SHOULD A SUBSTANCE deemed too dangerous for use in this country be licensed for export? An answer is still elusive despite years of study and debate, while reports of banned and untested substances have been growing. The key issues are these: Does the United States have a moral responsibility to prevent the export of a substance it knows -- or thinks -- is dangerous? Or does the making of such judgments constitute unacceptable intrusions on the sovereignty of other nations? And what effect would stricter controls have on an already shaky U.S. balance of trade?

No single, simple control policy -- for example, banning the export of anything that is banned domestically -- will sensibly cover the complete range of exports that include such items as Tris-treated pajamas, pesticides, effective but risky medicines, toxic chemicals and dangerous toys for children. In each case the nature of the risk will be different, as will the degree of certainty about whether or not a risk actually exists. In some cases, alternatives to a dangerous product will be available, in other not.

In many cases the conditions in an importing country -- rampant unemployment, exploding population growth, epidemics of insect-borne disease -- make U.S. standards of health or safety completely inappropriate. For example, Depo Provera, a long-lasting, injected contraceptive, has been banned in this country because of uncertain long-term risks. However, in a country whose number one problem is overpopulation, and the illness and mortality rates associated with it, the risk-versus-benefit judgment is different. And in fact, Depo Provera is licensed in more than 70 nations. Should U.S. firms then be prohibited from selling it?

An apparently satisfactory way to balance ethical responsibility, practical economic considerations and respect for the right of others to make their own decisions is for the United States to require only that the importing country be fully aware of the potential risks. In practice, however, this approach has many drawbacks.

A serious notification policy, for instance, would require full publication of the thousands of regulatory actions -- bans, suspensions, registrations, deregistrations, judicial injunctions, to name a few -- occurring each year. A document from the government of the importing country indicating that it has received and considered the information would also be required. Masses of paper work and thousands of additional man-hours would be needed. In this country all that would be possible, though unwelcome, but in many -- if not most -- others it would be impossible. Two years ago, for example, the Ministry for Environment in Nigeria (one of the larger and richer developing countries) consisted of the minister, one assitant and one secretary. A high level of scientific and technical expertise would also be necessary to evaluate the risk-benefit trade-offs posed by a possible import. And even if this step could be accomplished, many governments lack the procedures and the degree of central control necessary to set and implement standards for safe use.

Probably the only really workable solution lies in the creation of common international standards. But although some steps in this direction are being taken by a number of U.N. agencies, it will be many years, if ever, before they amount to much. Meanwhile, this country will have to find an acceptable set of standards for itself. The United States must accept some responsibility for its exports -- that much is clear. But where the line comes between appropriate care and becoming the world's environmental policeman -- against the will and wishes of importing countries with different priorities and standards and needs of their own -- is not so clear. Finding the right balance will be a thankless task: for every developing country that objects to becoming a dumping ground for the industrialized world, there is another that objects even more loudly to having the developed world's standards imposed on it. Nevertheless, the task is worth the effort. Lethal pesticides, toxic chemicals and dangerous drugs all have a way of coming back to haunt their makers. Mixed in the volatile brew of international relations, they can become explosive.