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  • Letter to the Editor
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Reply to “Agent Orange exposure modeling: fallacies and errors”

Journal of Exposure Science & Environmental Epidemiology volume 24, pages 445–446 (2014)Cite this article

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The letter titled “Agent Orange exposure modeling: fallacies and errors” by Drs. Steven D. Stellman and Jeanne M. Stellman1 criticized aspects of Ginevan et al.2 We would initially like to address some matters of fact. First, the version of the model we tested in our paper was reviewed (but not tested) by the Institute of Medicine (IOM).3, 4 The disk we used to install the model was obtained from the Academy’s public access records office.3 Second, we have published two papers evaluating the Stellman model. One paper2 shows that the predictions of the Stellman model differ dramatically from (a) measured deposition patterns and (b) predictions of other, well-validated, spray deposition models for the spray system used for over 90% of the herbicide application in Vietnam. The second paper5 indicates that the Stellman model is apparently not self-consistent as its predictions vary by more than 1000-fold for points that should have similar E4 scores.

The Stellman letter states that they were unable to match our calculations of E4 scores and provides tables in its supplementary materials to support this fact. It is true that their calculated numbers are not exactly the same as ours, but the differences are modest. For over half the locations reported in the study by Ginevan et al.,2 the difference between our results and theirs is less than 10%. Moreover, general patterns are similar. For the 18 points on the flight path, our E4 results range from 118,336 to 536,367 with an average of 315,328. The Stellman results for the same points range from 156,354 to 609,500 with a mean of 392,134. Similarly, for the 18 points 4 km from the flight path, our E4 scores range from 64,161 to 215,154, with a mean of 120,584 and the Stellman’s range from 64,161 to 215,254, with a mean of 121,190. The disagreements that do exist may be due to the fact that we did not provide exact latitude and longitude for our test data points. To avoid further confusion we have prepared two spreadsheets titled “TestPointsGinevanA.XLS” and “TestPointsGinevanB.XLS” and will make these available to interested parties. These include latitude and longitude coordinates for all test points from both our papers2, 5 listed by mission number, location code and dates. With this information anyone who has the version of the Stellman model tested in our papers can replicate our results.

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References

  1. Stellman SD, Stellman JM . Agent Orange exposure modeling: fallacies and errors. J Expos Science Environ Epidemiol 2014; 24: 444–445.

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  2. Ginevan ME, Ross JH, Watkins DK . Assessing exposure to allied ground troops in the Vietnam war: a comparison of AgDRIFT and Exposure Opportunity Index models. J Expos Science Environ Epidemiol 2009; 19: 187–200.

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  3. Institute of Medicine (IOM). The Utility of Proximity-Based Herbicide Exposure Assessment in Epidemiologic Studies in Vietnam Veterans. The National Academies Press: Washington, DC. 2008.

  4. HEA-V (Herbicide Exposure Assessment–Vietnam). CD-ROM, version 1.0.2. Software and accompanying electronic documentation. Columbia University: New York. 2003.

  5. Ginevan ME, Watkins DK, Ross JH, O’Boyle RA . Assessing exposure to allied ground troops in the Vietnam War: a quantitative evaluation of the Stellman Exposure Opportunity Index model. Chemosphere 2009b; 75: 1512–1518.

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  6. Ross J, Ginevan M Comments to the IOM Committee regarding discussions of exposure evaluation and modeling in two recent IOM reports. In public access file for the committee to review the health effects in Vietnam veterans of exposure to herbicides: Ninth Biennial update (received 24 October 2012) 2012.

  7. Ginevan ME, Watkins DK . Logarithmic dose transformation in epidemiologic dose-response analysis: use with caution. Regul Toxicol Pharmacol 2010; 58: 336–340.

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Authors and Affiliations

  1. M.E. Ginevan & Associates, 307 Hamilton Avenue, Silver Spring, 20901, Maryland, USA

    Michael E Ginevan & Deborah K Watkins

  2. risksciences.net, LLC, 5150 Fair Oaks Blvd., Suite 101-370, Carmichael, 95608, California, USA

    John H Ross

Authors
  1. Michael E Ginevan
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  2. John H Ross
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  3. Deborah K Watkins
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Correspondence to Michael E Ginevan.

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Ginevan, M., Ross, J. & Watkins, D. Reply to “Agent Orange exposure modeling: fallacies and errors”. J Expo Sci Environ Epidemiol 24, 445–446 (2014). https://doi.org/10.1038/jes.2014.29

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