Seveso dioxin

One toxic effect of the Seveso dioxin exposure was on reproduction. In the first 7 years after the accident, a very high proportion of females (46 females compared to only 28 males) were born to parents who were exposed to the chemical cloud. This was the first time a chemical had been observed to change the sex ratio, implicating dioxin as a hormone disrupter. TCDD is associated with increased fetal loss and reduced birth weight in animal studies. 

In this case, [b,e] is omitted after dibenzo since there is no other possibility for ring fusion. This compound is also known as TCDD or Seveso dioxin. 

Polychlorinated dibenzo-1,4-dioxins are extremely toxic compounds [127] which are difficult to degrade biologically. This especially applies to 2,3,7,8-tetrachlorodibenzo[l,4]dioxin 15 (Seveso dioxin, TCDD) which is teratogenic. TCDD (LD50 = 45 pg kg" in rats) is formed as a byproduct in the commercial synthesis of 2,4,5-trichlorophenol 14. It is an intermediate in the production of the germicide hexachlorophene 16 and the herbicide (2,4,5-trichlorophenoxy)acetic acid 17 ... 

Example (The permutational isomers of Seveso dioxin) We should like to evaluate the 22 permutational isomers of tetrachlorodibenzo-p-dioxin. The chemical formula is C12 H4CI4 O2, and the skeleton of this particular type of dioxin is of the following form ... 

As in the construction of the multigraphs and isomers of Seveso dioxin, we use the decomposition of the distributions S into distributions with the same content... 

The Seveso disaster took place on July 10,1976, when a toxic cloud escaped from the ICMESA chemical plant located in the community of Mead in Lombardy (Italy). The accident was caused by reactor overheating which served to produce 2,4,5-trichlorophenol. At the beginning, a certain vagueness was involved about the released product. There was some thought about 1,2,4,5-tetrachlorobenzene and of polyethylene, but the development of chloracne allowed identification of 2,3,7,8-TCDD, called the Seveso dioxin. 

Each industrial accident has provided valuable lessons for industriahsts and public authorities alike. The Seveso dioxin accident, for example, was the reason behind two European directives concerning industrial safety. Nevertheless, chemists know better than anyone else that there is no such thing as zero risk of accidents. The case of the AZF plant in Toulouse demonstrates that even an approved installation boasting a certificate of conformity with ISO norms can explode causing considerable damage. Despite the omnipresence of its products in our daily fives, therefore, chemistry remains a somewhat wild and unpredictable force. The apparently irreducible fact that chemistry poses a threat means that it needs to be strictly supervised and monitored. 

There have been suggestions of alterations in sex ratios following accidental environmental exposure to dioxin in Seveso, Italy, in 1976. Between 1977 and 1984, 74 births occurred in the most heavily contaminated zone which showed an excess of females (26 males and 48 females born). Preliminary evidence suggests that the excess was associated with high dioxin exposure in both parents. Over a later period, between 1985 and 1994, the ratio declined (60 males and 64 females) and was no longer statistically significant. 

Seveso, Italy, caused wide-spread pollution of the industrial site as well as its surroundings. Serious effects of dioxin were detected both in dontestic animals, such as cows and sheep, and in humans, the most serious early effects being a serious skin disease, chloracne, and alterations in the function of the immune system. Follow-up studies have demonstrated that this accident also increased the cancer risk in exposed individuals. ... 

The use of an unnecessarily hot heating medium led to the runaway reaction at Seveso, Italy, in 1976, which caused a fallout of dioxin over the sun ounding countryside, making it unfit for habitation. Although no one was killed, it became one of the best-known chemical accidents, exceeded only by Bhopal, and had far-reaching effects on the laws of many countries. 

Site-specific Dioxins (Seveso, Love Canal, and Times Beach)... 

Many accidents resulting from dangerous reactions have a history of repeating themselves over the years, without the lessons of history being properly drawn. For example, the accident at Seveso, arising from difficulties in controlling the reaction temperature of sodium hydroxide with 1,2,4,5-tetrachlorobenzene, had already happened three times a few years before. The symptoms due to acute intoxication caused by dioxin were already known. 

Fanelli, R., M.P. Bertoni, M. Bonfanti, M.G. Castelli, C. Chiabrando, G.R Martelli, M.A. Noe, A. Noseda, S. Garattini, C. Binaghi, V. Marazza, F. Pezza, D. Pozzoli, and G. Cigognetti. 1980a. 2,3,7,8-tetrachlorod-ibcnzo-p-dioxin in cow s milk from the contaminated area of Seveso, Italy. Bull. Environ. Contam. Toxicol. 24 634-639. 

A reaction at the interface caused by a loss of mixing can eventually lead to a runaway itself. Examples include nitration processes and the well-known Seveso incident where agitation stopped in a reactor during the manufacture of trichlorophenol this led to higher than normal temperatures and increased production of the undesirable side product 2,3, 7,8-tetrachlorodibenzo-p-di-oxin (commonly referred to as "dioxin"), ultimately resulting in a vapor release to the atmosphere. 

The 1976 runaway reaction at Seveso, Italy that resulted in the contamination of several square miles of land with dioxin... 

On July 9, 1976, in Meda, Italy, near Seveso, a chemical reactor incident caused a release of dioxin (TCDD), which is a highly toxic chemical. The regulatory requirements developed as a result of this incident are referred to as the Seveso Directive. 

Baccarelli A, Mocarelli P, Patterson DG, et al. Immunologic effects of dioxin new results from Seveso and comparison with other studies. Environ Health Perspect 2002 110(12) 1169-73. 

Most, if not all, occupational illnesses associated with 2,4,5-T (such as chloracne) have been found to be the result of product contamination with TCDD. TCDD is extremely toxic to animals, and exposure has also been associated with liver function impairment, peripheral neuropathy, personality changes, porphyria cutanea, hypertrichosis, and hyperpigmentation in humans. TCDD is a chlorinated dioxin, one of a large number of related compounds referred to as dioxins it has no functional use and is not intentionally produced. It has been identified as the responsible toxic agent in several industrial disasters, such as accidental releases at Nitro, WV in 1949, and at Seveso, Italy in 1976. " The role of dioxin contaminants must also be considered in the discussion of 2,4,5-T toxicology. 

A plant manufacturing 2,4,5-trichlorophenol in Seveso, Italy exploded and liberated substantial amounts of TCDD (dioxin). Although it caused quite a scare and the town was evacuated, there were no known deaths and no increase in birth defects reported. Some chloracne (a skin disease) occurred and one liver cancer was diagnosed. 

There have been occasions in which relatively large quantities of dioxins were released as the result of chemical or industrial accidents. Explosions at chemical plants in Seveso, Italy, in 1976 and at Bhopal, India, in 1984 are examples of such incidents. High levels of dioxin have also been found in animal feed on a few occasions the source and mechanism of this contamination have not always been clear. 

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