 What are Dioxins？ |
| The term"Dioxins" are defined to include
PCDDs, PCDFs, Co-planar PCBs by the Law Concerning Special Measures against Dioxins.The
general structures of dioxins molecule are shown on the Fig.1. The numbered positions in
this figure are attached by chlorine. |
Fig.1 |
| Kinds and Toxicity of Dioxins |
| There are 75 kinds of PCDDs, 135 kinds
of PCDFs and more than 10 kinds of PCDFs by the difference of attached position by
chlorine. And 29 kinds of Dioxins have toxicity. Toxicity of dioxins varies from compound
to compound. 2,3,7,8- TCDD (Fig.2) is known to possess the highest toxicity. |
Fig.2 |
|
| Characteristic of Dioxins |
| Dioxins are generally quite stable. They in general are
colorless solids with properties of high fats and oils solubility . They do not reacting
easily to other chemical substances and acids, but are tough to gradually decompose with
exposure of ultraviolet light. |
| Units |
| Even if the amounts of dioxins are extremely small,
their toxicity is so strong that we have to consider the influence on people and
environment. "ppt" is one of the measurement units, and
"ppt" is useful to indicate the micro level of concentration. "ppt"
means 10 to the minus 12. |
 |
|
 |
If water were held in a container of the size of Tokyo
Dome and a cube of sugar were dissolved in the water, the result would be 1 ppt
level |
|
| The acute toxicity of dioxins |
- This figure shows the acute toxicity comparison between dioxins, sarin,
cyanide and DDT. It is said that dioxins are “the most toxic of the man-maid
chemicals”.
|
|
 |
| Emissions of dioxins |
| It is assumed that about 90% of the dioxins emissions
comes from the incineration of household and industrial waste in Japan. |
 |
|
| Impact of dioxins on the environment |
| The average dioxin concentrations in the environment in Japan
revealed in a 1999 survey are about 0.18pg/m3 for the ambient air and about 6.5pg/g for
the soil and about 0.24pg/l for the water . |
| Summary |
| We should realize that a serious issue that we are
facing is not acute toxicity of high doses of dioxins but chronic toxicity of extremely
small doses of dioxins. Then we should do research on how much dioxin we take in every day
life and what the risks of dioxins to humans are. For those purposes, researches are
taking place about how dioxins are formed, environmental assessment of dioxins, analyzing
technique, concentration of dioxins in foods and breast milk. Dioxins are not produced
intentionally. Since dioxins are emitted by incineration, reducing the amount of
waste is an effective way to lessen dioxin release. So we should clearly recognize
the importance and emergency of dioxins issue one by one, and try to reduce dioxins
emission. Not only leadership of government, but also personal efforts can
contribute to the serious issue. |
| literature cited：Ministerial Council on Dioxins Policy 「Dioxins 2001」 |
