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Analytical Challenges and Environmental Relevance of ... QUASIMEME PFC... · Analytical Challenges...
Transcript of Analytical Challenges and Environmental Relevance of ... QUASIMEME PFC... · Analytical Challenges...
Analytical Challenges and Environmental Analytical Challenges and Environmental Relevance of Branched and Linear Isomers of Relevance of Branched and Linear Isomers of
Perfluorooctane Sulfonate and Related Perfluorooctane Sulfonate and Related Fluorinated Compounds in BiotaFluorinated Compounds in Biota
Robert J. LetcherRobert J. Letcher1,21,2, Shaogang Chu, Shaogang Chu11, , Wouter A. GebbinkWouter A. Gebbink22, Jason O, Jason O’’BrienBrien33
and Sean Kennedyand Sean Kennedy11
QUASIMEME Workshop, “Analysis of Perfluorinated Compounds”, Amsterdam, The Netherlands, Oct. 14-15, 2009
1 Wildlife Toxicology Section, Ecotoxicology and Wildlife Health Division, Wildlife and Landscape Science Directorate, Science and Technology Branch, Environment Canada, National Wildlife Research Centre, Carleton University, Ottawa, Ontario, Canada
2 Department of Chemistry, Carleton University, Ottawa, Ontario, Canada3 Department of Biology, University of Ottawa, Ottawa, Ontario, Canada
(contact e(contact e--mail: mail: [email protected]@ec.gc.ca))
C
O
OHS
O
OH
O
CF3(CF2)n S
O
N
O
Perfluorocarboxylic acids(e.g., PFCAs, n = >7 - 14) Perfluorosulfonic acids
(e.g., PFSAs, n = >5 - 9)
Perfluorosulfonamides(PFOSA, R=H, CH3, CH2CH3; e.g., n=7)
S
O
N
O
CH2CH2OH
Perfluorosulfonamidoethanols(PFOSE, R=CH3, CH2CH3; e.g., n=7)
CF3(CF2)nCF2CH2CH2OH CF3(CF2)n P
O
OH
OH
Examples of Fluorinated Surfactants Reported in (Biotic and Abiotic) Environmental Compartments
S
O
OPerfluorosulfonamidoacetic acids
(PFOSAA, R=H, CH3, CH2CH3; e.g., n=7)
Fluorotelomer alcohols(e.g., FTOH, n=4, 6 and 8)
Perfluorinated phosphonic acids(PFPAs, n = 5,7 and 9)
NCH2COH
O
CF3(CF2)n
CF3(CF2)n
CF3(CF2)n CF3(CF2)nR R
R
R
(M. Houde, J.W. Martin, R.J. Letcher, K. Solomon, D.C.G. Muir. 2006. Environ. Sci. Technol. 40:3463-3473) (C. Lau, K. Anitole, C. Hodes, D. Lai, A. Pfahles-Hutchens, J. Seed. 2007. Toxicol. Sci. 99:366-394)
e.g., N-Et-FOSE (N-ethyl-perfluorooctane sulfoamidoethanol)aliphatic or branched hydrocarbon
(e.g. aliphatic alkyl sulfonamide alcohol)
Synthesis, Production and Environmental Fate of Perfluorinated Sulfonic Acids (PFSAs)
Electrochemical Fluorination, e.g., PFOS (perfluorooctane sulfonic acid)
F3C SO
NCH2CH2OH
F F
F F
F F F F
F F F F
F F O
CH2CH3
F3C SO
OH
F F
F F
F F F F
F F F F
F F O
PFOS
PFOSAA (perfluorooctane sulfonamido acetic acid)
F3C SO
F F
F F
F F F F
F F F F
F F O
fluorine; electric current; replacement of all H by F
+linear and branched isomers and shorter
chain length impurities
H3C SO
NCH2CH2OH
H H
H H
H H H H
H H H H
H H O
F3C SO
O-
F F
F F
F F F F
F F F F
F F O
PFOS (conjugate base)
CH2CH3
PFOSE (perfluorooctane sulfoamidoethanol)
F3C SO
NHCH2CH2OH
F F
F F
F F F F
F F F F
F F O
PFOSA (perfluorooctane sulfonamide)
F3C SO
NH2
F F
F F
F F F F
F F F F
F F O
- environmental release- atmospheric transport- environmental degradation (e.g., metabolism)
NHCH2COH
O
pKa = -3.27 (cal.)strong acid
PFSA and precursor production:- 3M Company from the 1950s to 2001- 3M voluntary phase-out of its PFOSF-based chemicals in favour of shorter chain-length compounds- PFOS has been directly produced in China since 2003 - influence on global emission patterns
PFOS: Precursor Transformation/Degradation
Degradation of Perfluorosulfonamides to PFOSAbiotic degradation as well as in vivo & in vitro biotransformation in dogs, rats & rainbow trout
(Arrendale et al., 1989; Grossman et al., 1992, Tomy et al., 2004, Xu et al., 2004)
No furtherdegradation
N-Et-FOSA (N-ethyl-perfluorooctane sulfoamide)
F3C SO
NH
F F
F F
F F F F
F F F F
F F O
CH2CH3
F3C SO
O-
F F
F F
F F F F
F F F F
F F O
L-PFOS?
