Forwarded by Jim Tichacek, RAO Bulletin, firstname.lastname@example.org
The February edition of the Journal of Occupational and Environmental Medicine. contains a new analysis of cancer incidence among Air Force veterans of the Vietnam War. It found increased risks of prostate cancer and melanoma in those who sprayed Agent Orange and other herbicide.
The article, written by members of the Air Force Health Study on Operation Ranch Hand, indicates that a statistical adjustment for years served in Southeast Asia (SEA) reveals increased risks of prostate cancer, melanoma and cancer at any anatomical site among those with the highest dioxin exposure. Previous results of the Study's research had found no consistent evidence that Agent Orange is related to cancer.
The National Academy of Sciences will review this study along with many other studies on herbicide and dioxin exposure to make a report to the Secretary of Veterans Affairs to assist decisions related to compensation.
The study included veterans of Operation Ranch Hand, the unit responsible for the aerial spraying of Agent Orange and other herbicides in Vietnam, and comparison Air Force veterans who served in SEA during the war but did not spray herbicides. Since the first health examination in 1982, the Air Force has tried to determine whether long-term health effects exist in the Ranch Hand flyers and ground crew, and if they can be attributed to the herbicides used in Vietnam.
The study included two parts: external contrasts with the national population and internal contrasts with adjustments for years served in the SEA region. In both parts, researchers defined cancer as specified by the Surveillance Epidemiology and End Results (SEER) section of the National Cancer Institute. Contrasts with the national population revealed increased risks of melanoma in Ranch Hand veterans and an increased risk of prostate cancer in Ranch Hand and comparison veterans.
The significantly increased standardized incidence ratios ranged from 1.46 to 2.33. The elevated risks could be partly due to increased case finding as a result of extensive screening at the periodic Air Force Health Study physical examinations.
The study also found a significant decrease in cancer of the digestive system in the Ranch Hand group and a significant decrease in cancer of the urinary and lymphopoietic systems in the comparison group. No significant increase in the risk of death from cancer was found in either the Ranch Hand or the comparison group when compared to national rates.
The second part of the study contrasted Ranch Hands in high, low and background dioxin exposure categories with comparisons. Years in SEA confounded the analysis. Following standard statistical procedures, investigators stratified by this confounding variable. Among those who served no more than two years in SEA, Ranch Hand veterans with the highest dioxin levels were found to exhibit an increased risk of cancer at any anatomical site, prostate and melanoma. The relative risk for “any site cancer” in the high dioxin category was 2.02 with a 95 percent confidence interval of 1.03 to 3.95. Increases in the risk of prostate cancer and melanoma were higher but based on small numbers, and the confidence intervals were wide. Of 65 “any site cancers” in the Ranch Hand group, 21 were of the prostate and 11 were melanoma.
Study methods were derived from discussions with the Ranch Hand Advisory Committee, a non-governmental panel of scientists appointed by the Food and Drug Administration to oversee the study.
Dioxin exposures of members of the Ranch Hand unit were probably greater than those experienced by the average Vietnam veteran. The study is limited by its sample size, preventing detailed analysis of rare cancers, and by uncertainties regarding dioxin exposure. The dioxin determinations were accurate but were measured 15-30 years after service in the Ranch Hand unit.
The study interpretations are limited because other environmental exposures were not measured. Study strengths include record verification of all cancer cases and rigorous quality control. Extrapolation to other Vietnam veterans is not possible with these data.
Associations found in this study do not imply causation. Publication of the Ranch Hand data and findings in the peer-reviewed journal will allow further discussion of the conclusions and implications by the scientific community at large.
For more information, contact the Air Force Surgeon General's Office at (202) 767-4797 or access the Ranch Hand Study website www.brooks.af.mil/AFRL/HED/hedb/afhs/afhs.shtml.
Source: Secretary of the Air Force, Directorate of Public Affairs, Press Release - No. 0122046, dated 22 January 2004.