By Jonathan M. Samet, MD, MS,
and Thomas Burke, PhD, MPH

Our world has always been fraught with risk, but Sept. 11 and its aftermath have added terrorism to our concerns. Until the attacks, while we might have conceived of the possibility of a massive terrorist assault against the United States, most of us would have given a negligibly low probability to its occurrence. Now, we are frightened because we know that events that were previously unthinkable have happened.

We will not forget the images: planes flying into the World Trade Center and Pentagon; national symbols ablaze; and the Twin Towers collapsing. This tragedy meets every criterion for a dreaded event: unanticipated, massive, with thousands of identifiable victims and involuntary and unfair consequences. These are the same characteristics that made the Chernobyl and Bhopal disasters historical landmarks and that make airplane crashes and anthrax-laced letters front-page stories.

"Risk" refers to the likelihood of something adverse happening. Risk assessment offers an organized framework for describing patterns of exposure to risk and for quantifying the consequences of these exposures.

Unlike many past risk issues, these terrorist acts have the entire nation worried, engaged, and looking for information to understand and then reduce risks as much as possible. The fears extend from air travel to every aspect of everyday life, including opening one's mail.

The risk sciences can help us to put the Sept. 11 death toll in a comparative framework: the World Trade Center death toll is believed to be more than the annual number of deaths from fire in the United States (about 3,000) but less than the number from homicide (about 16,000).

Risk researchers also explore the factors that determine people's perceptions of risk, thus revealing why terrorist actions arouse such dread. Both fire and homicide deaths are dreaded but occur one by one, not all at once. And each year perhaps 150,000 people die from smoking-caused lung cancer and about 40,000 from motor vehicle accidents, but we are able to tolerate these risks because these deaths are anticipated and don't occur all at once.

Providing credible information in this era of the Internet, 24/7 news networks, and instant experts may be the toughest challenge to public health professionals. Although skillful communication is essential to managing risks, uncertainty about the next actions of the terrorists unfortunately constrains risk assessment and communication and leaves the public fearful and hungry for facts. We have also watched our government officials struggle with the challenge of presenting rapidly changing information about new risks in the midst of a continuing terrorist attack. Thus, early attempts at communicating anthrax risks proved to be inaccurate and misleading.

As quickly as possible, we in public health need to learn how to do better with characterizing and explaining risk, moving from lessons to solutions at an unprecedented pace. The School's faculty and students will be part of the solution to this extraordinary public health challenge.

Jonathan Samet is professor and chair of Epidemiology, and Thomas Burke is an associate professor of Health Policy and Management. They co-direct the Risk Sciences and Public Policy Institute at the School.




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