PFOSA (perfluorooctane sulfonamide)
F3C SO
NH2
F F
F F
F F F F
F F F F
F F O
What about isomer-specific transformation (metabolism) and degradation?
e.g., N-Et-FOSE (N-ethyl-perfluorooctane sulfoamidoethanol)
F3C SO
NCH2CH2OH
F F
F F
F F F F
F F F F
F F O
CH2CH3
PFOS and Precursors Are Not a Singles Compound But Composed of Various Isomers
production of PFOS derivatives from linear alkyl precursors using ECF is not a clean process
commercial PFOS claimed to be generally >98% pure, but based on purity assessments using e.g., acid/base titration method after ion exchange with a strong acid resin
commercial PFOS contained approximately 86% PFOS; 70% L-PFOS and ~30% branched isomers (by 19F NMR):
(G. Arsenault, B. Chittim, A. Mclees, R. McCrindle, N. Riddell, B. Yeo. 2008. Chemosphere 70:616-625)
F3C SO
O-
F F
F F
F F F F
F F F F
F F OL-PFOS
P1MHpS P2MHpS P3MHpS
P4MHpS P5MHpS P6MHpS
F3CSO
F F
F F
F F F F
F F F
O
F3CSO
F F
F F
F F F
FF F FO
F3CSO
F F
F F
F F F
FF
F
FCF3
OCF3
F3C
F3CSO
F F
F F
F FF
FF F F
O
F3C
F3CSO
F F
F F
F F F
FF
F
FCF3
O
F3CSO
F F
F F
F FF
FF F F
O
F3C
O-O- O-
O-O-O-
P35DMHxSP44DMHxS P45DMHxS P55DMHxS
F3C SO
F
F F
F FF
F F
O
F3C
F3C
F3C SO
F F FF FF
F F
O
CF3
CF3
F3C SO
F
F
FF FF
F F
O
CF3
F3C
F3C SOFF
FF FF
F F
O
F3C
F3C
O- O- O- O-
(M. Houde, G. Czub, J.M. Small, S. Backus, X. Wang, M. Alaee, D.C.G. Muir. 2008. Environ. Sci. Technol.)
Limited Analytical and Environmental Study on Isomer-Specific PFOS; None For Other PFSAs
Up to this study, little known about environmental presence and fate of PFOS isomers
total of 6 isomers, 3 M-PFOS and 3 DM-PFOS isomers as well as linear L-PFOS detected in technical mixture, water, sediment and biota
L-PFOS >88% of total PFOS in all compared to technical PFOS (77%)
T-PFOS; 76% L-PFOS, 20% M-PFOSs and 3.6% DM-PFOSs
High L-PFOS suggested a reduced uptake of branched isomers, more rapid elimination of the branched isomers and/or a selective retention of the L-PFOS
Trophic magnification factor of L-PFOS (4.6) was greater than M-PFOS isomers (1.3), whereas DM-PFOS isomers showed no biomagnification
LC-ESI(-)-MS/MS;MRM: m/z = 499-99 (SO3F-), m/z = 499-80 (SO3
-)Confirmation by LC-Q-ToF-MS
- homogenized sample in polypropylene centrifuge tube- IS spike: sodium perfluoro-1-[1,2,3,4-13C4]octane sulfonate (MPFOS); 100 ng/mL
Vortex Mixing and Filtration
- KOH (10 mM) acetonitrile/water (80/20 v/v) extraction- centrifuge, add water and vortex- pH = ~4 with 2% aq. formic acid- Oasis SPE-WAX (weak anion exchange) clean-up; pre-conditioned
Egg, Liver or Plasma sample
GC-MS(ECNI)
SIM m/z 137, 480, 499, 503
- 0.5 g tetrabutyl ammonimum hydroxide (TBAH) in 5 mL diethyl ether- sonication for 0.5 h, centrifugation, upper phase isolation- 100 uL of TBAH mixture added to sample fraction- addition 1 mL of ether added, centriguged and frozen at -20C- unfrozen ether phase transferred, to dryness and reconstituted in 100 uL ether
