Rick Nevin
Causation Indicator: Experimental Evidence

    Bradford Hill states that if “because of an observed association some preventive action is taken … [and it does] in fact prevent … Here the strongest support for the causation hypothesis may be revealed.” Regulations to eliminate the use of lead in gasoline and to reduce lead paint hazards in older housing anticipated societal benefits in excess of regulatory costs because of observed associations between preschool lead poisoning and MR, between even small elevations in blood lead and IQ, and between IQ and educational attainment and lifetime earnings.  Ecological trends suggest the magnitude of preschool lead exposure’s impact on MR and education achievement and attainment trends may have been underestimated in the past, but the direction of that impact was recognized as the basis for deliberate regulatory interventions that have achieved predicted results. 

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