PFAS, which stands for per- and polyfluoroalkyl substances, are a diverse group of chemicals that include PFCAs, PFOA, PFSAs, PFHxS, and thousands of others. These chemicals have been in commercial production since the 1950s and are now widely used in consumer and industrial applications. One characteristic of PFAS is their persistence in the environment, as they are extremely resistant to degradation. PFAS have emerged as contaminants of global concern because of their potential to accumulate in the human body and food chains. On 12-13 February 2024, a wide range of stakeholders, including governments, industry, non-governmental organisations (NGOs), and academics came together to discuss various topics related to PFAS. These topics covered areas such as country risk management approaches, innovation challenges for finding safer alternatives, effective risk communication strategies, monitoring techniques, waste management, and approaches to managing contamination.

1. Spatial and Temporal Trends of PFAS in
Oceans, Coastal Areas, and Air
on a Global Scale
Amila O. De Silva
Research Scientist
Environment and Climate Change Canada
Burlington, ON, Canada
Robert Letcher, Tom Harner,
Hayley Hung, Amandeep Saini

2. • 2005 paper “A Global Survey of Perfluorinated Acids in Oceans” by Yamashita et al.
• picogram per litre detection limits PFBS, PFHxS, PFOA, PFNA, PFOS, FOSA
• International research cruises in Pacific Ocean, Atlantic Ocean, South China Sea, coastal seawater
from Japan, China, Korea
PFAS in the Marine Environment
• 2021 Review
Nobuyoshi Yamashita et al. 2005. A global survey of perfluorinated acids in oceans. Mar Pollut Bull; 51(8-12):658-68

3. PFAS in the Marine Environment – Slow to Change
• Twenty years of PFAS data in oceans and coastal waters
• Perfluoroalkyl acids (PFAA): Persistence, high water solubility, and low partitioning to
organic matter
• Very slow removal in oceans:
outflow to other oceans,
vertical eddy diffusion, deep water
formation, and settling particles
Modeled Removal
Half-Life (years)1
North Atlantic
PFOS 5.8
PFOA 3.0
1 Zhang, X. et al. 2017. Global Biogeochemical Cycles. 31:1332-1343; Gonzalez-Gaya, B. et al. 2014. Environ. Sci. Technol.
48:13076-13084; Lohmann, R. et al. 2013. Environ. Pollut, 179:88-94.
Depth [PFAA]
mixed
layer
depth
(z)

4. Spatial Trends in PFAS in Oceans, 2010-2019
Sum of perfluorocarboxylic acids (PFBA to PFDoDA)
Sum of perfluorosulfonic acids (PFBS, PFHxS, PFOS, PFDS)
Muir and Miaz. 2021. Environ. Sci. Technol. 55, 9527-9537
• Results are lacking from coastal
areas:
• North America
• South America
• Africa
• India
• Australia

5. Casas, Gemma et al. (Dachs) 2023. Inputs, amplification, and sinks of perfluoroalkyl substances at coastal Antarctica. Environ. Pollut. 338: 122608.
PFAS in coastal Antarctica 2018
• Total PFAAs 50-1020 pg L-1
• Higher total concentrations in a few sites that also had PFUnDA, PFDoDA, PFTrDA (C11-13 PFCAs)
PFBS
PFOS
30 m

6. Casas, Gemma et al. (Dachs) 2023. Inputs, amplification, and sinks of perfluoroalkyl substances at coastal Antarctica. Environ. Pollut. 338: 122608.
PFAS in coastal Antarctica 2018
• Higher total concentrations in a few sites that also had PFUnDA, PFDoDA, PFTrDA (C11-13 PFCAs)
• Penguin colonies and likely guano wash off are a source of PFCA amplification
PFBS
PFOS
30 m

7. • 91 river estuaries sampled for surface waters
along the entire coast of China in 2018
• Measured concentrations (Criver, ng L-1 )and
discharge rate (Qriver, m3 year-1) to calculate
mass loading
PFAS in coastal China in 2018
Du, D. et al. (Yonglong Lu) 2022. Perfluoroalkyl acids (PFAAs) in water along
the entire coastline of China. Environ. International. 169: 107506.

