Abstract
In the past our principal concern has been with particulate emissions—smoke, fly ash, cinders, and dust. Nationwide, our regulatory and abatement practices reflect this early preoccupation. A growing concern are the gaseous emissions and the gaseous products resulting from atmospheric photochemical reactions. This is reflected, for example, in our present preoccupation with the automobile. Although interest in gaseous and particulate emissions will continue in the future, more attention will be paid to the particulate products resulting from atmospheric photochemical reactions. This will come from a recognition that not until the visible haze is lifted from our cities will they be truly livable.