Isomer-Specific PFOS Derivatization, GC-MS-Based Methodology
(S.G. Chu, R.J. Letcher. 2009. Anal. Chem. 81:4256-4262)(R.J. Letcher, S.G. Chu. 2009. Anal. Chem. 81:7856-7857)
- sample loaded on SPE- SPE washed with 2% aq. formic acid (1 mL), 2×1 mL H2O, 2×1 mL MeOH- PFOS isomer elution with 2×1 mL NH4OH (28-30%) in aq. MeOH (1/9 v/v)
GC-MS in-port derivatization
C8F17SO3H + (C4H9)4N+OH- → C8F17SO3-(C4H9)4N+ + H2O
C8F17SO3-(C4H9)4N+ → C8F17SO3C4H9 + N(C4H9)3
In-Port TBAH Derivatization, GC-MS(ECNI) Determination of Isomer-Specific PFOS
(S.G. Chu, R.J. Letcher. 2009. Anal. Chem. 81:4256-4262)(R.J. Letcher, S.G. Chu. 2009. Anal. Chem. 81:7856-7857)
[C4H9SO3]-[C8F17SO3-F]-
[C8F17SO3]-[C8F17SO3+ C4H9]- [C5F11]-
[C8F17-SO3-F]-
(S.G. Chu, R.J. Letcher. 2009. Anal. Chem. 81:4256-4262)(R.J. Letcher, S.G. Chu. 2009. Anal. Chem. 81:7856-7857)
Mass Chromatograms (In-Port TBAH Derivatization GC-MS(ECNI)) of Isomer-Specific PFOS
GREEN = m/z 137BLUE = m/z 480RED = m/z 499YELLOW = m/z 503
Butyl ether-PFOS technical mixture (potassium T-PFOS salt; Wellington Labs, Guelph, ON, Canada)
Butyl ether-PFOS isomer fraction from polar bear liver
Isomer-Specific PFOS in Representative Biological Environmental Samples
(S.G. Chu, R.J. Letcher. 2009. Anal. Chem. 81:4256-4262)(R.J. Letcher, S.G. Chu. 2009. Anal. Chem. 81:7856-7857)
~65% L-PFOS + ~35% branched isomers
K+PFOS- from 3 suppliers by LC-ESI(-)-MS/MS: L-PFOS consistently 67-79%(G. Arsenault, B. Chittim, A. Mclees, R. McCrindle, N. Riddell, B. Yeo. 2008. Chemosphere 70:616-625)
Isomer-Specific PFOS Determination: LODs, MDLs and Recovery Efficiency
(S.G. Chu, R.J. Letcher. 2009. Anal. Chem. 81:4256-4262)(R.J. Letcher, S.G. Chu. 2009. Anal. Chem. 81:7856-7857)
Unspiked
GC-MS(ECNI) mass chromatograms of spiked and unspiked pork fat with T-PFOS
Spiked
(S.G. Chu, R.J. Letcher. 2009. Anal. Chem. 81:4256-4262)(R.J. Letcher, S.G. Chu. 2009. Anal. Chem. 81:7856-7857)
GC injection port temperature effect: MS(ECNI) response of L-PFOS after pyrolytic
alkylation of L-PFOS using TBAH
Isomer-Specific PFOS Determination: Effects of Injection Port Temperature and Volume Injected
Effects of the sample injection volume: MS(ECNI) response of L-PFOS after pyrolytic alkylation
of L-PFOS using TBAH
PFCs and Trends in Colonial Herring Gulls From the Great Lakes
Canada
L. Ontario
L. Erie
L. HuronL. Michigan
L. Superior
U.S.A.
AgawaAgawa RockRock
Fighting Is.Fighting Is.
ChannelChannel--Shelter Is.Shelter Is.
Chantry Is.Chantry Is.
TorontoToronto
Niagara R. (above the falls)Niagara R. (above the falls)
Gull Is.Gull Is.
2007-collected, individual eggs; completed characterization and spatial trends of 21 PFCs and precursors in herring gull eggs
Granite Is.Granite Is.
