4. RESULTS OF SUBSYSTEM 1: HEALTH CONSEQUENCES AND RISKS RELATED TO AIR POLLUTION |
4.1 Organization of the monitoring activities
The subsystem includes the follow-up of selected indicators of population health and air quality. Information on the health of the population is obtained from general practitioners and pediatricians in out-patient as well as in-patient healthcare facilities (acute respiratory diseases) and from the parents of selected groups of children (allergies and quality of indoor air), namely in part from routine records and in part through a questionnaire investigation.
Information on levels of pollutants in the ambient air is obtained from the network of manual and automated observation units run by Public Health Centers in the monitored cities and from selected measuring points supervised by the Czech Hydrometeorological Institute (ČHMÚ) which meet the requirements of the Monitoring System.
4.2 Incidence of acute respiratory diseases
In 1998 the incidence of acute respiratory diseases (ARO) was followed up in the same way as in previous years in 25 cities (as against the past year, on the one hand the follow-up was terminated in Kolín and Klatovy, and on the other hand was begun in Děčín). In 1998 a total of 120 physicians (that includes 75 pediatricians providing care for 98 881 patients and 45 general practitioners caring for 86 879 patients). In all, 185 760 patients were studied (in question is the direct follow-up of morbidity, not incapacitation).
Results obtained in 1998 do not differ significantly from results of preceding years. The age distribution of acute respiratory diseases shows maximum incidence rate in the age groups of 0 - 1 year and 1 - 5 years (Fig. 4.1a, 4.1b). The monthly incidence rate of ARO varied from several tens to several hundreds of cases per 1 000 subjects of the given age group depending on the season of the year and the current epidemiological situation. This variation is especially apparent in the child age groups as follows from the summary of past years in Fig. 4.1c and 4.1d. It can be stated that the mean monthly incidence rate in 1998 in most residence areas is in the lower half of the interval of analogous values in the years 1995 through 1997. This phenomenon is apparent namely in the adult age category (Fig. 4.1d).
Between the indicator of health (incidence of ARO) and the indicator of air pollution (annual index of air quality) no correlation in 1998 was found, the distribution of values being random (Fig. 4.1a, 4.1b). That can be explained by that the basic pollutants in the air were not present on a long-term basis in concentrations that could apparently influence this indicator in the cities covered by the Monitoring System. The resulting morbidity is influenced more by individual factors, the epidemiological situation and climatic conditions rather than by effects of ambient air pollution.
A similar analogous to that found in previous years is given by the incidence of individual diagnostic entities from the whole spectrum of respiratory diseases under study. Inflammation of the upper respiratory tract is the most frequent respiratory affection in all age groups, 68 - 76% at an average. Influenza is the second most frequent (9 - 19%), followed by bronchitis (4 - 13%). Other diagnostic entities under study are rare: complications of upper respiratory tract infections (2 - 2.5%), lower respiratory tract infections (0.4 - 1%) and asthma (0.1 - 0.7%). In each of the monitored localities the distribution of diagnostic entities in the age groups is similar.
The incidence of ARO is an indicator in the description of the state of health. It reflects the situation in the occurrence of respiratory diseases, which still occur most frequently, namely in children.
4.3 Prevalence of allergic diseases in children
In 1998 there was carried out analyses of results in the whole series of children acquired by repeated prevalence studies over two consequent years (1996 and 1997). Summary results arranged according to kinds of allergy are presented for the age groups in Fig. 4.2a. Frequency analysis of the results in the whole series of 11 147 children from the point of view of allergies by their kind with regard to gender, age, onset of the disease and its verification by an allergologist, confirmed the results of both independent processing in the two preceding years: the series is balanced as to age with a moderate preponderance of boys; the number of allergic subjects increases with age and the occurrence of individual affections is very similar to the investigations conducted in each of the years 1996 and 1997.
In 9 949 children on whom there was obtained complete data from the specific questionnaire, a statistical investigation (logistic regression) was further performed from the point of view of assessing correlation between factors of the outdoor and the indoor environments of homes, as well as of data from the personal and family histories and the allergic affections as such. Processing the series from both periods of investigation together has confirmed that:
4.4 Hospital admission for acute respiratory diseases
In 1998, the pilot study “Hospital admission of children suffering from an acute state of the respiratory diseases” continued and nine Public Health Centers of the cities under monitoring participated, namely: Ústí n/L, Brno, Kladno, Mělník, Příbram, Most, Havlíčkův Brod, Hodonín, Prague 5 and Prague 10. At all these locations (except for Prague 5) there was followed up hospital admissions of patients to pediatric wards. Visits of pediatric standby wards were also followed up in Brno, Ústí n/L and Prague 5 and 10 (in Ústí n/L under follow-up were also admissions of adults to the departments of internal medicine and diseases of the lung).
