REGULATORY TOXICOLOGY AND PHARMACOLOGY s. 471-486 ( 1988) Reference Dose(RfD): Description and Use in HeaJthRisk Assessments 1 DoNALD G. BARNES Office o[Pesticides and Toxic Sllbsrances,Unired StaresEnvironmenral Prorection AgencJ'rUSEPA). 401 M Sr. SU" Washington, DC 20460 AND MICHAEL DoURSON Office QfResearch and De\'e/opment, United StatesEnvironmellta/ Protection Agent)' (USEP,4). 40/ M St, SH', JJ'ashington, DC 20460 USEPA REFERENCE DOSE (RID) WORK GROUP Cochairmen MICH"EL DoURSON. Office of Resf!arch and De\'elopmem PETER PREuss. Office of Research and Development ,\/embers DoNALD G. BARNES, Office 0/ Pesticides and Toxic Substances JUDITH BELUN. Office 0/ Research and Development CHRISTOPHER DEROSA, Office of Research and Developmenl RETo ENGLER. Office of Pesticides and Toxic Substances LINDA ERDREICH, Office of Research and Developmenl THEODORE F ARBERoOffice of Peslicides and Toxic Substances PENNY FENNER-CRISP. Office ofWaler ELAINE FRANCIS. Office of Peslicides and Toxic Subslances GEORGE GHAU. Office of Peslicides and Taxic SubSlances RICHARD HILL. Office o/Pestiddes and Taxic Subslances STEPANIE IRENE. Office of Peslicides and Toxic Subslances WILLlAM MARCUS. Office of Jt.ater DAVID PATRICK. Office of.4ir and Radiation SUSAN PERUN. Office of Policy. Planning, and Evalualion AGGIE REVESZ. Office of Pesticides and Toxic Substances REv A RUBENSTEIN. Officeo/Solid Waste and Emergency Response JERRY STARA. Office of Research and Development JEANElTE WILTSE. Office of Air and Radialion LARRY ZARAGOSA. Office 0;( Air and Radiation Rece;yedOct0ber8. /987 I The U.S. Government's right to retain a nonexclusive royalty.free license in and to the copyright cover- ins this paper. for governmental purposes. is acknowledged. 471 0273-1300/88 $3.00