Big Sister Is.Big Sister Is.
Middle Is.Middle Is.
Double Is.Double Is. Strachan Is.Strachan Is.
Snake Is.Snake Is.
HamiltonHamilton
Port ColbornePort Colborne
Completed analysis:- 10-13 individual eggs from selected years and from all 15 CWS monitoring sites to be analyzed for 21 PFCs and precursors
Photo: Craig Hebert
- homogenized sample in polypropylene centrifuge tube- IS spikes: 18O- and 13C-labeled PFCs- 3 mL MeOH/H2O (50/50) with 2 nM NH4OAc
Vortex Mixing and Filtration
- KOH (10 mM) acetonitrile/water (80/20 v/v) extraction- centrifuge, add water and vortex- pH = ~4 with 2% formic acid- SPE-WAX (weak anion exchange) cartridge clean-up
Liver or Plasma sample
LC-ESI(-)-MS/MS (tandem quad.)
Quantification of:10 PFCAs (C6 – C15)4 PFSAs (C4, C6, C8,C10)3 FTUCAs (6:2, 8:2, 10:2)
Acidic Fraction Neutral fraction- reconstitute in MeOH- centrifugal filter (0.2 µm Nylon) at 6000 rpm for 20 min.
Quantification of:PFOSA, N-Me-FOSA3 FTOHs (6:2, 8:2, 10:2)
LC-APPI(-)-MS/MS (tandem quad.)
13C PFHxA, PFOA, PFNA, PFDA, PFUnA, PFDoA13C/18O PFHxS, PFOS
d-N-Me-FOSA13C 6:2, 8:2, 10:2 FTOH 13C 6:2, 8:2, 10:2 FTUCA
Non-Isomer-Specific PFC, LC-MS-Based Methodology
(S.G. Chu, R.J. Letcher. 2008. J. Chromatogr. A 1215:92-99)
(W.A. Gebbink, C.E Hebert, R.J. Letcher. 2009. Environ. Sci. Technol. 43:7443-7449)
Arithmetic Mean Total PFOS Concentrations (±SE) (LC-ESI(-)-MS/MS) in the Eggs of Herring Gulls From the
Great Lakes of North America
0100200300400500600
PFO
S (n
g/g
ww
)
ChicagoChicago DetroitDetroit ClevelandCleveland
BuffaloBuffalo
HamiltonHamilton
TorontoToronto
CANADACANADA
USAUSA
±SE (n=10-13 individual eggs per site)
p<0.03
northern colonies
(W.A. Gebbink, C.E Hebert, R.J. Letcher. 2009. Environ. Sci. Technol. 43:7443-7449)
Arithmetic Mean Total PFOS Concentrations (±SE) (LC-ESI(-)-MS/MS) in the Eggs of Herring Gulls From the
Great Lakes of North America
0100200300400500600
PFO
S (n
g/g
ww
)
ChicagoChicago DetroitDetroit ClevelandCleveland
BuffaloBuffalo
HamiltonHamilton
TorontoToronto
CANADACANADA
USAUSA
±SE (n=10-13 individual eggs per site)
p<0.03
northern colonies
0
200
400
600
800
1000
2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2
p < 0.009r = 0.65002
PFO
S (n
g/g
ww
)
(δ15N) Trophic Position
n = 15
Trop
hic
Posi
tion
0
1
2
3
4
5
Gra
nite
Is
Aga
wa
Roc
ks
Big
Sis
ter I
s
Gul
l Is
Dou
ble
Is
Cha
nnel
-She
lter I
s
Cha
ntry
Is
Figh
ting
Is
Mid
dle
Is
Port
Col
born
e
Nia
gara
Riv
er
Ham
ilton
Har
bour
Toro
nto
Har
bour
Snak
e Is
Stra
chan
Is
Aquatic food web
Mammals
Birds Garbage
Terrestrial inputin the diet
(C.E. Hebert et al. 2008. Ecol. 89:891-897)
Terrestrial and Aquatic Dietary Inputs Into Herring Gull Explain PFOS (and Other PFC)
Exposure
(δ15
N)
Arithmetic Mean Total PFOS (±SE) in the Eggs of Herring Gulls From the Great Lakes:
LC-ESI(-)-MS/MS vs. GC-MS(ECNI) Quantification
0100200300400500600
PFO
S (n
g/g
ww
)
ChicagoChicago DetroitDetroit ClevelandCleveland
BuffaloBuffalo
TorontoToronto
CANADACANADA
USAUSA
(W.A. Gebbink and R.J. Letcher. 2009. In preparation)
(S.G. Chu, R.J. Letcher. 2009. Anal. Chem. 81:4256-4262)GC-MS(ECNI)
LC-ESI(-)-MS/MS
HamiltonHamilton
±SE (n=10-13 individual eggs per site)
(W.A. Gebbink and R.J. Letcher. 2009. In preparation)
