... Risk Ranking Approach Used by the Task Force 12al average concentrations for 1999 from EPA's National-scaleAir Toxics Assessment (NATA) (U.S. EPA, 2006d). A descrip-tion of NATA 1999 ... throat irri-tation, wheezing and coughing, difficulty breathing, aggrava-tion of existing respiratory and cardiovascular conditions,chronic respiratory disease, cancer, and premature death.Although ... a systematicprocess to survey the available information and compare rela-tive risks among air pollutants in Houston. There are health-based standards (NAAQS), as well as abundant health effectsinformation...