The new story on a recent study of drug testing of Boston postal workers {''Study Downgrades Pre-Employment Drug Testing,'' Nov. 28} overlooked an important point: that persons who use illegal drugs are more likely to make bad employees and to endanger themselves, their fellow workers and the public.

The study published in the Journal of the American Medical Association found that Boston postal workers who tested positive for marijuana or cocaine had 55 percent more industrial accidents, 85 percent more injuries and 78 percent more absenteeism than other employees.

True, some previous studies found higher rates of on-the-job problems among drug users. But these studies tracked only employees who were known to be heavy drug users, while the postal workers study followed all workers who tested positive for drugs, regardless of whether they were occasional users or addicts.

All of these studies document clearly the disruption employee drug use can have on the workplace. And they provide yet further proof that drug testing, when applied selectively and with rigorous standards of accuracy and respect for employees' confidentiality, can help make the workplace safer and more productive. More and more companies recognize this and are instituting drug testing as well as employee assistance programs to help rehabilitate employees with drug problems.

We readily agree that there are populations in our society with higher rates of drug use than the general workforce -- prisoners and arrestees to cite one obvious example. The administration supports more drug treatment for this group as well as more comprehensive drug testing. We have, in fact, proposed legislation to this end. But looking for drug use only among criminals and arrestees overlooks users who may be flying our airliners, delivering our mail, teaching our children or serving in our armed forces -- in short, those in whom we entrust our safety, welfare and livelihood.

If we are going to be serious about discouraging drug use throughout our society, the workplace must be a focus of our efforts. HERBERT D. KLEBER Deputy Director for Demand Reduction Office of National Drug Control Policy Washington