Commissioned officer United States Public Health Service, 1972, advanced through grades to assistant surgeon general, 1999. Criteria document manager National Institute for Occupational Safety and Health, Rockville, Maryland, 1972-1975, graduate trainee Cincinnati, 1975-1977, research biologist (toxicologist), 1977-1986, senior reviewer division standards development and technical transfer, 1986-1987, branch chief, 1987-1990, acting Acquired Immune Deficiency Syndrome coordinator Atlanta, 1988, deputy dir division standards development and technical transfer Cincinnati, 1990-1992, assistant director Washington, 1992—1993. Special assistant to assistant Secretary of Labor for Occpl.
Safety & Health, 1993—1994. Senior scientist Office of Director National Institute Occupational Safety and Health, 1994-1995, acting deputy director Atlanta, 1996, lead senior scientist Office of Director Washington, 1996-1998, deputy director Atlanta, 1998-2000, Bryan Hardin Consulting, Hilton Head, South Carolina, 2000—2003. Senior consultant GlobalTox, Inc., Redmond, Washington, 2001—2004.
Principal Veritox, Inc., since 2004. Member reproductive and development toxicology work group National Toxicology Program, 1980—1986. Member Toxic Substances Control Act Interagy.
Testing Committee, 1987—1989, vice chairman, 1988, chairman, 89. Member working groups on evaluation of carcinogenic risk of chemicals to humans International Agency for Research on Cancer, 1985, 92. Member task group for environmental health criteria documents International Program on Chemical Safety, World Health Organization, 1989.
Member working group drafting Principals and Methods for the Assessment of Risk from Exposure to Chemicals, 1990. Chairman expert consultation Harmonization of Chemical Hazard Communications, 1991. Member steering committee International Hazard Datasheets on Occupations, International Labor Organization, International Occupational Safety and Health Information Center, 1995—1998.
Member endocrine disruptor screening and testing advisory committee United States Environmental Protection Agency, 1996—1998. Advisory board for the risk education project American Chemical Society, 1997—2000. Adjunct associate professor environmental and occupational health Rollins School Public Health Emory University, Atlanta, 2000—2001.
Member American Industrial Hygiene Association Emergency Response Planning Committee, since 2001, secretary, 2009—2011, vice chair, since 2011. 1st lieutenant United States Army, 1966-1968, captain United States Army Reserve, 1968-1972.
Fellow: Academy Toxicol. Sciences; member: American College of Toxicology, American College Occupational and Environmental Medicine, Society Toxicology (elected councilor Occupational & Public Health Specialty section 2004-2006), American Industrial Hygiene Association, Teratology Society (public affairs committee 1985-1988, constitution and bylaws committee 1993-1996), Sigma Xi.