THE SCIENCE AND TECHNOLOGY JOURNAL

                    Copyright 1989 by William A.  Manly
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 | This is a combination commentary, pedagogical and informational column, |
 | published as the subjects recommend themselves to the author.  Subjects |
 | may be those presently "in the  news," but not adequately  explained or |
 | discussed  in  the  various news  articles publicly  available;  or the |
 | subject may be one which seems of general interest, but for some reason |
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 | is given to the many computer columns already posted.                   |
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STJ Column #1

THE RISKS WE PERCEIVE AND THE RISKS WE TAKE

Human beings are always taking risks.  If we do not take deliberate risks, we
take risks by being inactive.  Whether we recognize it or not, risk avoidance
and risk taking constitute the most common decisions we make, and many of
these decisions are made unconsciously.

Risks can be rated and quantified.  The most common way is to ask an "expert"
in the matter.  If the expert is trusted, and says that the risk is a small
one, we may judge that it is worth taking for the promise of some reward for
taking it.  Few individuals take risks for no reason, and when people take
risks for psychological rewards, we call them "foolish," "daredevils," or
other terms of reverse endearment.

Another way of judging risks is by statistics.  If we note that over history,
100 people have gone over Niagara Falls in a barrel, and only one has
survived, most people would judge this risk to be unacceptable for any
reason.  Yet people still try to do it.  If we note that the brakes on family
cars fail only at random and widely spaced intervals, we may elect to drive
on the freeway or a winding mountain road without even having the brakes
checked first.  Yet people die because the brakes fail on their cars.

There is nothing that we do or come in contact with which is not at some risk
to us or our loved ones.  We take these risks as part of everyday life, even
though we may give lip service to (and even profess to believe) that "some
things are too precious to risk."  We don't believe this.  We have all heard
that "human lives are too precious to have a price."  Lots of people say it,
but no one acts as if it were so.  Everything has a limiting price, and we
will not pay a greater price to protect it.  It would be  a great tragedy if
our children were to die on the way to school, but we do not hire bodyguards
and send them to school in armored vehicles, even though we can read in the
paper every week about children who have died going to school.  The risk is
real, but we will not pay above a certain price to protect them.  (If we can
get someone else to pay the price, so much the better.  Who pays for the
school crossing guards?)

We seem to make many mistakes in assessing risks, since as a society, we seem
intent on reducing risks to zero if we perceive that someone else pays the
bill, while we take much larger risks on our own.  We have blinders on where
the costs are concerned, even if they are paid from our own taxes or the
costs of the goods we buy; but we will not tolerate small inconveniences, and
we take large risks because of this intolerance.

Now RISK ASSESSMENT is a science.  There is also a science of making
decisions based on risks, which is called GAME THEORY.  This issue of the STJ
explores some of these risks, and shows the difference between our perception
of risks and the assessment.  A future issue will look at some of our
decisions which go completely contrary to the action recommendations made by
Game Theory.

RADIATION

We can be exposed to radiation in many ways.  Cosmic radiation takes a toll,
minute by minute.  We have all heard of radon gas, which comes out of the
ground and lingers in buildings.  A building made of granite has enough
radiation to excite a Geiger counter when you are near or in it.  We take in
radioactive potassium in our food, and radioactive polonium in tobacco smoke
(the tobacco plant selectively absorbs polonium from the soil).  We nearly
all have medical X-rays, and we take airline flights.  Then there are the
nuclear power plants, which so many of our population are determined to do
away with.  Lets look at the risks:

                      TABLE I

     Action                      Dose        Cancers caused if
                             (mrem/year)     total US Population
                                                Exposed

     Chernoble resident        5000          Not relevant
     Radon (1.5 pCi/liter)      500          13,500
     Cosmic Rad. (@ Denver)      65           1,800
     Medical X-Rays              40           1,100
     Cosmic sea level rad.       40           1,100
     Potassium in own body       30           1,000
     Transcontinental round
       trip by air                5             135
     Average within 20 miles
       of a nuclear plant         0.02            1

We had a reactor in U.S.  nuclear plant fail to destruction.  The containment
system worked completely and no radiation was transmitted outside the power
plant which would amount to even a hundredth of the dosage we get from
everything else, even for the closest people to the plant.  So we are
terrified of nuclear power plants, and continue the other exposures.  (How
many have had your homes checked for radon, and how many stay away from air
trips because of the radiation exposure?)  Is this ridiculous hysteria, or is
there something else involved?  Do people act irrationally, or do we just not
understand or know the risks?

