From1962to1971,theU.S.militarysprayedherbicidesoverVietnamtostripthethickjunglecanopythatcouldconcealoppositionforces,todestroycropsthatthoseforcesmightdependon,andtocleartallgrassesandbushesfromtheperimetersofUSbasecampsandoutlyingfire-supportbases.Mixturesof2,4-dichlorophenoxyaceticacid(2,4-D),2,4,5-trichlorophenoxyaceticacid(2,4,5-T),picloram,andcacodylicacidmadeupthebulkoftheherbicidessprayed.ThemainchemicalmixturesprayedwasAgentOrange,a50:50mixtureof2,4-Dand2,4,5-T.Atthetimeofthespraying,2,3,7,8-tetrachlorodibenzo-p-dioxin(TCDD),themosttoxicformofdioxin,wasanunintendedcontaminantgeneratedduringtheproductionof2,4,5-TandsowaspresentinAgentOrangeandsomeotherformulationssprayedinVietnam.

BecauseofcomplaintsfromreturningVietnamveteransabouttheirownhealthandthatoftheirchildrencombinedwithemergingtoxicologicevidenceofadverseeffectsofphenoxyherbicidesandTCDD,theNationalAcademiesofSciences,Engineering,andMedicinewasaskedtoperformacomprehensiveevaluationofscientificandmedicalinformationregardingthehealtheffectsofexposuretoAgentOrange,otherherbicidesusedinVietnam,andthevariouscomponentsofthoseherbicides,includingTCDD.Updatedevaluationswereconductedeverytwoyearstoreviewnewlyavailableliteratureanddrawconclusionsfromtheoverallevidence.VeteransandAgentOrange:Update11(2018)examinespeer-reviewedscientificreportsconcerningassociationsbetweenvarioushealthoutcomesandexposuretoTCDDandotherchemicalsintheherbicidesusedinVietnamthatwerepublishedbetweenSeptember30,2014,andDecember31,2017,andintegratesthisinformationwiththepreviouslyestablishedevidencedatabase.