THE RELATIONSHIP OF WATER TO HEALTH AND DISEASE While water is not technically a food, it is an essential article of the diet. In addition it bears an important relationship to personal hygiene, inasmuch as it is essential in the maintenance of proper cleanliness of the person, the clothing and other objects.
i. Relationship to Health and body requires an adequate daily supply for its physiologic uses. The amount required by the male adult represents the maximum consump tion for this purpose, varying from 'Soo to 2r00 c.c. of water ingested as such, with approximately 600 c.c. additional ingested with the solid food.
Water bears an important relationship to the communicable diseases, as it may be an important route in the transmission of several species of infective agents. The properties which make it important in this connection are the following: (a) It is ordinarily consumed raw, i.e., it has not been heated or otherwise subjected to any treatment that will destroy any infective agents present.
(b) In its normal cycle of circulation it comes in contact with a great variety of material spread over vast areas, hence if ex creta be present in the open, they will be transported, together with infective agents present, by the water. Furthermore many natural sources of water supply are frequently contaminated, very often grossly so, by the direct discharge of sewage.
Water also serves as a solvent for certain inorganic poisons.
2. Conditions which Favor the Contamination of Water and the Transfer of Infective Agents.—Of the relationship of water to disease, that in connection with the transfer of infective agents is of greatest importance. The following conditions render the employment of a contaminated and infected water possible and probable: (a) The use of water which receives the sewage of other towns; the sewage of the same town, the sewage of individual houses, institutions or factories, or the presence of privies on or over a stream.
(b) The rush of floods or heavy rains which transport excreta deposited on the surface of the ground into a water course.
(c) The use of double supplies coupled together, one for ordi nary domestic consumption, the other from an unsafe source for emergency fire protection.
(d) Contamination of a water shed from labor camps, rail road coaches, or excursionists.
The following factors influence the transfer of infective agents by water: (a) The quick transfer of infective agents from one patient (source) to the victim in the person of the consumer.
(b) The probabilities favor the short survival of infective agents in water, and in addition their multiplication in water is doubtful.
(c) Cold wa ter tends to prolong the period of their survival.
(d) The proportion of infective excreta to the vokime of the diluting water is usually very small, so the dilution of the micro organisms is enormous.
(e) Surface water supplies, which are most exposed to fecal contamination, are most frequently infected, while wells and springs are less often.
The foregoing factors have given water borne epidemics cer tain definite characteristics among which the following are the most conspicuous: (a) Epidemics occur most frequently, and endemic water borne typhoid reaches a maximum during the seasonal periods (winter, fall, spring) when the water is coldest.
(b) Water borne epidemics have an abrupt onset, rise rapidly to a maximum and rapidly decline, i.e., they are explosive.
(c) Investigation usually succeeds in revealing a nearby con tamination and frequently the actual source or sources of in fection.
(d) Present day evidence only indicates that water plays a role in the transmission of those infective agents which leave the body in the feces and urine, for example, typhoid, cholera, and bacillary dysentery.
Indirectly water is of importance as a breeding place for certain insects, such as mosquitoes, concerned in the transmis sion of other infective agents.
3. Inorganic Poisoning from poisoning from water is not unknown. Lead is not found in natural water, and when present is derived from the lead service pipes or some other lead object connected with the supply. The plumbo solvent power of water depends upon the following factors: (a) The presence of a free acid, such as carbonic acid, which is found in soft peaty waters, or, )(b) The presence of an excess of oxygen and little dissolved matter, such as soft water, or, (c) The presence of organic matter, nitrates or nitrites, or (d) The presence of chlorides, which exert a solvent power on the film of the lead carbonate coating the pipe.