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Historical Note As noted by Baker (1949), the quest for pure water began in prehistoric times. Recorded knowledge of water treatment is found in Sanskrit medical lore and in Egyptian inscriptions. Pictures of apparatus to clarify liquids (both water and wine) have been found on Egyptian walls dating back to the fifteenth century B.C. Boiling of water, the use of wick siphons, filtration through porous vessels, and even filtration with sand and gravel, as means to purify water, are methods that have been prescribed for thousands of years. In his writings on public hygiene, Hippocrates (460-354 B.C.) directed attention principally to the impor- tance of water in the maintenance of health, but he also prescribed that rain water should be boiled and strained. The cloth bag that he recommended for straining became known in later times as "Hippoc- rates' sleeve." Public water supplies, already developed in- ancient times, assumed added importance with the progressive increase in urbanization. But though they were clearly beneficial in distributing water of uniform quality, large numbers of people ran the risk of suffering adverse effects when the water was unsafe to drink. The first clear proof that public water supplies could be a source of infection for humans was based on careful epidemiological studies of cholera in the city of London by Dr. John Snow in 1854 (Snow, 1855~. Adthough Snow's study of the contaminated Broad Street pump is the most famous, his definitive work concerned the spread of cholera through water supplied by the Southwark and Vauxhall Company and the 1

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2 DRINKING WATER AND H"LTH Lambeth Company. The former obtained its water from the Thames at Battersea, in the middle of London in an area almost certainly polluted with sewage, whereas the Lambeth Company obtained its water considerably upstream on the Thames, above the major sources of pollution. In one particular area served by these two companies, containing about 300,000 residents, the pipes of both companies were laid in the streets, and houses were connected to one or the other sources of supply. Snow's examination of the statistics of cholera deaths gave striking results. Those houses served by the Lambeth Company had a low incidence of cholera, lower than the average for the population of London as a whole, whereas those served by the Southwark and Vauxhall Company had a very high incidence. As the socioeconomic conditions, climate, soil, and all other factors were identical for the populations served by the two companies, Snow concluded that the water supply was transmitting the cholera agent. Snow's study, a classic in the field of epidemiology, is even more impressive when it is realized that at the time he was working, the germ theory of disease had not yet been established. During the seventeenth to the early nineteenth centuries, a number of improvements in water supply were made, most of them related to improvements in filtration to remove the turbidity of waters. During this same period, the germ theory of disease became firmly established as a result of research by Louis Pasteur, Robert Koch, and others, and in 1884 Koch isolated the causal agent of cholera, Vibrio cholera. Importance of Water Filtration In 1892, a study of cholera by Koch in the German cities of Hamburg and Altona provided some of the best evidence of the importance of water filtration for protection against this disease (Koch, 18941. The cities of Hamburg and Altona both received their drinking water from the Elbe River, but Altona used filtration, since its water was taken from the Elbe below the city of Hamburg and hence was more grossly contaminated. Hamburg-and Altona are contiguous cities, and in some places the border between the two follows a contorted course. Koch traced the incidence of cholera in the 1892 epidemic through these two cities, with special attention directed to the contiguous areas. In such areas it was assumed that climate, soil, and other factors would be identical, the principal variable being the source of water. The results of this study were clear- cut: Altona, even with an inferior water source, had a markedly lower incidence of cholera than Hamburg. Since by this time it was well established that cholera was caused by intestinal bacteria excreted in

