Tim Barzyk works in the Exposure Modeling Research Branch in the EPA National Exposure Research Laboratory, Office of Research and Development. One of his primary interests is to develop screening level models that quickly and accurately assess the environmental stressors impacting communities. This work often involves looking at exposure surrogates, things that can tell a lot about exposure and risk short of taking actual concentration measurements. Exposure models provide many of the components and insights into this work. Developing comparative risk indices is a related interest, and would allow comparative ranking of different types of environmental stressors, and ideally a better idea of the integrated, or combined risk, of being exposed to them.