Clear Air and Unclear Science: Uncertainty and Ideology in the Federal Environmental Regulatory Process

The second half of the of the twentieth century saw the increasing awareness among scientists, policymakers, and the public as to the environmental costs of centuries of industrialization, as well as the rise of regulatory regimes designed to mitigate human-caused environmental damage. In the United States this took the form of a series of major federal laws, particularly during the 1970's, which gave federal agencies authority to implement and enforce environmental standards either alone or in concert with state and local governments. The Clean Air Act of 1970 was the most far-reaching and comprehensive of these environmental statutes, but early bipartisanship and optimism over its potential quickly gave way to increasingly combative debates over its scope and the place of scientific expertise in its development. As originally conceptualized by politicians and political scientists, the environmental policy process would involve sharply drawn roles: values would be set by democratically elected officials answerable to the people, while objective and impartial scientific experts would provide the optimal methods to reach those goals. As the history of the Clean Air Act has shown, scientists working on regulatory issues should be aware that the boundaries between scientific judgments and value judgments can often be blurred. Using the regulation of mercury emissions from coal-fired utility plants as a case study, this project carried out a systematic review of the 40-year-old regulatory and legal record concerning utility-sourced mercury emissions, the scientific and engineering literature, and media reports to investigate how debates over scientific uncertainty have impacted mercury control regulations. Particular focus is placed on the varying construction of mercury deposition models as different stakeholders had gained influence over the regulatory process. Results show that the oftentimes blurry distinction between purely scientific judgments and value judgments can lead to expensive and time-consuming debates and litigation and delayed regulations, and that atmospheric scientists should be aware of how their work can be framed and reframed during the policy process. The results of this case study may offer insight into future policy debates, particularly those regarding current and future Clean Air Act regulations on greenhouse gas emissions through which the U.S. is attempting to fulfill its obligations under the Paris Agreement.