5. HEALTH EFFECTS AND RISKS RELATED TO DRINKING WATER POLLUTION

5.1 Organization of monitoring activities

Since 2004, data pertaining to drinking water quality has been evaluated under a programme of nationwide monitoring of public water mains in the Czech Republic, using a newly created information system (IS PiVo). This information system is managed by the Ministry of Health. IS PiVo has been supplemented with data on drinking water quality markers for the years 2002 and 2003. The primary unit used for evaluation of drinking water quality in public water mains is the area supplied (defined under law No. 252/2004 as an area in which water quality is approximately equivalent, whether supplied by one provider or owner from single or multiple sources). In 2004, almost 3,800 localities supplied in this manner were monitored; whilst more than 3,000 of these are small areas catering to populations of less than one thousand inhabitants, 80 % of the population supplied by public water mains is attached to so-called larger areas which supply populations in excess of 5,000 inhabitants.

Comparison of number of inhabitants supplied by drinking water from monitored areas in 2004 (9.15 million) with the overall population supplied with public water (according to ÈSÚ, 9.18 million inhabitants – 89.8 % – were supplied by public water mains in 2003, and 9.37 million – 91.8 % – in 2004) shows that data was gathered from the vast majority of public water mains in the Czech Republic. Detailed distribution of the overall number of inhabitants supplied and the number of samples taken in 2004, depending on the size of a given distribution network, are presented in Fig. 5.1. Overall, 5,036 municipalities were connected to the water distribution network in 2003; nearly all municipalities in excess of 5,000 inhabitants receive tap water. A total of 1,218 municipalities were not connected. The greatest amount of municipalities both connected, and without access to public water mains is situated in Central Bohemian Region. The specific amount of water charged for per household was 103 L/person/day in 2002 and 2003.

Since 2004, the major source of data for nationwide monitoring comprises analyses by service providers, in the intervals and range as prescribed under existing legislation. According to law No. 258/2000 Sb. (in accordance with law No. 274/2003 valid from 1. 10. 2003) the results of analysed samples may only be incorporated into IS PiVo if their analysis was conducted in an accredited or authorised laboratory. As stipulated by law No. 252/2004, samples of drinking water must be representative of water quality in the whole water distribution network, as consumed during a 1-year period. Sampling takes place in areas covered by legislative requirements for consumption, e.g. places where drinking water is supplied by taps for human consumption. Markers of drinking water-quality in the database characterise the usual condition of the monitored water network. Data acquired from instances of breakdown or failure are categorised under a separate heading and are not included in the final evaluation.

The basis on which drinking water quality is evaluated is the Regulation of the Ministry of Health of the Czech Republic No. 252/2004 which fully correlates with Directive 98/83/EC concerning water quality approved for human consumption. The basis for evaluation of radiological markers is the Regulation of the National Institute for Nuclear Safety No. 307/2002 concerning radiation safety. Compliance with guideline values is evaluated.

5.2 Monitoring indicators of health damage

Data concerning the incidence of infectious diseases transmitted by contaminated drinking water are acquired from the EPIDAT epidemiological information system, which has yielded reported cases of water-associated aetiology. Of 66,309 registered infections, water quality was implicated in only 55 cases. Laboratory and epidemiological analyses proved that none of the above cases resulted from drinking water in the monitored public mains (Tab. 5.1).

5.3 Drinking water quality

Compliance with individual water quality markers was evaluated separately for areas supplying up to 5,000 inhabitants (small areas) and over 5,000 areas (large areas).

In 2004, almost 31,000 samples of drinking water were collected, yielding over 714,000 water quality markers, 323,000 in small areas and nearly 391,000 in large areas. Of the total sum, 1.1 % of samples in large areas supplying over 5,000 inhabitants exceeded the maximum limit value (MLV) and limit value (LV), against 2.9 % in small areas of under 5,000 inhabitants. Detailed categorisation of areas (Fig. 5.2a) reveals that the frequency of exceeded limit values (related to the total count of pertinent types of limit value) decreases as the supplied population increases. Fig. 5.2b characterises the development of drinking water quality supplied by public mains during the past 3 years. During the 2002–2004 period, the frequency of exceeded health-related markers (MLV) in the distribution network for large areas was recorded at less than 1 %, whilst in small areas the figure ranged between 1.3 % to 2 %. Population percentages as defined by the numbers of exceeded limit values are presented in Fig. 5.2c. Almost 6.3 million inhabitants were supplied by drinking water from the water mains in 2004 where no LV limits were exceeded. Conversely, 72,000 inhabitants were supplied in the same year with water in which MLV were exceeded in over 10 instances.

In the Czech Republic, 42 % of the population is supplied by underground water, 30 % from surface water sources and 23 % from mixed sources (Fig. 5.3). The highest frequency of exceeded MLV was detected during the 2002–2004 period in drinking water from underground sources.

In 2004, the large areas were characterised by non-compliance with water hardness parameters in over half of the samples and exceeded limit values for chloroform (trichlormethane) (8.2 %) and iron (7.2 %). Microbiological quality markers revealed the highest frequency of exceeded limit values for numbers of colonies at temperatures of 36 °C (5.8 %) and 22 °C (1.8 %). Exceeded limit values for the most important health-related markers were most frequently detected for nitrates (1.5 %) and the pesticide Atrazin (6 %).

