6. HEALTH EFFECTS AND ANNOYANCE FROM NOISE |
6.1 Organization of monitoring activities
This subsystem has been run over the last 12 years on a permanent basis in 19 cities. The monitoring includes noise level measurements and health questionnaire surveys. In each city, two localities were selected to be representative of its noisy and quiet parts. The same measuring equipment is available in all collaborating public health institutes and the measurements are conducted according to the same standard protocols. The primary noisy and quiet localities were selected to allow, by repeated measurements of noise levels, the monitoring of noise pollution for the whole area and resulting population noise exposure with an accuracy of more than 2 dB LAeq. Thus, variations in traffic intensity can be recorded; when expressing noise pollution by the equivalent acoustic pressure level, a 3 dB difference is observed if the number of noise incidents or traffic intensity either halves or doubles. Compliance with this criterion of accuracy was tested at several sites of each selected locality. Other selection criteria were as follows:
Noise levels are measured throughout 24 hour intervals. The measurements are performed once a month, alternately in a noisy and a quiet locality. The needed measurement accuracy is achieved by using the same measuring equipment in all localities and by strict adherence to the measuring protocols in line with the uniform measuring methods for Subsystem III and requirements of the Methodical Guidance of the Chief Public Health Officer of 2001.
Noise health effects were investigated by questionnaire surveys three times (in 1995, 1997 and 2002) over the last 12 years.
6.2 Noise measurement
As specified by the national legislation in force, the noise descriptor LAeq (equivalent acoustic pressure level A) shall be used for the assessment of safety limits. LAeq is an energy expression of the noise level at a given site. Another noise descriptor used in a standard way from the very beginning of the monitoring is – L90 (90% probability noise level), which describes constant noise in specific places or background noise level, i.e. the noise level recorded at the measured site for 90 % of the measuring time. In 2005, daytime and nighttime noise levels expressed as LAeq reached up to 75 dB and 69 dB, respectively, in noisy localities, falling to 50 dB and 40 dB, respectively, in quiet localities. As in previous years, the heaviest noise pollution was recorded in noisy localities of Plzeň, Prague 10, and Olomouc. As previously, the least noisy are the quiet localities in Kolín, Příbram and České Budějovice. Daytime and nighttime noise levels expressed as LAeq are given in Fig. 6.1a, 6.1b, 6.2a and 6.2b; L90 values are presented in Fig. 6.3a, 6.3b, 6.4a and 6.4b.
Since 2004, noise levels are expressed by a new descriptor called the European noise descriptor, in line with Directive 2002/49/EC of the European Parliament and of the Council on the assessment and management of environmental noise. This Directive will be transposed into Czech law by the Act on noise assessment and reduction. The use of the new noise descriptor will contribute to better comparability of noise pollution data within the EU member states. The noise indicator Lden or Lday + evening + night considers the round the clock environmental noise exposure. The European noise descriptor differs from LAeq currently used in the Czech Republic by covering also the evening interval from 6 p.m. to 10 p.m., with the daytime interval from 6 a.m. to 6 p.m. and nighttime interval from 10 p.m. to 6 a.m. being the same for both of the descriptors. In noisy localities, Lden varied from 62.4 to 76.3 dB. The highest noise level was recorded in the noisy locality of Plzeň and the second noisiest was the noisy locality in Olomouc with 76.2 dB. Plzeň (59.8 dB) was the noisiest among the quiet localities where the noise levels ranged between 49.2 and 60 dB.
6.3 Noise health effects
Noise is currently among the most widespread occupational and environmental pollutants. Noise is any unwanted sound which is considered as bothersome or annoying or has negative effects on human health. The hearing analyzer functions as an alarm system: most alarming signals from the environment are perceived by the ear. The body is unable to disconnect the hearing function; the CNS processes all auditory stimuli even in sleep. What is perceived as alarming noise in daytime is identified as such even in sleep and a stress reaction is involuntarily activated.
