|
|
|
Case Stated: The Dose Makes the Poison
Case
Stated: The Dose Makes the Poison
August
20, 2002
Managing Planet Earth: Personal Health; Risks
and Realities: In a World of Hazards, Worries Are
Often Misplaced—By Jane E. Brody
This article
has been reprinted by permission of the New
York Times.
Spared from
worry about whether they will have enough to eat today or a
roof over their heads tomorrow, most Americans have the luxury
of worrying about the hazards that may be lurking in their
air, water and food as a result of all this progress and affluence.
We are healthier, live longer, have more sources of pleasure and convenience
and more regulations of industrial and agricultural production than ever, but
we are also more worried about the costs to our health of environmental contaminants.
This is not to say there is nothing to worry about. In an ideal world, progress
would result only in benefits, no risks. In an ideal world, we would be able
to produce, organically and inexpensively, all the food we need and the food
our importers rely on. In an ideal world, manufacturing would leave no residues
in air, water or soil, and people would be smart and disciplined enough to
resist exposure to health-robbing substances like tobacco and consistent about
using protective devices like seat belts, helmets and condoms. But this is
not and never will be an ideal world, so bad things will occasionally happen.
Regulations cannot control every risk. Besides, every regulation has a price.
The millions or billions spent in compliance and enforcement might be better
used in ways that would save many more lives, and sometimes the cost is not
worth the potential benefit. I say ''potential'' because in many cases, the
risks involved are only hypothetical, extrapolations from studies in laboratory
animals that may have little or no bearing on people. For example, despite
widespread belief and laboratory studies in rats that link pollution to breast
cancer on Long Island, this month an $8 million federal study found no evidence
that environmental contamination from pesticides and industrial chemicals was
responsible.
Why People
Worry
''People
are scared about environmental dangers,'' noted Dr. Glenn Swogger
Jr., a psychiatrist in Topeka, Kan. ''Being scared affects
their ability to think realistically and use good judgment.''
Underlying these fears, he believes, are uncertainty about
the effects of exposures to certain substances, a tendency
to overreact and seek scapegoats in stressful situations, guilt
about our affluence and an unspoken wish to return to a simpler
and purer world. Experts in risk perception say people who
become agitated about real or potential risks are influenced
by a number of ''outrage'' factors. Prominent among them is
control. Is the risk voluntarily assumed or imposed by others?
A woman I know who eats only organically grown food enjoys
rock climbing, skiing and whitewater rafting, sports far riskier
than all the chemical fertilizers, pesticides and antibiotics
combined. Likewise, does it make sense for smokers to worry
about pollution from a nearby factory? In short, too often,
the risks people worry most about are out of proportion to
the actual dangers involved. Next is the fairness factor. Is
there a benefit to the consumer, or are consumers assuming
risks resulting from benefits gained only by the manufacturer?
A classic example is toxic waste dumped on a community. Or,
if there are some consumer benefits, are they out of proportion
to the risks? One example is the use of antibiotics in animal
production, a process that has led to the spread of antibiotic-resistant
bacteria. Is the hazard natural or caused by people? Although
there was a brief flurry of concern about radon, which emanates
naturally from soil and rock, perpetual and far more intense
concern arises over radioactivity from mine tailings and nuclear
power plants. Yet the known cost to lives from other energy
sources, including solar power, gas and oil, still far exceeds
that associated with nuclear power. How new or familiar is
the risk? People worry much more about possible accidents caused
by new technologies than about ones they have known about all
their lives. Traditional plant-breeding techniques have resulted
in no protests. But the introduction of genetically modified
foods has prompted some people to pay premium prices for foods
said to be free of any genetic manipulation, even if it results
in more wholesome products. Is there potential for a catastrophe?
Consumers have repeatedly ranked nuclear power as the No. 1
hazard among more than two dozen activities and technologies,
including smoking and handguns. Many people are far more frightened
of air travel, especially after a plane crash, than they are
of driving, which, mile for mile, presents a far greater risk.
