The US EPA is seeking to improve its National Air Toxics Assessment (NATA). The work computes risks to human health from Hazardous Air Pollutants (HAPs) listed in the Clean Air Act. An essential step is predicting air concentrations of the Hazardous Air Pollutants (HAPs). Currently, a Gaussian plume model makes the predictions. The model may be accurate for local scale effects on ambient concentrations from emitted HAPs that have short atmospheric lifetimes, slow loss rates and no photochemical production. For HAPs such as formaldehyde, acetaldehyde and benzene, several of the assumptions fail. These compounds contribute a large component of the calculated risk based on previous results from the NATA. EPA can then improve its risk assessments by using a model that better simulates the transport and fate of these compounds. The Community Multi-scale Air Quality model (CMAQ) is one candidate. This abstract describes evaluating a version of CMAQ to support future risk assessments.