Search results
Results from the WOW.Com Content Network
The uncertainty and variability in the dose–response relationship of dioxins in terms of their toxicity, as well as the ability of dioxins to bioaccumulate, have led WHO experts to recommending very low tolerable daily intake (TDI) of dioxin, 1-4 pg/kg body weight per day, i.e. 7x10 −11 to 2.8x10 −10 g per 70-kg person per day, to allow ...
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 in early 1983 due to TCDD (a type of dioxin) contamination, formerly the largest civilian exposure to the compound in the history of the United States.
TCDD and dioxin-like compounds act via a specific receptor present in all cells: the aryl hydrocarbon (AH) receptor. [6] [7] [8] This receptor is a transcription factor which is involved in the expression of genes; it has been shown that high doses of TCDD either increase or decrease the expression of several hundred genes in rats. [9]
They are commonly but inaccurately referred to as dioxins for simplicity, because every PCDD molecule contains a dibenzo-1,4-dioxin skeletal structure, with 1,4-dioxin as the central ring. Members of the PCDD family bioaccumulate in humans and wildlife because of their lipophilic properties, and may cause developmental disturbances and cancer .
Dibenzo-1,4-dioxin, also known as dibenzodioxin or dibenzo-p-dioxin (molecular formula C 12 H 8 O 2), in which two benzene rings are connected through two oxygen atoms. That is the parent compound of the dioxins (see next in which the dioxins comprise a key part of the class).
2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) is the reference chemical to which the toxicity of other dioxins and DLCs are compared. TCDD is the most toxic DLC known. Other dioxins and DLCs are assigned a scaling factor, or TEF, in comparison to TCDD. TCDD has a TEF of 1.0. Sometimes PCB 126 is also used as a reference chemical, with a TEF of 0.1.
(for details see Dioxins and dioxin-like compounds). Chlorinated pesticides can also contain impurities of dibenzo-p-dioxins and dibenzofurans (PCDD/Fs) and their precursors. "Precursor formation of PCDD/Fs can also be mediated by ultraviolet light (UV)" from sun (OCDD mostly). Changes in congeners ratio after UV exposition suggest that ...
[2] [3] For general population the most important source is food of animal origin like with other dioxin-like compounds. [ 4 ] [ 5 ] [ 6 ] The most relevant congener is 2,3,4,7,8-pentachlorodibenzofuran (2,3,4,7,8-PCDF) which is more toxic and based on relative toxicity more prevalent than other PCDFs.