Office of Research and DevelopmentNHEERL, Gulf Ecology Division, Gulf Breeze, FL 32561Office of Research and DevelopmentNHEERL, Gulf Ecology Division, Gulf Breeze, FL 32561

Mace BarronUSEPA Office of Research and Development

Dispersant ToxicologyEfficacy and Effects

Insert/replace photos

Of relevance to EDC tests

Outline

• Overview of oil spill dispersant efficacy and effects

• EPA dispersant testing program

• Implications for spill response

Background Reports:

• NRC (2005) oil spill dispersant efficacy and effects

• RSC (2015) Canada expert report on oil behavior and impacts

• EPA journal articles on dispersant testing

www.nap.edu/catalog/11283/oil-spill

-dispersants-efficacy-and-effects

www.rsc-src.ca/sites/default/

files/pdf/OIW%20Report.pdf

3

What is a dispersant?

• Many products, varied components

• proprietary formulations of surfactants, light petroleum, solvents

• break oil into tiny droplets

• facilitates biodegradation, dilution

• effective on <30% weathered oil

• moves oil from slick into the water column

• tradeoff between surface/shoreline impacts and water column effects

• increased toxicity to aquatic organisms below the surface

www.nalcoesllc.com/nes/documents/MSDS/

NES-LLC-COREXIT-EC9500A-March_2012.pdf

www.nalcoesllc.com/nes/documents/MSDS/NESLLC-

COREXIT-_EC9527A-March_2012.pdf

Corexit MSDS

• similar composition; 9500A contains light petroleum distilates

• lab tests show similar toxicity and efficacy

• intrinsic toxicity of oil does not increase

• moderately toxic and much less toxic than oil

• chemically dispersed oil similar toxicity as physically dispersed oil

• increase the concentration of oil in the water column

• greater bioavailabilty to aquatic life

• reduce risks to shorelines and surface species

• increased risk to subsurface species (top 30 feet of water column)

• impacts to sub-surface resources less obvious

Principles of Dispersant Toxicology

EPA 2010 DWH Testing Program

Test 8 dispersants on NCP Product Schedule: • identify lower toxicity alternatives (EPA Administrator)

• verify information on NCP Product Schedule

• test Louisiana crude oil (SLC) instead of fuel oil #2

• concerns for nonylphenol ethoxylate degradation

Laboratory testing program:

• efficacy of oil+dispersant

• in vitro endocrine and cytotoxicity screening

• acute toxicity to two Gulf estuarine species

dispersant alone; SLC oil+dispersant

Lab Determination of Dispersant Effectiveness

• Baffled Flask Test (BFT) at 41 and 77 oF with SLC oil

• 3 of 8 satisfactory dispersion results (>70% efficacy)

• similar results at cold and warm temperatures SLC

• Corexit 9500A 75-80% lab dispersion

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Cytotoxicity and Endocrine Screening

• only test dispersants (no oil)

• in vitro testing using 80 mammalian cell line assays

• determine cell death, estrogen and androgen receptor activity

• dispersant only: tested at concentrations up to 10,000 ppm

• similar results in all 8 dispersants

• no estrogenic or androgenic activity detected at 10,000 ppm

• test tube cell death above 10 ppm

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EPA ORD

NCPPracticallyNon Toxic

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Comparison of EPA DWH and

NCP Dispersant-only test results

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Preparing Dispersant + Oil Mixtures

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Dispersant + oil Testing

• similar toxicity as oil alone

• dispersant-only less toxic

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il

Conclusions from EPA DWH Testing

• max efficacy in lab ~80% dispersion

• in vitro toxicity in mammalian cell lines toxicity > 10ppm

• acute ecotox consistent with NCP dispersant testing

• dispersants less toxic than dispersant + oil mixtures

• Corexit 9500A: moderate toxicity; reasonable efficacy

New EPA Testing Program

• dilbits (diluted bitumens; Keystone, other transport)

develop baseline tox data fresh and weathered dilbits

marine, freshwater species; acute and sublethal testing

• crude oils (support for Subpart J proposed rule)

develop baseline data for new EPA reference oils (TBD)

evaluate selected dispersants to determine impact on listing

expand testing beyond 2 standard test species

evaluate and refine proposed toxicity test guidelines

• Effectiveness depends on:

– accuracy of application

– oil type and weathering (less effective on heavy, weathered oils)

– how well mixed with oil (sufficient wave energy)

• Reduce risks to shorelines and surface species (birds, turtles, dolphin)

• Increased risk to subsurface species (top 30 feet of water column)

– impacts to sub-surface resources less obvious

• Standard toxicity testing only evaluates short term exposures

– sublethal and long term effects possible; research ongoing

Implications for Spill Response

Determining Dispersant Use

• Will mechanical response be sufficient?

• Is the spilled oil known to be dispersible?

• Are sufficient chemical response assets available?

• Are environmental conditions conducive to successful application

and dispersion?

• Will application reduce water surface and shoreline impacts without

significantly increasing aquatic life impacts?

QUESTIONS?

Mace Barron

Barron.mace@EPA.gov

Gulf Ecology Division, U.S. EPA

1 Sabine Island Drive, Gulf Breeze FL 32561

(850) 934 9223