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Exposure opportunity models for Agent Orange, dioxin, and other military herbicides used in Vietnam, 1961-1971.
J Expo Anal Environ Epidemiol. 2004 Jul; 14(4):354-62.JE

Abstract

Nearly 19.5 million gallons of herbicides were sprayed on the Republic of Vietnam between 1961 and 1971 for military purposes. Amounts of spray and patterns of applications are available in an electronic file called HERBS that contains records of 9141 defoliation missions, including detailed coordinates of US Air Force Ranch Hand aircraft flight paths, along with chemical agent and gallonage sprayed. Two classes of models for use in epidemiological and environmental studies that utilize the HERBS data for estimating relative exposure opportunity indices are presented: a discrete "hits" model that counts instances of proximity in time and space to known herbicide applications, and a continuous exposure opportunity index, E4, that takes into account type and amount of herbicide sprayed, distance from spray application, and time interval when exposure may have occurred. Both direct spraying and indirect exposure to herbicide (or dioxin) that may have remained in the local environment are considered, using a conservative first-order model for environmental disappearance. A correction factor for dermal versus respiratory routes of entry has been incorporated. E4 has a log-normal distribution that spans six orders of magnitude, thus providing a substantial amount of discrimination between sprayed and unsprayed areas. The models improve on earlier ones by making full use of the geometry of the HERBS spray flight paths of Ranch Hand aircraft. To the extent possible so many decades after the War, the models have been qualitatively validated by comparison with recent dioxin soil and biota samples from heavily contaminated areas of Vietnam, and quantitatively validated against adipose dioxin obtained in epidemiological studies of Vietnamese. These models are incorporated within a geographic information system (GIS) that may be used, as one would expect, to identify locations such as hamlets, villages, and military installations sprayed by herbicide. In a novel application, the GIS also facilitates quantitative risk assessment in epidemiological and ecological studies by applying the models within a framework of historical reconstruction of exposure history of individuals based upon their location histories.

Authors+Show Affiliations

Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, NY 10032, USA. sds91@columbia.eduNo affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, Non-P.H.S.
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

15254482

Citation

Stellman, Steven D., and Jeanne M. Stellman. "Exposure Opportunity Models for Agent Orange, Dioxin, and Other Military Herbicides Used in Vietnam, 1961-1971." Journal of Exposure Analysis and Environmental Epidemiology, vol. 14, no. 4, 2004, pp. 354-62.
Stellman SD, Stellman JM. Exposure opportunity models for Agent Orange, dioxin, and other military herbicides used in Vietnam, 1961-1971. J Expo Anal Environ Epidemiol. 2004;14(4):354-62.
Stellman, S. D., & Stellman, J. M. (2004). Exposure opportunity models for Agent Orange, dioxin, and other military herbicides used in Vietnam, 1961-1971. Journal of Exposure Analysis and Environmental Epidemiology, 14(4), 354-62.
Stellman SD, Stellman JM. Exposure Opportunity Models for Agent Orange, Dioxin, and Other Military Herbicides Used in Vietnam, 1961-1971. J Expo Anal Environ Epidemiol. 2004;14(4):354-62. PubMed PMID: 15254482.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Exposure opportunity models for Agent Orange, dioxin, and other military herbicides used in Vietnam, 1961-1971. AU - Stellman,Steven D, AU - Stellman,Jeanne M, PY - 2004/7/16/pubmed PY - 2005/5/4/medline PY - 2004/7/16/entrez SP - 354 EP - 62 JF - Journal of exposure analysis and environmental epidemiology JO - J Expo Anal Environ Epidemiol VL - 14 IS - 4 N2 - Nearly 19.5 million gallons of herbicides were sprayed on the Republic of Vietnam between 1961 and 1971 for military purposes. Amounts of spray and patterns of applications are available in an electronic file called HERBS that contains records of 9141 defoliation missions, including detailed coordinates of US Air Force Ranch Hand aircraft flight paths, along with chemical agent and gallonage sprayed. Two classes of models for use in epidemiological and environmental studies that utilize the HERBS data for estimating relative exposure opportunity indices are presented: a discrete "hits" model that counts instances of proximity in time and space to known herbicide applications, and a continuous exposure opportunity index, E4, that takes into account type and amount of herbicide sprayed, distance from spray application, and time interval when exposure may have occurred. Both direct spraying and indirect exposure to herbicide (or dioxin) that may have remained in the local environment are considered, using a conservative first-order model for environmental disappearance. A correction factor for dermal versus respiratory routes of entry has been incorporated. E4 has a log-normal distribution that spans six orders of magnitude, thus providing a substantial amount of discrimination between sprayed and unsprayed areas. The models improve on earlier ones by making full use of the geometry of the HERBS spray flight paths of Ranch Hand aircraft. To the extent possible so many decades after the War, the models have been qualitatively validated by comparison with recent dioxin soil and biota samples from heavily contaminated areas of Vietnam, and quantitatively validated against adipose dioxin obtained in epidemiological studies of Vietnamese. These models are incorporated within a geographic information system (GIS) that may be used, as one would expect, to identify locations such as hamlets, villages, and military installations sprayed by herbicide. In a novel application, the GIS also facilitates quantitative risk assessment in epidemiological and ecological studies by applying the models within a framework of historical reconstruction of exposure history of individuals based upon their location histories. SN - 1053-4245 UR - https://www.unboundmedicine.com/medline/citation/15254482/Exposure_opportunity_models_for_Agent_Orange_dioxin_and_other_military_herbicides_used_in_Vietnam_1961_1971_ L2 - http://dx.doi.org/10.1038/sj.jea.7500331 DB - PRIME DP - Unbound Medicine ER -