Dioxin is popular name of polychlorinated dibenzo dioxin (Polychlorinated dibenzo-p-dioxin, PCDD) and we add polychlorinated dibenzo furan (Polychlorinated dibenzofurans, PCDF) to this and are referred to "dioxin".
It is PCDD by position of chlorine that chemical structure of dioxin connected two benzene rings with oxygen, and benzene ring had isomers and number: 75 kinds, PCDF: 135 kinds exist.
Physicochemical characteristic of dioxin is stable for heat, acid and alkali, and the resolution due to living thing is extremely slow material, too. In addition, solubility to water is low and has lipophilic property. Therefore, it is material which residual property is stably high in when formed once.
In the main absorption course to people, dioxin absorbed in digestive organ, skin, the lungs in the body gets on bloodstream and is accumulated to liver and adipose tissue mainly.
In addition, dioxin is generated in combustion processes in synthesis process of chemical substance.
Historic background of dioxin
As 2,4,5-T(2,4,5-Trichlorophenoxyacetic acid), defoliant called 2,4-D(2,4-Dichlorophenoxyacetic acid) are sprayed by the Vietnam War from 1962 through 1972, and dioxin was included as impurities in this weed killer, it is pointed out that child having congenital disease was born a lot then.
Explosion accident happens in Italy, pesticides factory in Seveso (Seveso) in the suburbs of Milan in 1976, and 120 kg of dioxin is scattered, and chicken, rabbit, cat die at the outskirts, and it is reported that the birth rate of deformed child became higher.
In addition, pollution by landfill of industrial waste including dioxin became clear in New York love canal (Love Canal) in the United States in 1978, and neighboring inhabitants 239 families moved out. Dioxin was detected in Japan in 1983 by ash of city incinerator and was greatly reported in newspapers.
Half causing death density is 5,000,000ng/kg in female hamsters said to that 600ng/kg, sensitivity are the lowest in the highest male marmot of sensitivity.
For symptom observed in people and laboratory animals, there are weight loss (consumptive syndrome), thymus atrophy, liver metabolism disorder, myocardium disorder, sex hormone and the thyroid hormone metabolism and influence, acne (pimple) to lipid metabolism such as cholesterol, the central nervous system disorder.
In the long-term revelation experiment using laboratory animal, carcinogenicity of 2,3,7,8-tetrachloride dibenzo Para dioxin (2,3,7,8-Tetrachlorodibenzo-p-dioxin, 2,3,7,8-TCDD) and relation compound is shown in hepatocytes cancer, increase of squamous cancer of the lungs in rat, mouse and hamsters.
It is suggested by person of occupation revelation, survivors, epidemiological investigation about veteran of Operation dead leaf of the Vietnam War into accident to be material having possibility to produce cancer in extensive part in the group of people who received highly-concentrated revelation. However, uncertain point is left a lot for revelation evaluation in these epidemiology data.
Reproduction and saikidokusei
We strongly show the toxicity of 2,3,7,8-TCDD for laboratory animal than mother's body at stage of embryo and fetus. Cleft palate, hydronephrosis are accepted as representative teratogenicity by mouse. In addition, dioxin affects drop of fertility index, the low weight of desei* and the estrous cycle in the rats and lets you cause endometriosis by rhesus monkey.
As for reproduction in people, the influence on outbreak, growth delay of child, lack of intellect are recognized for yusho (PCDF gets mixed) in Taiwan. In addition, association between defoliant revelation and risk increase of spina bifida of the child of Vietnamese war veteran is known.
It is observed 2,3,7,8-TCDD causing thymic atrophy with decrease in unripe thymocyte by the dosage experiment to mouse. In addition, we let you control antibody production, and it is suggested that we cause change of lymphocyte.
Influence on immune system in people does not reach before knowledge arrives at unified conclusion at insufficiency.
Quantity of revelation from general living environment in our country is estimated to be 0.3 - 3.5pg/kg/day from meal, the atmosphere, water, the soil. However, as for the quantity of personal real revelation, it is thought about by difference in area or eating habits there being considerable width. When intake from fish assumes big case, also, as for the quantity of revelation, quantity of revelation around the garbage incineration facilities thought to be main outbreak source of dioxin is estimated with 1.8 - 5.1pg/kg/day 1.9 - 5.3pg/kg/day.
That may become all under such specific condition at the same level with health risk evaluation guideline level (5pg/kg/day) of the Environmental Agency.
Therefore, it is expected by point of view lowering health risk more that we plan reduction of the density in environment of dioxin in future.
In addition, a part of the Air Pollution Control Act enforcement order was revised in August, 1997, and standard about restraint of dioxin discharge from refuse incineration facilities was established.
- The Environmental Agency Planning and Coordination Bureau environment Health Department
Dioxin risk evaluation review meeting report (extract), atmosphere environmentology bulletin, 32(4), 79-109, 1997
- Masaru Tanaka et al.
Techniques (until correspondence from the human body influence to guidelines) such as prevention of outbreak of dioxin kind to affect refuse disposal, N tea S, Tokyo, 1997
- Japanese environmental Chemical Society
Current situation of dioxin pollution and correspondence, the 21st Japan environment Chemical Society lecture proceeding, 1-88, 1997
- Toshikazu Fujiwara et al.
Latest circumstances over dioxin contamination and measures, resources environment measures, 33(8), 686-713, 1997