THE SANITATION OF AIR 23
deaths were charged to acute respiratory diseases and pulmonary tuber- culosis. During that period the deaths from these causes numbered 14,091. In the corresponding period of the year before they aggre- gated 10,890.
When we compare the efforts of the sanitary corps in this particular direction with the systematic and thorough work done in checking cer- tain epidemics, we can not fail to note the lack of a comprehensive system in fighting diphtheria, grip, pneumonia and other respiratory diseases, which now claim a majority of victims. The situation seems to be recognized, but is met only to a limited extent. Much good has been accomplished through sanitary inspection, stricter enforcement of the regulations against expectorating in public places, also by ex- hibits and other educational work, but there are many other possible lines of action which should be taken up as parts of an organized cam- paign for the sanitation of the air. Since the most promising measures must always be of the preventive order, we should, above all, study the causes which lead to unwholesome atmosphere.
The Causes of Impure Air
Quantities of smoke, vapor, dust and other offensive waste products are constantly discharged into the atmosphere of urban districts. The emanation of all this matter is so rapid that it becomes visible within a few hours whenever the purifying breezes die away, and yet the gathering gloom is not generally recognized as pollution of the air, but rather taken for a change in weather. According to the seasons, the solid particles like soot and dust will cause a haze, or encourage the formation of mist and fog, sometimes, during the winter, depriving a city for days of the life-giving sun.
The sources that contribute to this pollution of urban atmosphere naturally increase with the population, while the dispersal of impure matter by the natural air currents becomes more sluggish and uncertain with the growing areas of urban settlements. The density of popula- tion in certain metropolitan districts is easily ten times that of smaller cities. The rate of vitiation of the air through smoke and other waste matter must therefore be at least that much greater. Comparatively speaking, the conditions of health in a crowded community are like those prevailing on board ship. The living space is still smaller than that of the average city dwelling, but the elements contributing to the vitiation are about the same per capita, hence more concentrated and more in evidence. We know that extra labor and care are necessary on a vessel to maintain the air in a tolerable state, quite irrespective of ventilation. In cities, where dwellings and shops are built not only closer together, but are literally piled up on each other, the general contamination is likewise bound to become unwholesome unless special