The Environmental Protection Agency's (EPA) ability to effectively implement its mission of protecting public health and the environment relies largely on the integrity and transparency of (1) its assessments of the potential human health effects of exposure to chemicals and (2) its federal advisory committees, which are to provide independent, expert reviews of EPA's scientific work, among other functions. EPA's Integrated Risk Information System (IRIS) program is critical in developing the agency's scientific positions on the potential health effects of exposure to toxic chemicals. These positions, used as a basis for environmental risk management decisions by EPA and others, are maintained in IRIS' database of more than 540 chemical assessments. Since 2001, GAO has issued a number of reports addressing the importance of integrity and transparency to EPA's chemical assessments and to EPA's federal advisory committees. GAO work on EPA's advisory committees has focused on its Science Advisory Board--1 of 24 EPA federal advisory committees--which convenes panels to review many of the agency's scientific assessments and proposals. This testimony highlights scientific integrity and transparency issues GAO has reported on and relevant EPA reform efforts regarding (1) the IRIS assessment process and (2) federal advisory committee policies and procedures and appointment mechanisms. GAO has supplemented information from its prior reports with a preliminary review of the IRIS assessment process EPA issued on May 21, 2009, and the current appointment mechanisms for members of EPA's federal advisory committees.