Microplastics Expert Workshop Report
Trash Free Waters Dialogue Meeting
Convened June 28-29, 2017
EPA Office of Wetlands, Oceans and Watersheds
Primary Author: Margaret Murphy, AAAS S&TP Fellow
Report Date: December 4, 2017
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EPA Microplastics Expert Workshop Report
Executive Summary
Recent global efforts to better understand microplastics distribution and occurrence have detailed both the
ubiquity of microplastics and the uncertainties surrounding their potential impacts.
In light of this scientific uncertainty, the US Environmental Protection Agency (EPA) convened a Microplastics
Expert Workshop in June 2017 to identify and prioritize the scientific information needed to understand the risks
posed by microplastics (broadly defined as plastic particles <5 mm in size in any one dimension (Arthur et al.
2009)) to human and ecological health in the United States. The workshop gave priority to gaining greater
understanding of these risks, while recognizing that there are many research gaps needing to be addressed and
scientific uncertainties existing around microplastics risk management (e.g., waste management/recycling/
circular economy principles, green chemistry approaches to developing alternatives to current-use plastics).
The workshop participants adopted a risk assessment-based approach and addressed four major topics: 1)
microplastics methods, including deficits and needs; 2) microplastics sources, transport and fate; and 3) the
ecological and 4) human health risks of microplastics exposure. A framework document was developed prior to
the workshop to guide discussion. During the workshop, the participants recommended adopting a conceptual
model approach to illustrate the fate of microplastics from source to receptor.
This approach is helpful in describing the various scientific uncertainties associated with answering the
overarching questions of the ecological and human health risks of microplastics, the degree to which
information is available for each, and the interconnections among these uncertainties. Draft conceptual models
were developed during the workshop, and these draft models were the basis for more detailed models
developed through discussions and comments from the participants after the workshop. The resulting detailed
models are introduced and explained in the main body of this report.
The participants identified the following priority scientific information needs within each of the four research
topics discussed during the workshop:
Methods needs: Establish reproducible, representative, accurate, precise methods for
microplastics analysis that include appropriate quality assurance/quality control (QA/QC)
for: microplastics sample collection; microplastics extraction from surface and drinking
water, dust, sediment and tissue samples; microplastics characterization (size, shape and
chemical composition [polymer, as well as additive chemicals]); and microplastics
quantification, particularly for particles in the micron scale (>1 pim and <1 mm in size) for
which information is limited and which are relevant to human and ecological exposure risks.
Microplastics sources, transport and fate needs: Conduct research on the sources,
transport, fate, and distribution of microplastics in the environment to be used for exposure
characterization in risk assessment of human and ecological health impacts, particularly to
understand and characterize: (a) how consumer product use and wear, agricultural practices
and waste management processes (including sludge land application and landfill leachate) in
the US contribute to microplastics in the environment, and (b) how particle characteristics
such as chemical composition (i.e., polymer type) affect microplastics behavior (transport,
degradation, and distribution);
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Ecological assessment needs: Create standardized toxicity tests for microplastics in test
organisms and ecologically representative organisms and systems (including field studies) to
understand the ecological impacts of microplastics, considering whether standard
laboratory tests and endpoints can be applied to microplastics toxicity assessments,
bioavailability of microplastics and their additive chemicals (especially particle translocation
and chemical bioaccumulation), and how dose-response relationships can be developed for
microplastics to better understand the full range of their potential impacts; and
Human health assessment needs: Create methods and conduct research to characterize
human exposure to and impacts from microplastics in drinking water (including source
water), seafood, freshwater fish and indoor/outdoor dust, in order to assess potential
human health risks.
Of the needs identified above, the workshop participants echoed the conclusion of many
microplastics review papers and reports that the development of reliable, reproducible and high-
quality methods for microplastics quantification and characterization is fundamental and of
paramount importance for understanding microplastics risks.
These priority scientific information needs are reflected in the discussion and conceptual models presented
below. Graphic representations of the models are provided on pages 11, 14, 17, and 20 of this report.
