Purity of Water And Food Supplies
( Originally Published 1917 )
Water Supplies and Health.—Of all foods, water has caused the most terrible epidemics of disease. In cities and towns where the water supply is carefully protected, this is no longer the case, but we still hear now and then of epidemics of typhoid fever due to polluted water in places where people are neglectful. The most dangerous source of supply is a stream into which city sewers empty or into which pollution from outdoor closets may be washed in times of rain.
A famous example of water pollution of this kind was the epidemic of typhoid fever in the Merrimac River Valley in 1890-1891. At this time, the two large cities of Lowell and Lawrence in Massachusetts both used the water of the river for drinking, without any purification. In the fall of 1890 there were several cases of typhoid fever in the little village of North Chelmsford, situated on a brook running into the Merrimac River a few miles above Lowell. Because of the careless disposal of sewage, the water in the brook became infected, and between October and January there were 503 cases of typhoid fever in Lowell. The sewage of Lowell was carried down the river to Lawrence, and between November and February there were 223 cases of typhoid fever in Lawrence. After this unfortunate event, both cities provided for purifying their water supplies, in order to prevent such occurrences in the future.
Purifying the Public Water Supply.—No surface water from lake or stream is safe for drinking, unless it has been purified in some way, because pollution may anywhere get on to the ground and be washed in by rain. Many cities that use river water purify it for drinking by the processes of filtration, in which the water is passed through great beds of sand which strain out harmful bacteria (as discussed further in Chapter XXVIII).
Protection of Well Water.—Just as river water may be made pure by passing it through a sand filter, so the water in an ordinary well is often purified by its passage through the soil, for if soil is of the right kind it will strain out bacteria, as the filter does.
Too often, however, a well is not protected at the top against surface drainage, and is really not a well at all but a little pond; and sometimes there are cracks in the soil through which pollution finds its way underground. The well should always have a curb rising above the surface of the ground, and a tight cover. It is important also that the upper eighteen inches of the well should be made tight against surface drainage. In order to avoid danger of pollution through the soil, the well should be at least fifty feet away from the cesspool or outdoor closet or manure pile. It should not be on a lower level than these possible sources of pollution or between them and the nearest stream or pond, for the direction of flow of the underground water is generally toward the nearest body of surface water.
If there is any doubt as to the purity of drinking water, it should always be boiled. Boiling kills all disease germs and makes the most dangerous water safe to drink. Boiling drives out the air in the water and gives it a flat taste, but
the water will soon take in air again if it is allowed to stand in an open pitcher for a time or is poured back and forth from one pitcher to another.
The Individual Drinking Glass.—It is quite as important that water should be drunk out of a clean glass as that it should itself be unpolluted. Drinking from a glass previously used and soiled along the rim with germs from the lips is a common source of disease. This is the reason why many state and city laws forbid the use of common drinking cups. Every child in school should have his own individual glass, which should be kept in his desk and not left by the sink for others to use. It is still better for the school to be provided with a good type of bubble fountain, so that no glass is necessary. If you want a drink where there is not a clean individual glass or a bubble fountain, it is easy to make a drinking cup out of a clean sheet of paper by folding it as shown in Fig. 96.
Ice.—Cold does not kill germs, as heat does, but it pre-vents them from growing. When ice forms on the surface of a pond, most of the germs are thrown out—in the act of freezing—into the water below the ice. Those that are left will almost all die out while the ice is being stored, since it generally stands for some time before being used.
The most important danger from ice is that it may be polluted by handling just before it is used. On this account, it is safer not to put ice into the drinking water. The best plan is to cool the water by placing it near the ice in the ice box.
Dangers from Milk.—In most well-governed cities, the public water supplies are now carefully guarded. Milk, however, is still one of the commonest sources of disease and probably causes more epidemics than water. If the greatest possible care is not taken, there are many chances for dirt to get into milk, from the body of the cow, from the stable, from the hands and clothes of the milker, from cans and bottles, and in the various steps of cooling and bottling. The ordinary germs from dirt do not die out in milk, as they tend to do in water, but multiply so rapidly that if the milk is not kept cold there are soon many millions in a thimbleful; and even the disease germs may multiply in milk at times. The souring of milk is the result of the activity of certain microbes growing in it. The dirt germs often affect milk so as to make it poisonous to young children; and the chief cause of sickness among babies in summer is dirty cow's milk.
In addition to the common dirt germs, the germs of tuberculosis may get into the milk from diseased cows, and germs of such diseases as typhoid fever, diphtheria, and sore throat may get in from sick people or disease carriers who handle the milk.
