Is Milwaukee tap water drinkable
The health risk from infectious agents in drinking water is common. When infectious agents occur, unlike most chemicals, a single sip can lead to illness and death. This danger is still relevant today. Since 1991, cholera has appeared as a typical water-borne infectious disease in so many countries and with more cases than ever before (28). The largest drinking water-related epidemic ever described occurred in the USA in 1993. More than 400,000 people in the city of Milwaukee are infected with enterocolitis caused by the single cell Cryptosporidium parvum (17).
Doctors are confronted with hygienic aspects of water quality for various reasons: When looking for the cause of illnesses in their patients, as consumers, as those responsible for water quality in their own home, in their own practice or clinic and especially when using water-bearing medical devices and as opinion leaders in health issues.
In Germany, people trust that through legal regulations, responsible staff and high-quality technology, perfect water is always supplied. In the case of small and individual restorations, however, microbiological or chemical deficiencies have to be complained about relatively often. Investigations by the State Health Office of Baden-Württemberg, for example, revealed 31.9 percent more bacteriological complaints for individual and self-sufficient supplies than for large long-distance water supplies (16). The microbiological and chemical water quality can also deteriorate considerably in the house installation, which is not monitored at all for no particular reason (5).
The legal basis of the drinking water assessment is the Drinking Water Ordinance (TrinkwV) of 1990 (6) in Germany, and the 1980 EU directive on water for human consumption (19) throughout Europe. Recommendations to be observed worldwide are set out in the WHO guidelines on drinking water quality from 1993 (29). In addition, Germany has its own regulation for mineral and table water (7). From a microbiological point of view, your requirements are stricter for the moment of bottling than for drinking water, but any subsequent bacterial contamination is permitted.
Microbiological requirements and monitoring
According to Paragraph 1 of the Drinking Water Ordinance, the drinking water must be free from pathogens. Because the fulfillment of this requirement cannot be proven by tests, random samples (100 ml to 15,000 m3 or 30,000 m3) are tested for the faecal or contamination indicators E. coli and coliform bacteria, and on request also for faecal streptococci. If they are detectable in 100 ml, the above-mentioned requirement of the Drinking Water Ordinance is not considered to be fulfilled, rather a hazard from pathogenic faecal germs in concentrations relevant to health is assumed. In this situation, action must be taken immediately, if necessary also by notifying the public of a decoction by the health department. The principle of faecal indicators has proven itself epidemiologically, but finds its limits when pathogens do not originate from faeces or when they behave differently than E. coli during preparation and disinfection. In Germany, since Robert Koch, a non-faecal-specific indicator for the bacteriological effectiveness of the filtration in water extraction and for the recontamination of the water in the distribution process has been determined by determining the number of colonies ("total number of germs", reference value: 100 / ml) has proven to be very helpful in practice (14).
The water tests required by the Drinking Water Ordinance must be initiated by the utility company and, if the conditions are right, can carry them out themselves or commission other test laboratories. The health department carries out its own checks and examinations at set intervals (e.g. once a year or even less frequently). The microorganisms relevant for drinking water hygiene can be divided into several groups according to biological and epidemiological aspects.
Faecal-oral route of transmission
The greatest danger from contaminated drinking water comes from faecal contamination of the raw water by humans or animals (domestic animals and wild animals, e.g. water birds, muskrats) (table). Faecal contamination is therefore always to be expected in unpopulated areas if surface water, i.e. water from rivers and lakes, is used to obtain drinking water.
Combating cholera, the dysentery, and typhoid, which was endemic in all large cities in Europe, was the first task of drinking water hygiene. The properties of these pathogens still determine the requirements for drinking water treatment and monitoring today. The last two major drinking water-related epidemics in Germany were the dysentery epidemic in Ismaning in 1978 with around 2,400 cases (3) and the typhus epidemic in Baden-Württemberg with around 420 cases, the latter via potato salad, which was prepared using contaminated water from one unsupervised well was used (12). In Jena, too, water-related cases of typhoid fever occurred in 1980 (24). In all cases, the legal requirements for approval, monitoring and proper operation were not observed. You have made it clear
If these regulations are disregarded, major epidemics can quickly occur before measures to combat them can be taken, and the continuing importance of these bacterial intestinal diseases, which have become rare in Germany, for drinking water hygiene is shown.
Enteral viruses, such as the polio virus or the hepatitis A virus, are viable in surface or groundwater for many months and are sometimes found in large quantities in wastewater and surface water (2, 26, 27). Outbreaks of hepatitis A and E in particular have been reliably documented (1, 13). Other enteral viruses (table) are also easily transmitted with drinking water. The source is always the faecal contamination of the raw water with insufficient treatment and disinfection.
In principle, viruses can also be removed or inactivated using conventional preparation and disinfection methods. In some cases, however, longer exposure times or higher treatment intensities than with bacteria are required. In some hepatitis epidemics, the water, which is known to be heavily contaminated, was treated with chlorine and thus a sufficient bacteriological, but not virological, quality was achieved (11).
