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
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
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
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
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
In 2004, the large areas were characterised by
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
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
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
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
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
Two values assessing increased cancer risk were calculated for each of
the monitored contaminants: minimal risk estimate
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
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
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 |
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