Public health aspects of the water cycle: a review

Applied Geography (1991), II, 179-186

Public health aspects of the water cycle: a review

Frank Jones

AItweN Ltd and Centre,for Research into Environment and Health, Stockton Heath, Warrington WA4 6NL, Cheshire, UK

Abstract

The risks to health caused by water are reviewed. These range from microbiological infections with viruses, bacteria and parasites, through algal toxins to direct chemical pollutants introduced by society into the water supply system. The distinction is drawn between water-borne and water-related disease. Both categories have experienced a recent upsurge in disease reporting and the reasons for this increase are explained in both scientific and epidemiological terms. Finally, the health problems associated with the recreational use of waters and water-related disease in buildings are discussed to illustrate some contemporary problem areas.

Introduction

Good health is fundamental to the well-being of any community. It is also true that water is essential for life, but the association between water and disease has been recognized since ancient times. History has shown that water-borne disease, be it chemical or microbiological, has inflicted a heavy toll on the human race, and still does so in some of the economically poorer parts of the world where classical water- borne infections such as cholera, typhoid and schistosomiasis are stilf rife. The aetiological agents now associated with water-borne disease have increased in numbers since John Snow recognized that contaminated drinking water could infect a whole community that consumed it even though at that time it was not possible to identify the causal organism. The water-borne cholera epidemic which he identified was controlled merely by removing the water pump handle. Such control is not as easy to execute today.

Alexander Houston and others, at the beginning of this century, pursued the chlorination of public potable waters in the UK. They, and other sanitary engineers, were instrumental in dramatically reducing water-borne infection in this country and elsewhere. Thus, in the more developed countries, water treatment, disinfection and good sanitation have had a significant impact on drinking water quality. Incidents of water-borne infection in these areas have dramatically declined during this century. Nonetheless, there is no room for complacency, as indicated by Galbraith et al. f 1987), who reported an increase in water-borne and water-associated disease in the UK during the past decade when compared to previous years. The Bramham incident in 1980 (Short 1988) and, more recently, the first recorded incidents of giardiasis and cryptosporidiosis transmitted via drinking water in the UK, give cause for concern (Rush et a/. 1990). Chemical contamination of potable public water supplies has also induced ilIness or caused major concern (Packham 1990).

Furthermore, recent investigations have prompted questions about the use and ability of the halogen chlorine in water treatment (Fawell ef a/. 1987). Suggestions have been put forward that chemical by-products produced by the action of chlorine

0143~6228/91/03 0179.08 0 1991 Butterworth-Hcinemann Ltd

180 Public health aspects of the water cycle

on some waters produces compounds potentially hazardous to health. Additionally, outbreaks of zoonotic gastrointestinal infections associated with apparently adequately disinfected drinking water have been epidemiologically linked. Blue-green algae commonly occur in fresh and brackish waters and can produce massive growths as a consequence of the poor management of aqueous systems. The cyanobacterial species which often dominate these growths can produce toxins capable of causing fatal poisoning of agricultural livestock and other animals (Codd eta/. 1989). Indeed, a recently reported incident involved human recreators canoeing in a freshwater lake (National Rivers Authority 1990; Turner et al. 1990).

The Chernobyl accident has highlighted the possibilities of radioactive contamination to the environment, including water, even over great distances (Jones and Castle 1987). Castle (1988) focused attention on natural radioactive pollution of water sources as the potentially more disturbing aspect of health risk.

Water recreation and leisure activities have become steadily more intensified in recent years. Indeed, water-related sports now offer a diversity of activity such that, in some, innovative equipment is essential for their execution and enjoyment. These activities present greater possibilities for enhanced exposure through a full annual cycle and alternative modes of infection transmission. Increased potential for human infection is evident in both man-made water systems and natural fresh and marine waters (Jones and Watkins 1985; Jones and Bartlett 1985).

A significant increase in the use of vending machines has led to recent concern about the quality of water supplied for their use and the effect of this form of liquid dispensing on the quality of food and beverage dispensed. Points of importance to bear in mind are good design to limit water stagnation and the choice of construction materials that do not have a deleterious effect on water quality and have good hygiene, maintenance and service characteristics.

The discovery of more pathogenic organisms that have the ability to use the water cycle as a means of multiplication and a mode of transmissian has been remarkable over recent years. New and applied analytical techniques have led to the discovery of several causative agents of viral gastroenteritis. Bacteria such as Legionella, Campylobacter and parasites such as Cryptosporidium (Skirrow 1982; Casemore 1990; Dadswell 1990) have been identified and recognized as water-borne or water- related pathogenic organisms. It is reasonable to assume that other organisms capable of transmitting disease via the water route await discovery.

