[2] Millar began working for the National Institute for Occupational Safety and Health under then-director John Finklea.

Millar held the post, sorting out conflicts within the Institute, until Anthony Robbins was appointed director 1979.

[4] Following Robbins's appointment, Millar was hired as the director of the National Center for Environmental Health (NCEH).

He advocated the use of a rollover protective structure (ROPS) on every tractor in use, saying, "There is no scientific excuse for the persistence of this problem.

[9] In addition to his work at NIOSH, Millar chaired the executive committee of the National Toxicology Program (NTP) from 1989 to 1993.

He was named Honorary Fellow of the Faculty of Occupational Medicine, Royal College of Physicians, London (U.K.).

In 1993, Millar was given the William Steiger Memorial Award from the American Conference of Governmental Industrial Hygienists, the Health Watch Award for "outstanding contributions toward improving the health of minority populations", and the Surgeon General's Medallion for "exceptional skill and fortitude.

"[2] Millar retired from NIOSH and the US Public Health Service with the rank of Rear Admiral in 1993, turning his directorship over to Linda Rosenstock.