IX. SUMMARY
The main focus of Project III Monitoring health effects and noise disturbing
effects is the parallel monitoring of outdoor noise based on 24 hour noise
measurements and periodical questionnaire based surveys of noise effects on
the incidence of selected health indicators, such as non-communicable diseases,
sleep disturbances and neurotic symptoms (neurological disorders) in 42
selected localities. Daytime and nighttime noise in each locality is characterized
by a continuous series of sound levels. Based on comparison of the available 9-year
data, it can be stated that changes in noise higher than the limits of measurement
accuracy, i.e. ±1dB, were only recorded in a small number of localities. Generally
speaking, neither increase or decrease in noise exposure in the Czech Republic
can be reported since, on the one hand, demonstrable changes were only recorded
in a small number of localities, and on the other hand, possible increase in some
localities may be outweighed by possible decrease in other localities.
In 2002, a third questionnaire-based survey of population health was carried out
in 21 cities of the Czech Republic. The responsiveness rate in this survey reached
53 % and was by 18 % higher than that of the last questionnaire survey in 1997. As
many as 12 023 questionnaires were evaluated. Analysis showed that compared to the
last questionnaire survey, the number of respondents in the same houses increased
by 67 %, and at the same time, the findings remained practically unchanged. As in
all localities monitored the respondents are selected the same way, the data obtained
are comparable and thus usable in the study of noise effects. The results of the
questionnaire-based surveys are evaluated the following way: responses collected
in different localities are expressed either in percentages reflecting the incidence
rate of each of the phenomena studied or in averages for numerical data to be related
to the respective noise levels. A regression curve is plotted in the resulting point
field to express the relationship between the noise and the response to a given question
or a phenomenon studied. The analysis based on a continuous series of noise levels was
tested by STATA software which enables evaluation of the incidence of health indicators
in relation to three categories of nighttime noise, i.e. up to 45 dB(A), from 45 to 62
dB(A) and above 62 dB(A) and, at the same time, adjustment for confounders.
Most questions of the questionnaire concerning e.g. demographic and sociological data,
data on lifestyles and working environment etc. are just focused on identification of
possible confounders. If the other factors studied either do not differ significantly
between the given localities or do not copy the differences in noise between the
localities, the changes in health indicators can be ascribed to the noise effects.
The results of phase 3 of the monitoring are consistent with the previously found
relationship between the summary incidence of selected non-communicable diseases
(hypertension, myocardial infarction, gastric ulcer, lithiasis, diabetes, cancer,
frequent catarrhs of the upper airways) and noise. Statistically significant
relationships were found between noise and hypertension and frequent catarrhs of
the upper airways.
Based on the questionnaire results obtained, the relative level of risk of health
impairment due to environmental noise was estimated for the nearby regions.
LAeq - continuous equivalent sound pressure level in the characteristic A
dB - unit of the sound pressure level
L90 - sound pressure level A exceeded for 90 % of total measuring time expressed in dB