Name Your Poison, Search for Answers : Toxics: How deadly is the stuff of Agent Orange fame? Clear-cut answers aren’t likely soon, but concern is justified.
Sodium chloride--table salt--is a critical ingredient for all living things. But when a relatively small amount of it was accidentally substituted for the milk-sugar lactose in a baby formula, it caused fatal poisoning. Sodium chloride can be made in the laboratory by mixing about equal amounts of lye (sodium hydroxide) and hydrochloric acid. Both lye and hydrochloric acids are powerfully corrosive substances that can maim and kill in very small quantities.
But if a superlative can be used to describe a toxic chemical, it is ricin , a natural substance extracted from the castor bean: It is among the most toxic substances known to man. A minute quantity on the tip of a pin is enough to kill an adult human being. It was used by the secret police of Bulgaria, wielding an umbrella tipped with the poison, to assassinate a dissident writer, Georgi Markov, in London in 1978. But in still smaller quantities, ricin is a promising substance, used in cancer research. Take two aspirins and your headache vanishes. Take a few more all at once and you may be in serious trouble very quickly.
The point of all this is that toxicity by itself is a meaningless term. The toxicity of any chemical substance can only be meaningful when one specifies how it is administered, how much of it is administered, how fast, for how long and with what exact results.
A good example of this problem is the endless debate over the substance dioxin, a contaminant in such products as PCB, once used as a transformer coolant, and in the notorious defoliant Agent Orange, widely spread during the Vietnam conflict.
The question has surfaced anew as to whether dioxin is a deadly peril and whether it deserves the label “most deadly carcinogen known to man.” Another government study is in prospect. It will take a year, with the predictable outcome of all the past studies: It is not likely to resolve the problem.
The issue is important because the federal government has compelled cities and industry to spend billions of dollars to prevent the release of dioxin and to remove it from the environment. Vietnam veterans exposed to Agent Orange claim, with some justification, that Uncle Sam has not levelled with them. Indeed, the government has denied all 16,000 disability claims resulting from alleged exposure to dioxin.
Yet the facts on dioxin toxicity are pretty well established. Under specified conditions of exposure, dioxin is a highly toxic substance, but at worst it is a weak carcinogen. The caveats, alas, are many. The first one, of course, is “under specified conditions of exposure,” and most data arises from animal studies. One simply cannot expose a statistically significant number of human beings to statistically significant amounts of dioxin for long enough to find out for sure. There is also no way to determine after the fact with any degree of accuracy how much exposure the victims of dioxin have received, and whether they suffer from its consequences.
And despite the gross misrepresentations of the animal-rights movement, no computer now or in the foreseeable future can substitute for a living organism. As is the case with exposure to radiation, including victims of Hiroshima and Chernobyl, there is no proof that cause-and-effect damage is linear--meaning that one-tenth the exposure may not mean one-tenth as much damage.
We are stuck with this melancholy conclusion, which no amount of table-pounding and hair-pulling will change: There simply are no easy answers. Technology has not yet reached the point where clear-cut cause-and-effect relationships can be credibly obtained in situations involving toxic contaminants like dioxin.
Political decisions based on technical data must, therefore, be taken with concern for the worst-case scenario, based on solid scientific evidence. Getting to know something that well is extremely difficult under the best of circumstances. Obtained under intense political scrutiny, it is even harder to report data and honest conclusions without accusations of bias for political advantage.
In the case of dioxin contamination, the best available scientific evidence argues for a continued high level of concern to limit dioxin exposure, but against extremist doomsday scenarios that contaminate the political process.
