Environmental Engineering Reference
In-Depth Information
THE NO-THRESHOLD FALLACY
All things are poison and nothing [is] without poison; only the dosage determines that something is not
a poison.
—Paracelsus, sixteenth century
19
The world around us and our own bodies consist of chemicals. All of them, without a single exception, can
be poisonous to us if we are exposed to them in a certain concentration (which can be too high or too low)
or in a certain form.
A simple example of this is medication. In the right concentration, a given hormone, heavy metal, or
complex organic molecule can be lifesaving or can treat some nasty symptoms of a disease. Antibiotics
are essentially poisons to microorganisms inside our bodies. If we take too much of certain drugs, we will
die immediately.
The same is true for all substances in our bodies. Inside our bone tissue, for instance, there is a radio-
active potassium isotope in a low concentration. Even pure water, which is the main constituent of our
bodies, is a potential threat to our health. Drinking too much distilled water is dangerous because mineral-
poor water entering our metabolism causes a mineral imbalance on the cellular level. On the other hand,
pouring distilled, mineral-poor water on our skin is no threat.
A poison or pollutant is always a
combination
of substance and dose. If someone mentions just a sub-
stance to scare you, independent of the context or the dose, he has given you meaningless, misleading
information. He is assuming or expecting you to assume that if a substance is dangerous in
some dosage,
it is dangerous in
all dosages
. One variant of this argument used to attack shale energy is the claim that
fracking causes earthquakes.
20
This assertion is true in that fracking causes some amount of underground,
earth-moving activity, but in almost all cases, it is completely inconsequential and not even discernible
at the surface. A typical tremor that can be caused by hydraulic fracturing is −2 on the Richter scale, a
“quake” that is not felt at the surface, causes no damage, and can be measured only deep underground.
Such quakes are occurring continuously throughout the Earth, fracking or no fracking.
21
Whataboutaworst-casescenario?Manysaythatit'sbetween3and4ontheRichterscale,whichmeans
you can feel the quake but it's unlikely strong enough to cause damage.
22
And this is an incredibly unlikely
scenario. For this we are supposed to ban all fracking?
Even if fracking in a certain place had a high risk of a truly dangerous earthquake—say, because it is
near some seismically vulnerable area—that is an argument against fracking in that particular place, not an
argument against fracking as such.
23
Whenonetreatssomethingaspoisonousregardlessofdosage,heisdenyingtheexistenceofa
threshold
at which a substance goes from being benign to harmful. If you deny a threshold, you can make a case for
banning anything.
The no-threshold fallacy was used particularly insidiously in opposing nuclear power. People said we
should have zero tolerance for radiation—not knowing, apparently, that the potassium in their bone tissue
emits radiation, enough so that sleeping with a spouse gives you almost as much radiation as standing right
outside a nuclear power plant. Both activities are nowhere near harmful.
“No-threshold” plus “false-attribution” is a dangerous combination in the hands of activists and regu-
lators. They can keep claiming that nothing is clean enough and keep passing laws that regulate vital tech-
nologies, such as coal, out of existence. As always, whether we are talking about a natural substance or a
man-made substance, our standard needs to be human life.
That
determines the threshold of danger.