The history of city and state health departments is full of epidemics of typhoid fever, scarlet fever, diphtheria, and septic sore throat, caused by milk infected by a sick person or a carrier on a dairy farm. Fig. 97 tells the story of such an outbreak in a village on Long Island, New York. The daughter of a woman who owned a milk farm had a bad sore throat on April 16th, 1914. On May 9th the woman herself was taken ill, and on May 11th a man who did the milking and bottling became ill in turn. The germs of the disease got into the milk, and early in June septic sore throat broke out among the customers of the dairy. Over two hundred cases of the disease occurred before the epidemic was ended.
How to Make Milk Safe.—In order that uncooked milk shall be safe, it must come from cows that are free from tuberculosis 1 or other disease; the barn and dairy buildings must be kept scrupulously clean; people who have sore throats or any other signs of disease must not milk the cows or handle the milk in any way; and the milk must be cooled at once and kept cool, to prevent the growth of germs.
It is very hard to be sure that all these things are attended to all the time. Fortunately there is another precaution that may be taken—milk may be pasteurized; and this is the only way to make it really safe.
Pasteurization.—Pasteurized milk is milk which has been heated to a temperature of 145° Fahrenheit and kept at that temperature for thirty minutes. This process kills all the disease germs, and most of the other germs in milk, without making it indigestible. It is named for the great French-man, Pasteur, who first discovered that microbes cause disease.
On account of the great danger from raw milk, all milk for drinking, particularly for babies and young children, should be pasteurized. It is probable that some of the vitamins in milk are destroyed by heating, and when babies are fed only on pasteurized milk they should be given orange juice to make up for this deficiency.
In most cities it is easy to buy milk that is already properly pasteurized, but sometimes milk is sold as "pasteurized" which has been heated very hot for a few minutes or seconds only. This "flash" treatment, as it is called, is not pasteurization at all, and such milk is never safe.
How to Pasteurize Milk at Home.—Where properly pasteurized milk cannot be bought, the next best thing is to get good clean bottled milk and pasteurize it in the home. Never buy milk that is dipped out of a tank, for it is always dirty. It is almost as easy to pasteurize (or cook) milk as it is to cook any other food, and there is no more reason why we should drink uncooked milk than eat raw meat.
The best way to pasteurize milk is to set the bottles in a deep pan of water on the stove, put a milk thermometer into the water, heat up to about 145° or a little over, and then set the pan on the back of the stove, moving it back and forth now and then to keep the temperature, for half an hour, as near 145° as possible, say between 1400 and 145°. If you have no milk thermometer, it will do almost as well to heat the pan till the water boils, and then let it stand on the back of the stove for half an hour, although this may give the milk a slight cooked taste.
After the milk has been pasteurized, it should be cooled at once. Though pasteurization kills all the disease germs, it does not kill all other germs, and those that are left will increase and will spoil the milk if it is not kept cool. The greatest care should be taken not to let milk stand in open dishes or in warm places, but to keep it covered and cold.
An interesting experiment may be made with four bottles of fairly clean fresh milk. Pasteurize the milk in one bottle by heating it in a pan of water over an alcohol lamp in the classroom, or at home beforehand. Add some dirt to the milk in the second bottle. Then keep these two bottles and one of the others in a cold place, and the fourth bottle in a warm place. The bottles s h o u l d be examined every day to see when each one curdles.
The Dangers in Uncooked Food.—Besides water and milk, there are other foods that are eaten raw, such as oysters, lettuce, and celery, which sometimes cause disease if they are not clean. Fig. 99 shows how oysters which had been polluted with sew-age in a creek on Long Island, New York, carried typhoid fever to Goshen, Newburgh, and Suffern, three distant points in the state.
As a rule, cooking will destroy disease germs, but if the germs are in the inside of the food and the cooking is not thorough, they may survive. A disease called trichinosis (trik' i no sis), caused not by a bacterium but by a parasitic worm which infects the hog, sometimes follows the eating of raw or partially cooked pork products.
Care of Food in the Store and Home.—Care should al-ways be taken to protect foods from dust and flies, particularly cooked foods and those which are to be eaten raw. Flies may easily carry filth and disease germs to food, and it is important to keep the kitchen and the dining room screened and to buy only from stores which protect their food in the same way.
Food is also often polluted with disease germs by hand-ling. The danger of such happenings would be much less if people with colds or other signs that they are "coming down" with some disease would, so far as possible, keep away from the preparation and handling of food, and if every one who touches food would first wash his hands thoroughly.
