This episode's headline: Clearing the Air; Tackling Drugs; On the Stump. The guests include JAN VAN DUSER, National Football League; HARRY EDWARDS, Sociologist; IRA BERKOW, New York Times; JILL LIEBER, Sports Illustrated; LEE THOMAS, EPA Administrator; MAYOR FEDERICO PENA, Denver; GOV. MICHAEL DUKAKIS, Democratic Presidential Candidate; CORRESPONDENT: KWAME HOLMAN. Byline: In New York: ROBERT MacNeil; In Washington: JAMES LEHRER