Facts
to Consider
It is not
possible to anticipate, regulate and control every risk. Priorities
must be assigned for risk management, with time and money devoted
to those hazards best established and most likely to cause
the most harm. Not every regulation is a good investment. For
example, for each premature death averted, the regulation that
lists petroleum refining sludge as a hazardous waste costs
$27.6 million while the rule that does the same for wood preserving
chemicals costs $5.7 trillion per death avoided, according
to estimates from the Office of Management and Budget. The
asbestos ban, at $110.7 million per life saved, was a bargain
compared with the exposure limits placed on formaldehyde, which
cost an estimated $86.2 billion per death averted. Animal tests
that result in cancer caused by a suspect substance do not
necessarily apply to people. Half of all chemicals that have
been tested have caused cancer in one or another experimental
animal, but not always in all species or strains tested or
even in both sexes. Often animal strains genetically susceptible
to certain cancers are chosen for these tests. When very large
doses are used in animal tests, the result is often toxicity
and inflammation, which itself can cause cancer even if the
substance is not carcinogenic. A cardinal rule in toxicology
is ''the dose makes the poison.'' You can eat a dozen carrots
at once with no ill effect, but 400 carrots could kill you.
Animal studies rarely reveal the possible effects, or safety,
of long-term exposure to the kinds of low doses people may
experience. Keep in mind that we all have livers, which accrue
and detoxify small amounts of hazardous substances. Another
limitation of animal tests is their usual failure to detect
risks that may result from interactions between two or more
otherwise innocuous substances. Remember, too, that ''natural''
is not necessarily safer, and just because something is manufactured
does not make it a potential hazard. Nature is hardly benign.
Arsenic, hemlock and, despite its current medical applications,
botulism toxin are wholly natural but also deadly. For helpful,
detailed discussions of how best to consider environmental
threats, consult the new book ''How Much Risk? A Guide to Understanding
Environmental Health Hazards'' (Oxford University Press) by
Inge F. Goldstein and Martin Goldstein, who explain how controversies
are investigated and why scientists sometimes disagree and
fail to find definitive answers.
Copyright
2002 The New York Times Company
"Misplaced
Worries": Recent New York Times On-line Article Highlights
Continued Need for Public Education—SOT Perspective
by the SOT Committee on Public Communications
A recent
article entitled "In a World of Hazards, Worries are Often
Misplaced" by Jane E. Brody published on August 20, 2002,
in the on-line version of the New York Times (www.nytimes.com)
highlights the continued need for public awareness and understanding
of toxicology. In the article, Brody points out how U.S. citizens,
free from "worry about whether they will have enough to
eat today or a roof over their heads tomorrow…have the
luxury of worrying about the hazards that may be lurking in
their air, water and food as a result of all this progress
and affluence." While mulling over these concerns, the
same citizens may ironically spend their free time rock climbing,
sky diving, commuting on busy interstates, or in other potentially
lethal but entertaining or necessary activities. As Brody asks, "does
it make sense for smokers to worry about pollution from a nearby
factory?" How often do these citizens consider the time-honored
classic dogma of toxicology, "the dose makes the poison"?
Unfortunately, such misplaced worries by the general public
likely have significant and lasting effects on government regulations.
Brody provides several examples of estimated "cost per
life saved" of regulations affecting petroleum refining
sludge, wood preserving chemicals, asbestos, and formaldehyde.
The examples provide some public awareness of how priorities
for risk management are difficult to establish.
As members
of SOT, we may be well aware of the limitations of scientific
data that result in regulations regarding exposure limits.
But, our worries regarding toxicology may sometimes be misplaced
as well. Perhaps we spend too much time worrying about obtaining
the next grant to support our work and too little time worrying
about educating people? As toxicologists, we all spend our
time evaluating experimental results, calculating risks, speculating
about and delineating mechanisms of toxicity, writing and explaining
our results, planning experiments, and teaching. Whether we
like it or not, teaching is the most critical component of
our work because the audience has a significant impact on the
outcomes of our career. The students of our work are more diverse
than we routinely consider. They include: young aspiring undergraduate
and graduate students; reviewers of manuscripts and grants;
readers of our published work; audiences of our lectures and
invited seminars; family members who want to understand our
career choices; or the public in general. Some toxicologists
relish every opportunity to educate others while some view
the experience as a necessary, albeit arduous, component of
their career. Yet, we all need to be actively involved in teaching
at every level possible because politics and public perception
shape the budgets that support our careers.
|
