Dioxins: Congeners Congener: a member of the same class, or group Each individual PCdd or pCdF is termed a congener There are 75 pcdd congeners and 135 PCd congeners Dibenzodioxin Dibenzofuran PCDD PCDF c0、C!c Cl Cl CI o Cl 2378-TCDD 2378-TCDF
Dioxins: Congeners Congener: a member of the same class, or group. Each individual PCDD or PCDF is termed a congener. There are 75 PCDD congeners and 135 PCDF congeners. O O Dibenzodioxin PCDD O Dibenzofuran PCDF 1 2 3 4 7 8 9 6 9 8 7 6 1 2 3 4 O O 2378-TCDD O 2378-TCDF Cl Cl Cl Cl Cl Cl Cl Cl
Toxicity of Dioxins Extraordinary toxic to lab animals (LDso in male guinea pigs is only 0.6 ug/kg) Birth defects Cancer Skin disorders Liver damage Suppression of the immune systems Variation in toxicity among species is large Male guinea pig oral, LD50 is 0.6 ug/kg Hamster, intraperitoneum LD50 is 3000 ug/kg Risk to humans is less clear
Toxicity of Dioxins • Extraordinary toxic to lab animals (LD50 in male guinea pigs is only 0.6 mg/kg) – Birth defects – Cancer – Skin disorders – Liver damage – Suppression of the immune systems • Variation in toxicity among species is large. – Male guinea pig, oral, LD50 is 0.6 mg/kg. – Hamster, intraperitoneum, LD50 is 3000 mg/kg. • Risk to humans is less clear
Human risk of dioxin exposure USEPa concludes that dioxins likely increase cancer incidence WHo classifies 2378-TCDD as a probable human carcinogen. At high levels, PCDDs cause chloracne(氯痤倉),a painful skin inflammation Risk from breathing dioxin-laden air is minimal The main exposure route for human is dietary(meat, dairy products and fish). Due to bioaccumulation of dioxins) Absorption of dioxins by infant through mothers' milk is efficient
Human risk of dioxin exposure • USEPA concludes that dioxins likely increase cancer incidence. • WHO classifies 2378-TCDD as a probable human carcinogen. • At high levels, PCDDs cause chloracne (氯痤倉), a painful skin inflammation. • Risk from breathing dioxin-laden air is minimal. • The main exposure route for human is dietary (meat, dairy products, and fish). (Due to bioaccumulation of dioxins) • Absorption of dioxins by infant through mothers’ milk is efficient
Multiple exposure pathways Emissions Affected Water media Biological Domestic Animals Vegetation
Multiple exposure pathways