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Chemistry (including Biochemistry)/2,3,7,8 tetrachlorodibenzo-p-dioxin


QUESTION: Oncologist stated the chemical structure of agent orange is composed of benzene rings and it is as likely as not, that exposure to agent orange is tantamount to exposure to benzene.

Armed Forces Pest Management Board says no, that doctor is wrong about benzene.

Question: who is right ? who is wrong ? WHY ??

3D 2,3,7,8 tetrachlorodibenzo-p-dioxin
3D 2,3,7,8 tetrachloro  
3D Benzene
3D Benzene  

I think your doctor is partly right, and the Armed Forces Pest Management Board is right on a technicality. (Sneaky, no?)

Why is this?

Our understanding of benzene is that it a ring of six carbon atoms bonded each to each. The carbons in question each have one hydrogen atom poking off of it like teeth from a gear. If we map the electron density around a benzene, it averages out to a balloon like disc structure.
(See and below)

Why is benzene hazardous to your health?

1) Benzene is very non polar, or grease loving as opposed to water loving. Most biological compounds are polar or charged, and interact with water.

2) Because cellular barriers are non polar to keep water in, and benzene is non polar, it can slip between cellular barriers. If there's enough of it around, it can dissolve cellular barriers entirely. This is Not Good for the cell in question. (POP!)

3) Benzene's 3D shape and electron sharing habits make it so that it can slip between the base pairs of your DNA and hide there easily. Nucleic acid bases in DNA stack together like two towers of non polar half-coins, surrounded by a polar sugar and phosphate backbone. If you slip extra 'coins' in the stack, it creates lots of problems for the enzymes that read and copy the DNA. This results in lots more mutations than the cellular DNA error fixing enzymes can keep up with, and your chances for developing cancer skyrocket. (Uh oh)

So why is the AFPMB right on a technicality? Scientists and Army guys are very specific. If you ask them if there is benzene in something, they will look for evidence that C6H6 is there, and C6H6 alone. If they cannot find C6H6 in the sample, then there is none in there. End of story.

Why is your doctor partly right?

Agent Orange ( is made primarily of two compounds, and is often contaminated by a third. These two compounds are 2,4,5-Trichlorophenoxyacetic acid (,4,5-T) and 2,4-Dichlorophenoxyacetic acid (,4-D), with the contaminant 2,3,7,8 tetrachlorodibenzo-p-dioxin (,3,7,8-tetrachlorodibenzodioxin) you first asked about.

I'd suggest opening each of those wiki links and looking at the structures. We see attached to each chemical a familiar looking ring of six carbons arranged in a disc. However, because those rings aren't the entire compound, chemists, scientists, and Army guys do not consider that benzene. (The technicality.)

Your doctor and I know that because of the ring/gear shape, however, these compounds can still sneak through cell membranes and interfere with DNA base stacking. So the Agent Orange compounds will still hurt you in the same manner as benzene does, especially the double-wide version that is 2,3,7,8 tetrachlorodibenzo-p-dioxin. Those chlorines on the end and the oxygens hooking it together make it an even better 'substitute coin' that would interfere with a DNA stack.

Does this make sense? :) Let me know. In any case, don't go around drinking any Agent Orange. It will do you a mischief for sure.

Links for the two images in case the upload didn't work:

3D Benzene:

Agent Orange Main ingredients:


---------- FOLLOW-UP ----------

QUESTION: In 2008, I was diagnosed with Myelodysplastic Syndrome.  I filed a claim with the VA as I am a Vietnam Veteran.  My Oncologist/Hemotologist provided me with a letter stating that he had reviewed my medical history during my service in Vietnam.  He also stated it is his understanding that during that period I was exposed to Agent Orange.  He then wrote the chemical structure of Agent Orange is composed of Benzene Rings and is as likely as not that exposure to Agent Orange is tantamount to exposure to Benzene.  Benzene is a documented causative agent in the developement of Myelodysplasia.  It is my professional opinion that it is as likely as it is not that Mr. Spivey's exposure to Agent Orange is responsible for his3subsequent development of Myelodysplasia.  

The VA requested and got a report from AFPMB.  Based on this report they denied the claim stating the Dr. was all wrong and did not explain thoroughly why or how of his position.

With your expertise, would you, could you rebut this report supporting the Dr's position?  It would have to be strong enough for their review and understandable for the court.  If this is possible, I certainly would be happy to compensate you  what you feel is appropriate for this effort on my behalf.

My contact information is Tom Spivey,  

Hello Tom;

Let me know what the requirements would be; I am experienced in chemistry but not in law. I'm not sure I can help you, though I'm willing to give it a go.

I live in Houston, also, which may be a bit of a commute. ;)

I am also not a medical doctor (MD), though I was employed as a medical researcher for the last ten years.

If your lawyer could come up with an example for me to follow that won its case, that would be excellent in writing up a document for the court.

Good luck sir!