In the small areas, 71 % of samples did not comply with recommended water hardness parameters. Frequently exceeded LV were detected for the following markers: pH (15 %), iron (10.6 %) and manganese (6 %), coliform bacteria (10.3 %) and numbers of colonies at 36 °C (10.2 %) in the case of microbiological quality markers. Exceeded MLV health-related markers occurred with nitrates (6 %), and the pesticides Desethylatrazin (6.4 %) and Atrazin (4.6 %) (Fig. 5.4a–c). Comparison of supplied areas revealed that the large area have a more frequent exceeding of limit values for chloroform and chlorite, whilst the small areas suffer exceeded limit values of the other water quality markers.

The most serious threat to health is posed by nitrates and chloroform. In 2004, nitrates in drinking water were detected in 3,768 areas (99.4 %). In 235 areas the median concentration varied from 50–112 mg/L, i.e. reaching or exceeding the limit value for this marker (these areas comprise a total of 112,000 inhabitants; four of these areas are classed as large; supplying over 5,000 inhabitants and 219 are small; supplying up to 1,000 inhabitants). In a further 260 areas covering 158,000 inhabitants the median annual concentration of nitrates was 40 mg/L.

In 2004, chloroform was detected in drinking water samples from 2,153 (56.8 %) areas. In 39 areas supplying 546,000 inhabitants the median concentration value exceeded the 30 µg/L limit for chloroform content (17 areas classed as large, supplying over 5,000 inhabitants, including three areas supplying a population of over 50,000).

Currently, there is growing evidence concerning the health-related significance of optimal concetration of calcium and magnesium in drinking water. Monitoring has shown that a mere 6 % of the population (Fig. 5.5) is supplied with drinking water that contains the optimal magnesium content of 20–30 mg/L. The water supplied to the majority of the population (90 %) by means of public water mains contains magnesium at levels below the minimum recommended limit. Water containing the optimal calcium content of 40–80 mg/L is supplied to 22 % of the population, whereas 32 % and 46 % receive water with higher and lower calcium content, respectively. Water with optimal hardness (2–3.5 mmol/L) is supplied to 28 % of the population.

Radionuclide content in drinking water results in an average dose of 0.05 mSv/year. The slight increase against the previous year is caused by incorporation of all water mains, including areas, with a higher incidence of radionuclides, particularly in small-scale water networks.

5.4 Evaluation of exposure to selected substances

Selected contaminants (arsenic, chloroethene, nitrites, nitrates, aluminium, cadmium, manganese, copper, nickel, lead, mercury, selenium, trichloromethane) which have been assigned exposure limits by WHO or US EPA (see annex) were evaluated for population load from drinking water intake. Exposure evaluation was based on an average daily intake of 1 litre of drinking water from public main; recognized in a health and lifestyle questionnaire (HELEN). Exposure in each supplied area was calculated using the annual median concentration and 90% quantile concentration of the monitored contaminant. Average exposure for all areas was then adjusted according to the number of inhabitants supplied.

Nitrates comprise the major drinking water contaminant in the Czech Republic, reaching 6.2 % of the exposure limit (6 % in the large areas supplied and 6.7 % in the small areas). Higher than median exposure evaluation (using the 90% concentration quantile) yielded values of 7.8 % and 8.2 % of the exposure limit for large and small areas, respectively. Chloroform and selenium are slightly over 1 % of the exposure limit (Fig. 5.6). Concentrations of the other contaminants evaluated usually do not exceed the determination limit of the analytical method used; their exposure is therefore difficult to determine, although it may be safely asserted that it is less than 1 % of the exposure limit. Categorisation of the population according to the extent of exposure to contaminants in drinking water in 2004 is presented in Fig. 5.7. A total of 23.5 % of the supplied population in the Czech Republic draws over 10 % of the overall daily acceptable intake of nitrates by drinking potable water. The other contaminants do not exceed the 10 % mark. Acute health damage to the population by any of the monitored contaminants was not detected.

5.5 Evaluation of carcinogenic risk

A linear no-boundary model of the relationship between dose and effect was used to predict a theoretical increase of the risk of oncological disease resulting from exposure to contaminants in drinking water. Of the drinking water quality markers specified by Regulation No. 252/2004 the following contaminants were selected for evaluation: 1,2-dichloroethane, benzene, benzo[a]pyrene, benzo[b]fluoranthene, benzo[k]fluoranthene, bromdichloromethane, bromoform, chlorethene (vinyl chloride), dibromochloromethane, indeno[1,2,3-cd]pyrene, tetrachloroethene and trichloroethene. Data pertaining to the potential of these substances to increase the risk of oncological disease (cancer risk guidelines) were acquired from US EPA.

