Investigating Variability in HBCDD Diastereomer Profile in the Environment

Transcription

1 Investigating Variability in HBCDD Diastereomer Profile in the Environment Li LI 1,2, Frank WANIA 2 1. Peking University, P.R. China 2. University of Toronto Scarborough, Canada to Li Li: environ.li@mail.utoronto.ca

2 Hexabromocyclododecane (HBCDD) Brominated flame retardant applied in polystyrene foams Expanded polystyrene (EPS): insulation boards, packaging materials Extruded polystyrene (XPS): insulation boards Included into the Stockholm Convention in 2013 for elimination Diastereomers

3 Variability in HBCDD Diastereomer Profile Why can we observed diverse HBCDD diastereomer profile? Isomerization Guangzhou, urban air (n=32) (Yu et al., ES&T, 2008) Svalbard, air (n=152) (Mano et al., NILU, 2010) Technical HBCDDs (Heeb et al., Chemosphere, 2005) Shanghai, urban soil (n=27) (Wu et al., Sci. Total Environ., 2005) Tianjin, industrial soil (n=7) (Zhu et al., Environ. Pollut., 2017)

4 Modeling Strategy Lifecycle processes Waste disposal International trade Stocks of in-use goods Advection Degradation Diffusion Production of a chemical CiP-CAFE Lifecycle emissions to the Environment BETR-Global Concentration in environ. media A continuum from chemical production to concentration in environmental media Trace how diastereomer profile changes throughout the lifecycle of HBCDD-containing products

5 CiP-CAFE Model CiP-CAFE: Chemical in Product Comprehensive Anthropospheric Fate Estimation (Li and Wania, 2016; Li et al., 2017) Li and Wania (2016) Environ. Int., 94, Li et al. (2017) Environ. Sci. Technol., 51,

6 BETR-Global Model BETR-Global: Berkeley-Trent Global (MacLeod et al., 2005, 2011) MacLeod et al. (2005) Environ. Sci. Technol., 39, MacLeod et al. (2011) Environ. Pollut., 159,

7 Key Input Data Regional annual production/consumption of HBCDD diastereomers 50 -HBCDD Regional annual production of technical HBCDDs Use of HBCDDs in five applications EPS insulation XPS insulation textiles EPS packaging HIPS plastics Diastereomer profile of technical HBCDDs Annual production (kt a -1 ) HBCDD -HBCDD 0 * Future production & new use: The Stockholm Convention allows 5-year specific exemptions for EPS and XPS in buildings needed to give countries time to phase-in safer substitutes Year

8 Key Input Data Isomerization factor (IF) during thermal processing Relative change of the abundance of a diastereomer IF = Abundance of a diastereomer after isomerization Abundance of a diastereomer before isomerization Technical HBCDDs kinetic-controlled Increasing time at specific processing temperature IF(-HBCDD) keeps decreasing IF(-HBCDD) keeps increasing thermodynamic-controlled IF is a range: IF minimum < IF < IF maximum

9 Variability in Input Data Define 8 separate simulation scenarios Upper bound of the emission estimate: maximum of the 8 results Lower bound of the emission estimate: minimum of the 8 results Parameters with remarkable variability Boundary 1 Boundary 2 # of cases (A) Isomerization factor -dominant -dominant 2 (B) Emission factors of production & formulation Literature reported value 1 Literature reported value 10 2 (C) Emission factors in non-open use of insulation boards Literature reported value 1 Literature reported value Total 8

10 Model Performance Fed with the CiP-CAFE-derived emission estimate BETR-Global succeeds in reproducing most Σ 3 HBCDD concentrations observed in GAPS Σ 3 HBCDD concentration (pg m -3 ) 500,00 50,00 5,00 0,50 0,05 0,01 Measured (> LOQ/3) Modelled 12* 26** 29 35* 52* 54* 60* 61* 62* 63* 77* 79* 80* 85* 86* 90 93* 102* 104* 110* * 114* 115* 127* 132** 139** 140* 141** 159* 165* 176** 177* 182* 200* 214* LOQ/3 Data of the GAPS measurements from: Lee et al. Environ. Pollut. 2016, 217, Grid number in BETR-Global