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Historical Note 3 large numbers in the feces, it was concluded that the role of filtration was to remove the contaminating bacteria from the water. In the United States, cholera was not a problem after the mid- nineteenth century; the waterborne disease of particular concern was typhoid fever. In England, William Budd had shown by the mid- nineteenth century that typhoid fever was a contagious disease, and the causal agent was isolated and identified by Eberth in 1880 and Cranky in 1884 (Wilson and Miles, 1957~. Although the causal agent, now called Salmonella Delhi, is transmitted in a variety of ways, one of the most significant is by drinking water. Experiments on water filtration were carried out in the United States during the late 1880's and early 1890's, notably by the Massachusetts State Board of Health experiment station established in 1887 at the city of Lawrence. At this station the treatment of water as well as sewage was considered by an interdisciplinary group that included engineers, chemists, and biologists. A leader in this work was W. T. Sedgwick, a professor at the Massachusetts Institute of Technology (MID], and MIT's influence on water-supply research remained strong throughout the first quarter of the twentieth century. Much of the history of this work has been reviewed by Whipple (1921) and in the two editions of Hazen's book (1907, 1914~; the technical aspects are discussed and clearly illustrated by Johnson (1913~. One important technological advance that made water filtration adaptable even to rather turbid sources of water was the use of chemical-coagulation filtration processes, patented about 1884 by the brothers J. W. and I. S. Hyatt. While the Lawerence experiments were going on, an epidemic of typhoid swept through the city, hitting especially hard at those parts that were using the Merrimac River as its.water supply. As a result, the city of Lawrence built a sand filter, and its use led a marked reduction in the typhoid fever incidence. As reported by Hazen (1907), the death rate from typhoid fever in Lawrence dropped 79% when the 5-yr periods before and after the introduction of the filter were compared. Of additional interest was a reduction in the general death rate (all causes) of 10%, from 22.4 to 19.9 per 1,000 living. Another major series of filtration experiments were made in 1895-1897 at Louisville, Ky., where the source of water was the muddy and polluted Ohio River. These experiments were successful, and from an engineering point of view were of importance because they showed that it was possible to treat source waters of a rather poor quality (the Merrimac River at Lawrence may have been polluted, but at least it was a clear water, making filtration rather easier.) The success of the Louisville experiments and the other studies led to rapid establishment of filters as a

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4 DRINKING WATER AND H"LTH means of water purification; by 1907 Hazen could list 33 cities in the United States, some of comparatively large size, which were using mechanical filters, and 13 cities that were using slow sand filters. As discussed by Hazen, filtration led to an elimination of turbidity and color from the water, and to a removal of about 99% of the bacteria present. At that time these conditions were considered as a standard by which the quality of a treated water should be judged. As Hazen states: "There is no final reason for such standards. They have been adopted by consent because they represent a purification that is reasonably satisfactory and that can be reached at a cost which is not burdensome to those who have to pay for it ... . There is no evidence that the germs (characteristic of sewage pollution) so left in the water are in any way injurious. Certainly if injurious influence is exercised it is too small to be determined or measured by any methods now at our disposal." This last statement is of considerable importance when considered in the light of the important advance in water purification practice yet to come, chlorination. An excellent overview of the relationship between water quality and typhoid fever incidence was published at about this time by Fuertes (18971. He gathered typhoid fever statistics for a large number of cities in North America and Europe and grouped the data by type of source water and water treatment. Chlorination, The Most Significant Advance in Water Treatment Although a reading of Hazen's 1907 book might lead one to conclude that excellent water quality had been well established by filtration, the most important technological advance in water treatment was yet to come. The introduction of chlorination after 1908 provided a cheap, reproducible method of ensuring the bacteriological quality of water. Chlorination has come down to us today as one of the major factors ensuring safety of our drinking water. Calcium hypochlorite was manufactured industrially for use as a bleaching powder and was used in paper mills and textile industries. It was a cheap chemical, and hence readily adaptable to use on the large scale necessary for drinking water. The first practical demonstration in the United States of its use in water supply was at the filter plant of the Chicago Stock Yards, where it was introduced by Johnson in the fall of 1908 (Johnson, 1913~. The use of chlorination in an urban water supply was introduced in Jersey City, N.J., in the latter part of 1908. The circumstances surround- ing the Jersey City case are of some interest from a historical point of view and will be briefly reviewed. Jersey City received its water from a

