Death, Taxes and Clean Air?

"In this world nothing can be said to be certain, except death and taxes." -Benjamin Franklin, 1789

Over the past several years, scientists and policy makers have increasingly debated the issue of uncertainty in the scientific base of information that underlies public health policy decisions. What do we mean by “uncertainty”? One way to think of scientific uncertainty is the lack of precise knowledge of the “scientific truth.” Despite our best efforts, we can only reduce but never completely eliminate uncertainty through obtaining more information. In fact, you can think of the scientific method itself as an approach to obtaining more information that (hopefully) reduces uncertainty and improves our understanding of the “scientific truth”.

This issue of identifying and, where possible, quantifying uncertainty has become especially prominent with respect to the assessments of the health risks from environmental pollutants conducted at the US Environmental Protection Agency. Almost twenty years ago, a panel of experts convened by the National Academy of Sciences stated “…Any scientific risk assessment is likely to be based on incomplete knowledge combined with assumptions, each of which is a source of uncertainty that limits the accuracy that should be ascribed to the estimate.” While improving the accuracy of our understanding of the nature and magnitude of public health risks is certainly a worthy undertaking, three important questions come to mind related to how this issue of scientific uncertainty impacts public policy:

• at what point do we have sufficient confidence in the scientific accuracy of the available information to inform public health policy decisions?
• who should be making this policy-related assessment of the scientific evidence – EPA scientists, independent scientific experts, EPA policymakers, the White House Office of Management and Budget, Congress, some or all of these groups?
• what is the appropriate public health policy response when there is substantial scientific uncertainty regarding, for example, the lowest level of air pollution associated with health problems? Should national air quality standards be set at a level where there is a minimum of scientific uncertainty (given that 100 percent certainty will never be achievable) regarding the impact of air pollution on health? Or alternatively does substantial scientific uncertainty regarding possible health effects from air pollution suggest that we be even more precautionary in setting the standard at a level that would also protect against these less certain effects?  

Having posed the questions above, I’ll also take a shot at offering my views. First, taking a cue from civil law, scientific information should be considered sufficiently certain for inclusion in the public health policy process when it is more likely than not (51/49 %) that the information is consistent with “the scientific truth”. Second, while the final decision on the application of scientific information for setting national air quality standards ultimately rests with the EPA Administrator, great weight and deference should be given to assessments of the science (including levels of certainty) from EPA’s career scientists and independent experts (e.g., Clean Air Scientific Advisory Committee). With respect to the third question, displaying what some political cynics might view as surprising foresight, Congress anticipated this issue when revising the Clean Air Act in 1970, requiring that the health-based national air quality standards be set at a level that protects public health, especially for those most at risk of suffering health effects, with an “adequate margin of safety.” The legislative history of the Clean Air Act makes clear that this required additional margin of safety was to account for unanticipated or newly emerging scientific information for which the health significance was still quite uncertain.  Congress clearly provided the framework for response – scientific information that is less certain than that used to identify the level where there is clear evidence of a  health concern should inform the decision on the amount of additional health protection (“margin of safety”) to be provided by air quality standards. 

While Ben Franklin’s statement remains indisputable (at least regarding death), scientific uncertainty does not justify selecting environmental health policies that undermine public health protection especially for those most at risk of suffering health effects from environmental pollution.

Nickname
Comment
Enter this word:	Change