The Risks Digest

The RISKS Digest

Forum on Risks to the Public in Computers and Related Systems

ACM Committee on Computers and Public Policy, Peter G. Neumann, moderator

Volume 3 Issue 9

Friday, 20 June 1986


o Informing the Senate on SDI
Jim Horning
o A medical risk of computers
Karen R. Sollins
o Risks of VDTs
Alan Wexelblat
o Minor addition on Risks of Distributed Energy
Ted Lee
o [Additional material back-logged. Delay due to PGN travelling.]
o Info on RISKS (comp.risks)

Informing the Senate

Jim Horning <horning@src.DEC.COM>
Wed, 18 Jun 86 12:21:05 pdt
The information in this message is political, not technical. However,
it concerns the process of supplying technical information to those who
must make political judgements, so I believe that it is germane to Risks.

Recent news accounts have indicated that the outcome in the Senate of
requests for increased SDI funding is very unclear. Senators are having
to take positions on a matter they don't fully understand, and many of
them would like to be better informed.

I was contacted by an aide to Senator Proxmire for information about how
David Parnas's criticisms of SDI software are viewed in the professional
community. General Abramson and the SDIO have had some success in
spreading the message that David Parnas is an isolated crank who is not
taken seriously by those who actually build software.

I was able to express my own opinion and concerns, but cannot speak
credibly for the entire professional community. Pound-for-pound, Risks
probably contains more people qualified to make an informed judgement on
this issue than any other group I know how to reach. Whatever your views,
I would urge you to take the time to write a letter expressing them to

    Mr. Douglas Waller
    Office of Senator William Proxmire
    United States Senate
    Washington, DC 20510

Based on my experience, you can expect your letter to receive personal
attention, and to carry weight according to your credentials and the
cogency of your arguments. (This is in sharp contrast to my experience
writing to my own senators and congressman.)

In addition to stating your own views clearly, it would probably help to
indicate how they relate to Parnas's criticisms and (if you have read it)
to the Eastport Report. In my own letter, I also devoted a paragraph to
sketching my credentials; I don't much care for such self-advertisement,
but thought I should give a starting point for any checking they cared to
do, and the reasons why I felt qualified to comment on reliability and on
aerospace software.

Jim H.

a medical risk of computers

"Karen R. Sollins" <sollins@XX.LCS.MIT.EDU>
Fri, 20 Jun 1986 10:37 EDT
My particular concern in the story that follows is that the designers and
programmers probably can't know ALL the conditions for which to check.  We
all know that complete testing of complex systems is impossible.  All too
often we are put into a position of trading risks and benefits, and at least
the risks (as in this case) are not and cannot be known completely.

Of course, another difficult question here is who is responsible for what
happened and what should be done about it.  Clearly for those three
patients involved and their families and friends no amount of placing
responsibility, punishment, or compensation can make up for what was done
to them.
            Karen Sollins

(excerpted from The Boston Globe, June 20, 1986, p. 1)
by Richard Saltos, Globe Staff

A series of accidental radiation overdoses from identical cancer therapy
machines in Texas and Georgia has left one person dead and two others with
deep burns and partial paralysis, according to federal investigators.

Evidently caused by a flaw in the computer program controlling the highly
automated devices, the overdoses - unreported until now - are believed to
be the worst medical radiation accidents to date.

The malfunctions occurred once last year and twice in March and April of
this year in two of the Canadian-built linear accelerators, sold under the
name Therac 25.

Two patients were injured, one who died three weeks later, at the East
Texas Cancer Center in Tyler, Texas, and another at the Kennestone Regional
Oncology Center in Marietta, Ga.

The defect in the machines was a "bug" so subtle, say those familiar with
the cases, that although the accident occurred in June 1985, the problem
remained a mystery until the third, most serious accident occurred on April
11 of this year.

Late that night, technicians at the Tyler facility discovered the cause of
that accident and notified users of the device in other cities.

The US Food and Drug Administration, which regulates medical devices, has
not yet completed its investigation.  However, sources say that discipline
or penalty for the manufacturer is unlikely.

Modern cancer radiation treatment is extremely safe, say cancer
specialists.  "This is the first time I've ever heard of a death" from a
therapeutic rediation accident, said FDA official Edwin Miller.  "There
have been overtreatments to various degrees, but nothing quite as serious
as this that I'm aware of."

Physicians did not at first suspect a rediation overdose because the
injuries appeared so soon after treatment and were far more serious than an
overexposure would ordinarily have produced.

"It was certainly not like anything any of us have ever seen," said Dr.
Kenneth Haile, director of radiation oncology of the Kennestone radiation
facility.  "We had never seen an overtreatment of that magnitude."

Estimates are that the patients received 17,000 to 25,000 rads to very
small body areas.  Doses of 1,000 rads can be fatal if delivered to the
whole body.

The software fault has since been corrected by the manufacturer, according
to FDA and Texas officials, and some of the machines have been retured to

... (description of the accidents)

The Therac 25 is designed so that the operator selects either X-ray or
electron-beam treatment, as well as a series of other items, by typing on a
keyboard and watching a video display screen for verification of the

It was revealed that if an extremely fast-typing operater inadvertently
selected the X-ray mode, then used an editing key to correct the command
and select the electron mode instead, it was possible for the computer to
lag behind the orders.  The result was that the device appeared to have
made the correct adjustment but in fact had an improper setting so it
focussed electrons at full power to a tiny spot on the body.

