Article: Understanding risk

["Jacobus, John (OD/ORS)" <jacobusj@ors.od.nih.gov>]

I, and I am sure others on this list, have an interesting in understanding

and communicating risk, e.g., why are you so afraid of an airliner hitting a

nuclear reactor?  I found the following article that appeared in today's

Washsington Post to be interesting.  I like the author and have read several

of his books.  Hey, I was originally going to be an engineering, but found

physics to be more fun

.

-- John

John Jacobus, MS

Certified Health Physicist

3050 Traymore Lane

Bowie, MD 20715-2024

jenday1@email.msn.com (H)

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 To view the entire article, go to

http://www.washingtonpost.com/wp-dyn/articles/A64827-2002Jun29.html



 We've Got More Risk Than Our Brains Can Handle



 By Henry Petroski

  Risk is ubiquitous. Each of us is born with a life expectancy, and like it

or not we play the odds every day. Numbers can be put on the risks we face

from cradle to grave, but it is not possible to play life strictly by the

numbers. That is why each of us, in responding to risk, makes personal

decisions based not simply on quantitative measures but on qualitative

interpretations as well. We party on arsenic-impregnated decks. We play golf

in thunderstorms. We build multistory houses despite the risk of falling

down stairs. These days -- in a climate of heightened awareness of risk,

both real and perceived -- many public policy decisions appear to be made in

much the same way. Decisions come ultimately from the gut rather than from

the computer.



  It is telling that the Department of Homeland Security has introduced a

color scale -- a qualitative visual gauge -- instead of a more easily

remembered numerical scale for the level of alert. The kinds of risks that

terrorists present are virtually impossible to quantify. There is simply too

much that we do not know about their timetable, their tactics and their

technology. There is also very little historical precedent in our country

for the kinds of risks we now face.



  Numbers will no doubt in time be attached to a host of new risks, but

interpreting those numbers and assigning them colors will require judgment

and hard decisions. The possibility of a smallpox attack, for example,

requires a decision about whether to vaccinate the entire population when

enough vaccine becomes available. Because vaccination itself carries risks,

the correct policy is not obvious. Recently, an advisory panel recommended

vaccinating critical health care and law enforcementpersonnel against

smallpox but, because of the risk of complications, not the general public.

Does the real risk of complications outweigh the potential risk associated

with a smallpox attack? This is not an easy question to answer. The risks of

vaccinating are limited but fairly certain; the cost of an attack could be

immense, but its likelihood is completely uncertain. How can they be

measured against each other?



  The wildfires that continue to burn in several western states are clear

evidence that there are risks associated with living too close to nature.

Even if those risks could be quantified, the numbers will never tell us

exactly where the next fire will burn or how the wind will be blowing when

it does. It is doubtful that those who build and live in houses among the

trees base their decision on statistics. They choose to live where they do

because of the beauty and peacefulness that a sylvan setting affords. Public

policy on how to control forest fires -- or whether this should be done at

all -- is by all reports not a debate over numbers. It is a debate over

environmental philosophy.



  Discussions over whether or not airline pilots should be allowed to carry

guns in the cockpit have also revolved more around perceptions of risk than

quantifiable measures of risk. This is not surprising, for how can the risks

associated with armed pilots be determined? There haven't been guns in

cockpits, at least officially, and so there are no solid statistics on what

happens when there are. There are no numbers on which to base a quantitative

argument. Rather, the debate has involved imagined scenarios of what could

happen with pistol-packing pilots in control. No doubt policymakers'

opinions on the issue can reflect their views on guns at least as much as

their concern for passenger safety.



  Public debates about risk and other threatening concepts may be

accompanied by a lot of numbers and graphs and budgets, but in the final

analysis, decisions are often based on political and emotional grounds, if

not on confusing logic. A politician can seem to pay as much attention to

the numbers from opinion polls as to the numbers from scientific studies.

This happens especially when researchers themselves appear to disagree on

the fundamental scientific facts behind issues like global warming and its

risks. Scientists can also appear to have an odd perspective on risk.

