4. HEALTH CONSEQUENCES AND RISKS RELATED TO AIR POLLUTION |
4.1 Organization of monitoring activities
The Subsystem 1 is intended for the monitoring of selected indicators of population health and air quality. Information on population health status is obtained from general practitioners and pediatricians in out-patient facilities. Information on ambient air pollutant concentrations is obtained from the network of manual and automated units operated by the Public Health Centres in the cities monitored as well as from selected measuring facilities administrated by the Czech Hydrometeorological Institute, the location of which meets the requirements of the Monitoring System.
4.2 Incidence of treated acute respiratory diseases
4.2.1 Results of the year 2002
Acute respiratory diseases (ARD) account for the highest percentage of morbidity in children (particularly in pre-school children) and therefore the ARD incidence is used as an important indicator of population health.
The ARD monitoring database MONARO provides information on treated ARD morbidity and its development both in children and adult population. The database is an integrated system that allows continual collection, processing and evaluation of the data on ARD morbidity from general practitioners and pediatricians. The source of information are medical records on the first treatment given to patients presenting with acute respiratory disease. The basic outputs are absolute numbers of new cases of selected diagnoses in the population monitored and their incidence rates per 1,000 population of different age groups.
In 2002, 74 pediatricians and 44 general practitioners providing care to a total of 181,915 patients in 25 cities took part in ARD data collection. The central database is being regularly validated to clear possible redundant or incorrect records.
The data of 2002 do not markedly differ from those of previous years. Figures 4.1a and 4.1b show the highest and the lowest monthly ARD incidence rates and the mean monthly ARD incidence rates of 2002 and the range of the mean monthly ARD incidence rates for 1995–2002. The mean monthly ARD incidence rates recorded in 2002 in children aged from 1 to 14 years were mostly close to the lower limit of the mean values range of previous years, with the exception of the age group 1 to 5 years in Havlíčkův Brod, Ústí n. Labem, Most, Benešov and Kladno.
The monthly ARD incidence rates (excluding influenza) per 1,000 children of different age groups up to 18 years varied widely from 4 (Sokolov, Hradec Králové) up to 519 (Hodonín) in 2002. As in previous years, the highest morbidity was recorded in the age group 1 to 5 years. In most cities, the ARD morbidity shows seasonal trend with a typical downward tendency in summer. The monthly incidence rates of bronchitis and pneumonia per 1,000 children ranged from 0 to 212.
As in previous years, diseases of the upper respiratory tract were responsible for the major share in the total morbidity, accounting for 78 % of the morbidity on average (for all the monitored cities and age categories). Influenza was the second (9.8 %), followed by inflammation of the lower respiratory tract (9.0 %). The order of the remaining diagnoses monitored according to their frequency is the following: otitis media – rhinosinusitis – mastoiditis (1.9 %), pneumonia (0.6 %) and asthma (0.4 %).
4.2.2 Development of respiratory diseases incidence between 1995 and 2002
Statistical analysis of data on morbidity from selected ARD focused on long-term development over eight years and quantification of seasonal variations. Data on three age categories (children aged 1 to 5 years, children aged 6 to 14 years and adults aged over 18 years) and three selected groups of diagnoses (acute respiratory diseases excluding influenza, upper respiratory tract infections and bronchitis/pneumonia) were subjected to statistical analysis. A linear model weighted by the number of the individuals monitored and a two-factor ANOVA model for the year (long-term development) and month (seasonal trend) impact were used in statistical testing. The lack-of-fit test was used to check the adequacy of the linear model.
A seasonal trend was found for all age categories (Fig. 4.2a). It was most marked for the age group 1 to 5 years, slightly less marked for the age group 6 to 14 years and less marked for adults.
Linear model based long-term analysis for all the cities monitored (Fig. 4.2b) revealed a downward trend with all combinations of age and diagnosis groups. The downward trend was most marked for the age group 1 to 5 years, particularly for the groups of ARD and upper respiratory tract infections. The least decrease over the years was recorded for higher age groups and lower respiratory tract infections. Time trend analysis for individual cities is suggestive of a statistically significant linear decrease in the incidence rates (for one third out of 220 combinations tested) rather than of an increase: a statistically significant increase was only demonstrated in Liberec for the incidence of ARD excluding influenza in the age group 1 to 5 years. In the other cases, neither an upward nor downward trend was demonstrated using the above statistical procedures.
