise levels were found in the noisy areas of Prague 3 and 10, Plzeň, Ostrava and Olomouc. The least noisy areas where the quiet parts of Kolín, Příbram and České Budějovice. Noise expressed by equivalent levels in day and night-time measurements in given areas is described 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.
In 2002, a detailed statistical analysis of inter-annual changes in noise levels was elaborated, in the form of the linear and quadratic trends for quiet and for noisy areas and for day-time and night-time measurements. A linear decrease occurred in Prague 2, Prague 3, Liberec, and in České Budějovice. Noise has been on the increase in quiet areas, namely in Prague 10, Liberec, Žďár n. Sázavou, Kladno and Ústí n.Orlicí. An increase in noise levels in traditionally noisy areas was recorded in Ostrava and Olomouc. Noise levels have remained constant in Příbram, Hradec Králové, Brno, and Havlíčkův Brod.
6.3 Health consequences of noise
Noise is one of the most widespread harmful factors in the occupational and general environment. It has become a serious problem particularly in recent years as a result of accelerated development in traffic and industry. Noise is each unwanted sound which has a disturbing irritating character, or has harmful effects, irrespective of its intensity, which in many cases is not of major importance.
The hearing analyzer functions as an alarm 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 in sleep and a stress reaction is unconsciously activated. The health effects of excessive noise manifest by the accumulation of a number of negative factors only after a period of time, at least 10–15 years.
Epidemiological studies show that night-time exposure to noise from traffic at an mean level of 55 or more dB(A) leads to significantly elevated concentrations of stress hormones in blood (cortisol, adrenalin, noradrenalin) with subsequent negative effects for the exposed subject. Excessive noise acting on the hormonal and immune systems affects the central nervous and cardiovascular systems; this, combined with other negative factors, may give rise to civilization diseases, mental disturbance etc. At a level of 55 dB(A), a primary vegetative reaction occurs (i.e. a reaction unaffected by willpower), which raises nervous system activity and is reflected by vascular changes, increased heartbeat and blood-pressure, decreased blood circulation in peripheral organs. Other changes include increased levels of glucose, insulin, blood lipid counts, cholesterol and elevated release of magnesium from cells. Dietary deficiency of this element combined with exposure to noise leads to permanently lowered levels of cellular magnesium, leading to deterioration of reactions to all stimuli.
A further 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.
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. Therefore, for the assessment of the health effects of noise, so-called adjacent areas were selected. In such adjacent areas it is not possible, for reasons of working capacity, to conduct complete 24-hour measurements, and therefore an approximation procedure was selected for the determination of noise levels. This involves 60 minute measuring periods outside selected houses during the day. These values are approximated to expected night-time 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 even for a larger area, of course with a lower accuracy.
One of the major criteria for selection of adjacent areas is as much similarity as possible with respective primary areas (e.g. the same type of building development). Numbers of inhabitants of particular houses in adjacent areas (according to house numbers) are taken from updated electoral lists. The relative risk estimate does not involve inhabitants under 18 years of age since in this population group significant health damage from noise is not detectable yet.
For areas adjacent to the primary ones, relative health risk from outdoor noise is estimated at two-year intervals. In 2002–2003, health risk from noise was estimated for 4 % of about 42,000 population living in 16 adjacent areas, provided they are exposed at least for 10 years to the estimated noise levels. This health risk estimate involves by 0.6 % more population compared to previous period 2000–2001, but does not involve Prague adjacent areas owing to changes made to these areas.
Another output of health risk estimate in adjacent areas is the estimate of individual risk from outdoor noise, provided a given individual is exposed at least for 10 years to the estimated noise level, at 2 dB intervals (Tab. 6.1).
6.4 Partial conclusions
Noise measurements in 2003 regularly took place on 40 sites. Noise levels ranged 50 to 75 dB and 40 to 69 dB LAeq during the day and night, respectively.
The health-related part of the subsection is based on a questionnaire survey of demographic, sociological and medical data for the inhabitants of the areas monitored, performed periodically, last time in 2002. The next such survey is due in 2007.
Assessment of health risk from noise exposure was conducted through the adjacent areas technique; this is performed every two years. A slight increase in health problems was detected in 16 cities against the previous assessment of relative risk in the 2000–2001 period. The assessment does not include adjacent areas in Prague, where the number of adjacent areas has changed.
Tab. 6.1 Relative risk estimate of health impairment by the chronic exposure to noise
Noise levels – night |
Probability of health |
Noise levels – night |
Probability of health |
< 40 |
– |
56–58 |
6.2 |
40–42 |
0.4 |
58–60 |
6.9 |
42–44 |
1.1 |
60–62 |
7.6 |
44–46 |
1.8 |
62–64 |
8.3 |
46–48 |
2.5 |
64–66 |
9.1 |
48–50 |
3.3 |
66–68 |
9.8 |
50–52 |
4.0 |
68–70 |
10.5 |
52–54 |
4.7 |
70–72 |
11.2 |
54–56 |
5.4 |
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