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

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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