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Workshop Participants and Observers
Participants
Name
Agency/Affiliation
Invited Experts
Robert Hale
Virginia Institute of Marine Science
Paul Helm
Ontario Ministry of the Environment
Jenna Jambeck
University of Georgia
Kara Lavender Law
Sea Education Association
Chelsea Rochman
University of Toronto
Environmental Protection Agency
Christine Bergeron
Office of Water, Office of Science & Technology
Robert Burgess
Office of Research & Development, Atlantic Ecology Division
Bob Cantilli
Office of Research & Development, Office of Science Policy
Anna-Marie Cook
Office of Research & Development, Region 9 Superfund and Technology Liaison
Stanley Durkee
Office of Research & Development, Office of Science Policy
Kay Ho
Office of Research & Development, Atlantic Ecology Division
Greg Miller
Office of Water, Office of Science & Technology
Other Federal Agencies
Kathy Conn
US Geological Survey, Washington Water Science Center
Carlie Herring
National Oceanic & Atmospheric Administration, Marine Debris Program
Emanuel Hignutt
Food & Drug Administration, Center for Food Safety & Applied Nutrition
Amy Uhrin
National Oceanic & Atmospheric Administration, Marine Debris Program
Other
Margaret Murphy
AAAS Science & Technology Policy Fellow, Program Participant in the EPA Office of Water
Observers
Name
Agency/ Affiliation
Environmental Protection Agency
Sandra Connors
Office of Water, Office of Wetlands, Oceans & Watersheds
Kathryn Gallagher
Office of Water, Office of Science & Technology
Laura Johnson
Office of Water, Office of Wetlands, Oceans & Watersheds
Noemi Mercado
Office of Water, Office of Wetlands, Oceans & Watersheds
Kate O'Mara
Office of Research & Development, Office of Science Policy
Brian Rappoli
Office of Water, Office of Wetlands, Oceans & Watersheds
Grace Robiou
Office of Water, Office of Wetlands, Oceans & Watersheds
Surabhi Shah
Office of Water, Office of Wetlands, Oceans & Watersheds
Bernice Smith
Office of Water, Office of Wetlands, Oceans & Watersheds
Other
Juliette Chausson
ORISE Research Participant at the Office of Water, Office of Wetlands, Oceans & Watersheds, EPA
Claudia Gelfond
ORISE Research Participant at the Office of Water, Office of Science & Technology, EPA
Alix Grabowski
World Wildlife Fund
Mike Levy
American Chemistry Council
Emma Maschal
ORISE Research Participant at the Office of Water, Office of Wetlands, Oceans & Watersheds, EPA
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Introduction
Plastics pollution has raised concern worldwide, with a recent study estimating that 8 million metric tons of
plastics was released into the world's oceans in 2010 (Jambeck et al. 2015). Freshwater and terrestrial systems
are also affected by plastics pollution, and research over the past few decades has shown that plastic items such
as derelict fishing gear and plastic grocery bags can have detrimental effects on wildlife via entanglement and
ingestion (reviewed by Browne et al. 2015; Provencher et al. 2017). More recently, studies conducted around
the world have shown that microplastics, plastic particles <5 mm in size in any one dimension (Arthur et al.
2009), are widespread in marine and freshwaters, and may also have negative ecological impacts (GESAMP
2015; 2016).
Since its inception in 2013, the EPA's Trash Free Waters (TFW) program has pursued a multi-pronged approach
to reducing and preventing trash in US waters, including plastics. One part of this approach assesses the current
state-of-the-science of understanding the ecological and human health impacts of trash in the environment. As
part of this approach, TFW convened the "Expert Discussion Forum on Possible Human Health Risks from
Microplastics in the Marine Environment" in April 2014 (US EPA 2015). This discussion forum brought together
experts in plastics and microplastics to share their perspectives on microplastics pollution. The discussion at the
forum focused on microplastics as vectors for persistent, bioaccumulative and toxic substances (PBT), and the
participants determined that priority should be given to understanding the relative contribution of PBTs sorbed
to or present in microplastics in the context of other PBT sources to seafood to better assess human health risks.
Although microplastics have been identified as a potential environmental concern since the 1970s, research
efforts in this area have increased substantially in the last five years, and therefore TFW considered it relevant to
convene another expert group to make further recommendations toward improving our understanding of the
potential impacts of microplastics in the environment. The Microplastics Expert Workshop was convened on
June 28th and 29th, 2017 and included three of the experts who participated in the 2014 event.
Workshop Aims and Process
The central aim of the Microplastics Expert Workshop was to identify and prioritize the scientific information
needed to understand the risks posed by microplastics to human and ecological health in the United States. In
order to achieve this aim, a framework document and meeting agenda were prepared by an internal EPA
working group prior to the microplastics workshop as a means of guiding discussion using a risk assessment-
based approach (Appendices 1 and 2). The framework document was shared with the workshop participants
prior to the workshop for their comments, and their feedback was incorporated into the final version of the
document.
