In this thesis, I seek to answer the following questions: (1) Why do small stationary sources' emissions of air toxics pose different challenges to environmental policymakers than do large stationary source or motor vehicle emissions? (2) What are the most appropriate and effective policy instruments to use in order to reduce human health and environmental risks associated with exposure to one particular type of small stationary source air toxic emission, i.e., perchloroethylene ("PCE") released into the environment by Massachusetts dry cleaning shops?

To answer the first question, I examine the federal government's efforts to regulate small stationary air toxics sources over the past thirty years. I trace out the gradual evolution of the federal government's focus on small source emissions and its slow progression towards regulation of air toxics (as opposed to an earlier emphasis on other types of sources and pollutants). I also compare the regulatory challenges posed by small stationary source emissions with those posed by mobile and large stationary source emissions.

To answer the second question, I examine twelve policy instruments according to an original analytical framework comprised of four "screening factors": distributional equity, efficiency, political feasibility, and jurisdiction (i.e., governmental authority and suitability to implement a particular policy tool). To the extent appropriate, I assess each policy instrument in light of the following factors: patterns of PCE use and emission by dry cleaning shops, pathways for PCE releases to the environment, scientific uncertainty regarding human health and environmental risks associated with exposure to PCE, viability of alternative garment cleaning technologies, and administrative and compliance costs.

Based on this methodology, I recommend the use of four specific policy instruments to reduce the risks associated with exposure to PCE: a deposit-refund mechanism for spent PCE, a public information campaign focusing on risk communication/consumer education, modification of Federal Trade Commission rules regarding garment care instruction labels, and expansion of the scope of chemical reporting requirements to include all facilities emitting PCE. I also conclude that successful risk reduction efforts will entail the participation of both federal and state/local agencies and will depend on educated consumers' demands for garment cleaning services that pose fewer risks to human health and the environment.