Noise effects on human health are, on the one hand, specific, i.e. targeting directly the auditory organ, and on the other hand, systemic, i.e. influencing the whole body. The auditory organ is more likely to be affected by long-term occupational exposure to excessive noise levels. Noise pollution is known to have effects on the central nervous, hormone, immune and cardiovascular systems, thus contributing to the development of non-communicable diseases, mental disorders, etc. Primary vegetative reaction to noise, i.e. an involuntary reaction, has been reported at a noise level as low as 55 dB(A). It enhances sympathetic nervous system activity with subsequent changes in the vascular system, including increased heart rate, higher blood pressure, altered perfusion of peripheral organs, etc. Moreover, it results in increased muscular tonus, increased GIT motility, etc. These reactions become fixed with long-term noise exposure; noise can act as a chronic stressor and thus can be implicated in the development of cardiovascular and other non-communicable diseases with proved stress etiology. Other known negative noise effects are general metabolic changes such as increased levels of blood glucose, insulin, total lipids and cholesterol, which are risk factors for non-communicable diseases. Coexposure to noise and another factor (e.g. occupational load) leads to an increased release of stress hormones into the peripheral blood. A long-term (at least 5-year) noise exposure may lead to stress hormone induced vascular alterations responsible for hypertension.
Noise has also an important negative effect on sleep quality. Noise may prevent from falling asleep and alter sleep length and quality with such consequences as increased fatigability and reduced performance. Long-term sleep deprivation can play a role in alteration of immune competence of the body and increased proneness to infectious diseases.
Health effects of long-term exposure to various noise levels are investigated using regular questionnaire surveys of the population in the monitored localities. The last survey was conducted in 2002. Data were collected from about 12 thousand respondents in 19 cities. These questionnaire surveys investigate the relationship between noise pollution and incidence of selected noncommunicable diseases. A statistically significant relationship was most frequently found between increasing noise level and hypertension. The noise pollution level appeared to be significantly associated with the rate of subjective complaints of difficulty in falling asleep and sleep quality. A significant relationship was also found between the rate of subjective complaints of environmental noise annoyance and the noise level established by objective measurement. The increasing rate of noise annoyed individuals was significantly associated with the incidence of hypertension.
6.3.1 Estimating health effects of nighttime noise exposure in adjacent localities
Comparison between the selected primary noisy and quiet localities is helpful in the study of the relationship between noise levels and population health. As these primary localities cover a relatively small part of population in the monitored cities, health risks from noise are also studied in adjacent localities. One of the major criteria for selection of the adjacent localities was highest possible similarity to the respective primary localities (e.g. in type of built-up land). The numbers of persons living in separate houses in the adjacent localities are obtained from the updated polling lists (based on house numbers). For capacity reasons, 24-hour noise measurements are not feasible in the adjacent localities, and therefore, an approximation approach was used. Noise levels are measured for separate houses in daytime at 1-hour intervals. The results obtained are approximated to the expected night levels, based on the daytime to nighttime noise level ratio in each primary locality. Another input data is the updated resulting relationship between the noise level and summary incidence of non-communicable diseases as obtained from questionnaire surveys (in 1995, 1997 and 2002). Based on this approach, health risks from nighttime noise exposure can be estimated for larger areas, but with lower accuracy.
Results
6.4 Partial conclusions
In 2005, the obtained mean annual equivalent acoustic pressure levels A (LAeq), background noise levels (L90) and round the clock noise levels (Lden) showed consistency. The highest LAeq was 75 dB in daytime and 69 dB at nighttime for the noisiest localities and 50 dB and 40 dB, respectively, for the quiet localities. As previously, the highest noise pollution was observed in the noisy localities of Plzeň, Prague 10, and Olomouc. The least noise polluted were again the quiet localities in Kolín, Příbram and České Budějovice. When expressed by Lden, an indicator of round the clock noise exposure, the noise levels ranged between 62 and 76 dB for the noisy localities and between 49.2 and 60 dB for the quiet localities. The noisiest of the quiet localities was that in Plzeň (59.8 dB).
Noise pollution in the primary localities remains similar as in previous years. In general, it can be stated that increase in noise pollution in some localities is outweighed by reduced noise pollution elsewhere.
Health effects of long-term exposure to different noise levels are investigated by regular questionnaire surveys designed to collect demographic, sociological and health data from the monitored population. The last survey was conducted in 2002. Significant relationships were found between hypertension and nighttime noise level, rate of the population complaining of environmental noise annoyance and noise level established by objective measurement and noise pollution level and rate of the population complaining of difficulty in falling asleep and sleep quality.