Dioxin

"Dioxin" is kind of organic compound including chlorine (Cl) and, in "Act on Special Measures concerning Countermeasures against Dioxins" Article 1, is said with "material which might have a serious influence on human life and health".
As for the chemical substance made artificially, the material is made with "intention that it is going to produce", but when we burnt material including chlorine in the case of dioxin unlike this, it occurs, and it is material (material which we intended to make and did not make) generated as by-product generated at the same time in process to produce chemical substances or impurities non-intentionally, and it is said, "it is chemical substance occurring with a person's activity and does not originally exist during environment" with it is law Article 6.

Dioxin "…Not single material, it is generic name touched for group which bundled plural materials having similar chemical property as the name of kind shows.
In Act on Special Measures concerning Countermeasures against Dioxins Article 2, we define material included in three kinds of next groups varying in chemical structure as "dioxin".
1.　Polychlorinated dibenzo furan (PCDF)
2.　Polychlorinated dibenzo - Para - dioxin (PCDD)
3.　kopuranapori chlorinated biphenyl (Co - PCB)

(1)　PCDDs
"Polychlorinated dibenzo - Para - dioxin" which was 1,4-dioxin (figure 1), but is originally kind of organochlorine which is generated non-intentionally when burnt material including chlorine in the field in conjunction with environmental pollution with "dioxin" (PCDDs ： Plural s of the end called plural form) to express existing homolog "dioxin" generally.
Two (the) benzene rings (benzo) sandwich two (the = die) oxygen atoms (8-quinolinol) between, and chemical structure (figure 2) of this PCDDs is connected on the same plane, and, among eight hydrogen atoms (H) at position of 1-4 of these two benzene rings and position of 6-9 in total, 1-8 are doing substitution (polychlorinated) to chlorine atom (Cl).
The name dioxin comes from this chemical structure, and "dioxin" is English reading, and "dioxin" is German reading.

Basic structure consisting of two benzene rings is the same, but, in PCDDs, eight kinds of homologs that number of chlorine atom binding to two benzene rings is different exist (1 chloride - 8 chloride). Furthermore, the number of chlorine atoms binding to benzene ring is same (chemical formula agrees), but isomers that position where chlorine atom is connected is different exists 75 kinds theoretically.
2,3,7,8-tetrachloride dibenzo - Para - dioxin (2,3,7,8-TCDD) which four chlorine couples at position of 2, 3, 7 and 8 of benzene ring is said to be in dioxin if the toxic, and, in these 75 kinds of PCDDs, it is standard material (TEF = 1.0) when we evaluate density of dioxin (figure 5).

(2)　PCDFs
With structure chemically similar to PCDDs mentioned above, there is "polychlorinated dibenzo furan" (PCDFs) as organochlorine which is similar to the toxicity (figure 3).
This PCDFs has fewer one oxygen atom than PCDDs mentioned above and two benzene rings catch one oxygen atom between and are connected, and eight kinds of homologs and 135 kinds of isomers exist.
The name of "franc" comes from that we call five-cornered chemical structure such as home base of baseball sandwiched between two benzene rings with "franc ring".
PCDFs existed as impurities in "polychlorinated biphenyl" which was organochlorine used for insulating oil of transformer (PCB).
Generally we matched PCDDs with this PCDFs and called "dioxin" until the 1990s.
The Air Pollution Control Act was revised in August, 1997, and dioxin was added to substance regulated as "thing which must restrain the discharge or scattering immediately to prevent damage to affect a person's health among harmful air pollution materials", but dioxin of the verge was PCDDs and PCDFs.

(3)　Co-PCBs
Polychlorinated biphenyl (PCB) is organochlorine which some were substituted for with chlorine atom of hydrogen atoms constituting biphenyl (C12H10) which two benzene rings connected, but, unlike PCDDs and PCDFs mentioned above, two benzene rings are connected directly, and oxygen atom is not included, and ten kinds of homologs and 209 kinds of isomers exist.
Equivalence plane is, and there is thing having flat chemical structure (coplane-related: Coplanarity), and, in PCB, two benzene rings are called "kopuranapori chlorinated biphenyl" or "coplanar PCB" (Co-PCBs) from the chemical structure depending on position where substituted chlorine atom reaches (figure 4).
This kind of PCB resembles PCDDs and PCDFs in chemical structure to have plane structure, and it is known that it is toxic than other PCB.
In addition, there is not, and there is thing indicating the toxicity similar to dioxin in PCB doing twisted structure on the same plane, and two benzene rings classify these with "coplanar PCB" in total, and there is more than ten kinds of homologs, isomers.

