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The evolving landscape for monitoring PFAS contamination
in Michigan waters A. Daniel Jones
Departments of Biochemistry & Molecular Biology and Chemistry
Michigan State University
PFAS-contaminated sites in the USA
https://www.ewg.org/interactive-maps/2019_pfas_contamination/map/?_ga=2.218015830.1928543270.1557336601-58557188.1553190153
Relevance of PFAS to Michigan water resources
45% of Michigan citizens are served by groundwater (700 million gallons/day)
Public water supplies using groundwater serve 1.7 million Michigan residents
In 2016, US EPA issued a lifetime health advisory of 70 ppt (ng/L) of PFOA and PFOS combined in drinking water
https://www.michigan.gov/documents/deq/deq-wd-gws-wcu-groundwaterstatistics_270606_7.pdf
https://mdeq.maps.arcgis.com/apps/webappviewer/index.html?id=36c48f4a7d144c21a79291ba280cf50b
What are PFAS?
Per- and poly-FluoroAliphatic Substances
Chains of carbon (and oxygen) atoms of different lengths and end groups
More than 4700 different chemical substances (OECD, 2018)
Renowned for repelling both oils and water
Excellent lubricants over a wide range of temperatures
Per-fluorinated Poly-fluorinated
http://www.oecd.org/chemicalsafety/portal-perfluorinated-chemicals/
Most dataRegarding
toxicity
What are PFAS?, continued
Many exist in ionized forms in water
Low- to moderate-solubility in water
Transported through groundwater and surface water
Often enriched at water-air interface
Taken up by plants animals (fish)
Wang et al., (2017) Environ. Sci. Technol., 51, 2508−2518
PFAS propertiesThe C—F bond is the strongest
Non-flammableInert“Forever Chemicals”
Small molecules (surfactants; stain-resistant coatings)
Polymers (coatings; lubricants)
Accumulate by protein binding
“There are no known natural environmental processes in water and soil that can completely destroy perfluorinated chemicals….”
Scientific Evidence and Recommendations for Managing PFAS Contamination in MichiganMichigan PFAS Science Advisory Panel, December 2018
https://www.michigan.gov/documents/pfasresponse/Science_Advisory_Board_Report_641294_7.pdf
Environmental persistence of PFAS
Some PFAS are:
Persistent in the environment
Bioaccumulate in living organisms
Toxic at part-per-trillion (ppt) concentrations for PFOS and PFOA (ng/L or ng/Kg)
PFASChain length
Est. half-life in humans
PFBS 4 28 days
PFBA 4 3 days
PFHxS 6 5.3-8.5 yrs
PFHxA 6 32 days
PFOS 8 3.4-5.0 yrs
PFOA 8 2.1-3.8 yrs
F-53B 9 15.3 yrs
Longer chain PFAS are considered more toxic than short chain PFAS
PFAS in commercial products
http://www.surftechengg.com/Hard_Chrome_Plating.html
PFAS historical timeline
https://pfas-1.itrcweb.org/wp-content/uploads/2017/11/pfas_fact_sheet_history_and_use__11_13_17.pdf
2016 EPA issues a lifetime health advisory of 70 ppt for PFOS and PFOA (individually and in combination)
Linear and branched-chain PFAS
Blood serum specimen from the Isle of Wight (UK) from 30 years ago
LC/Qtof MS shows evidence of both
Branched isomers consistent with 3M electrochemical fluorination process
Branched Linear
Data courtesy Dr. Thilani Anthony, MSU
Aqueous film-forming foams (AFFF)47 compounds detected
WJ Backe et al., dx.doi.org/10.1021/es3034999 | Environ. Sci. Technol. 2013, 47, 5226−5234
****
Pathways of human exposure to PFAS
Atmosphere
Wastewater
Treatment
Plant (WWTP)
Production and
Large-scale Use
of PFAS Products
Landfill
Groundwater
Biosolids
Surface water
Soil
Crops
and
Food
Drinking water
Human
Exposure
Consumer
Products
Indoor dust
Pathways to human exposure
For the majority of the human population, most exposure to PFAS comes through the diet
Levels of PFOS and PFOA in blood are 100- to 1000-fold higher than “background” levels in drinking water
Drinking water becomes the dominant contributor in populations near contaminated sites (industrial, military)
Knowledge gaps regarding exposure in specific populations
Almost all of us are more contaminated than our drinking water