Water and disease

In reviewing the risk to health related to water one cannot do better than follow the approach taken by Galbraith et a/. (1987). Two broad categories have been identified: water-borne disease and water-related disease.

Water-borne disease

Water-borne disease is transmitted directly by drinking contaminated water. This contamination, which is capable of inducing water-borne infection or disease, may be microbiai, chemical or radiotogical in aetiology.

An outbreak of water-borne typhoid fever occurred in Croydon, Surrey in late 1937. Over 300 cases were identified with at least 43 deaths (Galbraith et al. 1987). It was shown that inadequately chlorinated contaminated source water was being pumped from the supply into the public distribution system. Although chlorination

Frank Jones 181

of drinking water during the twentieth century had become more commonplace, both in the UK and North America, this incident created so much impact that a public inquiry took place and chlorination of all public potable supplies in England and Wales became compulsory.

In 1980, another significant water-borne outbreak occurred in England due to microbial contamination of a public drinking water supply. This resulted in about 3000 cases of gastroenteritis in Bramham, Yorkshire. Again it was shown that unchlorinated contaminated water was being pumped from a borehole source to people’s taps. While this incident had obvious implications for the water industry, no public inquiry was instigated and the facts were not reported in the scientific literature until eight years later (Short 1988)! Significantly, samples of water which were taken and analysed before and after the incident for faecal bacterial indicator organisms produced positive analytical results but no effective management response from the water supplier. Indeed, the cause of the outbreak was only recognized after and because people actually became ill.

Bacteriological examination of drinking water supplies is standardized in the UK (HMSO 1983). However, the interpretation of simple microbiological analysis of water samples can sometimes be difficult. It must therefore be remembered that history, local knowledge, treatment processes, operational factors and analytical trends should always be taken into account when considering the findings of faecal indicator organisms in a sample. Furthermore, these simple tesets may not be sufficiently sensitive indicators of either parasitic or viral contamination in potable waters. However, one must never dismiss even the finding of a single Escherichia coli as a sampling contaminant, since it is virtually impossible to accidentally contaminate by sampling a lOO-ml water sample to that degree of sensitivity. This fact is especially important if, historically, the treated supply has consistently given indicator-free sample analyses, particularly if the same sampler and quality-controlled analytical procedures have been used.

Pathogenic viruses and parasites are often more resistant than some prime bacterial indicator species to traditional water disinfection processes. Thus it is possible to have situations where bacterial faecal indicators may be absent in a representative sample from a drinking water supply but at the same time it may contain other microbial pathogens. Interestingly, a case-controlled epidemiological study in 19X.5 demonstrated an association between diarrhoeal illness, the protozoan parasite G~ard~a /aJ??~/ia and the consumption of a treated public water supply in Bristol (Jephcott el al. 1986). This was the first outbreak of its kind identified in the UK which implicated a public treated water supply as the source of a water-borne pathogenic parasitic infection. More recently, water-borne outbreaks due to infection with Crypto- sporidium have been reported (Brown et al. 1989; ENDS 1989, 1990; British Medical Journal 1990; Casemore 1990; Department of the Environment 1990). Indeed, over the last few years the parasitic protozoan cr_~~to~poridiuJ~ has been the most significant causal agent in water-borne outbreaks associated with drinking water supplies in England. In addition, the possibility of post-treatment contamination due to ingress or water burst repair must not be overlooked, particularly when this occurs in rural situations or areas where pollution from domestic livestock, domestic animals or wildlife can more easily be a source of contamination to the supply and a means of zoonosis to the human consumer.

Both Galbraith et al. (1987), in their review report of water-borne and water- associated disease, and Benton et al. (1989), in their appraisal of the incidence of water-borne disease in Scotland, appreciated the increasing significance of water- borne outbreaks of chemical poisoning. Indeed the highest number of outbreaks


