https://collections.nlm.nih.gov/ext/dw/ ... 20170R.pdf
"THE whole Nation was shocked when 20 persons died and several thousand more became ill during the smog that enveloped the town of Donora, Pa., during the last week of October 1948. To most of us this was new and heretofore unsuspected source of danger. Although we have been concerned for many years with the general problem of pollution of the air in connection with smoke, we have regarded that as nuisance and annoyance rather than serious hazard to health. Our scientists tell us that the Donora episode was rare phenomenon. We hope and pray it will never recur. This study by the Public Health Service into the Donora episode, the most exhaustive ever made on problem in air pollution, is step toward positive assurance that such thing will not happen again. There is another way we may now use the knowledge we have gained at Donora. The episode has focussed our attention on the larger problem; that is, the almost completely unknown effects on health of many types of air pollution existing today. We must move to an attack on this new frontier of atmospheric pollution."