In chemistry, a chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs. These are limited to a single typographic line of symbols, which may include subscripts and superscripts. A chemical formula is not a chemical name since it does not contain any words. Although a chemical formula may imply certain simple chemical structures, it is not the same as a full chemical structural formula. Chemical formulae can fully specify the structure of only the simplest of molecules and chemical substances, and are generally more limited in power than chemical names and structural formulae.
Polychlorinated biphenyls (PCBs) are highly carcinogenic chemical compounds, formerly used in industrial and consumer products, whose production was banned in the United States by the Toxic Substances Control Act in 1976 and internationally by the Stockholm Convention on Persistent Organic Pollutants in 2001.
Polychlorinated dibenzodioxins (PCDDs), or simply dioxins, are a group of long-lived polyhalogenated organic compounds that are primarily anthropogenic, and contribute toxic, persistent organic pollution in the environment.
1,4-Dichlorobenzene (1,4-DCB, p-DCB, or para-dichlorobenzene, sometimes abbreviated as PDCB or para) is an aryl chloride and isomer of dichlorobenzene with the formula C6H4Cl2. This colorless solid has a strong odor. The molecule consists of a benzene ring with two chlorine atoms (replacing hydrogen atoms) on opposing sites of the ring.
The Seveso disaster was an industrial accident that occurred around 12:37 pm on 10 July 1976, in a small chemical manufacturing plant approximately 20 kilometres (12 mi) north of Milan in the Lombardy region of Italy. It resulted in the highest known exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in residential populations, which gave rise to numerous scientific studies and standardized industrial safety regulations, including the European Union's Seveso III Directive. This accident was ranked eighth in a list of the worst man-made environmental disasters by Time magazine in 2010.
Times Beach is a ghost town in St. Louis County, Missouri, United States, 17 miles (27 km) southwest of St. Louis and 2 miles (3 km) east of Eureka. Once home to more than two thousand people, the town was completely evacuated early in 1983 due to TCDD contamination, formerly the largest civilian exposure to the compound in the history of the United States.
Chloracne is an acneiform eruption of blackheads, cysts, and pustules associated with exposure to certain halogenated aromatic compounds, such as chlorinated dioxins and dibenzofurans. The lesions are most frequently found on the cheeks, behind the ears, in the armpits and groin region.
Dibenzo-1,4-dioxin, also dibenzodioxin or dibenzo-p-dioxin (dibenzo-para-dioxin), is a polycyclic heterocyclic organic compound in which two benzene rings are connected by a 1,4-dioxin ring. Its molecular formula is C12H8O2. The two oxygen atoms occupy opposite (para-) positions in the six-membered dioxin ring.
1,4-Dioxane is a heterocyclic organic compound, classified as an ether. It is a colorless liquid with a faint sweet odor similar to that of diethyl ether. The compound is often called simply dioxane because the other dioxane isomers are rarely encountered.
2,4,5-Trichlorophenoxyacetic acid, a synthetic auxin, is a chlorophenoxy acetic acid herbicide used to defoliate broad-leafed plants. It was developed in the late 1940s, synthesized by reaction of 2,4,5-Trichlorophenol and chloroacetic acid. It was widely used in the agricultural industry until being phased out, starting in the late 1970s due to toxicity concerns. Agent Orange, a defoliant used by the British in the Malayan Emergency and the U.S. in the Vietnam War, was equal parts 2,4,5-T and 2,4-D. 2,4,5-T itself is toxic with a NOAEL of 3 mg/kg/day and a LOAEL of 10 mg/kg/day. Agent Pink contained 100% 2,4,5-T. Additionally, the manufacturing process for 2,4,5-T contaminates this chemical with trace amounts of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). TCDD is a carcinogenic persistent organic pollutant with long-term effects on the environment. With proper temperature control during production of 2,4,5-T, TCDD levels can be held to about .005 ppm. Before the TCDD risk was well understood, early production facilities lacked proper temperature controls and individual batches tested later were found to have as much as 60 ppm of TCDD.
1,4-Dioxin (also referred as dioxin or p-dioxin) is a heterocyclic, organic, non-aromatic compound with the chemical formula C4H4O2. There is an isomeric form of 1,4-dioxin, 1,2-dioxin (or o-dioxin). 1,2-Dioxin is very unstable due to its peroxide-like characteristics.
1,2-Dioxin is a heterocyclic, organic, antiaromatic compound with the chemical formula C4H4O2. It is an isomeric form of 1,4-dioxin (or p-dioxin).