4.3 Monitoring of allergic diseases
In 2002, the data collected during investigation of the prevalence rates of allergic diseases among the population of 5, 9, 13 and 17-year-olds of 18 cities of the Czech Republic in 2001 were analyzed. A modified 1996 questionnaire was used with additional questions related to the pre- and perinatal periods. The data were obtained from medical records of 54 pediatricians and from parents during obligatory preventive check-ups. The data collected brought information not only on the prevalence of diseases and distribution of different diagnoses in each of the age groups, but also described prenatal and early childhood history, family lifestyle and environment. The objective of the year 2002 was to compare the rates of selected health history data in allergic and allergy-free children by diagnosis. A total of 7,868 children, of which 51 % males, were investigated. The questionnaire returnability was 93 %.
The results were described using frequency analysis. The hypothesis of congruence between the percentages of the categories in the contingency table was assessed using the c2 test of independence. The exposure/effect (disease) relationship is described by the odds ratio (OR) between the population groups exposed and non-exposed to a factor. A logistic regression model was used and the odds ratios were adjusted for gender, age, city and family history. The tests were performed at the 0.05 significance level.
The P-values are indicated as follows: * p < 0,05, **p < 0,01, ***p < 0,001.
4.3.1 Selected results
Allergic diseases diagnosed by pediatricians were recorded in 1,935 out of 7,850 children followed up, which means a prevalence rate of 24.7 %.
The following seventeen “risk” factors were identified based on the health history data collected (rates among the study group are indicated in brackets):
The incidence rates of the “risk” factors described for three of the basic diagnoses (asthma, pollinosis and atopic dermatitis), accounting for 73 % of all the allergies in the group monitored varied with diagnosis. The health history data shown in Table 4.1. proved significant.
The rates of nonspecific symptoms of allergic diseases (wheezing, cough, irritation of ocular and nasal mucous membranes unrelated to colds, skin eruption and food allergies) in non-allergic children ranged from 4.5 % (dry cough unrelated to colds or influenza) to 14.5 % (stuffy nose feeling, watery running nose, fits of sneezing unrelated to colds). Children with these nonspecific symptoms are to be considered as potential allergics.
Table 4.1 Risk factors of allergic diseases development
Parameter |
Allergy total |
Asthma |
Pollinosis |
Eczema |
Affection frequency in the followed-up group |
||||
24.7% |
5.1% |
11.1% |
7.1% |
|
|
Odds ratio |
|||
Gender – girls |
0.8*** |
0.68*** |
0.68*** |
1.2 * |
Age 9 years compared to 5 years |
1.4*** |
1.5* |
2.3*** |
x |
Age 13 years compared to 5 years |
1.6*** |
1.6** |
4.0*** |
x |
Age 17 years compared to 5 years |
1.8*** |
1.6** |
5.2*** |
0.8* |
Family history |
2.8 *** |
2.8 *** |
2.9 *** |
2.6*** |
Age of mother over 40 years |
x |
3.8 * |
x |
x |
Risk pregnancy |
1.2 ** |
x |
1.3 ** |
x |
Stress in pregnancy |
1.4 *** |
1.5 * |
1.5 ** |
x |
Smoking in pregnancy |
x |
x |
x |
x |
Contact with allergens in pregnancy |
1.2 * |
x |
x |
1.4** |
Term of delivery |
x |
x |
x |
x |
Parturient weight |
x |
x |
x |
x |
Complications during delivery |
1.3 ** |
1.8 *** |
1.3 ** |
x |
Repeated respiratory affections (5x and more) in 1. year of life |
2.5 *** |
3.3 *** |
1.3 * |
1.7 *** |
Dermal problems at least 3 moths in 1. year of life |
5.1*** |
2.6*** |
1.9*** |
12*** |
Repeated treatment by antibiotics in 1. year of life (3x and more) |
2.0*** |
2.4*** |
1.3* |
1.5** |
Repeated respiratory affections (5x and more) in 2.–5. year of life |
3.8*** |
7.4*** |
2.1*** |
2.4*** |
Presence of pet in dwelling (exposure duration considered) |
x |
x |
x |
x |
Smoking in dwelling (exposure duration considered) |
x |
x |
x |
x |
Moulds in dwelling |
x |
1.03 * |
x |
x |
Effect of industrial pollution |
1.01 ** |
x |
1.01* |
1.01 * |
Effect of traffic pollution |
1.009 * |
1.01 * |
x |
x |
statistical significance *p < 0.05 **p < 0.01 ***p < 0.001
x = not significant
Table 4.2 shows the rates of allergens identified (via health history data, skin test, detection of specific IgE antibody) in normal children population (7,868 children monitored).
