THE BROMINATED FLAME RETARDANT HEXABROMOCYCLODODECANE (HBCD) IN CENTRAL STOCKHOLM. MODELLING OF DIFFUSE EMISSIONS

An assessment of the emission sources and transport pathways for the brominated flame retardant hexabromocyclododecane (HBCD) in central Stockholm has been performed. The assessment is based on a methodology where material flow analysis (MFA) and multimedia models are combined. The year 2001 was used as a reference year. The main pools for HBCD have been identified and possible dispersion pathways have been discussed. Preliminary emission estimates were obtained using emission factors, based on the Usage Category Document for Plastic Additives, UCD (UK Environment Agency, draft 1998). Car inventories and XPS-materials were identified as the probable main HBCD-pools, followed by textiles. The largest emissions were estimated to be from car inventories to air and from XPS to soil. The annual inflow of HBCD in background air was estimated to be greater than the direct emissions to the Stockholm atmosphere. A multimedia fugacity model was used to predict the transport and fate of HBCD in Stockholm, once emitted. The overall environmental residence time of HBCD in the region was estimated to be 490 days. The findings should be regarded as preliminary, as there are large uncertainties in the input data data used in the calculations. However, the suggested methodology is very useful in synthesizing data on the use, emissions and environmental fate of a chemical, and helps to identify the most pertinent factors that determine the environmental impact of diffuse emissions in a region. One of the major uncertainties is connected to the emission factors used. Nevertheless, the suggested emission scenario represents a plausible explanation of the concentrations of HBCD detected in the Stockholm environment. The predicted environmental concentrations agree well with measured levels. This document is available on the Internet: http://www.ivl.se/rapporter/pdf/B1465.pdf (A)