Because this Co-PCBs was matter indicating the toxicity that was similar to dioxin, it was called "dioxin resemblance compound", but, in the World Health Organization (WHO), we added to previous PCDDs and PCDFs from May, 1998 and decided to include Co-PCBs in dioxin.
Therefore, in Act on Special Measures concerning Countermeasures against Dioxins Article 2 enforced in January, 2000, we define material included in these three groups where chemical structure and the toxicity are similar to as "dioxin" collectively.

Figure of chemical structure

Figure of chemical structure of three kinds of dioxin (in O oxygen atom) Some of hydrogen atoms (H) at green position replace with chlorine atom (Cl).

Figure of chemical structure

Figure of chemical structure of 2,3,7,8-tetrachloride dibenzo - Para - dioxin

Dioxin is hard to evaporate with colorless solid at normal temperature, and there is property that is easy to melt to oil (fat) although it is hard to melt in water.
In addition, it is hard to react with other chemical substances and acid, alkali and is material which is strong in heat, and is extremely stable.
In dioxin, thing having the toxicity that is extremely strong with very small amount exists.

Was chosen in one of 234 materials which might correspond to harmful air pollution material by report of the central environmental council of 1996.
Furthermore, was chosen in these 234 materials by one of 22 "approach materials given priority" which health risk was high in to some extent.
When review of harmful air pollution material was carried out in 2010, is chosen by one of 248 materials which may correspond to harmful air pollution material sequentially, and is chosen by one of 23 priority approach materials.
In addition, dioxin was substance regulated to fix for the Air Pollution Control Act, but was excluded from substance regulated of the Air Pollution Control Act with the enforcement of the Act on Special Measures concerning Countermeasures against Dioxins.

In dioxin, there is about 230 kinds of isomers by difference of position connected the number of of chlorine atom binding to two benzene rings and chlorine atom, but their toxic presence and toxic strength are different each, and thing having the toxicity is 29 kinds of those.
In addition, toxic strength of the whole dioxin is greatly different by the isomeric existence ratio of individual included in dioxin as plural isomers generally exists as mixing mixture as for dioxin in environment including the atmosphere and river.
In other words, even if it is sample of dioxin of the same quantity (weight), toxic isomers is included more, and the toxicity as the whole dioxin becomes stronger accordingly, too.
Therefore, we cannot decide toxic strength of the whole dioxin which is toxic different isomeric mixture only at weight of dioxin.
Therefore, at first, we quantify the toxic strength with some kind of standards for each individual isomers, and it is necessary to allow you to relatively compare toxic strength of every isomers when we express toxic strength (density) as the whole dioxin which is toxic different isomeric mixture.

Toxic strength (density) of dioxin is defined in the next expression.

TEQ ： Toxic equal amount (density)
fi ： Isomeric toxic equivalent dai i joint coefficient (TEF)
gi ： Isomeric abundance of dai i joint
n ： The total number of isomeric types

When we did toxic strength of toxic 2,3,7,8-tetrachloride dibenzo - Para - dioxin (2,3,7,8-TCDD) in dioxin with standard (1), with "toxic equivalent coefficient" in upper expression (TEF = Toxicity Equivalency Factor), we take value in the range of 0.0-1.0 at conversion factor that relatively expressed toxic strength of other isomers. Material of TEF = 0 is not toxic.
In addition, "toxic equal amount" (TEQ = Toxicity Equivalency Quantity) was agreement to express toxic strength (density) as the whole dioxin and, about, at first, individual isomers, we multiplied the toxic equivalent coefficient (TEF) by the abundance (weight) and calculated quantity of individual toxicity and added up quantity of toxicity about all isomers afterwards.

Based on Act on Special Measures concerning Countermeasures against Dioxins Article 7, the atmosphere, the quality of the water, environmental standard of dioxin about the soil were determined according to the next table by the Environmental Agency notification of December, 1999.
Then, by revision of environmental standard of July, 2002, environmental standard about quality of bottom of the bottom was added.