Arithmetic Mean Concentrations (±SE) of Monotrifluoromethyl-Branched PFOS Isomers in the
Eggs of Herring Gulls From the Great Lakes
ChicagoChicago DetroitDetroitClevelandCleveland
BuffaloBuffalo
HamiltonHamilton TorontoToronto
CANADACANADA
USAUSA
±SE (n=10-13 individual eggs per site)
ng/g
ww
0
2
4
6
8
10
12
14
16
P1MHpSP2MHpSP3MHpSP4MHpSP5MHpSP6MHpS
(W.A. Gebbink and R.J. Letcher. 2009. In preparation)
ChicagoChicago DetroitDetroitClevelandCleveland
BuffaloBuffalo
HamiltonHamiltonTorontoToronto
CANADACANADA
USAUSA
±SE (n=10-13 individual eggs per site)
Arithmetic Mean Concentrations (±SE) of Ditrifluoromethyl-Branched PFOS Isomers in the Eggs of
Herring Gulls From the Great Lakesng
/g w
w
0.00
0.05
0.10
0.15
0.20
0.25
0.30
P35DMHxSP44DMHxSP45DMHxSP55DMHxS
~95% L-PFOS~4% M-PFOS~0.1% DM-PFOS
T-PFOS:~65% L-PFOS~33% M-PFOS~2% DM-PFOS
in vivo biotransformation to PFOS?
PFOSA
N-Et-FOSAN-Me-FOSEN-Et-FOSE
N-Et-FOSA PFOSA
PFOSA
in vivo biotransformation to PFOS?
?
PFOSA
Degradation of PFOSA as an Additional Source of PFOS In Herring Gull and Food Chain
(W.A. Gebbink, C.E Hebert, R.J. Letcher. 2009. Environ. Sci. Technol. 43:7443-7449)
* Martin et al., 2004; Furdui et al., 2007
0
1
2
3
4
Log
[PFO
S/PF
OSA
]
Superior
Michigan
Huron
ErieOntar
io
smelt
alewife
Superior
Michigan
Huron
ErieOntar
io
Herring gull eggs Lake TroutSpatial Trend*
Lake OntarioFood web*
InvertebratesMysis, Diporeia
Prey FishSlimy Sculpin, Alewife, Rainbow Smelt
Predator FishLake Trout
(Isomer-Specific) PFOS in Circumpolar Polar Bears
Arctic OceanCanada
USA Russia
Norway
Greenland
60°N
70°N
80°N
Iceland55°N
East Greenland (EG)(n=20)
Svalbard (SVAL)(n=10)
South HudsonBay (SHB)
(n=14)
Lancaster / Jones Sound (LJS)
(n=13)
Davis Strait (DS)(n=8)
Beaufort Sea (BS) (n=38)
Bering-Chukchi Sea (BCS) (n=10)
Western HudsonBay (WHB)
(n=11)
Baffin Bay (BB)(n=14)
Foxe Basin / Gulf of Boothia (FB/GB)
(n=6)
E. Peacock
• Years: 2006-2008 (2005-2007 Bering-Chukchi) • n: 6–38 per zone (total 134)• Sex: ♀ and ♂; Age: 3+ yr• Season: Fall/Winter• liver (plasma for SVAL bears): plasma-liver conversion of
PFC levels, and males/females treated as a single group
• Years: 2006-2008 (2005-2007 Bering-Chukchi) • n: 6–38 per zone (total 134)• Sex: ♀ and ♂; Age: 3+ yr• Season: Fall/Winter• liver (plasma for SVAL bears): plasma-liver conversion of
PFC levels, and males/females treated as a single group
(Letcher et al. 2009. In preparation)
Photo: E. Peacock
Isomer-Specific PFOSs in Polar Bears(Letcher et al. 2009. In preparation)
Arctic OceanCanada
USA Russia
Norway
Greenland
60°N
70°N
80°N
Iceland55°N
East Greenland (EG)(n=8)
Svalbard (SVAL)(n=5)
Nunavut (NU)(n=10)
Beaufort Sea (BS) (n=17
Bering-Chukchi Sea (BCS) (n=5)
P1MHpSP2MHpSP3MHpSP4MHpSP5MHpSP6MHpS
~99% L-PFOS~<1% M-PFOS0% DM-PFOS
T-PFOS:~65% L-PFOS~33% M-PFOS~2% DM-PFOS
a) Sex/Reproductive status
b) Age
c) Seasonal fasting/nutritional status/body condition (lipid content)
d) Diet
a) Sex/Reproductive status
b) Age
c) Seasonal fasting/nutritional status/body condition (lipid content)
d) Diet
Factors Affecting PFOS Trends in Polar BearsFactors Affecting PFOS Trends in Polar BearsFactors Affecting PFOS Trends in Polar Bears