According to the Washington Times, a document uncovered recently in the

Environmental Protection Agency's files argued that dumping toxic waste into

the Potomac was good for fish because it drove them away from fishing areas.

Scientists, like policymakers, are nothing if not human.



  Qualitative considerations will always trump quantitative risk assessment

analyses in the public policy arena. Even when it may appear that policy

decisions are based strictly on the numbers, there is always some

overarching qualitative principle defining the choice. Numbers, and the

formulas that produce them, are not sufficient for decision making. This

fact has been clearly articulated by David Billington in his book "The

Innovators," which is about pioneers in engineering who put America on the

road to modernity.



  Billington noted that engineering formulas are not mere expressions of

scientific fact. They also have profound social implications relating to

safety and economy. In the case of risk, the numbers alone do not say what

is acceptable or unacceptable in the public policy sector. That

determination involves a judgment based not on hard numbers but on soft

emotions.



  The point is illustrated by considering the relative risks associated with

highway and air travel. Automobile accidents in the United States claim

about 40,000 lives a year, not to mention all the injuries suffered in

crashes. Commercial aircraft accidents in this country typically have

claimed no more than hundreds of lives a year, two orders of magnitude fewer

than highway accidents. The numbers partly reflect the fact that many more

people drive than fly. Still, the statistical risks are far higher on the

road. Yet many white-knuckled fliers prefer to drive their cars carelessly,

risking their own lives and the lives of others on the road. Among the

reasonsfor the irrational fear of flying relative to drivingis the sense of

individual control felt in a car, a clearly emotional response.



  Emotions overwhelm numbers all over the map. It remains inexplicable that

less risky airplane travel is subject to strict safety procedures, which

pilots and flight attendants review before each takeoff, while children

riding on school buses are protected mainly by the yellow color of the

vehicle in which they ride.



  Predictably, airplane travel is perceived to be even more risky since

Sept. 11. But on that day terrorists lost their main weapon, which was

surprise. Now, enhanced airport security combined with more secure cockpit

doors -- and most likely other measures that have not been publicly

revealed -- can be assumed to have made air travel less risky. The next

terrorist attack will likely not take place on an airplane, though we

second-guess terrorists at our peril, and so continued vigilance at airports

and in flight remains absolutely necessary. Letting down our guard is to

raise the level of risk.



  It is human nature to react the way we have to the terrorist attacks. We

all alter our perception of risk after something that was thought to be a

remote possibility becomes a clear reality.The 1993 truck-bomb attack on the

World Trade Center, though relatively unsuccessful, revealed the true risks

involved in allowing unfettered parking beneath the tallest building in New

York. Closing the parking garage to the public and instituting tight

security procedures reduced the risk of another bomb being carried into the

building, but attack by a fuel-laden airplane was not a very bright blip on

the risk radar screen. In retrospect, of course, the building was at risk

from air attack all along.



  Being human, public policymakers are as susceptible as laypersons to

minimizing the perception of risks that we all wish did not exist. However,

remote risks realized, as they were last September, provide a rude awakening

to us all. Everyone can now imagine risks where they were not acknowledged

before. The trick, of course, is to see all risks for what they are before

the fact. Indeed, they must be seen before the fact if there is to be any

attempt to quantify them. Unfortunately, when so many risks formerly seen as

incredible become credible, we face the danger of sensory and numerical

overload.



  In the coming months and years, questions of risk will continue to arise.

As with most such questions in the past, the answers will probably depend

upon the interpretation of numbers rather than on the numbers themselves.

Ordering risks will ultimately come down to political and emotional

decisions. It is imperative that, no matter what their math skills, our

elected leaders and decision makers are well prepared to deal with those

components of risk assessment.



 Henry Petroski is the A. S. Vesic Professor of Civil Engineering and a

professor of history at Duke University. His latest book is "Paperboy:

Confessions of a Future Engineer" (Knopf).





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