With respect to "analogy", Bradford Hill states: “With the effects of thalidomide and rubella before us we would surely be ready to accept slighter but similar evidence with another drug or another viral disease in pregnancy.” Similarly, the effects of blood lead trends before us should lend urgency to eliminating the remaining risk of preschool lead exposure and blood lead levels once considered safe. Bradford Hill concluded by addressing The Case for Action, with words that clearly apply to preschool lead exposure today:
"All scientific work is incomplete – whether it be observational or experimental. All scientific work is liable to be upset or modified by advancing knowledge. That does not confer upon us a freedom to ignore the knowledge we already have, or to postpone the action that it appears to demand at a given time."