Dioxin be the Most Toxic Substance

Eisler (2000) Handbook of chemical risk assessment, vol. 2. Lewis Publishers, Boca Raton, pp. 1021-1056. 

Kiviranta (2005) Exposure and human PCDD/F and PCB body burden in Finland. Ph. D. dissertation, Kuopio. 

Tuomisto, J. Tuomisto, M. Tainio, M. Niittynen, P. Verkasalo, T. Vartiainen, H. Kiviranta, J. Pekkanen (2004) Risk-benefit analysis of eating farmed salmon. Science 305 (5683), 476-All. http //www.sciencemag.org/content/305/5683/476 (last access February 25, 2014). 

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Tests with animals have revealed that dioxin is one of the most toxic substances known Toward mice it IS about 2000 times more toxic than strychnine and about 150 000 times more toxic than sodium cyanide Fortunately however available evidence in dicates that humans are far more resistant to dioxin than are test animals and so far there have been no human fatalities directly attributable to dioxin The most prominent short term symptom seen so far has been a severe skin disorder known as chloracne Yet to be determined is the answer to the question of... 

Chlorinated dibenzo-p-dioxins and dibenzofurans are among the most toxic substances known, especially 2,3,7,8-tetrachloro-p-dibenzodioxin (TCDD). These extremely hazardous compounds can be produced from 3,4,5- and 2,4,5-trichlorophenols by peroxidases [207]. However, the biological formation of such toxicants in nature or by microorganisms has not been described. 

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. 

Chlorinated dibenzo-p-dioxines and dibenzofurans are tricyclic aromatic compounds [4], characterized by a high chemical resistance and an ability to be accumulated in the nutritional chain. Some of them are extremely toxic, teratogenic, mutagenic and probably also carcinogenic. The most studied substances in this group are 2,3,7,8-tetrachloro-dibenzodioxine (TCDD) and 2,3,7,8-tetrachloro-dibenzofuran (TCDF), which are among the most toxic substances... 

According to the Bay Area Air Quality Management District in San Francisco, more than 5.5 million pounds of toxic chlorinated substances are released in the area annually. This includes approximately 13,000 pounds of chloroform, 1.4 million pounds of freon, 2 million pounds of perchloromethylene, and trace amounts of dioxin. (Dioxin is one of the most toxic chemicals known.) A report released in September 1994 by the U.S. Environmental Protection Agency (EPA) clearly describes dioxin as a serious public health threat. The public health impact of dioxin may rival the impact that DDT had on public health in the 1960s. According to the EPA report, not only does there appear to be no safe level of exposure to dioxin, but levels of dioxin and similar chemicals have been found in the U.S. population that are at or near levels associated with adverse health effects. The EPA report also confirmed that dioxin is a cancer hazard, exposure... 

Perhaps the most renowned example is the extensively-used 2,4,5-T (2,4,5-trichlorophenoxyacetic acid), or rather the 2,3,7,8-tetrachlorodibenzo- -dioxin (TCDD) impurity which sometimes accompanies it. During massive use of the herbicide as a defoliant in the Vietnam war, TCDD was found almost by accident to be one of the most toxic synthetic substances ever tested. Soon, it was shown to be present in domestic 2,4,5-T as well as in the chemical warfare agents. Tests in laboratory animals demonstrated that some of the observed levels indeed were quite high enough to cause toxic effects (32). 

Binding of chemicals to other substances can greatly affect toxicity. The classic example of this is the administration of charcoal or burnt toast to people who have ingested poisons, to adsorb the chemical and prevent GI absorption. Lipophilic chemicals for which this mechanism would be most likely (e.g., dioxins), tend to bind tightly to sediments, and therefore are filtered out in water treatment plants, so they do not get delivered to the tap. If found in tap water, their GI absorption is also likely to be low. 

The physical, chemical and hazardous properties of a number of highly toxic or flammable substances that were in the past or being currently used in the warfare have been discussed in detail in several chapters in this book. Some of these compounds are further discussed under specific chapters, such as. Sulfur Mustards, Nerve Gases, Dioxin and Related Compounds and Napalm. These and many other compounds are in most cases grouped together in this book based on their chemical structures along with their toxic or flammable properties. Presented below is a brief discussion on various types of chemicals weapons developed for military applications. Explosive substances have been omitted from this section. They are discussed separately in this book under topics such as Explosive Characteristics of Chemical Substances, Nitro Explosives, Oxidizers and Organic Peroxides and also under specific title compounds in various chapters. 

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