COMMONPLACE RISKS

Table I gave a risk assessment by dosage or exposure, and listed the number
of cancers caused in the whole U.  S.  population if all were so exposed. 
Now let's look at another way of expressing risks, with some commonplace
things with which we all have some familiarity.  The risks are given by the
decimal fraction of the people so exposed who would die from the action.

                     TABLE II

     Action                           Annual Risk

     Cigarette smoking, one pack/day     .0036
     All cancers                         .0028
     Mountaineer, mountaineering         .0006
     Motor vehicle accident (total)      .00024
     Policeman, line of duty, total      .00022
     Air pollution, Eastern US           .0002
     Police, line of duty, by felons     .00013
     Home accidents                      .00011
     Frequent flying consultant          .00005
     Motor vehicle accident, pedestrian  .000042
     Sea level radiation (except radon)  .00002
     Alcohol, light drinker              .00002
     Four Tablespoons peanut butter/day  .000008
     Electrocution                       .0000053
     Drinking water, EPA chloroform 
        limit                            .0000006
     Drinking water, EPA with
        trichloroethylene limit          .000000009

Now look at the things we regulate, and those we don't.  By all rights, we
should outlaw cigarette smoking.  We are working on cancer, but not on the
principal cause of cancer.  Mountaineering has no regulation (except at the
national parks).  We do work on air pollution to some extent, but don't do
much about home accidents, nor do we shield airline passengers from
radiation.  We seem to be leaning hard on taxing alcohol consumption out of
existence, but there is no law against eating peanut butter.  (The peanut
butter is dangerous due to the presence of aflatoxin, which is present in the
average fraction of 2 ppb in peanut butter, but can be much higher.)  We do
have a few warnings against electrocution.  BUT, the government, in the
vehicle of the EPA, has placed very stringent limits on chloroform (which is
produced during water chlorination to kill bacteria), and on
trichloroethylene (which is a common industrial solvent).  These last two
limits are expensive to the public - the first, in that a lot of bacteria get
into the drinking water, and the second in the increased cost of industrial
goods sold.  Why do we do this seemingly irrational thing?

(Note that the two tables can be linked through the sea level radiation,
which is in both.  Both tables assume linearity in the effects, which is by
no means certain.)

These risks may not be understandable to the general populace in the ways in
which they are expressed here.  There are some other ways in which the risks
might be more meaningful.  For instance, the reduction in life expectancy for
smoking, turns out to be five minutes per cigarette, which is just about the
same time it requires to smoke it.  Of course, if the smoker irritates
someone with the smoke, who then decides to clobber the smoker over the head
with his/her dinner plate, the life expectancy might be reduced much further.

If we look at the first item in Table I, the one which seems so horrible to
us, it may not seem so bad.  The total number of people in the primary
exposure area was 24,000.  This population would normally be expected to
develop a total of 5000 cancer deaths from other causes.  The accident killed
31 people in the plant, some from burns.  The radiation exposure to the
24,000 people would be expected to produce some 131 cancer deaths from the
radiation released from the exploded power plant.  This is only a 2.6%
increase in the total number of cancer deaths in a small population, so why
the worldwide flap?  The recent Bay Area earthquake was far worse, and the
earthquake they had recently in the USSR was orders of magnitude greater in
the numbers of deaths caused.

The amount we spend on saving lives by reducing risks varies by a factor of
over a million.  Americans could save countless lives in Indonesia by
contributing to immunization, as a cost of about $100 per life saved.  On the
other hand, we are so concerned with environmental protection, that we spend
over $1,000,000 per life saved, than on cures (about $50,000 per life, with
the $200,000 per life for kidney dialysis raising some objections).  We spend
still more on waste disposal and on radiation protection at nuclear power
plants.  Why do we not adjust things so that we are efficiently spending
about the same amount on everything to save human lives?  It can be argued
that we have destroyed our standard of living with our enormous expenditures
on nuclear power plants, environmental protection, and waste disposal.  Why
do we do this?

