Agent Purple

Agent Purple is the code name for a powerful herbicide and defoliant used by the U.S. military in their herbicidal warfare program during the Vietnam War. The name comes from the purple stripe painted on the barrels to identify the contents. Largely inspired by the British use of herbicides and defoliants during the Malayan Emergency, it was one of the so-called "Rainbow Herbicides" that included the more infamous Agent Orange. Agent Purple and Orange were also used to clear brush in Canada.

Ranch Hand UC-123B spraying defoliant in 1962

Agent Purple was chemically similar to the better-known Agent Orange, both of them were consisting of a mixture of the herbicides 2,4-D and 2,4,5-T and in both cases the 2,4-D and 2,4,5-T constituted equal shares of the Agent.[1] The difference was in the form of 2,4,5-T. While all the 2,4,5-T in Agent Orange was as the n-butyl ester, the 2,4,5-T in Agent Purple was itself mixture of n-butyl and isobutyl ester forms (60%:40% respectively).[1] The Agent Purple had then the following composition: 50% n-butyl ester 2,4-D, 30% n-butyl ester 2,4,5-T, and 20% isobutyl ester 2,4,5-T.[1]

Even prior to Operation Ranch Hand (1962-1971) it was known[2][3][4][5][6][7] that 2,4,5-T, and thus Agents Purple, Pink, Green and Orange, were contaminated with tetrachlorodibenzodioxin (TCDD), an extremely toxic and persistent by-product formed during synthesis. Dioxin-levels varied considerably from batch to batch, and even within the same batch; generally, agents produced earlier, such as Purple and Pink suffered from higher levels of contamination. A 2003 Nature paper by Stellman et al., which re-apprised the average TCDD content of Agent Orange from the 3 ppm that USAF had reported to a level of 13 ppm, also estimated that Agent Purple may have had 32.8 ppm of TCDD on average. A sample of Agent Purple archived at Eglin Air Force Base had an even higher content of 45 ppm TCDD.[8]

Agent Purple was used only in the earliest stages of the spraying program, between 1962 and 1965 as well as in earlier tests conducted by the US military outside of Vietnam.[9] About 500,000 gallons were sprayed in Vietnam total. (~1.9 million liters).[10] When the need to clear brush around CFB Gagetown in Canada arose, quantities of Agent Purple and Agent Orange were also sprayed there in a testing program during 1966 and 1967.[11][12]

References
  1. National Defence and the Canadian Forces: Health Information Summary for CF Members Archived 2012-12-09 at the Wayback Machine Date Modified: 2012-01-13; Subpage of DND CF The Use of Herbicides at CFB Gagetown from 1952 to Present Day Archived December 12, 2011, at the Wayback Machine Project
  2. Berufliche Akne (sog. Chlorakne) durch chlorierte aromatische zyklische Äther Von J. Kimmig und K. H. Schulz in Dermatologica Vol. 115, 1957, p.540-6 (German; with English and French summaries; cited in CA 1958:22227) (accessed 2013-07-29)
  3. Table TCDD-UNFÄLLE - Eine Bilanz des Schreckens pp. 54-59 in Seveso ist überall - Die tödlichen Risiken der Chemie by Egmont R. Koch, Fritz Vahrenholt; 1978, ISBN 3 462 012908 (accessed 2013-07-29)
  4. p. 49 in Seveso ist überall - Die tödlichen Risiken der Chemie by Egmont R. Koch, Fritz Vahrenholt; 1978, ISBN 3 462 012908
  5. Peter H. Schuck: Agent Orange on Trial: Mass Toxic Disasters in the Courts p. 17 (accessed 2013-07-29)
  6. "Chemical companies, US authorities knew dangers of Agent Orange" Archived 2016-08-22 at the Wayback Machine by Jon Dillingham; August 10, 2009 (accessed 2013-07-29)
  7. REPORT TO SECRETARY OF THE DEPARTMENT OF VETERANS AFFAIRS ON THE ASSOCIATION BETWEEN ADVERSE HEALTH EFFECTS AND EXPOSURE TO AGENT ORANGE Archived 2016-04-06 at the Wayback Machine as Reported by Special Assistant Admiral E.R. Zumwalt, Jr., May 5, 1990 (accessed 2013-07-29)
  8. Stellman, Jeanne et al. The Extent and patterns of usage of Agent Orange and other herbicides in Vietnam Nature, Vol. 422 (17 April 2003) pp. 681 - 687 (accessed 2013-07-29)
  9. Agent Orange: Herbicide Tests and Storage in the U.S. Veterans Administration Website
  10. Stellman Jeanne et al. page 682
  11. "The Use of Herbicides at CFB Gagetown from 1952 to Present Day" Archived December 12, 2011, at the Wayback Machine, Canadian Department of National Defence
  12. "Agent Orange and Agent Purple", CBC News, 21 August 2007
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