- The text on this page has been taken from an equivalent page of the IEHIAS-project. For the main article of this topic, see Dioxin.
- A theoretical maximum of 75 polychlorinated dibenzo-p-dioxins and 135 polychlorinated dibenzofurans.
- Dioxins are generally present as a mixture of compounds, and therefore toxicity and effects are expressed in toxic equivalency factors (TEFs).
- The most toxic dioxin, 2,3,7,8-TCDD has a TEF value of 1 and the toxicity of all other dioxins and furans is expressed relative to this value (range: 1-0.0003).
Dioxins as a biomarker
Sample collection and storage
- Adipose tissue but mainly blood and breast milk have frequently been used as matrices for dioxins
- Expressed on a lipid basis, correlations between different tissues are generally good.
- For the general population, more than 90% of the total daily intake is derived through food
- For different European countries, total daily intake is around 0,8-2 pg TEQ/kg body weight/day.
- Dioxins are generally very resistant to metabolization and excretion, with half-lives of several years.
Standard sampling methods for blood, adipose tissue or breast milk should be followed. Samples are stored at -20°C.
- Mostly combinations of high resolution gas chromatography and mass spectroscopy (HRGC/HRMS).
- Bio-analytical methods (in vitro and ligand binding assays) have been developed as a rapid, relatively cheap and sensitive alternatives, though they cannot replace chemical-analytical methods.
- For milk and serum, levels of detection for individual congeners are around 0,05 pg/g lipid.
- For almost 20 years, WHO/EURO has been coordinating inter-laboratory quality assessment studies for dioxins in breast milk ald blood.
- Generally good inter-laboratory comparability (relative standard deviations of 13%), though variability for individual congeners can be considerably higher.
Analytical methods have been validated by several international agencies (e.g. USEPA, EC).
Age, food patterns, body mass index and gender can have profound effects on dioxin levels in human tissues.
Concentrations reported in literature:
- Median dioxin levels in breast milk ranged from 3,34–22,3 pg/g fat
- Concentrations in blood are reported to be around 20-60 pg TEQ/g fat.
- Daily intake concentrations are estimated to be around 0,8-2 pg TEQ/kg bw/day.
- Critical total daily intake values are around 1-4 pg TEQ/kg bw/day
- Several dioxins are presumed to be human carcinogens, both for acute short term, and chronic long term exposure.
- Dioxin TEQ exposures within roughly 3-fold of current background levels may be carcinogenic.
- There are indications that in utero exposure to dioxins may result in (neuro)developmental delays, chloracne, alteration of thyroid hormone status and decreased long function.
Time trend, geographical variation, susceptibel groups:
- Dioxin levels in breast milk are decreasing, in some countries up to 50%.
- Global dioxin levels are highest in Western Europe highest.
- Babies, small children, and humans exposed through diet, are the most susceptible groups.