WASHINGTON — The new director of the Centers for Disease Control and Prevention is taking a pay cut after Senate Democrats and watchdog groups criticized the use of an exemption to pay him nearly double the rate of his predecessors.

Dr. Robert R. Redfield assumed the top post in March at a salary of $375,000 per year, far more than the heads of many other federal agencies, and much more than his predecessors Dr. Brenda Fitzgerald ($193,700), Dr. Thomas Frieden ($209,700), and Dr. Julie Gerberding ($207,000).

The unusually high rate was granted under a provision known as Title 42, which permits the Department of Health and Human Services (and the Environmental Protection Agency) to pay more than the approved government rate if the candidate fills a specific scientific need that cannot otherwise be met.

Senator Patty Murray, Democrat of Washington, questioned the use of the exemption in this case, suggesting last month that it might not have been appropriate. She asked the health and human services secretary, Alex M. Azar II, who oversees the C.D.C., to describe the “extensive and exhaustive effort” that was supposed to be made to find a director before hiring Dr. Redfield at the unusually high salary.