11 Global Emissions of HBCDD Diastereomers On the global scale, -HBCDD and -HBCDD are almost similarly abundant 45 Annual emissions (t a -1 ) Year -HBCDD -HBCDD -HBCDD 2100 Air concentration (pg m -3 ) Zeppelin (BETR-Global Grid #13) HBCDD HBCDD ,1 0,1 0,01 0,01 0,001 0, Year

12 Different Diastereomers, Different Dominant Sources -HBCDD -HBCDD -HBCDD Annual emissions (t a -1 ) 91% 96% of -HBCDD, 64% 80% of -HBCDD are associated with the use and end-of-life disposal of HBCDD-containing thermal insulation boards Year Highest estimate 55% 70% of cumulative emissions of -HBCDD originate from production & industrial processes Lowest estimate Consumer waste Use and consumption Industrial waste Production & industrial activities

13 Enrichment of Diastereomers in the Arctic Absolute Arctic Contamination Potential Percentage of enrichment of HBCDD diastereomers in Arctic (BETR-Global cells #1 48) surface media after a decade of emissions Amount present in Arctic surface media eacp 10 = Cumulative global emissions over the decade eacp 10 0,18% 0,15% 0,12% 0,09% 0,06% Classic eacp Geographic distribution of emissions is identical as that of the global population density Constant emission rate No isomerization Technical HBCDD 0,03% 0,00% Year

14 Enrichment of Diastereomers in the Arctic Absolute Arctic Contamination Potential Percentage of enrichment of HBCDD diastereomers in Arctic (BETR-Global cells #1 48) surface media after a decade of emissions Amount present in Arctic surface media eacp 10 = Cumulative global emissions over the decade eacp 10 0,18% 0,15% 0,12% 0,09% 0,06% 0,03% Classic eacp Geographic distribution of emissions is identical as that of the global population density Constant emission rate Considering the loss due to isomerization Technical HBCDD 0,00% Year

15 Enrichment of Diastereomers in the Arctic Absolute Arctic Contamination Potential Percentage of enrichment of HBCDD diastereomers in Arctic (BETR-Global cells #1 48) surface media after a decade of emissions Amount present in Arctic surface media eacp 10 = Cumulative global emissions over the decade eacp 10 0,18% 0,15% 0,12% 0,09% 0,06% Realistic eacp Realistic geographic distribution of emissions Realistic emission rate Considering the interconversion due to isomerization -HBCDD -HBCDD -HBCDD 0,03% 0,00% Year

16 Concern: -HBCDD is More Risky in the Environ. Example: In vitro biotransformation assay (Zegers et al., 2005) Laboratory rats and harbor seal: microsomal preparations of liver -HBCDD is hardly metabolized by cytochrome P450 enzymes -HBCDD was not significantly biotransformed after 90 min of incubation. - and -HBCDD are quickly metabolized by cytochrome P450 enzymes 69±16% of -HBCDD and 60±10% of -HBCDD disappeared within 90 min. Due to isomerization: The HBCDD mixture in the emission flow or in the environment, may be of more environmental concern than the mixture being produced. Zegers et al., Environ. Sci. Technol., 2005, 39,

17 Implications It is not appropriate to treat interconvertible mixtures as a unit in environmental fate studies. Environmental risk assessment of HBCDD is recommended to be conducted on a diastereomer-specific basis.

18 Thanks for Your Attention Questions Acknowledgement Scholarships from the China Scholarship Council & the Shanghai Tongji Gao Tingyao Environmental Science and Technology Development Foundation Related work 15:30 Abbasi et al. Global Inventory of PBDEs; from Production, Use and Waste to Environment Helga Engs hus, Auditorium 3