Investigation of Dioxin/Furan Composition in Emissions and in Environmental Media. Selection of Congeners for Modelling

MSC-E Technical Note 6/2001

N.Vulykh, V.Shatalov

ABSTRACT

This report describes investigations, which are a preparatory study of model evaluation of polychlorinated dibenzo-p-dioxins and furans (PCDD/F) airborne transport. This study is aimed at:
· selection of priority homologous groups and congeners for modelling and
· determination of an individual compound or congener characterizing the behaviour of the whole group of species with acceptable (permissible) accuracy.

The key criterion for the selection was the contribution of this or that congener to total equivalent toxicity of the mixture (here we use NATO Toxic Equivalents System).

All the data used for the analysis and calculations of contributions of different homologous groups and congeners to PCDD/F mixture total toxicity in emissions and environmental media are taken from works of different authors.

The procedure of priority homologous group selection is one and the same both for emissions and pollution levels in media. At first we specify the contribution of a homologous group to PCDD/F mixture total toxicity. The priority groups are selected in such a way that the sum of their contributions constitutes more than 50% of overall mixture toxicity.

Then we investigated the toxicity distribution with congeners inside a homologous group. In doing so only toxic 2,3,7,8-substituted congeneres were taken into account.

The first section of the Note gives a short description of PCDD/F stucture and properties.

The second section is aimed at the analysis of PCDD/F mixture composition in view of individual congener contributions to total toxicity of emissions from the main three types of sources - organic fuel combustion, waste incineration and secondary processing of non-ferrous metals.

The third section provides the results of investigations of homologous groups and congeners contributions to the total toxicity of samples taken from air, soil, vegetation and sea water.

PeCDF group makes the maximum contribution to the toxicity and it is most important for all the environmental compartments. HxCDF and PeCDD groups are also very important for air.

The list of priority groups specified as a result of analysis of emissions from different types of sources basically coincide with the list of priority groups defined by the analysis of measurement data.

The distribution of contributions of individual congeners to the total toxicity of air samples shows that 2,3,4,7,8-PeCDF is the most hazardous compound since its fraction in the total toxicity of air samples is maximum.

1,2,3,7,8-PeCDD is contained in air in less quantities and having equal toxicity coefficient in the NATO system with 2,3,4,7,8-PeCDF it takes the second place. When using WHO toxicity coefficient system they can interchange places. It seems quite natural that "light" congeners -- 2,3,7,8-TCDD and 2,3,7,8-TCDF make great contributions to air samples. Their airborne transport by mathematical simulation is planned in future.