reported in the Scottish review were due to chemical poisoning caused mainly by lead contamination and plumbo-solvency. The two most striking incidents of chemical poisoning due to chemical pollution of public water supplies that have occurred in the last decade in England and Wales are the Dee and Camelford outbreaks. This author was personally involved in the former, which was due to industrial pollution of the water source, the River Dee, with the toxic chemical phenol (Ashton 1985). Approxi- mately two million consumers were put at risk. Chemical spillages such as this highlight the need for water catchment control and the quick and efficient imple- mentation of emergency measures designed to protect the public. These should include the potential to provide alternative wholesome drinking water and procedures to restore the polluted supply to good quality as soon as possible. In practice, it may be easier to decide to close a water intake than decide when to reopen it. In the Camelford incident, high levels of aluminium passed into the potable water system serving approximately 10 000 people in that part of southwest England. This occurred when aluminium sulphate was accidentally delivered and poured into the wrong treatment tank. A retrospective epidemiological study identified a greater incidence of painful joints in the consumer group exposed to the contaminated water. Other recent epidemiological evidence has suggested a correlation between aluminium in potable water and Alzheimer’s disease, a dementia which particularly affects older people. However, Packham (1990) doubts the dominant role of water-borne aluminium in the aetiology of Alzheimer’s disease, finding it difficult to believe that it can be so much more bioavaiIable than other bodily intakes.

The lack of robust toxicological data to assess the health effects of an increasing range of chemicals which can now potentially pollute water systems is a matter of some concern. While we may know the toxic elements of many chemicals we do not know how these may damage health when present in drinking water or in water used for washing, when they may be absorbed through the skin and/or create cell-mediated reactions. Of special interest are trace organics and the possible acute and chronic long-term effects not only of elevated levels but of minimal levels consumed over very long periods of time. Epidemiological and ecological studies have linked water hardness with cardiovascular disease (Pocock et a/. 1980) and drinking water contamination with the incidence of leukaemia (Fagliano et al. 1990). Lead, nitrate, pesticides, trihalomethane and others have also been associated with risks to health that may be related to drinking water. Those most often at special risk are bottle-fed babies, those who may have an inborn error of metabolism, those who are immuno- compromised or those undergoing dialysis (although the latter are normafly rigorously protected by filter systems and other measures).

Water-related disease

Polluted water may contaminate food before, during or after preparation. The food may be eaten raw, such as fresh fruit or vegetables, or processed. Both treated and untreated waters polluted with pathogenic organisms from sewage or otherwise have been incriminated in contaminating milk, canned meat, fish, vegetables, fruit and other prepared foods, resulting in outbreaks of human disease.

Most of these documented incidents of disease have implicated a range of pathogenic organisms as causal agents (Galbraith et al. 1987). However, chemical contamination by accidental spillage, the use of chemicals in manufacture or by leaching from new plastics used in machinery or transporting water can be a source of trouble. Some of these effects may be transient, giving rise to taste and odour problems, but some may have an effect on health, either real or psychosomatic. Thus the Dee

Frank Jones 183

incident previously referred to resulted in a significant loss of dairy products and packed foods, such as fish prepared and processed using the phenol-contaminated supply. The EC directive relating to the quality of water intended for human consumption (80/778/EEC) recognizes these points. It includes all water supplied for consumption, or used in a food production undertaking intended for human consumption, or affecting the wholesomeness of the foodstuff in its finished form. It applies rigid values for toxic and microbiological parameters which constitute a public health hazard and to which derogations shall not apply.

Coastal, estuarine and fresh waters may be readily contaminated with raw or treated sewage, industrial effluents or agricultural runoff. In the UK, arable and pasture land has been traditionally used for the application of raw, partially treated or treated sewage and waste water. Sewage effluent may be used for irrigation purposes and surface waters commonly act as receiving vehicles for sewage and trade effluents. All of these ‘disposal’ systems can be acceptable when used in conjunction with approved guideline procedures and consent conditions. The advent of European Community directives such as those that apply to wastewaters, bathing waters, drinking water, water abstractions and natural mineral waters may now impinge upon these practices and potential sources of pollution. Nevertheless, special attention must be paid to protecting public health when applying raw or treated effluents or sewage sludge to salad or vegetable crops which may be eaten uncooked, or merely washed before consumption.

Hence foods grown and harvested from such environments are open to contamination by pathogenic organisms and toxic chemicals, including radiation. Shellfish, fish and watercress have not surprisingly been implicated in food poisoning incidents associated with sewage disposal. Shellfish contaminated with the natural marine bacterium I/ibrio paruhaemalyticus have also been identified with human food poisoning episodes. It is important to realize that some shellfish (bivalves) have the capacity to concentrate micro-organisms. They should therefore be harvested from good-quality waters or be processed by depuration to negate the potential health risk, particularly if eaten raw.