The workshop participants adopted a risk assessment-based approach and addressed four major topics:
1. Microplastics methods, including deficits and needs;
2. Microplastics sources, transport and fate;
3. The ecological occurrence and impacts of microplastics exposure; and
4. The human health effects of microplastics exposure.
The framework document includes brief summaries of what was known for each of the four major workshop
topics at the time of the workshop and associated key questions, as well as overarching considerations to be
taken into account during discussion. Briefly, these considerations were:
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a) Relevant microplastic size ranges for the four major topics, given that microplastics occur at sizes that
may encompass 6-7 orders of magnitude;
b) Plastic particle type/geometry/polymer, given the physical diversity of plastic polymers currently on the
market, and the large variation in microplastic shape, size and composition (reviewed by Andrady 2017);
c) Spatial and temporal heterogeneity, given that microplastics concentrations are known to be highly
variable across space and time; and
d) Future scenarios, given that plastics production is predicted to continue to increase in the next 5-10 years.
Two approaches were adopted for the four major topics during the workshop. Topic 1 was discussed according
to the framework document (Appendix 2), and a priority need was identified. In addition, the workshop
participants expressed that a conceptual model approach would be useful for identifying and prioritizing
scientific information needs for Topics 2-4 (microplastics sources, transport and fate; ecological exposure and
human exposure), and therefore this approach was adopted.
Conceptual Model Approach
Conceptual models were constructed to help guide the identification of the overall research priority for Topics 2-
4. Draft conceptual models were initially developed in the meeting room during the workshop, some of which
were relatively limited in scope. These draft models served as the basis for expanded models that were
developed in follow-up group conversations and communication with the workshop participants. Each of these
models is explained in detail in the corresponding sections for Topics 2-4 below.
The models share some common features: in each, color-coding is used to indicate the relative amount of
information currently available for that part of the model, with green, orange and red indicating most
information/good confidence, some information/moderate confidence and little information/low confidence,
respectively. These confidence levels were assigned by the workshop experts based on their knowledge of the
scientific literature and the quality of the data available therein, and are relative statements of confidence;
microplastics occurrence, exposure and effects data are generally lacking. Confidence levels were assigned by
group consensus. Priority areas for research are identified in the conceptual models and explained in the Notes
for each individual model.
Priority Information Needs Within Topic Areas
For each of the four topics, the priority need is presented first and then the flow of the discussion at the
workshop is briefly summarized. As Topic 1 underpins the other three topics, some specific methods needs were
also identified for Topics 2-4.
Icpic 1: Microplastics Methods
Priority need: Establish reproducible, representative, accurate, precise methods for microplastics analysis that
include appropriate quality assurance/quality control (QA/QC) for: microplastics sample collection; microplastics
extraction from surface and drinking water, dust, sediment and tissue samples; microplastics characterization
(size, shape and chemical composition [polymer, as well as additive chemicals]), and microplastics quantification,
particularly for particles in the micron scale (>1 /urn and <1 mm in size) for which information is limited and which
are relevant to human and ecological exposure risks.
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Much of the discussion of Topic 1 focused on the need to return to first principles of experimental design when
planning microplastics sampling and analysis. These first principles include considerations such as:
What is the research question being asked? For what purpose?
What are the impacts of the methods being used on the final results? What are the limitations of the
selected methods?
What is the acceptable uncertainty in the chosen methods, and how should this uncertainty be
accounted for?
What is the cost of the planned sampling and analysis?
The experts went into further detail by considering three broad steps of microplastics sampling and analysis:
microplastics field sampling; microplastics extraction, separation and cleanup; and microplastics quantification
and characterization. The relevant considerations for each of these steps as discussed by the participants are
presented in Table 1.
Table 1. Considerations when planning microplastics sampling and analysis.
Microplastics Field Sampling
Microplastics Extraction,
Microplastics Quantification and
Separation and Cleanup
Characterization
¦ Which sample type/matrix is
¦ What QA/QC methods can be
¦ What are the limitations of the
relevant?
used (e.g., to determine
methods used?
¦ What size range is relevant?
procedural recoveries or to
¦ Which polymers/particle types
prevent background
¦ Which particle/polymer types
contamination)?
are accounted for?
are relevant?
¦ What are the impacts of the
¦ How many samples are
chosen method on the final
¦ What are the detection limits
needed?
result? Will artifacts be
of the methods used?
¦ Will samples be kept discrete,
introduced?
homogenized or pooled for
¦ How can sorbed
analysis, and what does this
contaminants and microbes
mean for interpretation of the
be accounted for?
results?
¦ Which polymers/particle
¦ Which sampling method is
types are accounted for,
appropriate?
recognizing that some particle
¦ What sample volume is
types such as microfibers can
needed to get a
be challenging to extract and
representative sample?
may be lost?
¦ What quality assurance/
¦ What are the detection limits
quality control (QA/QC)
of the methods used?
methods are needed?
