Water Supply and Quality
6.2.1 Exposure to microbial con- con-tamination
The type of data available makes it difficult to assess the exposure of European
popu-6.2 Exposure
lations to microbial contamination. Much of the information is either in the form of non-compliance with standards or epidemics of disease, some of which are attributed to par-ticular organisms while others are not. It is particularly difficult to assess the incidence of low-level gastroenteric problems.
In western Europe, drinking-water is usually safe in microbiological terms because effective treatment processes have largely eliminated outbreaks of infectious diseases.
Although infant mortality is 2.31 and 2.97 times higher, respectively, in the CCEE and NIS compared with that in the European members of the Organisation for Economic Co-operation and Development (OECD), the contribution of waterborne communi-cable and diarrhoeal diseases to these figures is unknown [16]. Differences in infant mor-tality also occur locally and according to so-cioeconomic conditions. (See Chapter 4.)
Lack of a safe water supply can be associ-ated with the occurrence of cholera, typhoid fever, hepatitis A, gastrointestinal diseases and a number of parasitic diseases. Incidents of these diseases linked with poor water quality have been recorded in many coun-tries of the Region, but especially in the CCEE and NIS. The most common type of local epidemic would appear to be gastroin-testinal disease attributable to bacterial, viral or protozoal agents, but hepatitis A is of par-ticular concern in the NIS. The levels of gen-eral low-level morbidity are impossible to as-sess.
Diseases such as cholera are usually re-stricted to isolated outbreaks. In many coun-tries of the Region occasional cases of chol-era are “imported”. In other countries in-Box 6.1: The nitrate problem in European drinking-water sources
some (Greece, Ireland, Portugal and Spain) fertilizer use is increasing more rapidly [12].
The CCEE do not show a general increase in fertilizer use. Consumption in most of these countries has recently fallen dramatically, mainly because of changing economic condi-tions. In 1990 the average consumption of fertilizers (tonnes N/km2) was 7.1 in western Europe and only 3.7 in the CCEE [13]. It is important that further environmental ini-tiatives and control measures to reduce nitrate levels in European waters are developed.
digenous cases are reported: in 1993, for example, there were 165 indigenous cases in Tajikistan, 10 in Romania and 5 in the Rus-sian Federation (WHO, unpublished data, 1993).
Information is sometimes given on the proportion of samples exceeding standards or on the number of treatment works failing to meet technical standards. In some cases it might be possible to assess the consequent exposure of the population to contaminants, but this would only be at a very local level where detailed information is available. Non-compliance is a result of many factors, in-cluding poor raw water quality, inadequate treatment, contamination of treated water and the monitoring strategy. Non-com-pliance information rarely indicates by what degree the standards have been exceeded, or to how many people the water of substan-dard quality was supplied and for how long.
It may, however, give a useful indication of the effectiveness of treatment at treatment works and is useful for management and pol-icy purposes.
On average, 16 % of samples of drinking-water in the former USSR did not comply with quality standards. This figure varied widely between the former republics, from 7 % in the Russian Federation to 48 % in Georgia.a A recent ten-year study showed that only 21 % of 245 rivers were acceptable from the point of view of bacterial pollution.
Thirty-five percent of the water bodies exam-ined exceeded bacterial standards by factors of ten or a hundred. Those that were accept-able tended to be the larger rivers and lakes in the north.
In the Russian Federation, contaminated drinking-water has given rise to infectious diseases in St Petersburg, Volgograd and Murmansk, while some 60 % of the popu-lation are believed to be exposed to unsafe drinking-water [17]. The incidence of some bacterial diseases such as typhoid is falling, though salmonellosis is still a problem (16
a Data supplied in country responses to the Con-cern for Europe’s Tomorrow protocol.
outbreaks in 1990) and isolated outbreaks of cholera occur. There are particular problems with the suitability of bacteria as indicators of viral pathogens. Viral diseases are increas-ing and are now estimated to be responsible for 70 % of morbidity.a Large outbreaks of acute enteric infections and hepatitis A re-lated to the use of poor quality drinking-water have been “continuously reported” in the Russian Federation [18]. The use of con-taminated water in food processing and milk bottling plants is reported to have caused diarrhoeal diseases in a number of countries including Latvia. Sporadic hepatitis A out-breaks have been recognized in Riga in Lat-via following the drinking of contaminated and improperly treated water from the Dau-gava river. In one episode in 1988/1989, up to 2000 cases were reported. Cases of water-borne hepatitis A are also reported from Li-thuania, but evidence of occurrence in Esto-nia is poorly documented. It has been stated that in Estonia the water supply systems in many towns are obsolete and often break down, with resulting deterioration in the quality of the water [19].
Waterborne outbreaks of disease involving Campylobacter and Salmonella spp. have been described from Hungary, while in Po-land outbreaks over several years have in-volved Salmonella spp., Shigella spp. and E.
coli.a In Hungary, non-compliance of drink-ing-water with standards, on the basis of fae-cal indicators, is on average about 8 %.
In the former Yugoslavia, outbreaks of hepatitis A were recorded in 1987, 1989, 1990 and 1991 and involved around 7000 cases, in addition to other waterborne dis-eases.a Hepatitis A outbreaks were also re-ported from Romania in 1986, 1988 and 1989, as well as outbreaks of typhoid and other, unidentified, waterborne diseases. Lo-calized outbreaks of cholera have also been reported (see above). Waterborne disease incidents have also been reported in Bulga-ria.
