PFOS, Land Application of Residuals, Dairy Farms …...Andrew Smith, SM, ScD State Toxicologist...
Transcript of PFOS, Land Application of Residuals, Dairy Farms …...Andrew Smith, SM, ScD State Toxicologist...
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Andrew Smith, SM, ScD
State Toxicologist
Maine Center for Disease Control and Prevention
January 14, 2020
PFOS, Land Application of Residuals, Dairy Farms and Milk
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What is PFOS?(perfluorooctane sulfonic acid)
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Carbon backbone Acid Group
Octane
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Perfluorooctane sulfonic acid (PFOS)
C C C C C C C C
Maine Department of Health and Human Services
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PFOS is Toxic
Maine Department of Health and Human Services
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Toxicity Values for PFOS
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We are all exposed to
PFOS.
Source:National Report on Human Exposure to Environmental Chemicals – US CDC: https://www.cdc.gov/exposurereport/index.html
Why are we concerned about PFOS?
Maine Department of Health and Human Services
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PFOS stays in
our bodies for years.
Sources:Li et al.. Occup. Environ. Med. Vol. 75:46-51 (2018). Zhang et al. Envion. Sci. Technol. Vol 47:10619-27 (2013)
Why are we concerned about PFOS?
Maine Department of Health and Human Services
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PFOA PFOS PFHxS PFHpA PFNA
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Per-fluorinated Akly Substances
Half-Life in Human Body for Selected PFAS (years)
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PFOS is Persistent and Mobile- Stoneridge Farm -
151
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Soil / Hay in µg/kg, dw
Water / Milk in ng/L
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Maine Department of Health and Human Services
Soil
Hay
Milk
Water
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Is it the hay or the water?
PFOS levels for milk and
water in nanograms / liter
Milk 1400 ng/L
Ground Water
40 – 130 ng/L
Hay9.6 µg/kg,
dw
Kowalczyk et al. 2013.
Maine Department of Health and Human Services
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PFOS
2700 µg/kg, dw
Based on USEPA RfD of 20 ng/kg/day, 95th percentile incidental soil ingestion rate for a 1-6 year old child, 150 days / year.
PFOS Soil Screening Levels for Residential Soil Exposure Pathway - 2017
Maine Department of Health and Human Services
ST1ST2
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Slide 8
ST1 I would use the RAG here as the chapter 418 standard wouldn't necessarily be the applicable standard applied in this case, i.e., that is a
new site with contaminated soils where you don’t know the source. DEP would use the soil RAG to evaluate.Simones, Thomas, 9/11/2019
ST2 I would also use the 2018 RAG of 1700 ug/kg to avoid any confusion and mention that at the time of discovery the RAG was 2700.Simones, Thomas, 9/11/2019
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What would be a PFOS soil screening level for the dairy farming scenario?
Soil → Hay/Corn → Cow → Milk → Child
Maine Department of Health and Human Services
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EPA PRGR Soil Screening Level Equation
Agronomic Pathway
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Plant uptake and soil loading
Fraction of time exposed to contaminated feed
Animal ingestion rates
Transfer Factor from Intake to
Milk
Source:Modified equation from U.S. EPA Preliminary Remediation Goals for Radionuclides, consumption of milk back calculated to soil -https://epa-prgs.ornl.gov/radionuclides/users_guide.html
Fraction of time exposed to contaminated soil
Milk Action Level
“Adulterated”
Maine Department of Health and Human Services
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Plant Uptake – Plant Transfer Factors
Transfer pathways:
1. Root uptake
2. Translocation
3. Soil resuspension
1
Maine Department of Health and Human Services
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2
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PFOS Corn Transfer Factor (TFplant)
TFcorn = < 0.08
TFcorn = 0.04
TFcorn = 0.16Maine Department of Health and Human Services
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PFOS Hay Transfer Factor (TFplant)
TFhay = 0.07
TFhay = 0.1
TFhay = 0.5Maine Department of Health and Human Services
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Plant Soil Mass Loading Factor (MLF)
Source:*Hinton, T.G. 1992. Contamination of plants by resuspension: a review, with critique of measurement methods. Sci Total Environ. 121:117-193. DOI: https://doi.org/10.1016/0048-9697(92)90314-I**Pinder III, J.E. et al. 1989. Mass loading of soil particles on plant surfaces. Health Physics. 57(6):935-942.