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Trista Robichaud, PhD


No homework questions, especially ones copied and pasted from textbooks. I will answer questions about principles or give hints, but I do not do other's homework. I'm comfortable answering basic biochemistry, chemistry, and biology questions up to and including an undergraduate level of understanding. This includes molecular biology, protein purification, and genetics. My training/inclination is primarily in structural biology, or how the shapes of things affect their function. Other interests include protein design, protein engineering, enzyme kinetics, and metabolic diseases such as cancer, atherosclerosis, and diabetes. My chemistry weaknesses are that I do not know organic or inorganic synthesis well, nor am I familiar with advanced inorganic reactions. I will attempt quantum mechanics and thermodynamics questions, but primarily as they relate to biological systems. Furthermore, I cannot tell you if a skin photograph is cancerous, or otherwise diagnose any disease. I can tell you how we currently understand the basic science behind a disease state, but I cannot recommend treatment in any way. Please direct such questions to your medical professional.


I hold a PhD in Biomedical Science from the University of Massachusetts Medical School in Worcester. I specialize in Biochemistry, with a focus on protein chemistry. My thesis work involved the structure and functions of the human glucose transporter 1. (hGLUT1) Currently I am a postdoc working in peptide (mini-protein) design and enzymology at the University of Texas Health Science Center in San Antonio, Texas. I am in Bjorn Steffensen's lab (PhD, DDS), studying gelatinase A and oral carcinoma.

2001 American Association for the Advancement of Science
2007 American Chemical Society
2007 Protein Society
2011 UTHSCSA Women’s Faculty Association

Levine KB, Robichaud TK, Hamill S, Sultzman LA, Carruthers A. Properties of the human erythrocyte glucose transport protein are determined by cellular context. Biochemistry 44(15):5606-16, 2005. (PMID 15823019)
Robichaud TK, Appleyard AN, Herbert RB, Henderson PJ, Carruthers A “Determinants of ligand binding affinity and cooperativity at the GLUT1 endofacial site” Biochemistry 50(15):3137-48, 2011. (PMID 21384913)
Xu X, Mikhailova M, Chen Z, Pal S, Robichaud TK, Lafer EM, Baber S, Steffensen B. “Peptide from the C-terminal domain of tissue inhibitor of matrix metalloproteinases-2 (TIMP-2) inhibits membrane activation of matrix metalloproteinase-2 (MMP-2)” Matrix Biol. 2011 Sep;30(7-8):404-12. (PMID: 21839835)
Robichaud TK, Steffensen B, Fields GB. Exosite interactions impact matrix metalloproteinase collagen specificities. J Biol Chem. 2011 Oct 28;286(43):37535-42 (PMID: 21896477)

Poster Abstracts:
Robichaud TK, Carruthers. A "Mutagenesis of the Human type 1 glucose transporter exit site: A functional study." ACS 234th Meeting, Boston MA. Division of Biological Chemistry, 2007
Robichaud TK, Bhowmick M, Tokmina-Roszyk D, Fields GB “Synthesis and Analysis of MT1-MMP Peptide Inhibitors” Biological Chemistry Division of the Protein Society Meeting, San Diego CA 2010
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Catalytic Domain Exosites Contribute to Determining Matrix Metalloproteinase Triple Helical Collagen Specificities” Dental Science Symposium. UTHSCSA 2011
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Exosite Interactions Determine Matrix Metalloproteinase Specificities” Gordon Research Conference on Matrix Metalloproteinase Biology, Bristol RI 2011

Oakland University, Auburn Hills MI BS, Biochemistry 1998
University of Massachusetts Medical School, Worcester MA PhD, Biochemistry & Molecular Pharmacology 2001-2008
University of Texas Health Science Center, San Antonio TX Postdoc, Biochemistry 2009-Present

Awards and Honors
1998 Honors College Graduate, Oakland University
2009 Institutional National Research Service Award, Pathobiology of Occlusive Vascular Disease T32 HL07446
2011 1st Place, Best Postdoctoral Poster, Dental Science Symposium, UTHSCSA, April 2011

Past/Present Clients
Invited Seminars:
Robichaud TK, Fields GB. “Synthesis and Analysis of MTI-MMP Triple Helical Peptide Inhibitors” Pathology Research Conference, University of Texas Health Science Center San Antonio Pathology Department (June 18th, 2010)
Robichaud TK & Hill, B “How To Give A Great Scientific Talk” Invited Lecture, Pathobiology of Occlusive Vascular Disease Seminars, UTHSCSA (Nov 11th 2010), Cardiology Seminar Series, Texas Research Park (Feb 21st, 2011)
Robichaud TK; Tokmina-Roszyk D; Steffensen B and Fields GB “Exosite Interactions Determine Matrix Metalloproteinase Specificities” Gordon-Keenan Research Seminar “Everything You Wanted to Know About Matrix Metalloproteinases But Were Afraid to Ask” Bristol, RI (Aug 6th, 2011)

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