¦ Which units will be used for
the final results and what does
that mean for the
comparability of data?
¦ What are the detection limits
of the methods used?
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The group emphasized the importance of carrying out complementary analytical (instrumental) identification of
microplastics in addition to visual methods to help reduce the uncertainty inherent in these methods, which are
prone to error and can under- or over-estimate microplastics quantities, particularly for particles <1 mm in size.
The experts also expressed the need for high-throughput methods and instrumentation (including automation)
to increase the efficiency of microplastics analysis.
As reflected in the priority need for Topic 1, participants strongly emphasized the importance of including
appropriate QA/QC measures in microplastics sampling and analysis. In this area, they identified the needs
shown in Table 2. It should be noted that some microplastics types can be purchased commercially for use as
analytical standards; for example, polystyrene and polyethylene beads are available in a range of sizes. However,
most polymers cannot be purchased at standard sizes or in standard mixtures, leaving researchers to generate
their own microplastics for experimental use.
The experts shared their experience that the use of heat or corrosives (e.g., hydrogen peroxide) for sample
extraction led to loss of microplastics and/or waxes in samples, as well as losses of microplastics purchased for
use as analytical standards. The need for standardization also emerged repeatedly during the workshop
discussion, both with respect to methodology and terminology; for example, terms such as "foam", "film",
"fragment", etc. are currently commonly used to describe microplastics by shape, but there are no standard
definitions of these terms.
Table 2. QA/QC needs for microplastics sampling and analysis.
Microplastics Field Sampling
Microplastics Extraction,
Separation and Cleanup
Microplastics Quantification and
Characterization
¦ Methods to ensure the
statistical representativeness
of samples
¦ Consideration of the
implications of bulk sampling
versus pre-filtration/screening
¦ Use of appropriate blanks
(field and lab blanks) to assess
background contamination
¦ Use of appropriate methods
to reduce procedural
contamination in samples
¦ Standard reference materials
for microplastics in various
environmental media
¦ Analytical standards for
microplastics
¦ Use of appropriate blanks
(matrix and spikes)
¦ Use of aged particles rather
than pristine particles for
QA/QC, taking into account
relevant time scales of
environmental exposure for
the matrix being analyzed
¦ Use of individual versus
homogenized/pooled samples
¦ Instrumental library accuracy,
including pristine and
weathered microplastics
¦ Identifying and accounting for
analytical confounders
¦ Shape standard terms to
describe microplastics types
The experts discussed which information should be reported for microplastics data, and concluded that the
following parameters should be reported:
Particle sizes, including dimensions (if possible);
Particle shapes, taking into account the need for standardized terminology;
Polymer types;
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Particle quantity, taking into account the choice of units (e.g., mass/volume, mass/area,
particles/volume, particles/area);
Detection limits for the sampling and analysis methods used.
The group also discussed the need for different methods across sample matrices (e.g., water, sediment, tissue)
and whether different methods are needed for different plastic polymers, and noted that as researchers become
more confident in identifying polymer types, polymer-specific methods might be needed. The group further
discussed whether the types of plastics included in "microplastics" should be limited to the most widely
produced plastic polymers, but ultimately decided that qualitative limits were not needed.
Finally, the group emphasized that rigorous peer review was important to ensure that high-quality
microplastics data are available in the scientific literature.
Topic 2: Microplastic Sources, Transport and Fate
Priority need: Conduct research on the sources, transport, fate, and distribution of microplastics in the
environment, to be used for exposure characterization in risk assessment of human and ecological health
impacts, particularly to understand and characterize: (a) how consumer product use and wear, agricultural
practices and waste management processes (including sludge land application and landfill leachate) in the US
contribute to microplastics in the environment, and (b) how particle characteristics such as chemical composition
(i.e., polymer type) affect microplastics behavior (transport, degradation, and distribution).
The discussion of Topic 2 began with consideration of some of the questions included in the framework
document. The experts concluded that it was not necessary to limit the definition of microplastics to include
only widely-produced plastic polymers, but that it was important to consider how much of the plastics market is
currently captured by microplastics research (i.e., are all the polymers currently in use being investigated?). The
participants identified microplastics sources and processes that they considered important in the United States,
and these were incorporated into the conceptual model. The model was also used to determine relative levels
of confidence regarding microplastics occurrence data in the United States, as well as to identify priority
information needs (Model I).
See the graphic representation of Model I on page 11. The following bullets provide information on
how to read and interpret Model I.
Existing data on microplastics sources, transport and fate has been reviewed in detail by GESAMP
(2015; 2016).
Black rectangles represent abiotic environmental compartments. Each compartment is labelled in
UNDERLINED CAPITAL LETTERS.
