Agent Orange, toxicity

Stevens KM. 1981. Agent Orange toxicity A quantitative perspective. Hum Toxicol 1 31-39. 

The famous herbicide agent orange contained as an additive 2,3,7,8-tetrachlordibenzo-p-dioxin (2,3,7,8-TCDD), the most toxic chemical substance created by mankind. Dioxin makes up about 150-160 kg. in 24,000 tons of herbicide 2,4,5-T. This additive is enough to allow us to continue to discuss the consequences to humans and the environment in Vietnam from not one, but two wars the herbicide and the dioxin [65]. 

Herbicides are designed to kill plants, not animals, and in general have lower mammalian toxicity than insecticides. Most herbicides interfere with plant hormones or enzymes that do not have any direct counterpart in animals. The most serious human health concerns have been related to contaminants of the primary chemical herbicide. There is an enormous amount of animal and some human toxicity data on 2,4-D and 2,4,5-T, but it now appears that much of this toxicity is caused by the contaminant TCDD. Military personnel exposed to Agent Orange, often contaminated with TCDD, reported birth defects, cancers, liver disease, and other illness. These concerns led to improvement in the manufacturing process to reduce TCDD contamination and ultimately to a reduction in use of 2,4-D herbicides. There is also concern that some herbicides may affect wildlife. For example, atrazine, a persistent herbicide, may adversely affect frogs. Persistence of herbicides may also... 

Agent Orange A toxic defoliant containing dioxin, of which some 64 million liters were dropped by the U.S. on Vietnam during the war, subsequently causing deformations in babies. 

Green, Michael D. 1992. Expert Witnesses and Sufficiency of Evidence in Toxic Substance Litigation—The Legacy of Agent Orange and Bendectin Litigation. Northwestern University Law Review 86(3) 643-99. 

Le, K.S., 2002. Agent orange in the Vietnam War. Paper presented at the GEF Regionally Based Assessment of Persistent Toxic Substances First Technical Working Group Meeting, Singapore, February 2002. 

Dioxin is a common name for dibenzo-l,4-dioxane, which is 1,4-dioxane fused with two benzene rings. The name dioxin is often used incorrectly in the news media for 2,3,7,8-tetrachlorodibenzodioxin (TCDD), a toxic contaminant in the synthesis of the herbicide called 2,4,5-T or Agent Orange. Surprisingly, TCDD has been in the environment for many millions of years because it is also formed in forest fires. Most dioxins are toxic and carcinogenic (cause cancer) because they associate with DNA and cause a misreading of the genetic code. 

The Seveso disaster began on July 10, 1976 at the Industrie Chimiche Meda Societa Azionaria (ICMESA) chemical plant in Meda, Italy. This event became internationally known as the Seveso disaster, after the name of the most severely affected community. An increase in pressure due to an exothermic reaction in a 2,4,5-trichlorophenol-production reactor caused the rupture disk of the safety valve to burst. About 3000 kg of chemicals were released into the air. The release included 2,4,5-trichlorophenol, used in the manufacture of herbicides, and possibly up to 30 kg of the dioxin TCDD (2,3,7,8-tetrachloro-dibenzo-p-dioxin). Dioxin first came to widespread public notice during the Vietnam War, when it was identified as a component of the defoliant Agent Orange. Dioxin has also been considered to be the most toxic human-made substance. 

Agent Orange. A toxic herbicide and defoliant containing 2,4,5-trichlorophenoxyacetic acid (2,4,5-T) and 2,4-dichlorophenoxyacetic acid (2,4-... 

Dioxins are a family of heterocyclic hydrocarbons, mostly poisonous chemical by-products of the manufacture of certain herbicides and bactericides. The most toxic are polychlorinated dibenzo-p-dioxins (CDDs) and dibenzo-furans (CDFs, also called dioxins) [514,515]. Amongst the most dangerous are the isomers of the 2,3,7,8-tetrachlorodibenzo-para-dioxin (TCDD) and 2,3,7,8-tetrachlorodibenzo-furan (TCDF). The former occurs in small amounts in some herbicides and defoliants, including the so-called Agent Orange (a highly toxic herbicide sprayed as a defoliant in chemical warfare) [466]. 

---