<>Letter to the editor:
Washington Times January 29th 2005
We live in a risky world
The Jan. 12 Commentary
column "Ratty test rationale" by Dr. Elizabeth Whelan states a real
problem, identifies an incorrect cause and thereby comes up with the
wrong solution.
True, people are being scared to death by
inappropriate analysis of the risks of cancer. But to
blame the rodents is incorrect. My colleagues and I have studied
interspecies comparison of
carcinogenic potency for 25 years. We found, in agreement with others,
that the correlation between
cancer at a specific site in one species and cancer at the same site in
another species is only passable.
But the quantitative correlation in magnitude of carcinogenic potency
between rats and mice is quite
good when the site is ignored. If a mouse or rat develops cancer at one
site, does it matter for public
protection that we do not know the exact site where I might develop
cancer? The correlation of
carcinogenic potency between rodents and people is limited by accuracy
of data. Rodents don't tell
us as much as we would like, but that is no reason to ignore any of the
limited data we have.
The problem that people are being scared to death
would still exist if the correlation in
carcinogenic potency between rats and mice were exact. This shows that
the rodents are not the real
cause. The real cause is that the agencies, inspired by Congress,
insist on attempting to regulate
minuscule risks -- often one in a million in a lifetime pessimistically
calculated. I have argued for
25 years that the agencies cannot regulate such small risks
consistently and that an attempt to do so
is arbitrary, capricious and perhaps illegal on that ground. The
Environmental Protection Agency and
other regulators are unrepentant. But Food and Drug Administration
regulators have frequently
reminded us that natural carcinogens in foodstuffs pose larger risks,
using any reasonable
calculational method, than most chemicals that are regulated.
Nor should we accept that there is zero risk at a
low dose of a substance. It is implicit in the
multistage cancer theory of Sir Richard Doll that exposure to a
substance at low doses produces a
proportionately low (usually minuscule) risk. It is explicit in the
1975 work of Sir Richard Peto, who
pointed out that when a substance produces a medical ailment
indistinguishable from one that occurs
naturally, it is likely that the pollutant acts at some stage in the
process similarly to natural processes.
The fact that cancers occur implies that a biological threshold, if
any, is exceeded by the natural
processes. Then, as a mathematical consequence of Taylor's theorem, an
incremental increase in
cancer is proportional to the dose of pollutant. This argument applies
to a wide variety of
environmental problems: air pollution, radiation exposures and
chemicals in food. It has never been
refuted.
On average, between 1 percent and 2 percent of the
lifetime risk of death is from car accidents.
We do not ban cars, nor should we ban a chemical that poses a risk
10,000 times smaller than that
of cars. That the risk is minuscule does not mean that we should ignore
chemicals known to cause
cancer in rodents, as half of them do. It should mean that we, and
public agencies acting on our
behalf, admit that we live in a risky world and must accept risks of
small magnitude while rejecting
those of large magnitude. We must reject absolutes and rigidity -- both
the rigidity of the impossible
demand for zero, or even one in a million, lifetime risk and Dr.
Whelan's refusal to allow rodents to
tell us everything of which they are capable. We must also be alert to
the possibility that rodents may
not warn the world of real hazards, such as the carcinogenicity of
arsenic.
<>
RICHARD WILSON
Mallinckrodt Research Professor of Physics
Department of Physics
Harvard University
Cambridge, Mass.