Large waterborne disease outbreaks have occurred in Israel. In the period 1981–1985 there were 27 such outbreaks with 10 880 cases; just one outbreak was responsible for
186 Water Supply and Quality
over 9000 cases. During 1986–1990, docu-mented outbreaks of waterborne diseases in-cluded four from community and nine from non-community water sources. The inci-dence of typhoid has dropped since the 1960s, but there was a large outbreak in the Krayot communities in 1985. Shigellosis and hepatitis incidence have probably levelled off, but also peaked in the 1980s. Shigellosis, which peaked in 1985, was also due to a waterborne outbreak in the Haifa area (the Krayot). The organisms involved in recent outbreaks were predominantly Shigella spp.
(1376 cases), faecal coliforms (300 cases) and Salmonella spp. (151 cases). Empirical evidence suggests that mandatory chlorina-tion in 1988 and more stringent water stan-dards (such as the change in the definition of substandard water from 10 to 3 coliforms/
100 ml) have had an important impact on water quality, waterborne disease outbreaks and the total burden of enteric disease in Is-rael. The improvement in quality is suggested by a lower incidence of non-compliance with standards in drinking-water samples (8.4 % in 1989; 6.4 % in 1991). It has been suggested that the increased incidence of salmonellosis in recent years is attributable in part to food contamination.
In Finland, no waterborne epidemics were reported between 1982 and 1988. In 1989–1990 six epidemics were recorded, in-volving some 5000 people [20]. The cau-sative agents were Campylobacter spp., Sal-monella spp. or viruses. The Norwalk virus was considered responsible for a small out-break in eastern Finlanda arising from a con-taminated wastewater basin. Other disease outbreaks have been recorded in Finland and, although the agents have not been identified, viruses have been isolated from sewage-contaminated water. In one viral epi-demic, some 4400–5000 people contracted diarrhoea.
In Norway, it is estimated that infections from contaminated water cause several
a Data supplied in country responses to the Con-cern for Europe’s Tomorrow protocol.
hundred thousand days of diarrhoea each year [21]. Outbreaks of Campylobacter infec-tion have been reported, involving nearly 1000 people, as well as an outbreak of water-borne hepatitis A in 1990 and one of Nor-walk virus infection in 1992.a
In Sweden, waterborne outbreaks of Cam-pylobacter, Giardia, E. coli and viral infection have been described.a
As hepatitis A is not a reportable disease in many countries, and as most primary in-fections are subclinical, the number of cases is probably greatly underreported. Some studies in the United States show that 30–
50 % of the adult population has serological evidence of past infection. The infection rate in Belgium and the former Yugoslavia has been reported to be high.
A particular problem with drinking-water supplies is found in Tallinn, where ground-water resources are nearly exhausted. Conse-quently, Tallinn relies mostly on surface water from Lake Ulemiste where regular blue–green algal blooms can produce unsat-isfactory taste and odour, making the water unacceptable for drinking. Toxins are also produced, which may produce lethal effects in some animals, but information about ef-fects on human health is limited.
Blooms of blue–green algae are implicated in poisoning incidents worldwide [22].
There are no confirmed reports of deaths in humans attributable to toxins produced by these algae although deaths of farm animals, dogs, birds, amphibians and fish have been reported, especially following ingestion of algal blooms on the water surface [23].
Toxic blue–green algal blooms have been reported from 16 European countries: the former Czechoslovakia, Denmark, Finland, France, the former German Democratic Re-public, the Federal Republic of Germany, Greece, Hungary, Italy, the Netherlands, Norway, Poland, Portugal, the Russian Fed-eration, Sweden and the United Kingdom.
The occurrence of these algal blooms is much wider than could be inferred from sus-pected poisoning incidents: up to 75 % of all the blue–green algal blooms tested have been found to produce toxins [24]. Three
categories of toxins are produced: neurotox-ins, hepatotoxins and lipopolysaccharides.
Blue–green algae have been reported to produce allergic reactions, skin and eye irri-tation, respiratory problems and gastrointes-tinal disturbances in swimmers in freshwater lakes and reservoirs in a number of countries [25,26]. With the increase in eutrophication from fertilizers entering many lakes and res-ervoirs, the incidence of health effects from blue–green algae can be expected to in-crease.
Infection by Cryptosporidium spp. has been described, with a prevalence of 0.6–
20 % in western countries [27]. In the United Kingdom, a number of drinking-water-associ-ated gastroenteritis outbreaks have been documented around the country.a Where a cause of gastroenteritis was identified, Cryptosporidiumspp. was responsible for 8 % of cases in England & Wales and 13 % in Scotland, accounting for a total of 9147 cases in 1989. In the last six or seven years, a series of outbreaks ofCryptosporidium infec-tion in the United Kingdom (and in the United States) has drawn attention to water-borne transmission arising from inadequate water treatment and ineffective filtration, leaving oocytes present in drinking-water.
Where the cause of diarrhoea was estab-lished, Cryptosporidium spp. was the fourth most commonly identified cause after Cam-pylobacter spp., Salmonella spp. and viruses [28]. One waterborne outbreak of giardiasis has been reported in the United Kingdom [29]. Gastroenteritis outbreaks due to vi-ruses have been described in the United Kingdom in recent years, possibly as a result of increased surveillance and awareness.
Since symptoms are mild, however, most cases go unreported.
Such patterns of occasional outbreaks are similar in other western European countries, such as France, where individual outbreaks of salmonellosis and shigellosis were rec-orded in the late 1980s.
a Data supplied in country responses to the Con-cern for Europe’s Tomorrow protocol.