**4. Related challenges toward public/environmental health evidence**

Evidence on public and environmental health has been described as underpopulated, dispersed, as well as varied. The situation remains underpopulated since there are comparatively limited well-done appraisals of how public/environmental health impacts interventions (Type 2 evidence) while applying across varied cultural groups (Type 3 evidence). The criteria for making public/environmental health decision are much more varied than the clinical interventions evidence. Health impact evidence on built milieu, for instance, could be discovered in transportation planning. Lastly, evidence in public and environmental health is varied, in part since much of the interventions base science remains obtained from "natural experiments" or nonrandomized designs.