Rounded boxes represent biotic compartments (receptors).
Notched rectangles represent microplastics sources, and those outlined in bold black lines are
priority areas for research.
Parallelograms represent processes that are likely to occur in every abiotic compartment, except
for biodegradation/biotransformation, which are expected to occur in biotic compartments.
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Microplastics are expected to distribute between adjacent abiotic compartments (i.e., there are
double-headed arrows among all of the rectangular compartments).
Biota living in each abiotic compartment will be exposed to microplastics occurring in that
compartment at varying concentrations. "Sediment organisms" includes demersal, benthic and
infaunal species.
Biotic interactions within, between and among abiotic compartments will also affect the
distribution of microplastics (e.g., predator-prey interactions, trophic transfer, inhalation of
microplastics by air-breathing organisms, human consumption of food items from multiple
compartments).
"Combustion/Burning" includes industrial combustion; backyard burning of waste; fires; and
catastrophic events.
"Flow, Transport and Deposition" includes flow conditions; particle settling and dynamics; long-
range transport; and dry and wet deposition.
"Freshwater Organisms" and "Marine Organisms" include aquatic-dependent organisms such as
amphibians, waterfowl and seabirds.
Table 3. Expected distribution of microplastics among the abiotic compartments in Model I.
Microplastics Source
Distribution to Abiotic Compartments
Sludge Land Application and
Landfill Leachate
Primarily S, G; potential for transport to W, CW, IH; FW, MW
Combustion/Burning
All compartments
Deposition
All terrestrial and aquatic compartments except G (Includes W, CW, IH)
Product Wear
All compartments
Mismanaged Waste
All compartments
Wastewater Effluents
G, W, FW, CW, IH, MW
Human Aquatic Activities
W, FW, CW, IH, MW
S: Soils; G: Groundwater; W: Wetlands; FW: Freshwaters; CW: Coastal Wetlands; IH: Intertidal Habitats; MW: Marine Waters
Apart from the references included in the comprehensive GESAMP reports (2015; 2016) referenced above,
additional information on the some of the environmental sources, processes and compartments identified in
Model I is arranged alphabetically below. These references are updated as of November 30, 2017.
Sources and Processes:
Agriculture: There are limited data available for agricultural practices as a source of microplastics
in the US. Two studies have examined the use of polyethylene mulches (Li et al. 2014; Brodhagen
et al. 2017) in the US, while another has suggested that land application of biosolids could be a
source to agricultural soils in the EU and land application of biosolids has been suggested as a
potential source of microplastics to agricultural soils in the EU (Nizzetto et al. 2016).
Atmospheric deposition: As noted above, one study in France has measured microplastics in
atmospheric fallout (Dris et al. 2016).
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Model I: Microplastics Sources, Transport & Fate in the US
| Little information; low confidence
[Some information; moderate confidence
I Most information; good confidence
Sources:
Sludge Land Application
Sewage
Agricultural
Drinking Water
Industrial
Food Waste/ Compost
Landfill
Leachate
Product Use
& Wear
Agricultural
Plastics
Mismanaged Waste
Plastic Pellets
Litter & Illegal
Dumping
Wastewater
Effluents
¦ Municipal
Industrial
Combustion/
Burning
Fisheries &
Aquaculture
Human Aquatic
Activities
Processes:
Flow, Transport & Deposition
Physical & Chemical Degradation
Biodegradation/
Biotransformation
Environmental Occurrence & Fate:
AIR
SOILS
SOIL ORGANISMS
WETLANDS
FRESHWATERS
FRESHWATER SEDIMENTS
SEDIMENT ORGANISMS
GROUNDWATER
COASTAL
WETLANDS/
ESTUARIES/
INTERTIDAL
HABITATS
COASTAL/
ESTUARINE
ORGANISMS
MARINE WATERS
WATER COLUMN
DEEP SEAWATER
ESTUARINE & MARINE SEDIMENTS
SEDIMENT ORGANISMS
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Combustion/burning: The fate of microplastics formed during combustion/burning likely depends
upon both polymer type (Andrady 2017) and the pollution controls in place during combustion.
Fisheries and aquaculture: Reviewed in a recent FAO report (Lusher et al. 2017). This source
category includes both active and inactive fishing and aquaculture gear (e.g., nets, traps, buoys,
fishing line, tarps, tubing and any other gear used for fishery or aquaculture purposes).
Human aquatic activities: This source category is a broad one that includes both recreational
activities such as boating and diving and commercial activities (e.g., shipping and transportation).
It also includes sunken vessels and planes. The experts noted that ship paints may be a source of
microplastics in aquatic environments. This category also includes legal ocean disposal of waste,
such as of dredged sediments.
