The Advisories tables are revised periodically. Reference dose (RfD) values are updated to reflect the values in the Integrated Risk Information System (IRIS), and the Drinking Water Equivalent Level (DWEL) has been calculated accordingly. Thus, both the RfD and DWEL in the Tables differ from the values in the Health Advisory document if the IRIS RfD is more recent than the Health Advisory document value. RfD values from IRIS that differ from the values in the Health Advisory documents are presented in BOLD type. For unregulated chemicals with a new IRIS RfD, the lifetime Health Advisory was calculated from the DWEL using the relative source contribution value published in the Health Advisory. For regulated chemicals, where the revised lifetime value differed from the Maximum Contaminant Level Goal (MCLG), no lifetime value was provided in the Table. For regulated chemicals, the cancer group designation and 10(sup-4) cancer risk reflect the status at the time of regulation. For unregulated chemicals, the cancer group designation or cancer classification and 10(sup-4) cancer risk reflect the values presently on IRIS. New IRIS cancer designations and 10(sup-4) cancer risk values are presented in BOLD type. Several pesticides listed in IRIS have been re-evaluated by the Office of Pesticide Programs (OPP) resulting in an RfD other than that in IRIS. For these pesticides, the IRIS value is listed in the Table, and the newer OPP value is given in a footnote. In some cases there is a Health Advisory value for a contaminant but there is no reference to a Health Advisory document. These Health Advisory values can be found in the Drinking Water Criteria Document for the contaminant.