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]]]]]]]]]]]]]]]]]] R(Human) = R(Rodent) [[[[[[[[[[[[[[[[
(4/10/1989)
Editorial, The Wall Street Journal, 10 April 1989, p. A14:1
[Kindly uploaded by Freeman 10602PANC]
It's no wonder that Meryl Streep and the Natural Resources
Defense Council have been scaring people with the organization's
report on children, cancer and pesticides in food. It's based on
rats.
The role of rats in the Great Food Scare of 1989 doesn't get
much mention, say, when a ``60 Minutes'' publicizes it. This is
too bad, because if school systems across California are going to
ban apples or if people are taking the trouble to wash lettuce in
soapy water, they ought to have a better idea of the basis for
their fears.
It is derived in large part from equations of the sort
reprinted nearby, which attempt to extrapolate cancer risk in
humans, R(human), from cancer risk in rodents, R(rodent). This
equation appears in the NRDC's report as part of Appendix Three,
``Methodology for estimating pre-schooler cancer risk from
carcinogenic pesticides in food.''
We suspect Appendix Three didn't get much mention when the
public, nodding off in front of televisions all across America,
first learned about the problem with apples (``Cancer in apples?
More at 11''). It's probably asking too much to expect the
anchors to take an extra 20 seconds to discuss also the fact that
the study is based on something known as a ``lifetime rodent
bioassay.'' It wouldn't be too much, however, to ask everyone
who conveys the results of these food-cancer ``studies'' to put
the rats = humans argument into some perspective. In other
words, maybe public policy would be better served if the public
were given a chance to think rather than reasons to panic.
The NRDC's pesticides-cause-cancer report, for instance, came
out about the same time that other scientists were publishing
reports and studies on the same subject. Two months before the
NRDC report, the science magazine Nature published an article [15
December 1988, pp. 631-633] by researchers from Carnegie-Mellon,
Case Western Reserve and the University of Washington raising
questions about the usefulness of these rodent bioassay studies.
``Extrapolating from one species to another,'' they wrote, ``is
fraught with uncertainty.'' Indeed, they pointed out that ``rats
and mice are more similar biologically to each other than either
is to humans.''
Also about the time Ms. Streep and her friends had school
superintendents cowering from apples, the National Research
Council, an arm of the National Academy of Sciences, released an
exhaustive study of the available data on disease risk and the
American diet. It recommended that to cut the occurrence of
cancer and heart disease, Americans ought to eat more fruits and
vegetables. As to the chemicals that obsess the NRDC, the report
said, ``Exposure to nonnutritive chemicals individually, in the
minute quantities normally present in the average diet, is
unlikely to make a major contribution to the overall cancer risk
to humans in the United States.''
It may turn out that the brief panic the NRDC and its
publicists created over food chemicals was a good thing. The
extremist wing of the environmental and consumer movements has
been crying wolf like this for years. Some scientists, public
officials, judges and journalists have begun to decide it's time
to blow the whistle on these ``studies.'' A consumer columnist
for the Newark Star-Ledger, saying he normally cast his lot with
``the environmentalists and organic food mavens,'' called the
apple scare ``nothing more than a lot of hype and hustle
generated by the National Resources Defense Council.'' He wrote
that it was ``akin to economic terrorism.''
So let the NRDC and squads of frightened Hollywood actresses
continue to flog their food phobias on the nation's talk shows.
In time, the American public is likely to figure out what it
really thinks about nutrition, chemicals, risk and, most
important, rodents.
[The following insert appeared on p. A14:1-2]
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The risk in humans will be equal to that in rats if their
exposures in MG/KG^2/3 equals the rat exposure in mg/kg^2/3.
Thus, for these circumstances:
R(human) = R(rodent) = q1 * (rodent) x MG/KG^2/3 x 1/kg^1/3
or:
R(human) = q1*(rodent) x MG/KG x KG^1/3/kg^1/3= q1*(human)xMG/KG
if q1 * (human) = q1*(rodent) x K/G^1/3/kg^1/3.
Replacing C in Eq. 6 by the relationship of Eq. 13 we obtain:
[S]a MG /MG x f(KG ) x g(T )
a A a a
R(human) = q1*(human) x MG / KG ------------------------ Eq. 18
A A [S]a mg /mg x f(kg ) x g(T )
a A a a
[Note: [S] stands for the summation-sign.]
Thus, the effect of taking into account the time course of cancer
risk is to modify the usual EPA risk estimate, q1*(human)xMG/KG,
by the ratio of the time weighted average of the respective
carcinogenic effect in humans and rodents.
-- From: ``Intolerable Risk: Pesticides in Our Children's Food,''
The Natural Resources Defense Council.
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[The following is not part of the original article.]
William R. Havender. Of Mice and Men: The Benefits and
Limitations of Animal Cancer Tests. New York: American
Council On Science and Health, August 1984.
Lester B. Lave, et al. ``Information Value of the Rodent
Bioassay'', Nature 336, p. 631-633 (15 December 1988).
(``Tests for human carcinogens using lifetime rodent bioassays
are expensive, time-consuming and give uncertain results. For
most chemicals such tests are not cost-effective.'')
* * *
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