1961-1975 2004f-185 adverseeffects agentorange aircraft chemical chemicaldefoliants defoliants diseases epidemiology etiology healthaspects healthriskassessment herbicides medical occupationalexposure pharmacology respiratorytractneoplasms toxicology veterans veteranshealth vietnamconflict vietnamwar vietnamwar(1961-1975) vietnamwar(1961-1975)fast(ocolc)fst01431664 wa240 wa240i594v2004 warfare