Polybrominated dibenzodioxins and dibenzofurans

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General structure of polybrominated dibenzo- p- dioxins
General structure of polybrominated dibenzofurans

Polybrominated dibenzodioxins and dibenzofurans (abbreviated to PBDD / PBDF ) are a group of chemicals that correspond to the polychlorinated dibenzodioxins and furans both in their chemical structures and in their effects. They are caused by the combustion of leaded gasoline or the thermal decomposition of plastics that contain brominated flame retardants .

Emergence

Waste incineration is considered to be the main entry route into the environment. In the fly ash from waste incineration plants , the amount of bromine-containing PBDD / PBDF is only a few percent of the chlorinated dioxins and furans. This can be explained by the fact that household waste contains significantly more chlorine than bromine, the bromine content is between 1 and 4% of the chlorine content. The majority of this is due to plastics that contain brominated flame retardants.

Brominated flame retardants such as polybrominated diphenyl ethers or biphenyls , tetrabromobisphenol A and hexabromocyclododecane can already contain small residues of PBDD / PBDF. During production, the flame retardants are added to the plastics at around 300 ° C in the extruder . This process already leads to a sharp increase in the PBDD / PBDF content. In the event of a fire, burning flame-retardant plastics in waste incineration plants or pyrolysis , considerable amounts of PBDD / PBDF can be produced again. Far more polybrominated dibenzofurans than dibenzodioxins are formed in the examined pathways.

Content of polybrominated dibenzofurans in µg / kg in technical decabromodiphenyl ether (DecaBDE), a flame retardant formulation with 58% decaBDE and polybutylene terephthalate (PBT) to which this formulation has been added (approx. 7% DecaBDE)
Type of sample Manufacturing Br 4 DF Br 5 DF Br 6 DF Br 7 DF Br 8 DF
technical DecaBDE commercially nn nn 2.3 250 34
Flame retardant formulation with DecaBDE at 150 ° C 23 107 3470 2700 580
PBT plastic Extruder, 250 ° C 14-26 65-109 230-250 500-980 410-1600
PBT plastic Pyrolysis, 400 ° C, 10 min 1,405,000 1,101,000 252,000 43,000 2800

Polybrominated diphenyl ethers or biphenyls are direct precursor molecules for the formation of polybrominated dibenzofurans in combustion processes.

When recycling of electronic waste , especially by melting or smoldering of flame retardant containing circuit boards , significant amounts PBDD / PBDF are released.

Leaded gasoline contained the scavengers 1,2-dichloroethane and 1,2-dibromoethane , from which polyhalogenated dibenzodioxins and dibenzofurans (PXDD / PXDF) were formed during combustion. The contents of the brominated or mixed halogenated dioxin congeners in the exhaust gas were comparable to or higher than those of the chlorinated congeners.

PXDD and PXDF in car exhaust gas samples taken during driving cycle experiments (pg / Nm 3 )
Substances Leaded gasoline Unleaded, without cat Unleaded, with cat
Cl 1 -Cl 3 -PCDD 45,000 4970 12
Br 1 -Br 3 -PBDD 117,500 5090 13
Cl 4 -Cl 8 -PCDD 11,492 287 37.3
Br 4 -Br 8 -PBDD 1000 40 4th
Cl 1 -Cl 3 -PCDF 1,388,600 17,840 259
Br 1 -Br 3 -PBDF 3,214,400 12,930 232
Cl 4 -Cl 8 -PCDF 9733 478 25.1
Br 4 -Br 8 -PBDF 14,200 100 46

toxicology

Brominated dibenzodioxins and dibenzofurans are about as toxic as their chlorinated analogues. There are insufficient data on the toxicology of brominated and brominated / chlorinated dioxins and furans. It seems to be certain, however, that the congeners brominated at the 2,3,7,8-position have the greatest poisonous effect. PBDD / PBDF are not taken into account in the system of toxicity equivalents, however, there is information in the literature on their “relative potency” in relation to 2,3,7,8-TCDD, ie a kind of preliminary toxicity equivalent. The toxicity of brominated furans appears to be even higher than that of their chlorinated counterparts.

Relative potency (REP) in relation to 2,3,7,8-TCDD for some brominated dioxins, brominated furans and dioxins and furans mixed with bromine and chlorine
Substances REP
2,3,7,8-TBDD 0.65 or 0.75
1,3,7,8-TBDD 0.013
1,2,3,7,8-PBDD 0.3
1,2,3,7,8,9-HxBDD 0.03
2,3,7,8-TBDF 0.7 or 0.79
1,2,3,7,8-PBDF 0.5
2,3,4,7,8-PBDF 0.21 or 0.52
1,2,3,4,7,8-HxBDF 0.002
2monoBr-378tri-CDD 0.94
23diBr-78diCDD 0.69
37diBr-28diCDD 0.96 or 0.68
1monoBr-2378tetraCDD 0.60 or 0.32
2monoBr-36789pentaCDD 0.19

In Germany, the first limit values ​​for eight brominated dioxins and furans were set in 1993 with the Dioxin Ordinance.

Others

Spongiadioxin A , a natural dioxin

The spongiadioxin A produced by the sea sponge Dysidea dendyi is the polybrominated compound 1-hydroxy-3,4,6,8-tetrabromodibenzo [1,4] dioxin.

From PBDD / PBDF dissolved in solvents, bromine atoms are split off within minutes under UV light ( photolysis ). The standard solutions for the analysis of brominated dioxins and furans must therefore be stored away from light. In the atmosphere, rapid photolysis is only to be expected for the relatively small portion of the gaseous PBDD / PBDF, not for the particle-bound.

The 2,3,7,8-tetrabromodibenzofuran was the first "dioxin" to be discovered by a Japanese scientist in 1941 when he was investigating derivatives of biphenylene oxide.

Individual evidence

  1. ^ Donnelly et al .: Analysis of thermoplastic resins for brominated dibenzofurans . Biomed. Environ. Mass. Spectrom. 18: 884-896 (1989) doi: 10.1002 / bms.1200181008 ; quoted from Ballschmiter and Bacher (1996).
  2. ^ A b Karlheinz Ballschmiter , Reiner Bacher: Dioxins . Verlag Chemie (VCH), Weinheim 1996, ISBN 3-527-28768-X .
  3. ↑ Hagenmaier et al .: Emissions of polyhalogenated dibenzodioxins and dibenzofurans from combustion engines . Organohalogen Compounds 2: 329-334 (1990), cited in Ballschmiter and Bacher (1996).
  4. ↑ Dieter Lenoir , Stefan Leichsenring: Concepts and methods of environmental protection: the example of dioxins . Chemistry in our time 30 (4), pp. 182-191 (1996), doi: 10.1002 / ciuz.19960300404 .
  5. ↑ a b E. Eljarrat, D. Barceló: Toxicity Potency Assessment of Persistent Organic Pollutants in sediment and sludges in D. Barceló: Emerging Organic Pollutants in Waste Waters and Sludge , The Handbook of Environmental Chemistry, Vol 5 Part 1, Springer Verlag. , Berlin, 2004, pp. 99-140, ISBN 3-540-21365-1 .
  6. ↑ Umweltbundesamt Berlin: Dioxins , ab. August 19, 2007.
  7. ↑ Gordon W. Gribble: Environmental toxins from the gift table of nature ( Memento from January 26, 2009 in the Internet Archive ) (PDF; 416 kB). Spectrum of Science , June 2005, p. 38ff.
  8. ↑ Karsten Strey: The world of poisons. ISBN 3865414192 , p. 254 ( limited preview in Google Book Search).