Table 4.2 Frequency of proved allergens in child population 5–17 years of age
(from the total number of 7,868 children)
Allergen |
Absolute |
Relative |
Allergen |
Absolute |
Relative |
Allergen |
Absolute |
Relative |
Pollen |
1 008 |
12.83 |
Vegetables |
15 |
0.19 |
Metals |
5 |
0.06 |
Mites |
502 |
6.39 |
Nuts |
14 |
0.18 |
Solar |
5 |
0.06 |
Dust |
472 |
6.01 |
Cow milk |
12 |
0.15 |
Disinfection |
4 |
0.05 |
Hair and feathers |
430 |
5.47 |
Egg white |
11 |
0.14 |
Cold |
4 |
0.05 |
Moulds |
237 |
3.02 |
Limes |
11 |
0.14 |
Vaccine |
4 |
0.05 |
Bacteria |
201 |
2.56 |
Apples |
10 |
0.13 |
Poppy |
4 |
0.05 |
Antibiotics |
91 |
1.16 |
Chocolate |
8 |
0.10 |
Mucolyticum |
3 |
0.04 |
Histamine |
23 |
0.29 |
Strawberries |
8 |
0.10 |
Chlorine |
3 |
0.04 |
Sulphonamides |
23 |
0.29 |
Honey |
7 |
0.09 |
Cacao |
2 |
0.03 |
Insect |
21 |
0.27 |
Tobacco |
7 |
0.09 |
Kiwi |
2 |
0.03 |
Analgetics |
20 |
0.25 |
Gluten |
6 |
0.08 |
Legumes |
1 |
0.01 |
4.4 Air pollution in the cities
In 2002, air pollutant concentrations were measured in 75 stations (46 and 32 operated by the Ministry of Health and the Ministry of the Environment, respectively) located in 27 cities included in the Monitoring System (see Table 3.1 and Fig. 3.1). In 2002, sulphur dioxide (SO2 measurements in the PHS network was terminated at all the manual stations; in the cities where a station of the Czech Hydrometeorological Institute is not located, measurements were made during the heating season only), nitrogen oxides – NO/NO2/NOx, particulate matter (TSP and/or PM10 fraction), and mass concentrations of selected metals (arsenic, chromium, cadmium, manganese, nickel and lead) in particulate matter samples were monitored in all cities of the Monitoring System. Concentrations of carbon oxide, ozone, polyaromatic hydrocarbons (PAHs) and volatile organic substances (VOCs) continue to be monitored selectively in a number of the cities followed-up.
The criteria of Government Regulation No. 350/2002 of August 14, 2002, laying down ambient air pollution limit values and conditions and ways of air quality monitoring, assessment, evaluation and management, were applied to assess the recorded and calculated concentrations of the pollutants monitored. Reference values set by the air hygiene working group were used for pollutants, for which no limit had been established, and orientation values representing the limit concentrations in force until 2002 were used for TSP fraction and sum of nitrogen oxides.
4.4.1 Pollutants monitored in all cities of the Monitoring System
In 2002, the long-term trend in development of some commonly monitored pollutants continued.
4.4.2 Selectively monitored pollutants
Polycyclic aromatic hydrocarbons
In 2002, the monitoring of polycyclic aromatic hydrocarbons (PAHs) was conducted in seven cities (Prague, Brno, Plzeň, Ústí nad Labem, Hradec Králové, Karviná and Žďár nad Sázavou). The following polycyclic aromatic hydrocarbons were monitored according to US EPA TO–13: phenanthrene (reference concentration = 1,000 ng/m3), anthracene, fluoranthene, pyrene, benzo[a]anthracene (reference concentration = 10 ng/m3), chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene (limit 1 ng/m3), dibenzo[a,h]anthracene, benzo[g,h,i]perylene and indeno[c,d] pyrene. The data obtained within the special monitoring in Ostrava on eight selected PAHs have also been included in the database. The ambient air sampling was performed every sixth day.