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Historical Note 5 private company that used a large reservoir at Boonton, an impoundment of the Rockaway River. The water was supplied to the city unfiltered, although some settling took place in the reservoir. Several years before 1908 the city raised the contention that the water being supplied was not at all times pure and wholesome for drinking, as was required by the terms of its contract with the private company. At certain times of the year, the water in the reservoir became polluted as a result of sewage influx from communities on the river above the reservoir. Rather than undergo the expense of a filtration plant, or attempt to control the sewage influx from the various communities, the private company chose to introduce a chlorination system. The results were dramatic. A marked drop in total bacterial count was obtained, and at a cost far lower than any other procedure. After many months of operation, further testimony before the court was held, to determine whether the company, was meeting its contract, and the court decided that the evidence was favorable to the company. As stated by the court examiner: "I do therefore find and report that this device [chlorination] is capable of rendering the water delivered to Jersey City pure and wholesome for the purposes for which it is intended and is effective in removing from the water those dangerous germs which were deemed by the decree to possibly exist therein at certain times." The dramatic effect that chlorination had on water-supply problems is well illustrated by comparing the first and second editions of Hazen's book (1907 and 19141. In the first edition, barely any mention of disinfection is made (merely a remark about ozone being too expensive), but in the second edition Hazen waxes enthusiastic about the advantages of chlorination. As he says, chlorination could be used "at a cost so low that it could be used in any public waterworks plant where it was required . tar ariv~nt~a`~ When the advantages to be obtained by this ~ ~'.'~t)-~ Be . . . . .... .. simple and inexpensive treatment became realized, as a result of the n'~hlicitv given bv the JerseY Citv experience, the use of the process rim ~ ~ , , , . . ... ~ ~ ~ - 1-, ~.-1 _~ ~ ~ ~ {llilAN extended with unprecedented raplulty, until al Ine present slyly' ills greater part of the water supplied in cities in the United States is treated in this way or by some substitute and equivalent method." Interestingly from the point of view of the present report, the introduction of chlorination also changed markedly the established ideas about water-quality standards: "The use of methods of disinfection has changed these standards radically. By their use it has been found possible to remove most of the remaining bacteria so that the water supplied can be as easily and certainly held within one-tenth of one percent of those in the raw water, as it formerly could be held within one percent .... Even today the limit has not been reached. It may be admitted that the

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6 DRINKING WATER AND H"LTH time will come when a still higher degree of bacterial efficiency will be required. Present conditions do not seem to demand it, but we must expect that in some time in the future conditions will arise which will make it necessary. When additional purification is required it can be furnished." (Hazer, 1914~. The importance of Hazen's book is that Hazen was a major consulting engineer for a wide variety of water works, and was very influential in recommending treatment methods. Chlorination was introduced at about the time that adequate methods of bacteriological examination of water had developed, permitting an objective evaluation of the efficiency of treatment. This evaluation was not based on the incidence of typhoid fever directly, but was based on an indirect evaluation using bacterial or coliform counts. Soon after chlorination was introduced, it was possible to obtain firm epidemiological evidence that cities chlorinating water had lowered incidences of typhoid fever (G. C. Whipple, 1921~. Filtration was introduced in 1906 and chlorination in 1908, and both led to marked reductions in the incidence of typhoid fever. Another dramatic example derives from observations at Wheeling, W.Va., in 1917-1918 (Gainey and Lord, 1952~. The incidence of typhoid fever in Wheeling was 155-200 per 100,000 during these years. Chlorination was introduced in the latter part of 1918, with the result that during the first 3 months of 1919 only seven cases were recorded. For 3 weeks during April 1919 chlorination was discontinued, with the result that the number of cases increased to 21, or a 300% increase. Chlorination was continued thereafter, and only 11 cases were recorded for the last 6 months of the year. Other examples of this sort could be cited (Gainey and Lord, 1952~. Summary We thus see that by the beginning of World War I the essential features of water purification techniques were known, and their worth }lad been well established. Since that time there have been many refinements made at an engieering level, but no changes in the basic concepts. It is clear that the prime motivation for the development and introduction of purification methods has been to protect the public health, with special concern for controlling the spread of typhoid fever. An ancillary consideration has been esthetics, showing concern for the appearance, taste, and odor of the water. One point worth emphasizing is that the availability of adequate treatment methods has influenced the standards for drinking water. This point was implied in the books by Hazen (1907 and 1914), but is most