Product wear: Limited information is available on how rapidly microplastics are generated from
the breakdown of plastic products. Data on the degradation of several plastic types has been
reviewed by Fotopoulou & Karapanagioti (2017), and tire wear has been reported to be a major
source of microplastics in some European countries such as Norway (Sundt et al. 2014) and has
been reviewed in a recent paper (Kole et al. 2017). The generation of plastic microfibers by the
use and laundering of synthetic fabrics has also raised concern (Browne et al. 2011; Hartline et al.
2016; reviewed by Salvador Cesa et al. 2017). Wear rates are likely to be highly product- and
condition-dependent.
Compartments:
Air: There are no data available for microplastics in air in the US. The only studies worldwide have
been carried out in France and Iran, and reported that microplastics were present in indoor and
outdoor dust samples and atmospheric fallout (Dris et al. 2015; 2016; 2017; Dehghani et al. 2017).
Groundwater: There are no data available for microplastics in groundwater in the US. Some
states (e.g., Florida) discharge wastewater treatment plant effluent into subterranean aquifers
(http://www.dep.state.fl.us/southeast/water/uic.htm), and one of the workshop experts noted
that plastic filters are often used during the injection process.
Marine waters: Reviewed in a recent publication (Law 2017).
Marine waters, sediments and biota: Reviewed in a recent publication (Auta et al. 2017).
Sea ice: Two studies have reported the occurrence and release of microplastics from Arctic sea ice
(Obbard et al. 2014; Bergmann et al. 2017).
Surface freshwaters: Most of the data for surface waters are for particles >333 nm because of the
use of plankton nets for sampling (recently reviewed by Horton et al. (2017)). Among US
freshwaters, the Great Lakes have been comparatively well studied (Driedger et al. 2015; IJC 2016).
Soils: There are limited data available for soils in the US. The terrestrial compartment is home to
the vast majority of plastics in either contained (landfills) or uncontained (litter) form. Terrestrial
microplastics pollution was recently reviewed by Horton et al. (2017).
Global climate change may also affect microplastics occurrence and distribution, for example by causing large-
scale release of microplastics from sea ice (Obbard et al. 2017), or through stronger storms and subsequent
flooding that result in sewage overflow and micro- and macro-debris making its way to coastal and freshwaters
more frequently and in larger amounts.
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Topic 3: Ecological Occurrence and Impacts of Myoplasties
Priority need: Create standardized toxicity tests for microplastics in test organisms and ecologically
representative organisms and systems (including field studies) to understand the ecological impacts of
microplastics, considering whether standard laboratory tests and endpoints can be applied to microplastics
toxicity assessments, bioavailability of microplastics and their additive chemicals (especially particle
translocation and chemical bioaccumulation), and how dose-response relationships can be developed for
microplastics to better understand the full range of their potential impacts.
After initial discussion of the information presented in the framework document, the workshop participants
divided into two groups to consider the potential ecological impacts of microplastics in aquatic systems and in
air/soils in the US. An objective of this exercise was to prepare a corresponding conceptual model. The
participants considered priority information needs, confidence levels based on the available data in the
literature, and uncertainty. The products generated by both groups were merged into a single conceptual model
(Model II) and then further expanded through conversations with the participants after the workshop.
Microplastic occurrence and toxicity data for North American species are limited, and therefore Model II
represents a general accounting of the current state of knowledge of the ecological occurrence of microplastics
around the world in various feeding guilds. Data from field studies on microplastics impacts are also very limited
(e.g., Goldstein et al. 2012; Welden & Cowie 2016). For this reason, the priority need for Topic 3 focuses on
toxicity testing and on obtaining the high-quality laboratory data and toxicity values that are necessary to
conduct ecological risk assessments.
Because risk assessments also rely upon high-quality concentration data, both in the environment and for
confirmation of exposure levels in toxicity testing, the paramount importance of the Topic 1 priority need (i.e.,
reproducible, representative, accurate, precise methods for microplastics analysis) is clear. Understanding
microplastics sources, distribution and fate is also key to understanding ecological exposure and potential
impacts.
See the graphic representation of Model II on page 14. The following notes provide information
on how to read and interpret Model II.
The model structure, shapes and labels are the same as in Model I. Sources and Processes have been
removed for the sake of simplicity.
Existing data on ecological exposure to microplastics have been reviewed in detail by GESAMP
(2016).
Feeding guilds are used to indicate broad categories of organisms for which microplastics data are
available within each biotic compartment based on field studies.
