Lead investigator Peter A. Lurker, an environmental engineer with many years of experience evaluating environmental exposures in the U.S. Air Force, said during the Vietnam War "Operation Ranch Hand" involved 34 C-123 aircraft that sprayed approximately 20 million gallons of herbicides, including around 10.5 million gallons of dioxin-contaminated Agent Orange.
These aircraft were subsequently returned to the United States and used by Air Force reserve units between 1971 and 1982 for transport operations.
After many years without monitoring, tests revealed the presence of dioxin. All but three of the aircraft were smelted down in 2009.
Current policies stipulate "non-biologically available dried residues" of chemical herbicides and dioxin would not have led to meaningful exposures to flight crew and maintenance personnel, and the Air Force and Department of Veterans Affairs deny benefits to these crew members making them ineligible for Agent Orange-related benefits, medical examinations and treatment.
The study, published in the journal Environmental Research, said the models suggest the potential for dioxin exposure to personnel working in the aircraft post-Vietnam is greater than previously believed and that inhalation, ingestion and skin absorption were likely to have occurred during post-Vietnam use of the aircraft by aircrew and maintenance staff. The estimated dermal -- skin -- and oral exposure exceeded U.S. standards, the study said.
"Our findings, the results of three different modeling approaches, contrast with Air Force and VA conclusions and policies," said senior author Jeanne Mager Stellman, professor Emerita of Health Policy and Management at the Mailman School of Public Health at Columbia University in New York.
"The VA concept of a 'dried residue' that is biologically unavailable is not consistent with widely accepted theories of the behavior of surface residues. Aircraft occupants would have been exposed to airborne dioxin-contaminated dust as well as come into direct skin contact, and our models show that the level of exposure is likely to have exceeded several available exposure guidelines."