Polychlorinated dibenzofurans (PCDFs) are a family of organic compounds with one or several of the hydrogens in the dibenzofuran structure replaced by chlorines. For example, 2,3,7,8-tetrachlorodibenzofuran (TCDF) has chlorine atoms substituted for each of the hydrogens on the number 2, 3, 7, and 8 carbons. Polychlorinated dibenzofurans with chlorines at least in positions 2,3,7 and 8 are much more toxic than the parent compound dibenzofurane, with properties and chemical structures similar to polychlorinated dibenzodioxins. These groups together are often inaccurately called dioxins. They are known developmental toxicants, and suspected human carcinogens. PCDFs tend to co-occur with polychlorinated dibenzodioxins (PCDDs). PCDFs can be formed by pyrolysis or incineration at temperatures below 1200 °C of chlorine containing products, such as PVC, PCBs, and other organochlorides, or of non-chlorine containing products in the presence of chlorine donors. Dibenzofurans are known persistent organic pollutants (POP), classified among the dirty dozen in the Stockholm Convention on Persistent Organic Pollutants.
Octachlorodibenzodioxin is one of polychlorinated dibenzodioxins (PCDDs).
The Irish pork crisis of 2008 was a dioxin contamination incident in Ireland that led to an international recall of pork products from Ireland produced between September and early December of that year. It was disclosed in early December 2008 that contaminated animal feed supplied by one Irish manufacturer to thirty-seven beef farms and nine pig farms across Republic of Ireland, and eight beef farms and one dairy farm in Northern Ireland, had caused the contamination of pork with between 80 and 200 times the EU's recommended limit for dioxins and dioxin-like PCBs i.e. 0.2 ng/g TEQ fat. The Food Safety Authority of Ireland moved on 6 December to recall from the market all Irish pork products dating from 1 September 2008 to that date. The contaminated feed that was supplied to forty-five beef farms across the island was judged to have caused no significant public health risk, accordingly no recall of beef was ordered. Also affected was a dairy farm in Northern Ireland; some milk supplies were withdrawn from circulation. Processors refused to resume slaughter of pigs until they received financial compensation.
Dioxins and dioxin-like compounds (DLCs) are a group of chemical compounds that are persistent organic pollutants (POPs) in the environment. They are mostly by-products of burning or various industrial processes or, in the case of dioxin-like PCBs and PBBs, unwanted minor components of intentionally produced mixtures.
Chlorinated polycyclic aromatic hydrocarbons (Cl-PAHs) are a group of compounds comprising polycyclic aromatic hydrocarbons with two or more aromatic rings and one or more chlorine atoms attached to the ring system. Cl-PAHs can be divided into two groups: chloro-substituted PAHs, which have one or more hydrogen atoms substituted by a chlorine atom, and chloro-added Cl-PAHs, which have two or more chlorine atoms added to the molecule. They are products of incomplete combustion of organic materials. They have many congeners, and the occurrences and toxicities of the congeners differ. Cl-PAHs are hydrophobic compounds and their persistence within ecosystems is due to their low water solubility. They are structurally similar to other halogenated hydrocarbons such as polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and polychlorinated biphenyls (PCBs). Cl-PAHs in the environment are strongly susceptible to the effects of gas/particle partitioning, seasonal sources, and climatic conditions.
2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) is a polychlorinated dibenzo-p-dioxin (sometimes shortened, though inaccurately, to simply 'dioxin') with the chemical formula C12H4Cl4O2. Pure TCDD is a colorless solid with no distinguishable odor at room temperature. It is usually formed as an unwanted product in burning processes of organic materials or as a side product in organic synthesis.
Toxic equivalency factor (TEF) expresses the toxicity of dioxins, furans and PCBs in terms of the most toxic form of dioxin, 2,3,7,8-TCDD. The toxicity of the individual congeners may vary by orders of magnitude.
1,2,3,4,6,7,8-Heptachlorodibenzo-para-dioxin (often referred to as 1,2,3,4,6,7,8-HpCDD) is a polychlorinated derivative of dibenzo-p-dioxin and can therefore be categorized as polychlorinated dibenzo-p-dioxin (PCDD), a subclass of dioxins which includes 75 congeners. HpCDD is the dibenzo-p-dioxin which is chlorinated at positions 1, 2, 3, 4, 6, 7, and 8. It is a polycyclic heterocyclic organic compound, since HpCDD contains multiple cyclic structures (two benzene rings connected by a 1,4-dioxin ring) in which two different elements (carbon and oxygen) are members of its rings. HpCDD has molecular formula C12HCl7O2 and is an off-white powder, which is insoluble in water.
