THE PRODUCTION OF DISEASES BY

SEWER AIR

THE Composition of sewer air is at least as variable as that of sewerage. According to Henry R. Kenwood (Public Health Laboratory Work, Philadelphia, 1893, p. 232) its reaction is generally alkaline. Oxygen is variously diminished, according to the efficiency of the sewer ventilation; it is sometimes in normal proportions. Carbonic acid is variously increased from the same cause; it probably does not average more than twice the normal amount. Ammonia, sulphureted hydrogen, ammonium sulphide, and carbon bisulphide are present in small quantities. Marsh gas is small in amount or absent. The fœtid and putrid organic vapors of sewage are, according to Odling, allied to the compound ammonias, and are probably carbo-ammoniacal, and contain traces of ptomaines and leucomaines (i. e., animal alkaloids). Moulds, fungi, and bacteria (chiefly bacilli) and their spores, together with animal and vegetable débris, appear to constitute almost the entire suspended matter. Micro-organisms average about six per litre in the air of a good sewerage system.

The atmospheric air always contains bacteria, mostly, it is true, dead, and mineral parts. The presence of pathogenic germs has been denied; but there must be some in the air, and living ones too, for contagion, unless it result from immediate physical contact of the sick and the well, must take place through the air. Tubercle bacilli are found on the walls of rooms; before they enter the lungs of inmates, they must be carried through the air with other dust. It is true, they have been found there but rarely; but von Eiselsberg claims to have seen Streptococcus erysipelatos (Langenbeck's Archiv, vol xxxv, 1886) and Pawlowsky Pneumococcus Friedlander (Berl. klin. Woch., No. 22, 1885). Indeed, the general statement of

Tyndall, not contradicted, always reaffirmed (Essays on Floating Matter of the Air, New York, 1882), that the apparently purest air contains dust with micro-organisms, makes the frequent presence of pathogenic organisms at least probable.

But the atmosphere is certainly no favorable medium. Germs are heavy and fall to the ground; thus it is not unreasonable to believe, but it can not be proved, that a walking child of two feet in height may inhale them more readily than an adult whose respiratory inlet is more than five above the surface. The dryness and light of the sun destroy them; even micrococci die in sunlight in a few hours (Duclaux, Microbes et maladies, p. 34). It is only when locked up that spores were found normal after many (twenty-five) years. Koch retained virulence in his tubercle bacilli five or seven days in diffused light, but only a few minutes or at most hours under sun rays.1

Indeed, pathogenic bacteria have a hard time of it. They live in high temperatures only, and die soon in a low one; they are readily destroyed in water containing saprophytes or any other non-pathogenic bacteria. In the thoroughly soiled water of the River Seine, at Paris, which holds no oxygen, there are no pathogenic bacteria; while a few miles further down, near Meudon, the Seine contains again both oxygen and pathogenic bacteria. Hence, sewage is not a promising place for them to thrive or live in. Great dilution destroys them or renders them innocuous. For two thousand years Rome has emptied all its fæces and other refuse into the Tiber, and no impurities of a dangerous character were detected by Celli and Scala a few miles below the city.

Now, what is valid for air outside a sewer is so for that inside it, with this difference, that there are more germs found in the atmosphere than in sewer air. Billings states emphatically that there are fewer micro-organisms in the air of sewers than in that of the streets. He quotes 1 The statements occasionally made that Achorion Schönleini, plasmodia, erysipelas cocci, also tubercle and typhoid baccilli, and vibrio cholera may undergo multiplication in the air, lacks confirmation.

Carnelly and Haldane (Proceedings of the Royal Society, London, 1847, p. 51), who report that the London and Dundee sewers contain twice as much carbonic acid, three times as much organic matter as outside air, and fewer micro-organisms, and remarks that this air in the sewers is better than in naturally or even mechanically ventilated schools. It is only when there is splashing in the sewers that (temporarily) there can be more organisms in their air. Otherwise moist surfaces do not give them off. It is only under favorable circumstances that they can be carried off and upward into the houses and escape through ventilating shafts. Into living rooms they could escape only either where there are no traps, or where the traps are empty either from disuse or from being sucked out or from upward pressure. In this way, Billings suggests, pyogenic organisms and Fehleisen's coccus appear to be conveyed through house drains. At all events the opportunity for microbes to get out of the dwellings is greater than to get into them. When they get into the drains from inside, they are flushed out. It is evident, however, that the flushing out of substances entering the sinks from inside depends on the structure and size of the drain, the nature of the trap, and the amount of the water poured through it, also on the use or non-use of disinfectants employed in the households. Less rainfall, and consequently less flushing of sewers, gives rise to accumulation of more filth. Badly constructed brick sewers have the same result. Outfall sew

3

2 The epidemic of enteric fever in Croydon, 1875, was attributed by Buchanan to the entry of infected sewer air into houses through untrapped drains and openings into the drains. The pipe sewers were of small size, six or nine inches in diameter, and were ventilated at distances of a hundred and fifty to two hundred and fifty yards by petty openings which were blocked by charcoal trays.

3 The quantity of refuse from rooms and houses is very large indeed. Pettenkofer calculates the daily amount of fæces for the average person at 90 grammes, of urine 1,170 grammes; for a thousand persons per annum, fæces, 34,000 kilogrammes; urine, 428,000 litres. If you add to that figure 159 litres of water daily for each individual, the sum total of daily sewage for a

ers terminating below water are apt to be choked. Thus, while Russell's analysis yielded a fair standard of purity of sewer air, Parent Duchatelet found only 13.79 per cent. of oxygen and 2.99 per cent. of sulphureted hydrogen. Thus gas is undoubtedly developed to a great extent, bubbles are constantly breaking on the surface (Frankland on The Transport of Solid and Liquid Particles in Sewer Gases, Proceedings of the Royal Society, April, 1877), and may enter houses through untrapped drains whenever they are not permitted to leave the main sewer otherwise.

Under these circumstances, as the specific germs of infectious diseases may be contained in the liquid disseminated by the bursting of bubbles, sewer air may certainly become specifically infected. Some of the germs may find a favorable medium in the organic material, the ammonia and the phosphates of sewage, while others are more liable to be destroyed by the saprophytes of putrefaction. As to typhoid, the cases are very numerous. In regard to cholera Parkes refers to its introduction into Southampton in 1866, where it was probably due, in his opinion, to the passing of pumped sewage, infected with cholera evacuations, in a frothy and agitated condition along an open conduit. He adds the remark that, as soon as the latter was covered over, the epidemic (or rather endemic) abated. The latter remark is suggestive. A sewer disconnected from houses by good traps is no longer an open conduit; and it appears that unless sewer air is forced upward, no amount of cholera bacilli or toxin will annoy the population of houses properly secured by traps and by ventilating shafts both in the houses and in the streets.

But granted that sewers are infested with bacteria, how do they get into the air of sewers, of streets, of houses? thousand persons is 160,000 litres. That explains in part the wrath of Andrew Fergus, M. D. In the Proceedings of the Medico-Chirurgical Society of Glasgow, of October 2, 1868, he broadly states that water-closets and canalization are opposed to revelation and Bible, that they are contrary to Nature, inasmuch as they rob the soil, are the sole cause of pollution of rivers, anu fill the sewers with noxious gases which enter the houses in spite of traps.