David Parnas, a programming specialist at Queens University in Kingston,
Ontario, said that from a description of the problem, it appeared there
were two types of programming errors.

First, he said, the machine should have been programmed to discard
"unreasonable" readings - as the injurious setting presumably would have
been.  Second, said Parnas, there should have been no way for the
computer's verifications on the video screen to become unsynchronized from
the keyboard commands.

        [This story was also reported by Jim Kirby.  It is very rare that I
         get MULTIPLE copies of such a report.  Statistically, that suggests
         that there must be many things that never get reported...  PGN]

Risks of VDTs

Alan Wexelblat <>
Mon, 16 Jun 86 11:50:07 CDT
Excerpted from an article by Loren Stein of the Center for Investigative
Reporting in San Francisco, published in the July 1986 issue of the

"[...]Effictive with the 1986 budget, the Reagan administration has cut off
$1.5 million in funds for the non-ionizing radiation [the kind emitted by
VDTs] research program in North Carolina's Research Triangle Park, a
program in operation since [...] 1971.  `For several years,' says Jerold
Mande, an assistant to Albert Gore Jr. of Tennessee, `the administration
has tried to eliminate the program and each year the House defended it.
But the last time around, they gave up.'

"[...]Until recently, many scientists believed that non-ionizing radiation
could not affect the body unless its electric field produced heat or an
electric shock.  But in 1984, _Spectrum_, a leading engineering journal
declared that `a growing mass of evidence has virtually ended that debate.'

"`Evidence of the effects [of non-ionizing radiation] on the nervous system
and the immune system of animals was already well-established by the end of
the '70s,' wrote Eric Lerner, a former contributing editor of _Spectrum_
`while evidence of effects on the genetic material has accumulated most
rapidly over the past few years.'  These discoveries may mean that our
bodies are far more sensitive to non-ionizing radiation than previously
thought [...].

"Two of the EPA's most important experiments in non-ionizing radiation -
now shelved - underwent years of detailed preparation and were on the verge
of actual testing.  One involved the lifelong exposure of rats to low-level
radio-frequency radiation.  `I really looked forward to this experiment,'
says Tell.  `We had finally, after five years, gotten all the facilities
set up to support the experiment.  It took so much time, manpower, and
money.  Now it's through.'

"Another key project tried to replicate some dramatic findings for Jose
Delgado's research laboratory in Madrid, Spain.  In 1982, associates at
this labe discovered that extremely weak-pulsed magnetic fields - only one
five-hundredth the strength of the Earth's natural magnetic field - caused
chick embryos to develop malformed hearts and central nervous systems.

"[...]The EPA [...] will not participate in an international effort to
verify Delgado's findings - an effort made possible by the EPA's
development of equipment that is being shipped to Canada, Sweden, and three
other places to create identical test environments. [...]

"Funding for non-ionizing radiation research has been slashed in other
Government programs as well.  An eagerly anticipated reproductive study
involving 4000 VDT operators of child-bearing age by the National Institute
of Occupational Safety and Health was among the casualties.

"The EPA research branch is no longer necessary, claim some officials,
because the agency will soon publish voluntary guidelines for exposure to
RF radiation; overexposure can raise body temperature, which animal
research indicates may be harmful to pregnant women and their unborn
children. [EPA claims there's no conclusive evidence of harm.]

"Other experts [say] the EPA guidelines will suffer from the dismantling of
the agency's non-ionizing radiation research team. [...]Tell's office is
issuing the soon-to-be-published RF radiation guidelines; he says
`Obviously, we need biological experiments.  They've helped us tremendously.'

[Senator Gore has an interest in this and fought to keep the research.
Technical comments will be given to the EPA on the guidelines and the EPA
will not have the expertise to evaluate them.]

Alan Wexelblat
UUCP: {ihnp4, seismo, harvard, gatech, pyramid}!ut-sally!im4u!milano!wex

Minor addition on Risks of Distributed Energy

Wed, 18 Jun 86 10:54 EDT
Two observations to add to Chuck Ferguson's comment on distributed
energy.  In the debate over the safety of nuclear energy it has been
proposed that a further alternative to the ones mentioned in Risks is
solar energy.  Those so doing ignore the fact that (whether the weather
cooperates or not in terms of percentage of sun) in the part of the
country he and I come from it would be necessary to clear the snow off
some types of solar energy devices in the winter.  The number of likely
deaths from people climbing on their roofs to shovel off their solar
cells is guaranteed to exceed the probable number of deaths from a
nuclear power plant accident.

The point here is not the specific technologies involved, but the two
recent messages on the topic just prompted to think of this one more
example (its going to be hot and humid here today, and somehow snow came
to mind) of how in comparing risks of various potential solutions one
must take everything into consideration.  (Isn't it also true that
coal-fired plants actually release a fair amount of low-level radiation
that somehow gets ignored?  and how many more deaths and injuries are
there amongst coal-miners than uranium miners ...  oops, got carried
away.  Note of course that any of these conjectures may be wrong and one
would have to insist on credible statistics before making any


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