title: Post-Vietnam military herbicide exposures in UC-123 Agent Orange spray aircraft.
abstract: BACKGROUND
  During the Vietnam War, approximately 20 million gallons of herbicides, including ~10.5 million gallons of dioxin-contaminated Agent Orange, were sprayed by about 34 UC-123 aircraft that were subsequently returned to the United States, without decontamination or testing, to three Air Force reserve units for transport operations (~1971-1982). In 1996, observed dioxin contamination led to withdrawal of these UC-123s from public auction and to their smelting in 2009. Current Air Force and Department of Veterans Affairs policies stipulate that "dried residues" of chemical herbicides and dioxin had not lead to meaningful exposures to flight crew and maintenance personnel, who are thus ineligible for Agent Orange-related benefits or medical examinations and treatment. Sparse monitoring data are available for analysis.
  
  
  METHODS
  Three complementary approaches for modeling potential exposures to dioxin in the post-Vietnam war aircraft were employed: (1) using 1994 and 2009 Air Force surface wipe data to model personnel exposures and to estimate dioxin body burden for dermal-oral exposure for dried residues using modified generic US Environmental Protection Agency intake algorithms; (2) comparing 1979 Air Force 2,4- dichlorophenoxyacetic acid and 2,4-5-trichlorophenoxyacetic acid air samples to saturated vapor pressure concentrations to estimate potential dioxin exposure through inhalation, ingestion and skin contact with contaminated air and dust; and (3) applying emission models for semivolatile organic compounds from contaminated surfaces to estimate airborne contamination.
  
  
  RESULTS
  Model (1): Body-burden estimates for dermal-oral exposure were 0.92 and 5.4pg/kg body-weight-day for flight crew and maintainers. The surface wipe concentrations were nearly two orders of magnitude greater than the US Army guidance level. Model (2): measured airborne concentrations were at least five times greater than saturated vapor pressure, yielding dioxin estimates that ranged from 13.2-27.0pg/m(3), thus supporting the likelihood of dioxin dust adsorption. Model (3): Theoretical models yielded consistent estimates to Model 2, 11-49pg/m(3), where the range reflects differences in experimental value of dioxin vapor pressure and surface area used. Model (3) results also support airborne contamination and dioxin dust adsorption.
  
  
  CONCLUSIONS
  Inhalation, ingestion and skin absorption in aircrew and maintainers were likely to have occurred during post-Vietnam use of the aircraft based on the use of three complementary models. Measured and modeled values for dioxin exceeded several available guidelines. Deposition-aerosolization-redeposition homeostasis of semivolatile organic compound contaminants, particularly dioxin, is likely to have continually existed within the aircraft. Current Air Force and Department of Veterans Affairs policies are not consistent with the available industrial hygiene measurements or with the widely accepted models for semivolatile organic compounds.
authors.affiliation: Germantown Consultants, LLC, Germantown, OH, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Lurker
authors.affiliation: The Center for Research on Occupational and Environmental Toxicology, Oregon Health and Science University, Portland, OR, USA.
authors.forename: Fred
authors.initials: F
authors.lastname: Berman
authors.affiliation: Boston University School of Public Health, Boston, MA, USA.
authors.forename: Richard W
authors.initials: RW
authors.lastname: Clapp
authors.affiliation: Department of Health Policy & Management, Mailman School of Public Health, Columbia University, 600 West 168th Street, 6th floor, New York, NY, USA. Electronic address: jms13@columbia.edu.
authors.forename: Jeanne Mager
authors.initials: JM
authors.lastname: Stellman
mesh_terms: D015085:2,4,5-Trichlorophenoxyacetic Acid / Q000032:analysis* / Q000633:toxicity; D015084:2,4-Dichlorophenoxyacetic Acid / Q000032:analysis* / Q000633:toxicity; D000075182:Agent Orange; D000401:Aircraft; D004147:Dioxins / Q000032:analysis* / Q000633:toxicity; D004781:Environmental Exposure / Q000032:analysis*; D006540:Herbicides / Q000032:analysis* / Q000633:toxicity; D006801:Humans; D008297:Male; D008889:Military Personnel; D008962:Models, Theoretical; D000072317:Polychlorinated Dibenzodioxins / Q000032:analysis* / Q000633:toxicity; D014481:United States; D047829:Vietnam Conflict
chemical_list: D004147:Dioxins; D006540:Herbicides; D000072317:Polychlorinated Dibenzodioxins; D015084:2,4-Dichlorophenoxyacetic Acid; D000075182:Agent Orange; D015085:2,4,5-Trichlorophenoxyacetic Acid
keywords: Agent Orange; Dioxin; Exposure modeling; Phenoxyherbicides; Veterans; Vietnam War