Food Poisoning.—It sometimes happens that a number of people are made ill by eating meat, fish, or some other food that has become spoiled. Such attacks of food poisoning, also called ptomaine poisoning, are not caused by the common germs of decay. Indeed, some kinds of cheeses and other foods are generally eaten when they are decayed, without doing any harm. It is only when special kinds of germs are present that there is danger. Only a bacteriologist, after elaborate study, can tell whether these dangerous germs are present or not, and their presence cannot be detected by any special taste or odor. In order to be on the safe side, one should avoid all food, particularly meat or fish, that is spoiled or tainted to such an extent that it smells or tastes bad, or looks soft, slimy, or discolored, for such food is likely to contain the germs of food poisoning.
Meat that has been chopped up into small pieces, as in hashes or fricassees, is particularly likely to spoil on account of the amount of surface exposed to the germs of decay. All such dishes should be watched with special care.
Preservation of Food.—In order to avoid the danger of food poisoning, and to prevent the loss of good food by spoiling, it is important that all foodstuffs should be care-fully guarded against decay. Since decay is caused by the growth of microbes, anything that will keep microbes from growing will keep foods from spoiling.
One way of doing this is by canning or preserving. In these processes the microbes already present in the food are killed by heat, and the can or jar is then sealed so that no more microbes can get in. Tinned foods should be removed from the cans as soon as they are opened, for food standing in the open tin may absorb poisonous substances dissolved from the can by bacterial action.
Cold is another excellent preservative. It does not kill the germs, as high heat does, but it checks their growth; and in cold storage warehouses where food is kept at freezing temperature or below, it will keep sweet and good for months or years. Food preserved in this way spoils quickly when it is taken out, and should be handled with care and used promptly. We cannot, of course, get temperatures as low as freezing in the home, but the ice chest is cool enough to check the growth of germs and helps greatly in keeping food fresh.
Another way of preserving foods is by the use of chemicals which stop the growth of germs. Sugar, salt, and vinegar are used in the household for this purpose; and other chemicals, like sodium benzoate, are used by manufacturers. Some of these commercial preservatives may be poisonous when they are used in too large amounts.
Keeping food clean always helps greatly in preserving it. If food is exposed to dust or to crawling insects, or if it is kept in dirty dishes or handled with dirty hands, it is likely to spoil. Special pains should be taken to keep the ice chest clean and free from odors, which are readily absorbed by many foods.
QUESTIONS FOR DISCUSSION AND REVIEW
1. Why is it not safe to drink the surface water of a lake or stream?
2. Why is the water in wells not always pure? What measures should be taken to protect it?
3. Where does the water supply of your school come from? Your home? What measures are taken to insure the purity of this water?
4. Is lake water more dangerous before or after a heavy rain? Why?
5. By what simple method may any drinking water be made safe, in the home?
6. Have you your own drinking cup at school? Learn how to make one of paper, preferably paper with a glazed finish so that the water will not soak in easily.
7. Did you ever use a bubble fountain? What is its advantage? How high should the water in the fountain rise above the metal base?
8. Does freezing kill disease germs? Why do they die when stored in ice for some time?
9. Why do germs grow faster in milk than in water? Compare the chances of disease germs getting into water and into milk.
10. What causes milk to sour? Will it sour if there are no disease germs in it?
11. What steps should be taken to keep milk clean and relatively free from germs? Have you ever seen a model dairy? What measures are taken in such a dairy to make everything sanitary?
12. What is pasteurization? What does this process do to milk?
13. What could you learn in the experiment with the four bottles of milk (page 255)?
14. What are vitamins? Review pages 76-81, and see what vitamins do in the body and what conditions arise when they are not present.
15. There are dangers in uncooked foods. Does that mean that we should eat only cooked foods?
16. Does cooking always destroy germs and their toxins?
17. What is the cause of so-called ptomaine poisoning?
18. A government meat inspector found in a butcher shop some beef which was dark and slimy and had an unpleasant odor. The proprietor insisted that he did not intend to sell the meat to his customers. It was to go into a consignment to a sausage factory. What do you think of his defense?
19. What causes the spoiling of foods? Describe some ways of preventing or postponing such spoiling.
20. What do we mean by cold storage? What can you say for and against it?
21. When manufacturers' bottled or boxed foods are marked "Guaranteed under the Food and Drugs Act, June 30th, 1906," what does it mean? (See page 84, Chap. VII.) Does it mean that foods so marked are guaranteed as good to eat?
22. A housekeeper said, "If my kitchen and bathroom are clean, I never worry about the rest of the house." Explain.
23. Write to the Board of Health of New York City (or any large city near you) for the Sanitary Code. Find out what the city demands for the care and protection of food from dirt and infection.