The group of symptoms due to offensive effluvia is, as Dr. Ballard remarks, a tolerably constant one, and consists of loss of appetite, nausea, headache, giddiness, faintness, and a general sense of depression, with, in some cases, vomiting and diarrhoea. But it is usually impossible to prove by statistics that these phenomena are due to a given effluvium complained of, for those who suffer from it are usually exposed to other causes of ill-health, such as poverty, overcrowding, collection of filth, etc.; and, on the other hand, many of those exposed to the effluvium seem to suffer very little, if at all, from their surroundings. And so true is this, that in the carefully prepared report upon effluvium nuisances recently issued by Dr. Ballard,2 it will be found that as a rule no attempt is made to prove that the effluvia from any particular branch of industry are injurious to health; the test practically applied is that they produce offensive odors.
2 Report in respect of the Inquiry as to Effluvium Nuisances arising in connection with various Manufacturing and other branches of Industry. By Dr. Ballard, London. Her Majesty's Stationery Office, 1882, 8vo.
The legal view of this subject is given in the various decisions as to what should be considered a nuisance, the essence of which is the use of one's own property in such a way as to inflict damage upon, and injure the rights of, another. If a man collects on his own premises, for his own use, any material, such as water or filth, he is bound to retain it within his own premises or to let none of it escape in such a way as to damage others; and this holds good as regards gases, vapors, and odors. The decision of Mansfield, in the case of Rex vs. White, is often quoted approvingly by jurists, viz.: "It is not necessary that the smell be unwholesome; it is enough if it renders the enjoyment of life uncomfortable." But, practically, the question as to whether the discomfort produced is sufficient to produce ill-health will be the one upon which the physician is called to give evidence, and the one also upon which he will find it most difficult to obtain data sufficient to enable him to form a positive opinion.
III. IMPURE WATER.—Of all the various preventable or removable causes of disease to which the attention of the physician engaged in practice in the small towns and rural districts is directed, it will usually be found that the water-supply is the most important, because it is in these localities that it is most liable to become contaminated in such a way as to produce sickness.
All water used for drinking purposes is impure in the chemical sense, since it contains some inorganic matters or salts, and in most cases organic matter also. It is difficult to define precisely what should be considered an impure water in a sanitary sense, and the best we can do is to indicate probabilities in the absence of positive evidence of the production of disease by the suspected water. So far as inorganic impurities are concerned, the most important, from the sanitary point of view, are the salts of lead, magnesia, and lime, but in this country these are so rarely the cause of disease that they hardly require special notice. The physician should, however, bear in mind possibilities of lead-poisoning in some obscure cases which he will meet.
The diseases due to impure water are certain specific fevers, diarrhoeal diseases, and some affections due to parasites which find entrance to the body through this medium. The water-supply is to be suspected in case of prevalence of diarrhoeal disease in a community, and especially if the outbreak be sudden and affect a number of persons and families. Sudden outbreaks of cholera, typhoid fever, or malarial fever, confined to a limited locality, should lead to careful examination of the water-supply. The impurity in water which causes these diseases is supposed to be either organic or the product of organic life, and at present the prevailing opinion is that the really dangerous impurities consist of minute living organisms or germs. It is usual to estimate the impurity of water by the amount of organic matter present, but it is evident that this alone can give no positive information, since by this standard milk and soup would be very dangerous. Much depends upon the character of the organic matter, whether it is derived from the animal or vegetable kingdom—whether it is in a state of fermentation or putrefaction, etc. etc.; but the presence of specific germs in it is the most important part of all, and at the same time the most difficult to ascertain. Nitrogenous organic matter in a state of decomposition is dangerous, yet it does not always produce disease, even when ingested in comparatively large quantity, as in case of "high" game or tainted meat; and it is easy to find instances where water strongly polluted with sewage has been used for a considerable period without producing marked ill effects. It is, however, so extremely probable as to be for practical purposes certain, that water contaminated with the discharges from persons suffering from certain diseases will produce similar diseases in those who drink it, and there is also enough evidence that water containing filth of various kinds either produces or promotes disease to warrant much more attention to this subject than has heretofore been bestowed upon it.
The chemical examination of a suspected water is by no means a simple process, and in most cases had better be referred to an expert in such matters. It is highly desirable, however, that the physician should have sufficient technical knowledge to be able to make a rough analysis at least, if for no other reason than that he may be able to appreciate the results reported by the chemist. As a rule, when a water is so polluted with decomposing organic matter as to be positively dangerous it will have an unpleasant odor, which is best developed by half filling a quart bottle with the water to be examined and shaking it thoroughly. The so-called simple and ready methods which are from time to time advocated in the newspapers, such as the addition of sugar to the suspected water and allowing fermentation to take place, the use of tannin as a precipitant, or the decolorization of a solution of potassium permanganate, are really of very little value and should not be relied upon. In the hands of an expert the best simple method of determining the quality of a water is by evaporation of a known quantity and the ignition of the solid residue. From the amount of the total residue, the quantity left after ignition, the amount of blackening produced, and the odor, a very fair opinion can be formed as to the amount of organic matter present, and whether it is of animal or vegetable origin.
It is not within the province of this paper to describe the methods used by chemists in water analysis, of which the principal are known as the Franklin and Armstrong, the Wanklyn, and the permanganate methods. A careful examination of these methods has recently been made under the direction of the National Board of Health, and a preliminary note of the results, prepared by Professor Mallet, has been published in the Bulletin. From this it appears that the chief value of chemical analysis is, first, the verification of gross pollution, which will usually be detected by the appearance and smell of the water; and, second, in periodical examination of a water-supply to detect changes from the normal or usual character of the water, which may be taken to have a certain local standard of purity. Special importance is attached to the careful determination of nitrates and nitrites in water to be used for drinking, these being the results of oxidation of organic matters, and therefore giving evidence of previous contamination.
Prof. Mallet concludes that "there are no sound grounds on which to establish such general standards of purity as have been proposed, looking to exact amounts of organic carbon or nitrogen, albuminoid ammonia, oxygen of permanganate consumed, etc., as permissible or not. Distinctions drawn by the application of such standards are arbitrary and may be misleading." While this is perfectly true, considered from the standpoint of scientific precision, it does not sufficiently take into account the value of probabilities in these matters, considered as motives to action. It is perfectly true that there can be no fixed standard—that a water which the chemist would report as relatively pure might be much more apt to produce disease than one which he would pronounce impure—but it is nevertheless true that from the results of chemical analysis, taken in connection with evidence as to the source and history of the water, an opinion can be formed as to the danger from its use which is sufficiently reliable to be acted upon in the absence of positive evidence, such as the production of disease.
In many cases the matter must be doubtful, and Prof. Mallet truly says that it will not do in all such cases to forbid the use of the water, for it often happens that this should not be done unless it is absolutely necessary; but there are many other cases in which there is very little doubt, and where action should be governed by the probabilities.