ABSTRACT
The polluted areas tend to expand and the pollution is not digested in the areas where the old life has been destroyed. Some cities find that the easiest way to dispose of the branches cut from the trees in their streets and parks is to burn them, and this has to be done in an expensive incinerator, not in bonfires, in order to avoid obnoxious pollution by smoke. Only a few very old or young or infirm are killed, and these are few compared with the daily slaughter on the roads or the terrible death rate from smoking diseases. Even suicide is a cause of more deaths than air pollution. Nevertheless smogs and other kinds of air pollution cause much squalor and unpleasantness in cities. Where too much pollution is emitted it overwhelms the biological mechanisms which digest it normally, and the forms of life in the water are changed, and changed for the worse.