Data for 1997 and 1998 were processed with the aid of descriptive indicators (Fig. 4.2c). Morbidity in the course of the year in a given locality is expressed as the incidence for the whole age group, for preschool children (1 - 5 years), and school children (6 - 14 years). The highest values of monthly incidence rate were registered in Havlíčkův Brod and in Hodonín. The range in incidence rate was wide, e.g. in Havlíčkův Brod it was from 4.24 to 33.07 in children of 1 - 5 years of age, similarly in Hodonín from 1.40 to 4.74 in children of 6 - 14 years of age. The lowest rate of hospitalized morbidity in all the age groups studied was found in large cities (Prague 10 and Brno). These low values were approximated in Mělník and to the contrary Ústí n/L moved in its position to the group of cities with medium incidence rate values. There came about a stabilization of marked fluctuations of hospitalized cases within one city and in part also mutually between residential areas.
In 1998 there has been carried out a statistical processing of data on the first year of follow-up of the frequency of in-patient admissions of children afflicted with respiratory disease with some of the indicators of ambient air pollution (SO2, NOx and particulate matter). In the evaluation there was filtered out effects of the epidemiological situation, outdoor temperature, and population numbers in each residence area, order of days in the week and year, including the so-called autocorrelation of data. Statistical processing of the data series of 1997 and 1998 together shall be carried out in 1999. In this way, in addition to the supplementation of the temporal series, there shall also be ensured a year-to-year comparison. The processing of the whole two-year study shall be published separately.
4.5 Ambient air pollution
In 1998 levels of polluting substances in the ambient air were measured in 27 cities included in the Monitoring System (Tab. 3.1, Fig. 4.3a, 4.3b, 4.3c, 4.3d, 4.3e, 4.3f, 4.3g, 4.3h, 4.3i). Within the framework of preparations for amending the project of Monitoring for the period beginning with the year 1999, in the first half of the year 1998, there was elaborated an optimization of the measuring network operated by the Public Health Service in ten residential areas with more than two measuring units each (Prague, Brno, Ústí n/L, Kladno, Benešov, Kroměříž, Plzeň, Příbram, Děčín and Hradec Králové). The analysis was based on the processing of fundamental values measured at each of the measuring units over the period 1991 through 1996 and included were also measuring units operated by the ČHMÚ in the named residential areas. Conclusions of the optimization (lowering of requirements for results from 23 units) were discussed in the second half of 1998 and the resulting talks led to further specifications, to control measuring and in several cases contributed to improvement in the quality of measuring.
In the anthropogenic layer of the atmosphere, in all the residential areas sulphur dioxide, particulate matter (fraction TSP and fraction PM10), the sum of nitrogen oxides is measured, as well as mass concentration of selected metals (arsenic, chromium, cadmium, lead, nickel and zinc) in the samples of particulate matter. In several cities under monitoring there are also measured selectively the immission levels of polyaromatic hydrocarbons (PAH), ozone, nitrogen monoxide, nitrogen dioxide, carbon monoxide and of the metals found in particulate matter, in addition: beryllium, manganese, copper, mercury and vanadium.
4.5.1 Pollutants monitored in every city under the Monitoring System
In 1998 there continued a long-observed trend in the levels of routinely monitored pollutants (Fig. 4.4a, 4.4b, 4.4c, 4.4d, 4.4e, 4.4f, 4.4g, 4.4h):
4.5.2 Selectively monitored pollutants
In 1998 the monitoring of polyaromatic hydrocarbons (PAH) in seven cities continued (Prague, Brno, Plzeň, Ústí n/L, Benešov, Karviná and Žďár n/S). Twelve hydrocarbons were followed up (phenanthrene, anthracene, fluoranthene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perylene and indeno(c,d)pyrene). These are among the most important from the public health point of view. Recommended daily limits of admissible levels for three of the substances are set: phenanthrene (1 000 ng/m3), benzo(a)anthracene (10 ng/m3) and benzo(a)pyrene (1 ng/m3).
From the results (Fig. 4.3i) it is apparent that in Karviná the levels of polyaromatic hydrocarbons reach values twice those as in other cities under monitoring. This difference is greater than in 1997 because in Karviná there occurred an increase in the levels of PAH, whereas the values measured in other cities mostly decreased.
