The national drug problem has taken its toll on employees of the District's Department of Corrections, but substance abuse has not affected the "safety and security" of the agency, its director said yesterday.

Walter B. Ridley, appearing before the D.C. Council's Judiciary Committee, said a year-old task force working in the corrections system has reduced the consumption of narcotics among inmates, one of a number of measures taken to tackle the problem.

As a result, the number of inmates at Lorton who have tested positive during random drug tests has dropped to 3.4 percent this year, down from 8.5 percent before the task force was formed in May 1988.

There have been several highly publicized cases detailing drug use among corrections officers, most recently in a five-part series in The Washington Post.

Seven guards at Lorton were arrested recently for bringing drugs into the complex, and Ridley said yesterday that other officers are under investigation.

The director, who testified for about 40 minutes, said the department would be remiss if it did not recognize that a substance abuse problem existed. But he said a few cases have drawn considerable attention and distorted the issue.

"Unfortunately, there is a small percentage of employees who, for reasons both job-related and personal, succumb to the perils of substance abuse," he said. "They have been singled out by the news media, which results in an inaccurate portrayal of the general work force."

Asked how extensive the problem may be, Ridley said 5 to 7 percent of the department's 4,000-plus employees, including prison guards, may have a substance-abuse problem.

The figure, he emphasized, was a rough estimate that mirrored society's drug problem in general.

"We do know that we have current employees who are currently involved in these activities," said Ridley. "We have been very vigilant and diligent in pursuing those who are violating the law."

In the last three years, substance abuse has resulted in 13 employee dismissals. One employee resigned and two others are being dismissed, Ridley said.

Between January 1988 and last month, 40 employees were referred to substance abuse treatment programs, 19 for alcohol, nine for cocaine and 12 for problems with both.

The cases of 32 visitors stopped while allegedly trying to smuggle drugs into the system have been referred to the U.S. attorney's office, said Ridley.

Of those, several have been convicted and sentenced to two-year prison terms, he said.

Under questioning from the committee's chairwoman, Wilhelmina J. Rolark (D-Ward 8), Ridley said the department is still weighing some form of random drug testing for corrections workers.

Recruits are now tested, but no such program exists for current employees.

Ridley, who has been discussing the proposal with labor leaders, said any form of drug testing must insure that employees are treated in a "fair and just manner."