The Agency for Toxic Substances and | Disease Registry (ATSDR) determines | public health implications associated with | hazardous waste sites and other environmental releases. Since its inception, ATSDR | has continued to improve its approach to | evaluating public health hazards in light of | evolving science. For example, in response | to concerns about the clarity, meaning, and | understandability of the fi ve conclusion | categories outlined in its Public Health Assessment Guidance Manual (www.atsdr.cdc. | gov/HAC/PHAmanual/index.html), ATSDR | established an ad hoc work group to evaluate and recommend changes to the categories based on health and risk communication science. | All site-specifi c public health assessment | reports must include a statement that assigns a hazard conclusion category to the | site, a time period for exposure (e.g., past, | current, or future), or an exposure pathway, | as appropriate. This statement refl ects one | of the following: that the site does not pose | a public health hazard, that the site poses | a public health hazard, or that data are insuffi cient to determine whether any public | health hazard exists. The language used to | convey these categories, however, was diffi cult for community members and lay audiences to understand because it was not written clearly.