Recreational use of water

The recent increase in water recreational leisure sports, on natural and artificially created recreational facilities, has resulted in greater awareness of the potential of such activities in transmitting infection and disease. Water used for recreation or leisure may contain pathogens harmful to recreators. These pathogens may be algal, viral, parasitic or bacterial in nature, and may have gained access to the water via natural or human-orientated means. If higher bather loads are experienced it is possible that infections are spread from bather to bather rather than being water transmitted. Skin, gastrointestinal and respiratory infections, together with con- junctivitis, primary amoebic meningoencephalitis and leptospirosis (Weil’s disease) have been reported. The recent increase in water recreational and leisure sports has inevitably resulted in greater awareness of the fact that infection and disease can be transmitted by such pursuits. Furthermore, legal implications may become apparent with the greater active encouragement of the use of such water facilities, should they be identified as specific risks to health and safety.

Those responsible for managing these water environmental hazards have had little guidance. The setting of formal scientific health standards, particularly for fresh recreational waters in the UK, has mainly been avoided and little or no microbiological analysis has been undertaken until quite recently (Jones and Godfree 1989).


The recent increase in the number of designated, or identified, coastal waters as ‘bathing areas’ and the ‘Rossi Report’ (House of Commons Environment Committee 1990), have highlighted the lack of robust epidemiological data on the risk to health caused by swimming in sewage-polluted waters (Godfree et al. 1990; Jones et al. 1991).

Hospital-acquired infection and water

Hospitals, of necessity, are linked with those in the community who are ill. Patients may be severely immuno-compromised, undergoing major stress or surgery, or be at the extremes of the age spectrum. They are more vulnerable to infection, particularly from opportunistic pathogens, some of which are known to thrive in water and use it as a vehicle of transmission. Hence greater attention should be paid to hospital water supplies in general and in particular those supplies to operating theatres, intensive care units, dialysis units and the like.

Disease associated with man-made buildings

Services

The recognition that systems such as hot and cold water services, evaporative cooling systems, whirlpools and spas can provide environments conducive to microbial colonization by organisms injurious to mankind, has now been well demonstrated. These systems, if badly designed, improperly cleaned or maintained, poorly operated or treated, constitute a continuing reservoir of infection to the human population exposed to them. Occupancy of a building may pose potential risks to health arising from:

1. construction materials (such as asbestos); 2. building contents (insulating material, lighting, and so on); 3. specialized procedures carried out within and adjacent to a building (use of toxic

chemicals and solvents, for example); 4. cooling towers and hot and cold water systems (microbial transmission of

pathogens such as Legionella); 5. air-conditioning and humidifier systems (sick building syndrome, humidifier fever

and extrinsic allergic alveolitis, for example).

A number of these phenomena are linked to water systems, water content or aerosol contamination within or near buildings. These may be vehicles of microbial and/or chemical contamination and hence pose a risk to health.

Legionella pneumophila is a Gram-negative bacterium which is widespread in the environment. Man-made water systems such as hot and cold water supplies, evaporative cooling systems and whirlpools have all been found to contain the organism and have been implicated in outbreaks of legionellosis and incidents of Legionnaires’ disease. It is strongly believed that the route of infection is inhalation of the bacterium suspended in small droplets or in aerosol form. Aerosols may be readily generated from evaporative cooling systems, whirlpool spas or through the impact of water hitting wash basins, sinks or baths, from showers and taps. Inter- estingly, Legionnaires’ disease is now notifiable in Scotland but not in the rest of the UK. Further information may be had from Chartered Institute of Building Services Engineers (1987) or British Standards Institution (1987).

Frank Jones 185

Conclusion

Our understanding of the range of possible water-borne and water-related health effects is growing. The effect of this recent advance in scientific understanding is to increase public awareness of the potential dangers which derive from inappropriate uses of water if insufficient attention is given to public health protection through sanitary control and hygiene. The traditional engineering solutions may not always be sufficient to safeguard the purity of potable supplies unless accompanied by a high level of monitoring expertise and surveillance and rigorous process control measures. This point is illustrated by recent problems with both chemical contamination of riverine sources, such as the Dee and at Camelford, and microbiological contamination of surface and potable waters with Cryptosporidium. Both the public awareness of these problems and the moving scientific frontier generate a significant require- ment for strategic research on water-related health effects. This research effort may not fit within traditional academic boundaries of engineering, microbioiogy, chemistry, biology, hydrology, and so on. It requires a broader, multidisciplinary vision and presents a challenge as immediate and exciting as that faced by John Snow in the last century.

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Documents

Public health aspects of the water cycle: a review