Fig. 4.7a shows that the annual limit for benzo[a]pyrene was exceeded in most of the cities monitored. The highest burden from benzo[a]pyrene was found in Ostrava with an annual mean concentration of 7.8 ng/m3 (93.2 % of the 24-hour-concentrations exceeded 1 ng/m3) and the highest values of November and December reached more than 30 ng/m3. The limit was also markedly exceeded in Karviná (4.6 ng/m3) and Prague (2.3 ng/m3). Values slightly above the limit were recorded in Ústí n. Labem (1.4 ng/m3) and Plzeň (1.2 ng/m3). The limit was not exceeded in Brno, Žďár n. Sázavou and Hradec Králové where the annual mean concentration was below the limit for the first time since the beginning of the monitoring in 1997.
The annual arithmetic means of benzo[a]anthracene levels varied widely from 0.6 ng/m3 in Brno to 8.6 ng/m3 in Karviná. Unlike previous years, the recommended reference concentration was not exceeded in any of the cities. In most localities, the annual level was lower than one-third of the recommended reference concentration; markedly higher contamination slightly below the reference concentration was recorded in Ostrava (8.2 ng/m3) and Karviná (8.6 ng/m3).
The phenanthrene levels did not exceed the reference concentration in any of the cities monitored.
The total annual mean PAHs concentration expressed as the PAHs sum was highest in Karviná (Fig. 4.7a), reaching two to three times lower levels in the other localities monitored. The PAHs sum could not be calculated for Ostrava where only selected PAHs have been monitored.
The PAHs include several compounds varying in health significance; those considered as probable carcinogens differ in health effects as well. Based on comparison of carcinogenic effects of the concentrations measured for different PAHs with that of benzo[a]pyrene (BaP) as one of the most toxic and best studied carcinogenic polycyclic aromatic compounds, the carcinogenic potential of PAHs in air may be expressed using the TEQ. The following toxic equivalent factors (TEFs) pursuant to the US EPA were used for calculation of TEQ:
Converting benzo[a]pyrene TEQ factors (US EPA)
PAH |
TEF |
PAH |
TEF |
PAH |
TEF |
Benzo[a]pyrene |
1 |
Benzo[b]fluoranthene |
0.1 |
Dibenz[a,h]anthracene |
1 |
Benzo[k]fluoranthene |
0.01 |
Benzo[a]anthracene |
0.1 |
Indeno[c,d]pyrene |
0.1 |
The concentration of each PAH identified in the mixture is multiplied by the respective TEF of benzo[a]pyrene and the sum of all products obtained is the TEF of the PAH mixture studied. The TEQ values related to the localities monitored are shown in Fig. 4.7a and 4.7b. The highest carcinogenic risk from PAHs in 2002 was recorded in Ostrava (annual mean of 11.5 ng/m3) and Karviná (annual mean of 7.4 ng/m3), followed by Prague 10 (3.6 ng/m3). The values recorded in Ústí nad Labem, Plzeň and Hradec Králové were around 2 ng/m3. The results of the BaP TEQ over the period from 1997 to 2002 shown in Fig. 4.7b demonstrate that Ostrava and Karviná bear the highest burden over the entire monitoring period. The lowest concentrations are recorded on a long-term basis in Brno and Žďár n. Sázavou.
Volatile organic compounds
In 2002, volatile organic compounds (VOCs) were monitored in five cities (Prague, Ústí nad Labem, Karviná, Hradec Králové and Sokolov). In winter, the ambient air sampling was carried out on the same days as that for PAHs, from April to September every twelfth day. Forty-two organic compounds were followed up (pursuant to US EPA TO - 14); nevertheless, only twenty-three of them were taken into account since the remaining ones were present in concentrations falling below the respective detection limits. The data on 8 selected VOCs obtained in Ostrava using another method, and those of the Czech Hydrometeorological Institute, monitoring concentrations of selected aromatic hydrocarbons (BTX) by means of automatic analyzers located in Prague 4, Prague 5 and Most, were also included in the database.
An annual concentration limit of 5 µg/m3 has been established for benzene by Government Regulation No. 350/2002 Coll. Among other important VOCs for which reference concentrations had been set, are aromatic hydrocarbons (toluene, sum of xylenes, styrene, sum of trimethylbenzenes) and chlorinated aliphatic and aromatic hydrocarbons (trichloromethane, tetrachloromethane, trichloroethene, tetrachloroethene, chlorobenzene, sum of dichlorobenzenes).