Most of the available data address microplastics occurrence in species belonging to the listed guilds,
and is for non-North American species. Field data on the effects of microplastics exposure in
organisms are extremely limited.
The model does not include information for organisms which are known to ingest macroplastic (e.g.,
seabirds, marine mammals, terrestrial consumers, among others).
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Model II: Ecological Occurrence & Impacts of Microplastics
^Jsome information; moderate confidence
| Most information; good confidence
AIR
SOILS
SOIL ORGANISMS
-Detritivores
WETLANDS
[>];¦
mm
FRESHWATERS
FRESHWATER
ORGANISMS
- Zooplankton
- Decomposers
- Detritivores
- Filter feeders
- Predatory
invertebrates
- Predatory fishes
- Predatory
seabirds &
waterfowl
FRESHWATER SEDIMENTS
SEDIMENT ORGANISMS
COASTAL
WETLANDS/
ESTUARIES/
INTERTIDAL
HABITATS
COASTAL/
ESTUARINE
ORGANISMS
Zooplankton
Decomposers
Detritivores
Predatory
fishes
Predatory
seabirds
Predatory
mammals
MARINE WATERS
MARINE ORGANISMS
¦ Zooplankton
- Decomposers
- Detritivores
- Filter feeders
- Predatory invertebrates
- Predatory fishes
- Predatory seabirds
- Predatory mammals
Predatory reptiles
GROUNDWATER
ESTUARINE & MARINE SEDIMENTS
SEDIMENT ORGANISMS
-Detritivores
14
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The workshop participants then considered whether existing toxicity testing methods and dose-response
relationship approaches were relevant to microplastics, and how these could be tied into higher-level biological
effects, such as using the Adverse Outcome Pathway (AOP) approach (Ankley et al. 2010). The group referred to
a review by Connors et al. (2017) ("Needed improvements in microplastic research").
The participants noted that the use of lethality as a toxicity endpoint was likely not sensitive enough to account
for the majority of microplastics effects, and suggested that sub-lethal endpoints or biomarkers such as changes
to tissue structure that capture the potential physical effects of plastic particles, or changes in developmental
patterns or reproductive success should also be investigated. One participant suggested that existing toxicity
tests should be reviewed for their appropriateness for microplastics research and recommendations made as to
which tests are most relevant.
The toxicokinetics/toxicodynamics of microplastics in a representative organism are detailed in Model III. This
model was constructed after the workshop to identify potential uncertainties and concerns related to the
toxicokinetics and toxicodynamics of microplastics, and to determine relative levels of confidence regarding
toxicological data for microplastics.
The priority information needs for Model III are for data on (1) particle translocation within organisms (e.g.,
from the digestive tract to other organ systems) and (2) exposure to and bioaccumulation of additive
chemicals (i.e., chemicals added to the plastic polymer during the manufacturing process) in tissues
(reviewed by US EPA 2016; Hahladakis et al. 2017; Hermabessiere et al. 2017). To date, only one field study
has reported translocation of microplastics from the digestive tract to other tissues (in European anchovies;
Collard et al. 2017).
See the graphic representation of Model III on page 17. The information contained in Model
III applies to both Topic 3 (Ecological Occurrence and Impacts) and Topic 4 (Human Exposure
and Health Impacts), below. The following bullets provide information on how to read and
interpret Model III.
The rounded box at the top of the model represents the relevant receptor, hexagons represent
exposure pathways, rectangles represent toxicokinetic/dynamic processes and trapezoids
represent additional relevant considerations.
Boxes outlined in bold black lines are priority areas for research.
Microplastics exposure potentially includes a particle effect (physical), a chemical effect, and the
combined effect of particle + chemical.
Additive chemicals in microplastics are likely to be present at much higher concentrations than
environmental contaminants (e.g., persistent organic pollutants (POPs)) sorbed to microplastics
surfaces (reviewed by Hahladakis et al. 2017; Hermabessiere et al. 2017).
Research on engineered nanomaterials may be informative in understanding the toxicokinetics
and toxicodynamics of microplastics, especially at smaller size ranges.
Particle retention time may be influenced by physiology (e.g., ability to egest particles, digestive
tract structure).
15
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Biomarkers may be relevant to all toxicokinetic/toxicodynamic processes shown in the model.
Pathogens present in biofilms on microplastics (the "plastisphere") may be relevant to
microplastics effects (reviewed by Keswani et al. 2006; Harrison et al. 2018).
The participants also noted the various challenges of conducting toxicity tests with microplastics. Like
engineered nanomaterials, microplastics do not dissolve in solution and may instead aggregate and/or sink, and
therefore traditional aquatic exposure methods might not be appropriate.
