THE ALARM that has been raised in response to Rep. Richardson Preyer's candidacy for the chairmanship of an influential House subcommittee is apparently intended to signal a threat to ethical purity in the conduct of public affairs. It strikes us, however, that there is a false alarm here and that the congressman's situation might be a useful starting point for a general refinement in thinking about what has become muddled concept-conflict of interest.

Mr. Preyer, a North Carolina Democrat, is the leading candidate to succeed the newly retired Paul Rogers (D-Fla.) as chairman of the subcommittee on health and the environment. The succession is a matter of broad interest, since the subcommittee's jurisdiction embraces a wide range of politically sizzling issues, such as federal stanrdards for clean air and safe drinking water, the nationwide planning system for health services, health manpower, community mental-health programs and, possibly, national health insurance.

Then, too, the subcommittee has jurisdiction over the Food and Drug Administration, which is in legislative midstream on an ambitious attempt to overhaul its basic charter for reviewing and certifying new pharmaceutical drugs. It is on this last item that questions have been raised about Rep. Preyer's suitability for the chairmanship, since he is the grandson and an heir of the foujder of the Vick Chemical Company, which eventually became the Richardson-Merrell Corporation, a major pharmaceutical manufacturer.

By virtue of this connection, Mr. Preyer owns some $2 million worth of the company, stock. The holdng, however, is in a blind. Mr. preyer insists that he has nothing to do with the firm' smanagement or policy-making, and that the reason he doesn't sell the stock is that he plans to pass it along to his five children, and that, for tax purposes, it is advantageous for him to retain ownership.

An unwilling conscript to the health subcommittee when he was first elected to Congress in 1968, Mr. Preyer has abstained from voting on drug-related matters and says that, as subcommittee chairman, he would continue that practice. This, in turn, has inspired critics and rivals to warn that Mr. Preyer would be either an "absentee" chairman or a conflict-of-interest chairman and that, therefore, he ouggt to drop out of the running. Nothing personal, they insist, noting that Mr. Preyer, a former federal district judge and member of both the House assassinations committee and ethics committee, is held in high esteem by his congressional colleagues. But the message is that none of this counts-that salvation can only be found in strict adherence to the God-like commands of the conflict-of-interest principle.

It seems to us, on the basis of legislative experience, temperament, good sense and competence, that Rep. Preyer is preeminently qualified for the chairmanship he seeks. Further, since a great many government people in positions of awesome responsibility-from peanut farmer Jimmy Carter on down-manage to get along with disclosure rather than divestiture as the answer to conflict of interest, we don't understand why Mr. Preyer's very conspicuous disclosure should feel compelled to abstain from voting on drug-related matters, as it is unlikely that a chairman under so bright a spotlight will be bartering his vote for an improved dividend.

It is important, very important, that the conduct of public business be uncontaminated by conflict of interest. It is equally important that, within that principle, competent people be encouraged to take part in public affairs.One sure way to discourage them, however, is to turn a sound principle into a nit-picking set of rules that seem to serve, but actually defeat, the public interest.