The unicellular intestinal parasites Giardia lamblia (G. l.) And Cryptosporidium parvum (C. p.) Have a particularly high resistance to disinfection processes. The pathogens enter the waters primarily with the excretions of wild animals (G. l.) Or domestic animals (C. p.), Namely calves and lambs, in which the disease is quite common and well-known to veterinarians (22). There they are present as permanent enzystierte forms that are not killed by the chlorination of the water (illustration). The water is then still infectious despite the best bacteriological findings. The importance of cryptosporidia as pathogens in humans has only been recognized in recent years. They cause diarrhea in some cases fatal in AIDS patients, while spontaneous healing occurs in immunocompetent patients after one to two weeks. Investigations in children with diarrhea showed a proportion of 0.5 percent with C. p. (30). The disease also occurs sporadically in Germany, especially in contact with animals and consumption of raw milk. In contrast to the USA and England, there have so far been no indications of drinking water-related epidemics.
Pathogen of non-fecal origin
Some pathogens can multiply in the pipe network or other water-carrying facilities in clean, nutrient-poor water (4). These are the pathogens listed in the text box. Since they do not come from faeces in the quantities found, their occurrence shows no correlation with E. coli or coliforms. On the other hand, together with them, the number of colonies is often increased, which indicates recontamination. With the exception of the Aeromonas species, oral ingestion of these pathogens is usually harmless, but there is a different route of infection.
Legionella are probably the most common pathogen causing waterborne infections and deaths in our country at the moment. Legionella grow in symbiosis with other bacteria, but above all with amoebas, in which they can multiply, just like in macrophages and leukocytes (21, 23). Infectious concentrations are found after multiplication in hot water networks, especially in widely ramified systems, in the water of cooling towers and air conditioning systems, but also in water that stagnates at room temperature (8). The water-carrying systems of dental treatment chairs are also frequently colonized with Legionella, so that increased antibody titers have been observed in dental staff (13, 20). Most diseases are caused by Legionella pneumophila (L. p.) Serogroup 01, but infections with other serogroups and with species other than L. p. on. Immunosuppressed persons and intensive care patients are at great risk, so that the prophylactic examination of the warm water system and other known sources of infection for Legionella in hospitals makes sense.
Pseudomonas aeruginosa (Ps. A.) Is primarily known as a causative agent of infections, especially of the urinary tract and respiratory tract and of wounds in hospitals, outside of it, for example, as the cause of otitis externa or whirlpool dermatitis. In both diseases, the pathogen is cleared through the maceration of the skin after a long period of moisture penetration. The germ is otherwise less invasive and therefore of little importance for healthy people, on the other hand it can easily be brought by medical or nursing measures to places where it can lead to the above-mentioned infections. Because of its modesty, it reproduces very easily in an aqueous environment, even in distilled water, often with the formation of slimy biofilms that protect it from the effects of disinfectants. In addition to ion exchangers, filters and other installations, water-bearing medical and dental devices are also typical locations (4, 13). If problems with Ps. A. are to be feared, it is advisable to critically examine the quality of the water used for the various purposes.
In contrast to Mycobacterium (M.) tuberculosis and M. leprae, the so-called "atypical" mycobacteria occur in the wild and are often found in water, soil and on plants, for example M. avium-intracellulare. They can colonize pipes and containers for tap water or even distilled water and under certain circumstances form a large proportion of the microorganisms in walled biofilms (25). In Germany, pool granuloma (caused by M. marinum) has occasionally been reported. In the USA, the colonization of tap water with mycobacteria in connection with granulomatous diseases was noticed in peritoneal dialysis patients (9, 18).
Free living, non-parasitic amoeba of the genera Acanthamoeba and Naegleria multiply in the water and mainly feed on the bacteria that are abundant, especially in biofilms. They are often found on faucets. In very rare cases, these amoebas can cause encephalitis. They are not mentioned here because of this, but because they can cause severe, therapy-resistant keratitis if they are brought into the eye with contact lenses (16). Native tap water is therefore not suitable for rinsing contact lenses. In addition, of hygienic interest is the already mentioned fact that Legionella multiply in the amoeba and can be carried along with them.
The other pathogens mentioned in the text box will not be discussed further. In Germany they have so far either not been noticed to a large extent or only in hospitals as water-associated infectious agents. The selected examples show that safe drinking water, favored by stagnation and temperature increase, can experience a health-relevant microbial colonization. While it is mainly the utility companies that have to ensure that the pathogens mentioned of faecal origin are not found in the water, microbial colonization does not exclusively, but above all, affect domestic installations. This replenishment of germs can have a disadvantageous effect when preparing perishable foods, when used by locally or generally immune-impaired patients and when used in medical-technical devices.
How this article is cited:
Dt Ärztebl 1996; 93: A-2142-2144
The numbers in brackets refer to the bibliography in the special print, to be requested from the author.
Prof. Dr. med. Konrad Botzenhart
Hygiene Institute at the University of Tübingen
General and Environmental Hygiene Department
Wilhelmstrasse 31 72074 Tübingen
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