Any of the reference concentrations was not exceeded in any of the localities monitored. Fig. 4.6 shows the annual mean benzene concentrations in 1999 to 2002. At the beginning, benzene was only monitored by the public health service, but since 2002 the Czech Hydrometeorological Institute has joined the activities. The figure shows that the concentration limit was not exceeded at any of the monitoring unites in 2002. Annual mean benzene concentrations reached over 4 µg/m3 in Prague 10, Karviná, Ostrava and Hradec Králové, did not exceed 3 µg/m3 in the other localities and the lowest concentration was recorded at the Czech Hydrometeorological Institute station in Prague-Libuš.
The monitoring of the substances which, under opportune conditions, may be responsible for the formation of photochemical reaction products in the atmosphere, i.e. nitrogen monoxide, ozone (Fig. 4.3m, 4.3n) and organic substances continues to be of concern.
4.4.3 Metals in particulate matter
The mass concentrations of selected metals were obtained by analysis of 14-day-cumulative samples of particulate matter. Air pollution with the elements monitored between 1995 and 2002 either shows a slightly downward tendency (lead, arsenic) or is rather stable (cadmium, chromium), without any significant oscillations.
Figs. 4.8a and 4.8d give information on this air pollutant in units of carcinogenic risk (UCR) as indicated by the WHO for two different levels of theoretical estimation of probable increase in risk to population of developing cancer (1*10-6 and 1*10-5) if exposed long-life to the given concentrations of metals in air. Analysis of the metal concentrations must also take into account probable frequency of such exposure (a conservative scenario is to be used, in which among others, 24-hour exposure to a given concentration level is expected).
The annual mean concentrations of the metals monitored in particulate matter can be described as follows:
4.5 Assessment of exposure to major pollutants
4.5.1 Air quality index
The Air Quality Index is used to provide air quality information as required by the Government Regulation No. 350/2002. The Air Quality Index (AQI) is based on annual arithmetic means of concentrations of SO2, NO2, PM10, As, Cd, Pb, benzene and BaP. The Air Quality Index was calculated for two groups of localities – one comprised 20 localities where common pollutants are monitored (group 1) and the other comprised 8 localities with additional monitoring of polycyclic aromatic hydrocarbons (group 2).
The AQI values in group 1 range from class 1 – unpolluted air (Svitavy, Most, Klatovy, České Budějovice, Hodonín, Liberec and Havlíčkův Brod) to class 3 – moderately polluted air (Prague 2 and Prague 9).
In group 2, Žďár n. Sázavou falls into class 1, Ústí n. Labem, Hradec Králové, Plzeň and Brno into class 2, Prague 10 into class 3 and Ostrava and Karviná into class 4. The AQI values are comparable to those of 2001. The AQI values related to each of the groups are shown in Fig. 4.4a and 4.4b.
4.5.2 Exposure to pollutants from ambient air
The degree of air pollution can also be expressed as potential exposure of the population of a given locality to a certain calculated mean pollutant concentration level. The mean long-term exposure to major pollutants, for which the annual concentration limits (IHr) are set, is characterized in this manner. Proportions of the total population of the cities monitored, exposed to a certain concentration range of pollutants in ambient air are shown in Fig. 4.5. The non-measured locality of Šumperk with 0.9 % of the total population monitored, was also included in this calculation.
4.6 Partial conclusions
The incidence rate of treated acute respiratory diseases (ARD) in 2002 was similar to that of previous years. The monthly ARD incidence rate varied widely in the individual localities monitored from units to hundreds of cases per 1,000 population of the given age group. Highest morbidity is traditionally reported in the age group 1 to 5 years. Upper respiratory tract infections were the most frequent (78 %) among the ARD monitored. Lower respiratory tract infections (bronchitis and pneumonia) account for different proportions of the total ARD morbidity rates in different cities. They are most frequent in the age group 1 to 5 years.
Statistical analysis demonstrated a significant seasonal trend for all age groups, that appears to be most marked in children aged 1 to 5 years and its significance decreases with increasing age. A slowly declining trend was found for the set of all cities monitored with all combinations of age and diagnosis groups. Morbidity declines most markedly in the age group 1 to 5 years (ARD and upper respiratory tract infections). The decline decreases with increasing age. The year-to-year analysis indicated a general statistically significant linear decline in morbidity in most cities with the only exception of Liberec showing a statistically significant increase in ARD excluding influenza for age group 1 to 5 years. Any other trend was not identified.