RISK PERCEPTION

Our perception of risk depends upon just who we are.  C. Starr has
interviewed a number of groups of people, including those expert in the
evaluation of risks, and found the following:

                     TABLE III - ORDER OF PERCEIVED RISK

     Activity or       League of   College   Active   Experts
     Technology          Women     Students  Club  
                         Voters              Members

     Nuclear power        1           1        8        20
     Motor vehicles       2           5        3         1
     Handguns             3           2        1         4
     Smoking              4           3        4         2
     Motorcycles          5           6        2         6
     Alcoholic beverages  6           7        5         3
     Private aviation     7          15       11        12
     Police work          8           8        7        17
     Pesticides           9           4       15        18
     Surgery             10          11        9         5
     Fire fighting       11          10        6        18
     Large construction  12          14       13        13
     Hunting             13          18       10        23
     Spray cans          14          13       23        26
     Mountain climbing   15          22       12        29
     Bicyles             16          24       14        15
     Commercial aviation 17          16       18        16
     Electric power (non
         nuclear)        18          19       19         9
     Swimming            19          30       17        10
     Contraceptives      20           9       22        11
     Skiing              21          25       16        30
     X-Rays              22          17       24         7
     Football (HS and
         college)        23          26       21        27
     Railroads           24          23       29        19
     Food preservatives  25          12       28        14
     Food coloring       26          20       30        21
     Power mowers        27          28       25        28
     Prescription 
        antibiotics      28          21       26        24
     Home appliances     29          27       27        22
     Vaccinations        30          29       29        25


Now, let's have the computer do a bit of work for us, and look at this table
sorted on the "experts" column, and assume that this is the real risk of
these activities or technologies:

                     TABLE IIIa - ORDER OF PERCEIVED RISK

     Activity or       League of   College   Active   Experts
     Technology          Women     Students  Club  
                         Voters              Members

     Motor vehicles       2           5        3         1
     Smoking              4           3        4         2
     Alcoholic beverages  6           7        5         3
     Handguns             3           2        1         4
     Surgery             10          11        9         5 *
     Motorcycles          5           6        2         6
     X-Rays              22          17       24         7 *
     Electric power (non                                 
         nuclear)        18          19       19         9 *
     Swimming            19          30       17        10 *
     Contraceptives      20           9       22        11 *
     Private aviation     7          15       11        12 *
     Large construction  12          14       13        13
     Food preservatives  25          12       28        14 *
     Bicyles             16          24       14        15
     Commercial aviation 17          16       18        16
     Police work          8           8        7        17 *
     Pesticides           9           4       15        18 *
     Fire fighting       11          10        6        18 *
     Railroads           24          23       29        19 *
     Nuclear power        1           1        8        20 *
     Food coloring       26          20       30        21
     Home appliances     29          27       27        22
     Hunting             13          18       10        23 *
     Prescription                                       
        antibiotics      28          21       26        24
     Vaccinations        30          29       29        25
     Spray cans          14          13       23        26 *
     Football (HS and                                   
         college)        23          26       21        27
     Power mowers        27          28       25        28
     Mountain climbing   15          22       12        29 *
     Skiing              21          25       16        30 *

There is a kind of general agreement as we go down, but there are some
enormous discrepancies, which are tagged with an asterisk (*).  It almost
seems as if the people who are most likely to do something or make use of it,
think that it is not very dangerous.  Exceptions to this are skiing, and the
use of spray cans.  Probably the largest discrepancy comes in the use of
nuclear power, which is seen as extremely dangerous by everyone except those
who know something about it.  Note also that surgery, X-Rays, and non-nuclear
power plants are really quite dangerous, but are not perceived as dangerous
by the general public.

Much of the information for this issue of the STJ came from various papers in
SCIENCE, 17 April 1987, V. 236, No. 4799.  This was a general issue on risk
assessment.  A future issue of the STJ will take up why we perceive risks in
such a different way from the experts, and how and why we seem to violate the
principles of game theory in our risk-taking actions.

                                William A. Manly
                                    MS 62391