Shifting Sands: The Limits of Science in Setting Risk Standards

106 Pages Posted: 20 Oct 2003 Last revised: 19 Mar 2012

See all articles by Cary Coglianese

Cary Coglianese

University of Pennsylvania Carey Law School

Gary E. Marchant

Arizona State University - College of Law


Regulators need to rely on science to understand problems and predict the consequences of regulatory actions, but over reliance on science can actually contribute to, or at least deflect attention from, incoherent policymaking. In this article, we explore the problems with using science to justify policy decisions by analyzing the Environmental Protection Agency's recently revised air quality standards for ground-level ozone and particulate matter, some of the most significant regulations ever issued. In revising these standards, EPA mistakenly invoked science as the exclusive basis for its decisions and deflected attention from a remarkable series of inconsistencies. For example, even though EPA claimed to base its standards on a singular concern for public health, it set its standards at levels that will still lead to hundreds, if not thousands, of deaths each year. In other ways, EPA's positions were like shifting sands, changing at points that apparently were expedient for the agency. Such an outcome should not be unexpected when an agency misuses science as a policy rationale, but it also need not be inevitable if agencies accept the limits of science in justifying risk standards. We conclude by offering a set of principles to give direction to standard setting by EPA and other agencies. In the case of EPA's air quality program, Congress will likely need to amend the Clean Air Act to enable EPA to break free of the conceptual incoherence in which it now finds itself mired. Decision makers in any setting, though, can avoid the problem of shifting sands by carefully understanding what science can and cannot do.

Keywords: Risk management, administrative law, environmental regulation

JEL Classification: K23, K32, Q25

Suggested Citation

Coglianese, Cary and Marchant, Gary E., Shifting Sands: The Limits of Science in Setting Risk Standards. University of Pennsylvania Law Review, Vol. 152, p. 1255, 2004, KSG Working Paper No. RWP03-036, Available at SSRN: or

Cary Coglianese (Contact Author)

University of Pennsylvania Carey Law School ( email )

3501 Sansom Street
Philadelphia, PA 19104
United States
215-898-6867 (Phone)


Gary E. Marchant

Arizona State University - College of Law ( email )

Box 877906
Tempe, AZ 85287-7906
United States
(480) 965-3246 (Phone)
(480) 965-2427 (Fax)

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