In 1998, the recommended admisssible concentration of phenanthrene was not exceeded in any of the cities under follow-up. The recommended value of admissible benzo(a)pyrene levels was exceeded in all the localities in almost half of the samples analyzed. The worst situation is in Karviná where 80% of the results were greater than 1 ng/m3 and the mean annual concentration of this substance is 7.8 ng/m3. On the other hand, in Žďár n/S the annual concentration of benzo(a)pyrene is almost ten times lower, 0.9 ng/m3. Likewise, in 1998 the annual mean levels of benzo(a)anthracene were found to be in a wide range, from 1.2 ng/m3 in Žďár n/S to 17.4 ng/m3 in Karviná. The recommended admissible value for this substance was exceeded only exceptionally: in Prague in 7% of samples, in the other cities up to 5%, only in Karviná over one third of the samples analyzed had values greater than 10 ng/m3.
The significance of the substances under follow-up, which may under unfavorable conditions cause the formation of photochemical reaction products on the atmosphere, i.e. nitrogen monoxide, nitrogen dioxide, ozone and organic substances (Fig. 4.4e, 4.4f, 4.4h), continues.
4.5.3 Metals in particulate matter
The mass concentration of selected metals was obtained by analysis of 14-day cumulative samples of particulate matter. The results (Fig. 4.5a, 4.5b, 4.5c, 4.5d, 4.5e, 4.5f) can be summarized as follows:
4.6 Exposure assessment to major pollutants
According to values of the annual index of air quality, IKOr, (Fig. 4.6) 16 out of 36 evaluated sites and Prague districts belong to the third to fourth category (ambient air moderately polluted to polluted), of which two Prague districts (Prague 5 and 10) and Děčín are in the fourth category. The other sites under follow-up fall within the second category and one site (Benešov) falls into the first category. In working out the index there was included levels that were measured for SO2, NOx, TSP and PM10. A comparison with values for preceding years (1994 - 1997) cannot be carried out due to a change in methodology for calculating IKO in 1998.
The situation concerning ambient air quality can also be expressed as the potential exposure of the population of a given locality to a certain concentration level. In Fig. 4.7 there is demonstrated the mean long-term exposure to major polluting substances that have a set annual immission limit (IHr). The result reflects the proportion of the population in cities under monitoring that is exposed to pollutants in the ambient air.
The mean long-term exposure to sulphur dioxide is low, for 96% of the population of sites under follow-up it did not exceeded the level of 20 µg/m3, i.e. 1/3 of the exposure limit. That means a further decrease as opposed to 1997 when still over half of the population under follow-up was characterized by an exposure level of 1/3 to 2/3 of the exposure limit. Exposure to nitrogen oxides is greater than to sulphur dioxide. Only 20% of the population in the sites under follow-up are exposed to concentrations below 1/3 of the annual immission limit, 41% to concentrations in the range of 1/3 to 2/3, 37.3% to concentrations of 2/3 to 1 IHr. 1.6% of the population (Děčín) is exposed to concentrations exceeding the immission limit. The distribution of exposure levels can be considered to be stable over the past several years. The population is exposed to the highest mean concentrations in the case of particulate matter in which 80% of the population under follow-up are exposed to concentrations between 2/3 IHr and 1 IHr. In comparison with 1997 when 39.3% of the population were exposed to concentrations above the annual immission limit, it is possible to gain the impression that there occurred a significant improvement. The major cause of this difference is a moderate decrease in the median value calculated in summary for all the Prague districts and that oscillates around the value of the annual immission limit. In view of the share of Prague in the population of all the cities under the Monitoring System, every such change, be it small, means a marked shift in the proportions of the exposed population.
4.7 Mobile measuring systems
In 1998 there continued the processing of results obtained in the first phase of measuring with the mobile system in Prague with regard to the relationship between localities measured and the existing units of the national immission network. The greatest attention was focused on ambient air pollution in connection with traffic. The aim of the processing was:
For all AIM units, in collaboration with the ČHMÚ, synchronous data on nitrogen dioxide was found; for ozone there have been selected paired data from ČHMÚ units: nám. Republiky, Libuš, and Vysočany. For both substances so-called correlation maps were constructed on which the field of correlation is marked with isolines. That facilitated to mark out those parts of Prague territory that have a significant correlation with at least one AIM unit. In this case, as significant the value of the correlation coefficient greater than 0.8 was considered. For selected measuring points lying within such areas with a high correlation, regression relationships between values from mobile and stationary measurements were calculated.
