De Minimis, Risks, and Radon

[Fritz Seiler <faseiler@nmia.com>]

Comment # 1 by Fritz Seiler and Joe Alvarez on the
"De Minimis, Radon and Societal Risk" Thread.

We have read with great interest the debate on the ‘de minimis' concept,

societal and individual risks, and on radon exposure in RISKANAL.
We have essentially three comments: One, a scientific rationale for the
de minimis concept has already been defined; Two, a loss of life
expectancy can sometimes be taken as a near equivalence of fatalities in

a societal sense; and Three, the radon problem will soon become quite
a bit more complicated and thus much more interesting.  This third
comment will be given in a separate post.

First, we can use an analogy between the ‘de minimis' concept and radio
reception which is quite close: A nearby radio station will yield a
signal
which is way above the noise ("static"); meaning that it has a high
signal-
to-noise ratio.  As we move the transmitter further away from the
receiver, the ratio becomes smaller and smaller.  Sooner or later we
come to a point where communication is seriously impaired by the noise,
even with an excellent receiver with low amplifier noise.  Further away,

the message becomes unintelligible due to the external noise, and
finally
we come to a distance at which it is not even possible to discern that
there is an attempt at communication.  From the point of view of the
receiver, there are now two possibilities: The transmitter is either not
on
the air or the signal is there, but it is buried in the noise.  The
receiver
cannot determine which is the case.  To assume that the signal is there
is unscientific because we just do not know that, to assume that it has
the characteristics that we have decided to assign to it, is outright
anti-
scientific.  To be honest, we have to admit that we simply do not know
what is there, if anything.  In the radon example in a subsequent post
we will show that the relative lung cancer risk is not linear in the
exposure to radon and its daughters as the assumption goes.  Rather it
goes to values less than 1 and we thus have actually beneficial effects,

all hidden down in the noise of the ‘acceptable' radon measurements.
But more on this later.  Right now, we just note in our radio analogue
that whether we choose the lack of understanding the message or the
lack of discerning the presence of the message as a limiting criterion
is
not important.  What is important is the fact that there is such a
limit.
Now, we do not know of any physical or biological effect for which
this argument does not hold.  Sooner or later, as the ‘signal'
decreases,
the ‘noise' will swallow it.  In many of these cases, the role of noise
is
played by the random errors of the value, by the background of counts
or by the background cancer incidence, but the analogue holds.  We
used this kind of argument in the form of the ratio of "error of value /

value" to define the concept of a minimum significant risk (Seiler,
F.A.;
Alvarez, J.L. The Definition of a Minimum Significant Risk. Technol. J.
Franklin Inst. 331A: 83-95; 1994).  At a level somewhat below or
just near that risk, it is obviously justified to claim that the Roman
Law
maxim ‘de minimis non curat lex' can be applied, i.e., that the law does

not concern itself with trifles.

Second, in the form that Vickie Bier stated it, there is indeed no
societal equivalence of average loss of life expectancy and the
corresponding number of fatalities.  There are, however, other ways
of formulating the problem: When the Pyramid in Las Vegas was
planned, it was estimated that three work-related fatalities would
occur during construction.  This is a global ‘a priori' estimate for all

construction workers which cannot be further refined due to the
limitations inherent in the actuarial data base.  To keep things simple,

let us assume that N workers are employed there full-time.  As long
as these N workers cannot be further distinguished in terms of risk
(i.e., divided into subclasses of job descriptions involving different
levels of occupational risk), each worker carries an ‘a priori' risk of
3/N which can also be given in terms of  the potential loss of life
expectancy.  In this manner the two numbers are equivalent, and it
is these ‘a priori' numbers which are used to make risk based
decisions.  Admittedly, we know the ‘a posteriori' situation a lot
better, namely we know that there was actually one fatality during
construction.  Now the situation is different, as the individual
concerned is known.  He and he alone was the expression of that
risk, and his actual loss of life expectancy can be calculated using
life tables.  The N - 1 other workers got off scot-free and suffered
no loss of life expectancy.  It is important here to distinguish very
carefully between ‘a priori' risk estimates and the ‘a posteriori'
knowledge of the manifestations of that risk.  Clearly, the societal
impacts of the projected risk and actually manifest consequences
are quite different.


*************************

Fritz A. Seiler, Ph.D.
Principal
Sigma Five Associates
P.O. Box 14006
Albuquerque, NM 87191-4006
Tel.    505-323-7848
Fax.    505-293-3911
e-mail: faseiler@nmia.com

**************************

Joe Alvarez
Auxier & Associates, Inc
10317 Technology Dr, Suite 1
Knoxville, TN 37932
Email: jalvarez@auxier.com
Tel: 423-675-3669
FAX: 423-675-3677

**************************


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