A QUARTER of million Canadians were evacuated from their homes two weeks ago because of a train derailment that released deadly chlorine and phosgene gases. The story made front-page news for one day and was quickly forgotten -- which illustrates the strange and often perplexing ways in which society responds to the myraid risks of industrialized living. One can only imagine how bleak the future of nuclear power would be if 250,000 people had had to be evacuated from the vicinity of a nuclear reactor.

What accounts for the phenomenon that produces yawns over chemical accidents and instant headlines about even the hint of a nuclear danger? It is not just a reaction to the ghostly qualities of radioactivity, though that is a part of it. Radioactivity can kill you without your ever having seen, smelled, heard or felt it.But there are also many chemicals -- carbon monoxide, for example -- that are colorless, tasteless and deadly. Nor is the fifference simply that nuclear energy is relatively new and unfamiliar. Commercial nuclear power has been around for two decades now, and that is substantially longer than, for instance, people have recongnized the relationship between chemicals and cancer.

Society, in other words, reacts differently to risks that a mathematician would say were equally grave. Coal, for example, is almost certainly more dangerous than nuclear power if the combined risks of mining accidents, black lung, air pollution, acid rain and carbon-dioxide buildup are considered. But Jane Fonda, et al., have yet to hold an anti-coal rally. We live happily with one technology, the automobile, that causes 50,000 deaths a year -- an astronomical figure. And of course there is smoking. The death rate of smokers is double that of non-smokers, regardless of age. And smoking also increases the danger from a variety of other sources: asbestos workers who smoke, for example, get lung cancer at nearly 100 times the rate of their non-smoking co-workers.

People are naturally more willing to accept the risks of a voluntary activity -- especially one from which they receive a direct and obvious benefit -- than the risks of an involuntary one. But a larger part of the explanation lies in a general public confusion. Recently it has begun to seem as though just about everything is dangerous to your health -- nuclear power, chemical wastes, pesticides (which DuPont now advertises as "crop protection chemicals"), occupational hazards, antibiotics in animal feed, air pollution and on and on. Just about everything seems to cause cancer -- what you do, what you eat (or don't eat), where you live. In the face of such a system overload, it is difficult to be very rational.

Are the risks of ordinary living really increasing, or are they merely being advertised better? The answers aren't clear. We are running out of empty space where wastes can be dumped and forgotten. We are also able to measure tiny amounts of chemicals and traces of pollution that would have been undetectable only a few years ago. We have a slightly better understanding of which substances are likely to be carcinogenic, and a much improved appreciation of how closely various parts of the environment interact. In short, we are much more aware of risks that have been around for some time. But it may also be true that, because of more people, more industrial activity and delining natural resources, new dangers are now being generated faster than ever before.

A central theme of the 1980s will be coping with the discrepancy between the technical capacity to generate, detect and measure risks, and our much more rudimentary social abilities to control, accommodate and manage them.