It was found that on the territory of Prague there exist vast areas in which ozone levels are closely correlated with data measured by AIM units: nám. Republiky, Libuš and Vysočany. A low correlation had measuring points lying in traffic-laden localities. Correlation fields for nitrogen dioxide are very nonhomogeneous for all the stationary units. Marked singularities appeared in traffic-laden environs.
The results obtained point out the direction of further effort for which it is needed:
Besides the complex measuring of ambient air quality in the city of Děčín and preparation for the accrediting process for the mobile system at ČIA, further activities of the mobile system were concentrated on ensuring the correct function of the QA/QC system, especially of the transfer of the correct value into the network operated by the Public Health Service. In question is a process parallel to activities of the calibration laboratory at the NIPH.
The environmental burden in Brno in 1998 was followed-up continuously at 12 measuring points of the measuring network. The original scope of measuring in a rectangular network formed by a total of 64 measuring points delineating the territory of interest of about 150 km2, after two years, was narrowed down to 12 points localized into the center of the city and its immediate vicinity. The newly defined territory of interest has an area of 20 km2. The system of measuring in the network was modified so as to preserve the randomness of sampling in relation to the calendar week and simultaneously to broaden the part of the day that is measured.
Regular measurements in these selected localities began January 7, 1998 and ended December 23, 1998. In the course of the year 1998 593 30-minute immission concentrations were measured. From the results obtained it follows that the present series of measurements have a high degree of non-symmetry. Detailed results of measurements by this mobile unit shall be published in a separate specialized report.
4.8 Evaluation of seasonal trends
For the evaluation of seasonal trends (Fig. 4.8a, 4.8b, 4.8c, for better clarity, on the vertical axes, an identical module of tapping the limit was selected) there were selected three sites: Havlíčkův Brod, Děčín and Hradec Králové. Each of the cities represents a certain relatively homogeneous group of sites from the Monitoring System. Decisive for the selection was the population number (under 25 thousand, over 50 thousand and over 100 thousand) and an expected different structure of sources of ambient air pollution (share of traffic, local sources and long-distance transport of pollutants). In each city, for the evaluation basic verified and validated values of all measured substances from one automated unit was applied and that represents the mean value for the whole city (NIPH unit No. 1200 in Havlíčkův Brod, No. 396 in Hradec Králové and ČHMÚ unit No. 1014 in Děčín).
The evaluation of the seasonal character was carried out in three seasons of the calendar year, i.e. non-heating (May, June, July and August), transitional (March, April; September, October) and heating (January, February; November, December). For each season, from basic 30-minute measurements of over the period of 1994 through 1998, mean values of tapping the 30-minute immission limit, were calculated (in the case of O3 the only existing limit, i.e. that of 8 hours, was applied).
In the interpretation of the trends obtained, it can be stated that:
The results obtained point to the fact that the seasonal level of pollution is connected with the size of the city. This piece of knowledge includes within itself differences in heating, kind of fuel used, and the numbers and importance of industrial and transportation sources. In smaller cities (represented by Havlíčkův Brod) the priority source of pollution is the heating of homes and therefore its effect manifests itself in the heating season. In larger sites with populations of over 100 000 (Hradec Králové) the level of ambient air pollution is more stable in the course of the calendar year, differences between the seasons being less marked. An exception to this is the city of Děčín, namely its heating season that is not in line with the conclusions mentioned. The reason for this may be its localization in the industrially burdened region of Northern Bohemia (mining and processing industries) as well as its specific orography that increases the probability of the occurrence of unfavorable immission situations, namely in the heating season.
In order to be able to generalize these conclusions drawn up for each category of cities, it shall be necessary to verify their validity on data series from other sites similarly grouped.
4.9 Quality of the indoor environment
In the course of 1998 there took place the preparatory stage of the project “Monitoring of the Indoor Environment”. The project is an extension of a pilot study conducted in the years 1994 through 1997 dealing with the description and evaluation of the occurrence of chemical, physical and biological factors in the indoor environment as well as with fundamental aspects of the lifestyle of the population under follow-up. The basic idea of the original project is broadened by determining and defining the exposure to pollutants from the indoor environment for children attending kindergarten. The monitoring shall be conducted just like in the pilot study, in four cities of the Czech Republic: Brno, Ostrava, Hradec Králové and Plzeň.