8. Total mass loading (all rivers)
= 131 tonnes ∑PFAA in 2018
Du, D. et al. (Yonglong Lu) 2022. Perfluoroalkyl acids (PFAAs) in water along the entire coastline of China. Environ. International. 169: 107506.
∑PFAA concentrations:
1.6 to 620 ng L-1
Mean: 40 ng L-1 PFOA
17 ng L-1 PFBA
12 ng L-1 PFBS
• 7013 fluorochemical industries in
mainland China; 69% are in coastal
provinces;

11. Han, T. (Xiuping He) et al. 2022. Spatial distribution, vertical profiles and transport of legacy and
emerging per- and polyfluoroalkyl substances in the Indian Ocean. J. Hazardous Materials, 437:
129264
Spatial Distribution of PFAAs in Indian Ocean
Northwest
Pacific Ocean
Joint -Asian-
Indian-Pacific
Southwest
Indian Ocean
Northeast
Indian Ocean
• Sampling in 2019-2020
• 92 surface water
samples
∑PFAA
(pg L-1)
• NEIO 44
• SWIO 24
• JAIPO 64
• NWPO 219
• PFOS detection frequency was
< 20% in all regions except
northwest Pacific (80% d.f.)
• Mostly PFHxA and PFHpA
• Data quality? PFBA and PFPeA

12. Spatial Distribution of PFAAs in Canadian Arctic Ocean
Barrow Strait Lancaster Sound
Devon Island
Cornwallis
Island
Bathurst
Island
Ellesmere
Island
Somerset
Island
Prince of
Wales
Island
Jones Sound
Melville
Sound
Resolute
Bay
Grise
Fiord
• Under ice sampling in May
• Barrow Strait near Resolute Bay, Nunavut,
Canada
• PFBA is the major PFAA unless you include
shorter PFAAs
De Silva, Kirk, Muir et al. Northern Contaminants Program M-15

13. • Sea spray aerosols are enriched in
PFAAs
• 48 hours of aerosols collected over 2
years
• Two coastal locations in Norway
• Highest concentrations were PFOA
and PFNA
• Mechanism for delivering PFAS from
ocean to land

14. Tom Harner, Amandeep Saini, and Hayley Hung
Air Quality Research Division, Science and Technology Branch
Environment and Climate Change Canada (ECCC)
Measurements of PFASs in Air:
Globally (GAPS Network), Arctic
(AMAP, NCP) and in the Great Lakes
Basin

15. 15
The Global Atmospheric Passive Sampling (GAPS)
• Address needs under Canada’s Chemicals Management Plan and the Global Monitoring Plan
• Currently ~60 sites under core GAPS network (since 2005) and 23 sites under GAPS-Megacities
(since 2018)
polar
background
rural
agricultural
urban
megacities

16. Saini et al., Environ. Pollut. 2023
GAPS Network - 2017

17. Saini et al., Environ. Pollut. 2023
GAPS Network - 2017
FTOHs PFCAs

18. Saini et al., Environ. Pollut. 2023
GAPS Network - 2017
FASAs PFSAs
FOSEs

19. PFASs (2017)
Latest Paper - Saini et al., Environ. Pollut. 2023
LC-PFASs
(2017)
Saini et al., Environ. Pollut. 2023
Passive air samples in GAPS-2017
PFAS congener distribution

20. 20
GAPS
MEGACITIES
23 countries
(since 2018)

21. ×
Seasonal cycle Trend Measured
• Active air sampling using PUF-XAD-PUF
• Observe declines but lagging behind industry shifts and
regulatory decisions
• Presence in landfills and in existing products may prolong
emissions
• Similar to ice core deposition results.
Alert, Nunavut
PFAS Monitoring in Arctic Air – Alert, Nunavut
Northern Contaminants Program (NCP)
PFOA PFOS
ln
concentration
(pg
m
-3
)

22. • 2014 polar bear livers samples from Arctic Canada
• Western Hudson Bay (WHB), n= 17; Southern Hudson Bay (SHB), n=24
• Apex marine mammal, year-round resident to Arctic
PFAA in an Arctic Apex Predator: Polar Bears
• Long chain C8-16PFCAs consistently
detected
• Most ocean measurements are C4-
C10 PFCA with low concentrations
of PFNA and PFDA
• Wildlife monitoring demonstrate
the presence of long chain PFCAs in
the marine environment
Letcher, R.J. et al. 2018. Sci. Tot. Environ. 610-611: 121-136.