Processes for transfer of soil to plant surface• Rain splash• Wind erosion• Soil disturbance by mechanical equipment
USEPA PRGR Defaults• Default = 0.25, range 0.001 to 0.5• Geometric mean of 11 studies* = 0.034
(pasture plants only)
MLF = 0.034
CORN**0.0014
Maine Department of Health and Human Services
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Dairy Farm Scenarios
Grass-fed Dairy Farm
“Average” Maine Dairy Farm
Corn Silage (20%)
Grain (15%)
Hay (65%)
Corn Silage (37%)
Grain (35%)
Hay (20%)
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Soil Ingestion while Grazing
Maine Department of Health and Human Services
USEPA PRGR Defaults
• 2 % of total dry matter intake
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PFOS Milk Transfer Factor (TFmilk )
Source:Kowalczyk et al. 2013. Absorption, distribution, and milk secretion of the perfluoroalkyl acids PFBS, PFHxS, PFOS, and PFOA by dairy cows fed naturally contaminated feed. J Agric Food Chem. 61(12):2903-12. https://doi.org/10.1021/jf304680jVestergren et al. 2013. Bioaccumulation of perfluoroalkyl acids in dairy cows in a naturally contaminated environment. Environ Sci Pollut Res Int. 20(11):7959-69. https://doi.org/10.1007/s11356-013-1722-x
PFOS in Milk Feeding Study
• ObservedTFmilk = 0.005• Steady-state TFmilk = 0.02 to 0.08
Maine Department of Health and Human Services
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Milk Exposure Limit
Action Level
270ng/L
210ng/L
Relative Source
Contribution80%
Toxicity Value20 ng/kg/day
90th Percentile Milk Intake
0.074 L/kg/day
Action Level for “adulterated” Milk
1-2 year oldMaine Department of Health and Human Services
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Example Soil SL Calculation for Hay
Source:Modified equation from U.S. EPA Preliminary Remediation Goals for Radionuclides, consumption of milk back calculated to soil -https://epa-prgs.ornl.gov/radionuclides/users_guide.html
13,800 ng/kg dw(13.8 µg/kg dw) 204 ng/kg
0.02 day/kg
6.5 kg/day
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1
0.07 0.034 0.13 kg/day
1
0.68 kg/day
1 0.5
0.065 kg/day
Maine Department of Health and Human Services
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Example Soil SL Calculation for Corn Silage
Source:Modified equation from U.S. EPA Preliminary Remediation Goals for Radionuclides, consumption of milk back calculated to soil -https://epa-prgs.ornl.gov/radionuclides/users_guide.html
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204 ng/kg
31,300 ng/kg dw(31.3 µg/kg dw)
0.02 day/kg
8.7 kg/day
1
0.04 0.0014
1
0.32 kg/day
Maine Department of Health and Human Services
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Example Soil Screening Levels
for Dairy Farm Scenarios
EPA “Subsistence Dairy Farm”
• Diet: Hay (65%) Corn (20%) Grain (15%)
SSL = 6 µg/kg, dw
Average Maine Dairy Farm
• Diet: Hay (28%) Corn (37%) Grain (35%)
SSL = 10 µg/kg, dw
Maine Department of Health and Human Services
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Ground-truthing Model Predictions
151
759
99.5
878
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98.2
62.7
6.7
0.6
5.4
1.8
4.7
0.7
ND
Soil / Hay in µg/kg, dw
Water / Milk in ng/L
4.6
3.6
Maine Department of Health and Human Services
Milk 680 - 1400
ng/L
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Model Estimated PFOS Milk Levels based on
Stoneridge Farms Average Soil Levels
Stoneridge Farms PFOS site-wide soil level estimates (ug/kg dry weight)
Model estimated PFOS milk (ng/L)
123 (arithmetic average)
3,808
25 (geometric mean)
734
Initial average measured PFOS milk levels at Stoneridge Farms = 1,117 ng/L
NOTE – Does not include water contribution, which could add 90 – 200 ppt to milk.
Maine Department of Health and Human Services
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Next Steps
Soil-to-Corn PFOS Uptake Study (DEP, MECDC, DACF)
• Collected matched soil and silage corn samples for PFOS analysis
• Identified a laboratory to perform plant PFOS analyses• Awaiting plant data to derive a transfer factor
Ongoing model refinements
• Evaluating consensus on toxicity values• Monitoring new literature / reports on plant uptake• Looking for more farms to test model against
Maine Department of Health and Human Services
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Thomas Simones, PhDToxicologist
Maine Center for Disease Control and Prevention
Questions?
Andrew Smith, SM, ScDState Toxicologist
Maine Center for Disease Control and Prevention