RECENTLY IN THIS space we wrote about the difficulties caused by the use of relatively new tests that can reveal an individual's genetic makeup. Some of these tests identify genetically determined traits that cause no visible symptoms, but that may make an individual more susceptible to the effects of certain toxic substances, and therefore more vulnerable to occupationally caused disease.

One of the examples we cited was a program at E. I. Du Pont de Nemours & Company in which black employees and prospective employees were tested for the presence of the sickle-cell trait. This gene may make the affected individual more susceptible to damage from chemicals that attack red blood cells. The program appeared highly questionable because Du Pont did not test members of certain white ethnic groups who carry a related genetic trait at equally high frequency.

As it turns out, our sources were wrong. We owe Du Pont an apology, herewith rendered. The sickle-cell tests were in fact initiated at the request of the Black Du Pont Employees Association, whose president writes: "It seemed to us an important part of a medical profile."

The incident demonstrates, among other things, the kind of problems and misunderstandings likely to occur with increasing frequency on this kind of question. Knowledge of the human genome (the full genetic endowment) is expanding rapidly. New laboratory techniques can identify the presence and activities of individual genes, and computer-assisted epidemiology can uncover previously undetectable associations between certain exposures (to chemicals, saccharin, air pollutants and so forth) and their clinical effects. So, in the next few years, we can expect to identify many more gentic traits that affect an individual's potential for different health problems.

Just this week, for example, the discovery of a gene that leads to a highly increased risk of breast cancer was reported. If the report is confirmed, the new knowledge should bring benefits in specially designed medical care for the affected women. But other discoveries, especially those that affect decisions in the work place, are going to pose problems. Society is still much better at detecting risks than managing them. We react irrationally to many relatively small risks and often ignore the real killers -- including the Big Four: guns, cars, cigarettes and alcohol.

This is not to suggest that occupational hazards should be ignored or minimized. On the contrary -- considering the enormous number of possible gentic differences and the equally large number of potentially dangerous chemicals, the emphasis of government and business should be on removing the hazards, not selecting out people. It does, however, indicate that greater sophistication and sense of priorities will be needed, not just from the regulatory agencies, but from the Congress that defines their missions.