Based on data from the allergy prevalence analysis in 2001, the so-called “risk” factors were identified for each type of allergy. High-risk pregnancy and stress during pregnancy were the most frequent of the pre-natal factors. Health history data confirmed that allergic children suffered more frequently from recurrent respiratory morbidity during the first year of age, at the toddler age and pre-school age and were treated with antibiotics more frequently. Higher morbidity rates were found not only for children with respiratory allergy, but also for those with skin and food allergies. On the other hand, skin problems during the first year of age are associated not only with atopic dermatitis, but also with asthma, pollinosis and food allergy. Traffic pollution was significantly involved in respiratory symptoms and asthma while industrial pollution had significant effect on skin allergies.
The mean annual concentrations of sulphur dioxide did not exceed 20 µg/m3 in any of the cities monitored. Nitrogen oxide pollution is stable in nature although its concentrations slightly increased compared to those of 2001. In some localities, the concentrations of the sum of nitrogen oxides were close to 80 µg/m3 (the concentration limit effective in 2001) and higher levels were found in Prague 1, 5 and 8. The annual concentration limit of nitrogen dioxide (40 µg/m3) was exceeded only in Prague 1 and 5 (43.2 and 43.7 µg/m3, respectively) while the annual mean values recorded in all the other localities ranged from 20 to 30 µg/m3. Higher concentrations of carbon monoxide in ambient air persist in the Prague conurbation with heavy traffic, up to 20 % of them exceeding the daily limit of 5,000 µg/m3. The rate of pollution with particulate matter, i.e. fractions TSP and PM10, is rather stable, with moderate growth in some localities. The annual PM10 concentration limit (40 µg/m3 or 35 exceedances of the mean 24-hour-value of 50 µg/m3) was exceeded in seven cities – Prague, Děčín, Ústí n. Labem, Ústí n.Orlicí, Karviná, Olomouc and Ostrava. The mean values in all the other cities were higher than the concentration limit (20 µg/m3) to be achieved in 2010. Air pollution with the elements monitored between 1995 and 2002 shows either a slightly decreasing trend (lead, arsenic) or remains rather stable (cadmium, chromium, nickel) without any important oscillation, with the only exception of arsenic in Ostrava where the annual concentration limit of 0.0064 µg/m3 was exceeded. The effective concentration limits of the other elements set in the Government Regulation No. 350 were not exceeded.
Benzo[a]pyrene as the most relevant contaminant among the polycyclic aromatic hydrocarbons continues to be of concern at all localities; the annual arithmetic means exceeded the concentration limit (1 ng/m3) in Plzeň, Ústí n. Labem, Prague 10, Karviná and Ostrava (the limit was most markedly exceeded in Ostrava – 7.8 ng/m3 – where over 93 % of the 24-hour-concentrations exceeded 1 ng/m3). Unlike the year 2001, the levels of benzo[a]anthracene dropped in all localities and the annual arithmetic means did not exceed the reference concentration (10 ng/m3) in any of the localities. The highest carcinogenic potential of the monitored sum of polycyclic aromatic hydrocarbons (TEQ) was recorded in Ostrava (11.1 ng/m3) and Karviná (7.4 ng/m3); the value recorded in Ostrava was approximately three times as high than those in Prague and Plzeň and five times as high as those in Ústí nad Labem and Hradec Králové.
The annual benzene concentration limit of 5 µg/m3 was not exceeded in any of the localities, although the annual mean concentrations recorded in Prague 10, Hradec Králové, Karviná and Ostrava ranged from 4 to 4.5 µg/m3.
The reference concentrations of VOCs (toluene, sum of xylenes, styrene, trimethylbenzene) were not exceeded in any of the localities.
The Air Quality Index was adjusted to comply with the latest legislation (Government Regulation No. 350/2002). The AQI values recorded in 2002 are comparable to those of 2001. Two Prague districts (Prague 2 and Prague 9), Karviná and Ostrava are classified into air quality classes 3 and 4.
Potential exposure to PM10 is long term of highest significance. As many as 57 % of the population monitored are exposed to concentrations exceeding the exposure limit and 89 % of the population monitored are exposed to PM10 annual mean concentrations exceeding 20 µg/m3.