The Puget Sound Clean Air Agency conducted this screening study to identify chemicals and emission sources that pose the greatest potential health risks to citizens in the Puget Sound region. We also hope to better characterize the potential health risks to our three million residents from a group of air contaminants referred to as air toxics. This study is intended to assist the Agency in focusing resources on those emissions and sources that may pose the highest risks. The results should also help improve air toxics regulations and voluntary programs. The estimates of cancer and non-cancer health effects should not be viewed as actual cancer or noncancer cases resulting from air pollution but as an estimate of relative impact of the evaluated toxic-air pollutants so the Agency can prioritize its efforts to reduce air pollution.