The present project has four parts. The first part of the project is a questionnaire. The objective of the questionnaire is to describe certain aspects of lifestyle and living conditions in families with preschool children. Including questions concerning the most frequent health problems and their possible connection with the home environment extended the questionnaire used in the pilot study. The questionnaire contains 58 questions, it was consulted with pediatricians, a psychologist and Public Health Service workers in the field in the cities under monitoring. It is divided into three parts each of which dealing with the child’s regime of life, its difficulties and health problems and with the follow-up of the quality of the home’s indoor environment.
The second and third parts deal with the measuring of selected factors of the indoor and outdoor ambient air. In each city there shall be conducted measurements of the indoor environment in 15 homes selected from a group of consenting respondents and there shall also be followed up the ambient air quality of kindergartens in order to be able to evaluate not only the exposure at home but the sum exposure to all indoor environments. In each site 4 - 5 kindergartens shall be selected so that all types of buildings are represented.
Measurements shall take place twice a year, in the heating (November - February) and the non-heating (May - August) seasons. In the homes and kindergartens there shall be followed up the following parameters:
The fourth part of the project represents the follow-up of ARO morbidity in children in a selected kindergarten.
In as the set uniform time interval for measuring air quality indicators in selected homes describes the exposure of the child the study is aimed at, only partially, a separate part of this project is also the follow-up of the daily and weekly variability in concentrations of the substances under monitoring. That part of the project shall be implemented in Prague and in Hradec Králové.
The project of Monitoring the indoor environment shall be tackled over a period of two years with the beginning of the measurements in the non-heating season of 1999.
4.10 Partial conclusions
The incidence of ARO reflects the situation in the occurrence of respiratory diseases which continue to be the most frequent, namely in children. The mean monthly incidence rate in 1998 in most of the sites was below the level of half the interval of these values for the years 1995 through 1997. The series of children and results of the prevalence survey of allergies from 1996 and 1997 shall be utilized next year in an extended study of cases and controls, devoted to children with combined serious allergies. The prevalence survey in full extent of the original methodology shall be repeated in the year 2001. 1998 was the second year of the pilot study “Hospital admission of children for acute state of respiratory diseases”. Simultaneously, there was carried out a statistical processing of data from the first year of follow-up that tentatively does not give evidence of the acceptability of this indicator for the monitoring. Therefore, hospitalization is not included among the indicators required for follow-up in 1999 and on. The processing of the study that will include conclusions for further application will be published separately.
The mean annual concentration of sulphur dioxide exceeded the value of 20 µg/m3, i.e. 1/3 of the immission limit in only three cities (Děčín, Most, and Ústí n/O). Pollution with nitrogen oxides vacillates around the limit value, which it exceeds in Prague 5 and 8 and in Děčín. Significant is also levels of pollution with particulate matter. No value of the annual arithmetical mean of the metals under follow-up exceed the set or recommended values of immission limits. Pollution of the ambient air with polyaromatic hydrocarbons in seven sites approximates the recommended values of admissible concentrations and in the case of benzo(a)pyrene it exceeds it in almost half of the measurements. The annual arithmetical mean of benzo(a)pyrene was greater than 1 ng/m3 (the recommended value of admissible concentration) in six out of seven sites.
In assessing trends in the levels of individual pollutants during the years of the Monitoring System it can be stated that in most cities there occurred a significant fall in the concentrations of sulphur dioxide, in half of them a decrease in levels of particulate matter. In the other pollutants the situation is stabilized, without marked changes. In general, it can be stated that in none of the pollutants under follow-up does there take place any significant increase in concentrations or exposure to them. Changes recorded namely in metals found in particulate matter can in no way be considered to be a systemic trend.
The annual index of air quality, evaluated from three major pollutants, falls into the third category in most of the sites, i.e. moderately polluted air. Potential exposure to concentrations exceeding values of applied exposure limits was found in 1.67% of the population under follow-up in the case of the sum of nitrogen oxides. In the case of particulate matter (fraction TSP) 69% of the population were exposed to levels between 2/3 of the limit and the limit itself.
The results obtained indicate that the seasonal level of ambient air pollution is connected with the size of the residential site. This characteristic also includes within itself differences in heating, in the fuel used, and the number and significance of industrial and transport sources.
A new project of Monitoring of the Indoor Environment has been prepared, which is in continuation of the pilot study materialized in the years 1994 through 1997. Monitoring shall be conducted just as in the pilot study in four cities (Brno, Ostrava, Hradec Králové and Plzeň) and shall deal with the description and evaluation of the occurrence of chemical, physical and biological factors in the indoor environment, as well as with the basic aspects of lifestyle in the population under follow-up. The basic idea is extended by the description of exposure to pollutants from the indoor environment in kindergarten children.