Diseases Due to Soil.—A great many diseases have been thought to be due to the influence of the soil. An ætiological relation had been sought between soil and the following diseases: malaria, paroxysmal fevers, tuberculosis, neuralgias, cholera, yellow fever, bubonic plague, typhoid, dysentery, goitre and cretinism, tetanus, anthrax, malignant Œdema, septicæmia, etc.
Sites.—From what we have already learned about the soil, it is evident that it is a matter of great importance as to where the site for a human habitation is selected, for upon the proper selection of the site depend the health, well-being, and longevity of the inhabitants. The requisite characteristics of a healthy site for dwellings are: a dry, porous, permeable soil; a low and nonfluctuating ground-water level, and a soil retaining very little dampness, free from organic impurities, and the ground water of which is well drained into distant water courses, while its ground air is uncontaminated by pathogenic bacteria. Exposure to sunlight, and free circulation of air, are also requisite.
According to Parkes, the soils in the order of their fitness for building purposes are as follows: (1) primitive rock; (2) gravel, with pervious soil; (3) sandstone; (4) limestone; (5) sandstone, with impervious subsoil; (6) clays and marls; (7) marshy land, and (8) made soils.
It is very seldom, however, that a soil can be secured having all the requisites of a healthy site. In smaller places, as well as in cities, commercial and other reasons frequently compel the acquisition of and building upon a site not fit for the purpose; it then becomes a sanitary problem how to remedy the defects and make the soil suitable for habitation.
Prevention of the Bad Effects of the Soil on Health.—The methods taught by sanitary science to improve a defective soil and to prepare a healthy site are the following:
- (1) Street paving and tree planting.
- (2) Proper construction of houses.
- (3) Subsoil drainage.
Street Paving serves a double sanitary purpose. It prevents street refuse and sewage from penetrating the ground and contaminating the surface soil, and it acts as a barrier to the free ascension of deleterious ground air.[12]
Tree Planting serves as a factor in absorbing the ground moisture and in oxidizing organic impurities.
The Proper Construction of the House has for its purpose the prevention of the entrance of ground moisture and air inside the house by building the foundations and cellar in such a manner as to entirely cut off communication between the ground and the dwelling. This is accomplished by putting under the foundation a solid bed of concrete, and under the foundation walls damp-proof courses.
The following are the methods recommended by the New York City Tenement House Department for the water-proofing and damp-proofing of foundation walls and cellars: