IT IS THE DOSE THAT MAKES THE POISON

A friend and subscriber, who ought to know better because he is an M.D., once told me accusingly, "According to you nothing is dangerous." He might as well have said "everything is dangerous," as indeed it is. What makes a danger dangerous is only the dose, or the quantity of the harmful agent received. Most people would agree that milk, honey, sunshine and water are wholesome, because what they subconsciously mean is "in normally consumed, reasonable quantities." But all four can, in fact, kill you. Try and drink 3 gallons of milk or water in one hour; maybe you will succeed, but you will die shortly afterwards, as surely as if you had received a dose of 1,000 rem all at once. Yet both milk and radioactivity in small quantities are known to be beneficial.

So the question that the Greens evade is really this: what is there in the environment that threatens to come in lethal doses? Hurricanes, floods, tidal waves, earthquakes, they would probably agree, though as technophobes they would undercut any research that might one day give effective protection against them.

That is why many scientists believe that there is only one preventable lethal threat in the environment (hurricanes, floods, and earthquakes are not yet preventable). It is a tiny, but nevertheless real threat, and the Greens have never even heard about it: collision with an asteroid.

In the collision with heavenly bodies, we are back to the dose making the poison (or adverse event). The small meteorites burn up in the atmosphere, at a rate of no less than 1 to 10 kilotonnes (kt) per day. About 5 kt are big enough to be seen as "shooting stars," and about 1 kt per day actually reach the earth. Once every 300 years on the average an object of some 100 m (about 33 ft) in diameter will hit the earth, as it did in Arizona and Siberia. [Source: Brockhaus ABC der Astronomie, 1960; could be some-what outdated.] Although a chunk of that size may devastate an area of some 5,000 km (a circle with radius 40 km or 25 miles) its effect is local and the threat to life has, because of the rarity of the event and the tiny size of impact on the entire area of the globe, a laughably small probability: the probability that an individual will be killed by such a collision is about 0.00000003 per year. Lethal, yes, but to almost nobody. (On the other hand, that's just one order less than the probability of being killed in an aircraft accident.)

But then there are the real big bodies, asteroids, which could devastate much of the life on the entire globe. Such a collision is estimated to fake place on the average every 500,000 years. As reported earlier [AtE May 82], Nobel Prize winner Prof. L. Alvarez noted that the geological layers after the demise of the dinosaurs contained an inordinate amount of iridium, an element much more common in other heavenly bodies than on Earth. The collision stirred up dust and debris that darkened the Sun for years and led to the extinction of many species, including dinosaurs. This is, of course, the theory from which Ehrlich, Sagan and other quacks stole the Nuclear Winter theory, as if a crummy 10,000 nuclear bombs could reach to the ankles of the energies unleashed by nature on earth, let alone by cosmic forces. Alvarez' theory is, however, by and large accepted now.