Two values assessing increased cancer risk were calculated for each of the monitored contaminants: minimal risk estimate Rmin (values below the determination limit were replaced by zero) and maximum risk estimate Rmax (values below the determination limit were replaced by value of the determination limit). The range of mean values Rmin and Rmax for the markers in question adjusted by the population count in the various areas supplied is shown in Fig. 5.8. The annual potential for increasing cancer risk as a result of drinking water intake does not reach 10-7 in any of the substances evaluated. The maximum estimate Rmax moves between values 10-8–10-7 for bromodichloromethane, chloroethene (vinyl chloride), dibromchloromethane, tetrachlorethane and trichloroethene. The overall estimate of increased cancer risk was calculated as the sum of individual contributions by all evaluated contaminants. Consumption of drinking water may therefore contribute to the annual increase of cancer risk probability by a value of 10-7, which means 1–10 additional cases of cancer per 10 million inhabitants.

Calculations of exposure and risk were performed by routine methodology; nonetheless, the factors used for determining exposure are always subject to a degree of uncertainty such as a limited spectrum of monitored substances, actual individual consumption of drinking water from the water mains, varied rates of absorption in the organism etc.

5.6 Water quality in public and privately owned wells

The nationwide water quality-monitoring project also collects data into IS PiVo pertaining to public and privately owned wells (the latter being used for commercial purposes). In 2004, a total of 2,600 samples were collected from 220 public and 1,024 commercial wells; this sum is only a part of the total number of wells registered in 1999 (3,700 public and 5,800 commercial wells). Of a total of over 57,000 values from water quality markers, 3,758 cases were recorded where limit values for water quality were not adhered to. Maximum limit values for health-associated markers of water quality were exceeded in 495 cases.

Frequent findings comprised exceeded limit values of all microbiological water quality markers: Clostridium Perfringens (4.2 %), enterococci (11.6 %), E. coli (7.2 %) and coliform bacteria (20.6 %). Other frequently exceeded limit values comprised pH (19.7 %), manganese (16.5 %), iron (15.7 %), nitrates (6.8 %) and recommended water hardness values (81 %).

5.7 Partial conclusions

Maximum limit values for drinking water quality markers in public water mains were exceeded in 2,224 cases (0.3 %). Limit values primarily defining the organoleptic properties of drinking water were not adhered to in 12,500 cases (1.8 %). The frequency of inappropriate limit values decreases as the population in a supplied area increases. In 2004, almost 6.3 million inhabitants were supplied with drinking water with no findings of exceeded maximum limits. Exceeded MLV in over 10 cases were recorded in water mains supplying a population of 72,000 consumers.

Toxic load on the population of the Czech Republic is dominated by nitrates which reach a mean value of 6 % and 6.7 % of the exposure limit for large and small areas, respectively. A value of 1 % of the exposure limit was exceeded by chloroform and selenium. Acute population health damage by the monitored substances was not detected.

A linear no-boundary model was used to predict the probability of oncological disease resulting from chronic exposure to 12 organic substances in drinking water. Results showed that consumption of drinking water might theoretically contribute to the annual increase of the probability of oncological disease by a value of 10-7, which means 1–10 additional cases per 10 million inhabitants.

Data gathered from nationwide monitoring of water quality in 2002, 2003 and 2004 reveals no significant changes in drinking water quality distributed by public water mains during the monitored period.

Tab. 5.1 Incidence of notified waterborne infectious diseases in 2004

Diagnosis
Code*

No. of cases

Total

Transmission water**

Public water supply

Amoeboisis A06

15

not stated

0

Ankylostomosis B76.0

11

not stated

0

Enteroviral meningitis A87.0

160

0

0

Gastroenteritis vs. infections A09

2,910

1

0

Campylobacteriosis A04.5

25,492

26

0

Giardiosis A07.1

102

0

0

Other bacterial intest. infections A0.4

2,824

4

0

Legionellosis A48.1

9

5

0

Leptospirosis A27

22

8

0

Salmonellosis A02

30,724

7

0

Shigellosis A03

325

4

0

Tularaemia A21

51

0

0

Viral intest. infections A08

3,590

0

0

Viral hepatitis A B15

70

0

0

Typhoid fever A01

4

0

0

Total

66,309

55

0

* ICD, 10. revision
** not solely drinking water

Fig. 5.1 Distribution of supplied population and drinking water samplings by size of supply area, 2004
Fig. 5.2a Drinking water quality by size of supply area, 2004
Fig. 5.2b Exceeding of limit values in supply areas (below 5,000 and over 5,000 population) in 2002–2004
Fig. 5.2c Distribution of the supplied population by the number of limit value exceedings, 2004
Fig. 5.3 Distribution of the population by type of crude water source, 2004
Fig. 5.4a Microbiological and biological indicators of drinking water quality, 2004
Fig. 5.4b Drinking water quality in consumer network, 2004, chemical and physical indicators with limit value
Fig. 5.4c Drinking water quality in consumer network, 2004, chemical and physical indicators with maximum limit value
Fig. 5.5 Distribution of the supplied population by Mg and Ca level in drinking water, 2004
Fig. 5.6 Population exposure to selected contaminants from drinking water, 2002–2004
Fig. 5.7 Distribution of the population by the exposure to contaminants from drinking water, 2004
Fig. 5.8 Theoretical estimate of relative cancer risk increase from drinking water intake, 2004

Main page

CONTENTS