Vestergren and Cousins (2009), Env. Sci. Technol. 43: 5565
Targeted PFAS analysis using LC/MS/MS
Sample prep (EPA method 537.1)
Add 13C-labeled internal standards
Pass 250 mL of water through 0.5 g polystyrene-divinylbenzene SPE cartridge
Elute with methanol
Evaporate to dryness
Dissolve in 1 mL 96% methanol/4% water
Special precautions for LC/MS/MS analysis of PFAS
No fluoropolymer tubing
No PTFE liners in sample collection bottles or vials
Isolator column to delay elution of PFAS present in solvents or HPLC
“New” generation fluorinated ether PFAS surfactants
New PFAS compounds are introduced as others are phased out
Accelerated diversity in PFAS chemistry can be expected in coming years
Reference standards for new PFAS are becoming available
Not yet expected to be of serious concern in Michigan
PFAS analytical challenges
EPA Method 537 Rev. 1.1 (14 target analytes in drinking water only)
SPE gives poor capture of short-chain PFBA and PFPeA
Modified method 537.1 (18 targets, Nov 2018)Added perfluoropolyethers HFPO-DA (GenX), ADONA, 9Cl-PF3ONS (F-53B), 11Cl-PF3OUdS
Validated methods for other matrices (including groundwater) are under development
Current and pending PFAS analytical methods
Analyte# of
C
EPA 537
(2009)
EPA 537.1 (2018)
ASTM D7979
ASTM 7968-17a
MDEQ IPP
PFBS 4 X X X X X
PFBA 4 X X X
PFPeS 5 X
PFPeA 5 X X X
PFHxS 6 X X X X X
PFHxA 6 X X X X X
4:2 FTS 6 X
HFPO-DA 6 X
PFHpS 7 X
PFHpA 7 X X X X X
ADONA 7 X
PFOS 8 X X X X X
PFOA 8 X X X X X
FOSA 8 X
6:2 FTS 8 X
9Cl-PF3ONS
8 X
PFEcHS 8 X X
FHEA 8 X X
FHUEA 8 X X
Analyte# of
CEPA 537 (2009)
EPA 537.1 (2018)
ASTM D7979
ASTM 7968-17a MDEQ IPP
PFNA 9 X X X X X
PFNS 9 X
PFDA 10 X X X X X
PFDS 10 X
8:2 FTS 10 X
11Cl-PF3OUdS
10 X
FOEA 10 X X
FOUEA 10 X X
FHpPA 10 X X
PFUnA 11 X X X X X
NMeFOSAA 11 X X X
PFDoA 12 X X X X X
NEtFOSAA 12 X X X
FDEA 12 X X
PFTriA 13 X X X X X
PFTreA 14 X X X X X
# 14 18 21 21 24
Proposed legislation (US Senate)
PFAS Action Act of 2019
“the Administrator of the Environmental Protection Agency shall designate all per- and polyfluoroalkyl substances as hazardous substances”
How does one distinguish PFAS chemicals from other organofluorine chemicals (e.g. herbicides, refrigerants)?
Most telomer alcohol-based PFAS are not currently measured
Oxidative (aerobic) degradation converts polyfluorinated telomer alcohol-based compounds to perfluorocarboxylates (PFCAs) which are resistant to further degradation
Oxidative degradation of telomer precursors of PFCAs can lead to higher measured PFCA levels after wastewater treatment
Presence of telomer alcohol precursors of PFCAs can be revealed using the Total Oxidizable Precursor (TOP) assay
LC/MS/MS analysis of each sample performed twice; with and without sample oxidation (hydroxyl radicals)
Alternative methods for PFAS in water
Total organic fluorine/ Total adsorbable fluorine rely on combustion ion chromatography (CIC)
Concentrate organic fluorine on a weak anion-exchange (WAX) solid phase extraction cartridge
High-temperature combustion forms CO2 and HF (trapped in water)
Fluoride is quantified using ion chromatography
T ~ 1050˚C
CIC struggles to achieve low ng/L detection limits
Interference from fluorine-containing herbicides
Compromises between eliminating inorganic fluoride and retaining
short-chain PFAS
Most organic fluorine in wastewater treatment goes undetected using targeted LC/MS/MS
U. Eriksson et al., Per- and polyfluorinated alkyl substances (PFASs) and total organofluorine (TOF) in sludge and water from Swedish waste water treatment plants (WWTP)
Summary
There are many aspects of PFAS contamination that we do not understand.
Current analytical methods focus on a small number of target analytes
Commercial production of PFAS continues to shift to a different mix of chemicals (ethers)
Proposed legislation may change future water testing
TOP assay (and untargeted LC/high resolution MS analyses) likely to become more important for assessing contamination by PFAS precursors
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