EDB in perspective

Thought boggles at the chemist's ability to detect minute amounts of toxic chemicals in food, air, or water. Such ''contaminants'' often are present at a concentration of only a few parts per billion. But once the analysts come up with such minuscule numbers, there is dispute as to what they mean in terms of any hazard to human health.

The current flap over ethylene dibromide (EDB) illustrates this. It has been present at low concentration in the US diet for many years. But as detection techniques have improved in recent years, that presence has been emphasized. Now with a flare-up of publicity, many people have become afraid of their food.

While it is wise to err on the side of caution where food and water quality standards are concerned, there is no evidence of imminent danger from EDB-contamination. Bruce N. Ames of the University of California - an expert who has often warned of chemical hazards - notes that naturally occurring poisons in black pepper, celery, mustard, or peanut butter should be considered more dangerous than the EDB in muffin mix - if mere levels of concentration and absolute toxicity of chemicals are the criteria.

Dr. Ames and other experts have been explaining that we thus eat tiny amounts of known poisons every day. But, in the amounts ingested, they are no threat.

EDB needs to be seen in this perspective. The Environmental Protection Agency is wise to set a low tolerance level for it in food. It may also be wise in acting to phase out use of the chemical entirely. But there is no reason to strip grocery shelves of grain products or to create fear among the public.

EDB contamination is not an isolated problem. Similar safety concern will be raised again as the chemist's sensitive analytical techniques pick up traces of other toxic compounds in food and water. Thus there is an urgent need for the EPA, state health authorities, and toxicologists to define the health hazards more clearly. Regulators need such understanding to decide when trace amounts of a chemical do constitute a perceived danger.

Meanwhile, state health authorities should abide by the federal standards for EDB in food. The regulatory confusion some states are causing by adopting different standards and the needless fear that has been aroused are not worth the questionable ''safety margin'' such actions supposedly give.