Based on the results of our survey, 85 percent of the EPA survey respondents reported that they have used IRIS as their primary source for cancer values and 81 percent have used IRIS as their primary source for non-cancer values. More than half (51 percent) of the survey respondents who reported using IRIS as the primary source for cancer values indicated a reason they did so was because it was required for the activity they were conducting. Similarly, more than half (52 percent) of the survey respondents who reported using IRIS as the primary source for non-cancer values indicated a reason they did so was because it was required for the activity they were conducting. About one-third (34 percent) of the survey respondents reported that they have used an alternate source for toxicity values when an IRIS value was available. The primary reason selected for using an alternate source was that the alternate source was more up-to-date with current scientific practice or information. We found no EPA policy mandating the use of any toxicity database including IRIS. The Office of Solid Waste and Emergency Response has issued a directive that recommends using EPA's IRIS as the first tier source of human health toxicity values. Sixty-seven percent of the respondents to this survey reported that they have used IRIS for Superfund program activities. Sixty-five percent of respondents also indicated that there are standard operating procedures regarding how to choose a source of toxicity values. Sixteen percent of respondents identified the Office of Solid Waste and Emergency Response directive as this standard operating procedure. All survey responses were self-reported by the EPA respondents and were not verified by the Office of Inspector General.