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Historical Note 7 clearly seen in the preamble to the 1925 Federal Standards, which superseded the brief 1914 Standards (see Standard Methods, 7th edition, 1933, p. 136, for the complete 1925 Standards). The following quote is relevant: The first step toward the establishment of standards which will insure the safety of water supplies conforming to them is to agree upon some criterion of safety. This is necessary because "safety" in water supplies, as they are actually produced, is relative and quantitative, not absolute. Thus, to state that a water supply is 'safe' does not necessarily signufy that absolutely no risk is ever incurred in drinking it. What is usually meant, and all that can be asserted from any evidence at hand, is that the danger, if any, is so small that it cannot be discovered by available means of observation. Nevertheless, while it is impossible to demonstrate the absolute safety of a water supply, it is well established that the water supplies of many of our large cities are safe In the sense stated above, since the large populations using them continuously have, In recent years, suffered only a minimal incidence of typhoid fever and other potentially waterborne infections. Whether or not these water supplies have had any part whatsoever in the conveyance of such infections during the period referred to is a question that cannot be answered with full certainty; but the total incidence of the diseases has been so low that even though the water supplies be charged with responsibility for the maximum share which may reasonably be suggested, the risk of infection through them is still very small compared to the ordinary hazards of everyday life. At present other considerations make it necessary [for us] to be less confident than was the 1925 Committee on Standards. Typhoid fever and Cholera are dramatic diseases whose causal agents are transmitted by the water route. Typhoid fever statistics have provided some of the best evidence of the efficacy of treatment systems, but it should be kept in mind that other diseases, not so easily diagnosed, might also be kept under control at the same time. The so-called Mills-Reincke theorem held that, for every death from waterborne typhoid, there were several deaths from other diseases for which the causal agents were transmitted by water (Shipple, 1921~. At present, the incidence of typhoid fever in the United States is so low that no useful information on the electiveness of recent changes in water-purification practices can be obtained from an examination of the statistics. During the years 1946-1970, there were 53 outbreaks of waterborne infectious disease due to typhoid, but there were 297 outbreaks due to other bacterial or viral agents, including 178 outbreaks of gastroenteritis of undetermined etiology (Craun and McCabe, 1973~. Of the outbreaks, 71 percent resulted from contamination of private water systems, but most of the illness (echo) was associated with community water systems. During the period 1946-1960 there were 70 outbreaks of waterborne disease in communities served by public utilities (Weibel et al., 1964), of which only 6 were typhoid fever. When data

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~ DRINKING WATER AND H"LTH during this period for the number of outbreaks are examined, the incidence of typhoid is even lower 103 cases out of a total of 19,928 (for a percentage of O.5~o). Even considering that typhoid is more likely to be fatal than infectious hepatitis or gastroenteritis of unknown etiology, the Mills-Reincke theorem does seem to have considerable merit. Thus, the rationale that has been used in devising standards for microbiological contaminants (see quotation above from the 1925 Standards) does not necessarily hold up on careful examination. The coliform standards may have ensured freedom from typhoid fever, but we do not have the same assuredness that they have guaranteed freedom from other infections. Even granted that most of the outbreaks reported have occurred because of breakdowns in the proper functioning of water systems, the results show that intestinal infections other than typhoid are common and, because of their often ill-defined nature, may be improperly diagnosed. Finally, only "outbreaks" find their way into public health statistics, whereas sporadic, random cases of gastroenter~tis generally go unreport- ed. The epidem~ological significance of the present microbiological standards warrants continuing investigation to bring about further refinements in meeting the goal of maximum protection of public health. REFERENCES Baker, M.N. 1949. The Quest for Pure Water. Am. Water Works Assoc., New York. Craun, G.F., and L. J. McCabe. 1973. Review of the causes of waterborne-disease outbreaks. J. Am. Water Works Assoc. 65 :74. Fuertes, J.H. 1897. Water and public health. John Wiley, New York. Gainey, P.L., and T.H. Lord. 1952. Microbiology of water and sewage. Prentice-Hall, Inc., New York. Hazen, A. 1907. Clean water and how to get it, 1st ed. John Wiley, New York. Hazen, A. 1914. Clean water and how to get it, 2d ed. John Wiley, New York. Johnson, G.A. 1913. The purification of public water supplies. U.S. Geol. Surv. Water- Supply Paper 315. Koch, R. 1894. Professor Koch on the Bacteriological Diagnosis of Cholera, Water-filtration and Cholera, and the Cholera in Germany during the Winter of 1892-93. Translated by G. Duncan David Douglas, publisher, Edinburough. Snow, J. 1855. A reprint of two papers by John Snow, M.D., 1936. The Commonwealth Fund, New York. Weibel, S. R., F. R. Dixon, R. B. Weidner, and L.J. McCabe. 1964. Waterborne-disease outbreaks, 1946-60. J. Am. Water Works Assoc. 56:947-958. Whipple, G.C. 1921. Fifty years of water purification. In M.P. Ravenel, ed. A Half Century of Public Health, pp. 161-180. American Public Health Association, New York. (Reprinted 1970 by the Arno Press and the New York Times.)