- Other genetic and physiological (e.g. metabolic) variation, environmental or ecological factors (e.g., associated with Arctic warming)
- Other genetic and physiological (e.g. metabolic) variation, environmental or ecological factors (e.g., associated with Arctic warming)
1. Inter-population variation: 1. Inter-population variation:
AMAP, 2004
2. Inter-individual variation: 2. Inter-individual variation:
a) Regional contamination-emissions + LRT (atmos. + oceanic) to the Arctic
a) Regional contamination-emissions + LRT (atmos. + oceanic) to the Arctic
Norstrom et al. 1998; Henriksen et al. 2001; Polischuk et al. 2002Norstrom Norstrom et al.et al. 19981998; Henriksen ; Henriksen et al.et al. 20012001; Polischuk ; Polischuk et al.et al. 20022002
Various concentrations of PFOS technical mixture were injected into the air cell of domestic chicken eggs prior to incubation
Eggs were incubated until pipping, at which time embryos were euthanized and livers were excised
Hepatic PFOS concentration was determined by liquid chromatography-mass spectrophotometry
RNA was extracted from liver tissues using Trizol and reverse transcribed into cDNA
Relative quantity of PPARα regulated genes was determined using real-time reverse transcription PCR
PPARα regulated genes were:Peroxisomal acyl-CoA oxidase (ACOX)Bifunctional enzyme (BIEN)
Liver fatty acid binding protein (L-FABP)Peroxisomal 3-ketoacyl thiolase (PKT)
(J.M. O'Brien, A.C. Carew, S.G. Chu, R.J. Letcher, S.W. Kennedy. 2009. Comp. Biochem. Physiol. Part C.149:524-530)
Regulates genes involved in:-peroxisome proliferation-lipid metabolism-cholesterol metabolism-cell cycle
PFOS Isomer-Specific Toxicokinetics and Effects on Gene Expression in Chicken Eggs Injected With Technical PFOS
Liver PFOS Concentration of Exposed Embryos Increases With Dose
0.01
0.1
1
10
100
untreated DMSO 0.1 5 100Dose Group (ug/g)
Tota
l PFO
S (u
g/g
ww
)
(J.M. O'Brien, A.C. Carew, S.G. Chu, R.J. Letcher, S.W. Kennedy. 2009. Comp. Biochem. Physiol. Part C. 149:524-530)
Significant increase (p<0.05)±SE (2×3 sets of replicates)
Conclusions
New in-port GC-MS based method allows for complete quantitative assessments of all geometrical isomers known to be present in T-PFOS mixtures
Isomer-specific processes that favour L-PFOS occur in abiotic and more so in biotic compartments (e.g., wildlife and fish); selective uptake, bioconcentration, degradation, metabolism and/or bioaccumulation
As typified by Great Lakes herring gulls and circumpolar polar bears; highly conserved PFOS isomer pattern and enriched L-PFOS suggest isomer-specific processes occurring lower on the food web
PFOSA metabolism appears to occur in gulls and bears as a source of bioaccumulative PFOS: Isomer-specific?
Isomer-specific PFOS, as well as other precursors and PFCs (e.g., PFCAs and PFPAs), are currently not or under studied
Acknowledgements and Funding
Natural Sciences and Engineering Research Council (to R.J.L.)
Environment Canada’s Chemicals Management Plan (CMP)
Northern Contaminants Program (to R.J.L.)
Canadian International Polar Year (to R.J.L.)
Molson Foundation (to R.J.L.)
Danish Department of the Arctic Environment; Norwegian Polar Institute
Thank you
F3C SO
O-
F F
F F
F F F F
F F F F
F F O