23.  Continue to track PFAS on spatial and temporal scales
 Assess effectiveness of international control measures (e.g., Stockholm
Convention)
 Air: Extend target lists to include novel PFASs and ultra-short chain PFASs
 Air: Are there other volatile precursors? Total organofluorine methods or
TOP assays?
 Water: Aqua-GAPS to achieve full spatial extent
 Wildlife: Consider short chain and ultrashort chain ecotoxicity using
environmentally relevant concentrations
 Wildlife: Monitor fluorotelomer precursors x:3 FTCA
 All media: fluoropolymers?
 Include PFASs hotspots for air (e.g. cities) and water and linkages to
ecosystem and human toxicity (assays)
Future Directions
Amila.desilva@ec.gc.ca

24. Extra slides

25. Volatile
precursors:
FOSAs
(MeFOSA+
EtFOSA);
FOSEs
(MeFOSE,
EtFOSE)

26. Volatile precursors (continued): FTOHs in Alert Air
8:2 FTOH 10:2 FTOH
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
2006
2007
2008
2009
2010
2011
2012
2013
2014
2015
2016
2017
2018
6:2 FTOH was added in 2010. Concentrations are similar to 8:2 FTOH

27. Saini et al., Environ. Pollut. 2023 GAPS Network – PFASs Temporal Trends

28. Application of Passive Samplers to the
Marine Environment
• Successful in deploying passive samplers for PFAS but not PFBA
• PFAAs detected in very deep water.

29. SHB
WHB
Temporal Trends of PFAAs in Hudson Bay Polar Bears
WHB; PFNA
2005 2010 2015 2020
0
250
500
750
1000
6.1 % yr-1
SHB; PFNA
2005 2010 2015 2020
0
500
1000
1500
2000
0.80 % yr-1
2005 2010 2015 2020
0
20
40
60
80
100
120
SHB; PFOA
-2.7 % yr-1
WHB; PFOA
2005 2010 2015 2020
0
20
40
60
80
1.5 % yr-1
2005 2010 2015 2020
0
1000
2000
3000
4000
5000
6000
SHB; PFOS
Medians: -5.8 % per yr
Subadults, 15N adj - 8.7 % per yr
WHB; PFOS
2005 2010 2015 2020
0
500
1000
1500
2000
2500
median + 0.30 % per yr
Subadults, 15N adj + 4.4 % per yr
(Letcher et al. 2024. Environ.
Pollut. In prep.)
• PFOS declining or no
change
• PFNA increasing or no
change.
• Similar trends in ringed
seals
• Climate change food
web shifts

30. Long-chain PFCAs - Stockholm Convention
9
carbons
10
carbons
11
carbons
Alert, Nunavut

31. Long-chain PFCAs - Stockholm Convention
9
carbons
10
carbons
11
carbons
Alert, Nunavut

32. PFOS and PFOA in Precipitation and Surface Water in Great Lakes
ln
(C/
ng
L
-1
)
Volume
of
Precipitation
(L)
Gewurtz et al., EST2019
PFOS
PFOA

33. Great Lakes Basin (GLB) Monitoring & Surveillance Program
• Canada/US Great Lakes Water Quality Agreement (GLWQA)
 Air and precipitation monitoring for POPs started in late 80s.
 PFAS monitoring in precipitation since 2006
 Monitoring in air started 2018 at Point Petre and 2019 in Evansville
Air Concentrations of PFASs

34. PFAS Analysis Difficulties
INCORPORATION OF POLAR ANALYTES
INTO LCMS METHOD
MATRIX EFFECTS AND RECOVERY
Improvement of retention of short-chain ionic PFAS (TFA,
PFPrA, TFMS, PFPrS, PFBA, PFBS) with a switch of LC column
and separation conditions
Recovery issues found in select PUF samples, by examining the injection
and surrogate standards one can get a hint to if the issue was
inappropriate spiking, ionization suppression, or both
13C4-PFOA Surrogate
0
20
40
60
80
Relative
Abundance
5.4 5.6 5.8 6.0 6.2
Time (min)
Very low
recovery in the
PUF extract
(< 10 %)
100
0
20
40
60
80
100
Relative
Abundance
GFF MeOH extract
PUF/XAD/PUF MeOH extract
13C8-PFOA Injection Standard
Injection
standard area
counts within
+/- 20 %,
therefore not an
ionization
suppression
issue