Fauser. P., Hansen, K.M., Christensen, J.H., Sørensen, P.B. & Vorkamp, K. 2022. Modelling long-range transport and emissions from local sources of new contaminants in the Arctic. Aarhus University, DCE – Danish Centre for Environment and Energy, 87 pp. Scientific Report No. 499 http://dce2.au.dk/pub/SR499.pdf
This study addresses seven current-use flame retardants (FRs), which have been detected in the Arctic environment. These include three organophospho-rous FRs (OPFRs): tri(2-chloroethyl) phosphate (TCEP), tri(chloroiso-propyl) phosphate (TCPP) and triphenyl phosphate (TPHP), three brominated FRs (BFRs): 2-Ethylhexyl-2,3,4,5-tetrabromobenzoate (EH-TBB), bis(2-ethylhexyl) tetrabromophthalate (BEH-TEBP) and hexabromobenzene (HBBz), and the chlorinated FR dechlorane plus (DP).
The purpose of the study was to quantify contributions from local emissions and long-range transport, respectively, in the Greenland environment in Nuuk. Long-range transport was studied with the atmospheric chemistry-transport model DEHM, based on emissions from production, plastic and tex-tile use and waste treatment in nine global regions. Local concentrations were calculated using a local site model and emissions to air, soil and water from local use of plastic and textile products as well as waste incineration.
A number of assumptions, approximations and adjustments were made in the model calculations, including the following: Emission factors (EFs) were taken from the polybrominated diphenyl ethers (PBDEs) decaBDE and pen-taBDE. EFs to air were adjusted for differences in molecular weights, vapour pressure (Vp) and temperature (in the case of outdoor product use and waste treatment). Uncertainties in EFs were taken into account by considering a low and a high emission scenario.
A comparison of model simulations showed that the air concentrations from local sources were two and three orders of magnitude (OM) higher than the air concentrations calculated for long-range transport for TCEP, TCPP, TPHP (high emission scenario) and EH-TBB. For TPHP (low scenario), BEH-TEBP, HBBz and DP the local sources contributed one OM or less to the air concentrations, compared to the contribution from long-range transport. For soil, marine water and biota, local sources were significantly more influential than long-range transport (four to six OM) for all FRs, except for TCEP and HBBz. TCEP and HBBz have the highest EFs (and Vp) to air among the OPFRs and the BFRs, respectively, which had a strong influence on this result. BEH-TEBP and DP have the lowest EFs to air.
The comparison with measured values was limited to relatively few studies reporting air, soil and water data for these seven compounds. The majority was from Svalbard. There was good agreement (≤ one OM) between modelled and measured air concentrations for TCEP and TCPP, and for one of the emission scenarios for EH-TBB, BEH-TEBP and HBBz. There was poor agreement for TPHP (≥ two OM) and even more so for DP. For the soil compartment, all FRs, except TCEP, had modelled concentrations that were comparable and up to two OM lower than measured soil concentrations. No soil measurements were found for BEH-TEBP. Modelled TCEP soil concentrations were between four and five OM lower than the measured concentrations. For seawater, modelled concentrations of TCPP and TPHP (low scenarios), and BEH-TEBP and HBBz (high scenarios) were comparable (≤ one OM) to measured concentrations. For all other FRs the modelled concentrations were between two and five OM lower than the measured concentrations. No measurements were found for EH-TBB. Measurements in fish (Atlantic cod) and seal are scarce, but for EH-TBB and HBBz in cod the modelled concentrations were up to two OM lower compared to the measurements. Modelled values of EH-TBB in seal blubber are comparable (one OM lower) to measured values, and modelled values of TPHP and DP are four to five orders of magnitude lower than the measured values.
Simulations with the atmospheric chemistry-transport model DEHM showed that the contributed fraction to the Arctic from Europe was higher than the region’s share of the total global emission, whereas the opposite was the case for China, Japan and the rest of Asia. This was due to the prevailing transport pattern, in which the transport from Europe and the Asian part of Russia into the Arctic was the largest transport route.
A human risk from indirect FR exposure via the environment, estimated from the derived environmental concentrations and standard daily intake values of air, fish and seal, showed no or low risk (Risk Characterization Ratio < 1E-04). The same OM for the environmental risk towards cod was found. However, toxicity data were missing or limited, which compromised the accuracy of the risk estimate.