In addition, interactions with natural organic material affect the bioavailability of microplastics in the laboratory
and the field. Testing single polymer types is not representative of environmental exposure, and does not
capture the diversity of biofilms that may form on different polymers (reviewed by Rummel et al. 2017), or the
additive chemicals that may be present in polymers. Also, testing pristine microplastics may give different
results than weathered microplastics.
The experts suggested the use of complex microplastics mixtures and experimental setups such as mesocosms
that allow for multi-species and community-level assessments would generate better and more realistic data for
understanding microplastic impacts. The participants also emphasized the importance of selecting ecologically
relevant species for testing. For example, microplastics in shellfish (e.g., bivalves) may be of concern for both
human and ecological health, and there is also an economic component in testing commercially-important
species. Marine species are generally under-represented in toxicity testing.
16
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Model III: Microplastics Toxicokinetics/Toxicodynamics
| Little information; low confidence
|some information; moderate confidence
I Most information; good confidence
/(Orga nism k
Macroplastic Ingestion/
Entanglement
Biomagnification
Sensory Cues
Egestion
Excretion
Nutritional
Effects/
Energetics
Particle
Toxicity?
Ingestion
(Incidental/
Intentional)
Bioavailability
l
Inhalation/
Gill Uptake
Impacts on Ecological
Communities
~4
Dermal
Exposure
J
"Plastisphere'
Pathogens
Particle Retention Time?
Particle Toxicity/Tissue Damage?
Ejection
No Absorption
Particle Retention/Absorption/Assimilation
1
\
Translocation H Bioaccumulation I Detoxification/1 Excretion of
of Particle | of Chemicals Excretion of || Particle
(Additives) Chemical
Tissue/
Cellular Damage
t
Chemical Toxicity
Chemical
Metabolism
Immune Response
i
Behavioral Effects
17
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Topic 4: Human Exposure and Health Impacts of Microplastics
Priority need: Create methods and conduct research to characterize human exposure to and impacts from
microplastics in drinking water (including source water), seafood, freshwater fish and indoor/outdoor
dust, in order to assess potential human health risks.
A conceptual model was used to identify the exposure pathways relevant to potential human health impacts of
microplastics in the US, to determine relative levels of confidence regarding available microplastics data relevant
to human health in the US, and to identify priority information needs (Model IV). The priority research needs
identified to better understand human exposure and health impacts of microplastics are based on other
priorities identified in this report: the availability of reliable and reproducible methods for microplastics analysis,
an understanding of microplastics sources, and toxicokinetic/toxicodynamic information for microplastics.
See the graphic representation of Model IV on page 20. The following bullets provide
information on how to read and interpret Model IV.
Existing data on human exposure to microplastics have been reviewed in detail by GESAMP
(2016). Study results released in August 2017 reported the widespread occurrence of
microplastics in drinking water from various countries (Orb Media, 2017), but these results have
not yet been peer-reviewed. One additional study of microplastics in sea salt in Spain was recently
published (Iniguez et al. 2017).
Ovals represent exposure modes, rectangles represent microplastics sources, hexagons represent
exposure pathways, and the rounded box represents the relevant receptor. Boxes outlined in bold
black lines are priority areas for research.
In the "Intentional/Incidental" category:
o Pharmaceuticals (including toothpaste) may be intentionally ingested, inhaled or dermally
applied, but exposure may also be incidental via these pathways;
o Glitter may be a cosmetic ingredient or have household applications and may be applied
intentionally, or inhaled or ingested incidentally;
o Cosmetics are intentionally applied dermally, but may be incidentally inhaled or ingested
during application or use; and
o Dust exposure occurs incidentally via ingestion, inhalation and dermal contact.
Food preparation methods may affect exposure (e.g., consumption of raw shellfish versus cooked
seafood).
Food sources may also be an important factor (e.g., potential differences in microplastics exposure
due to consumption of wild-caught versus aquacultured seafood).
It is important to consider which human susceptible populations and life stages are relevant to
exposure considerations; for example, workers who may be occupationally exposed; infants and
children; women of childbearing age and the fetus; and subsistence fishers. The relevance of
economic strata to exposure should also be considered.
18
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Soot may originate from wildfires, house/domestic fires, backyard burning and/or catastrophic
events.
Microplastics impacts in humans have been studied in relation to occupational exposure and the
use of plastic medical devices (reviewed by Wright & Kelly 2017).
The existing exposure and toxicity data on microplastics in humans comes from the medical literature, where
plastic devices have been in use for decades, and from occupational exposure (reviewed by Wright & Kelly
2017). In contrast to the ecological context, human physiological responses to particulate matter are relatively
well-known, particularly for the inhalation exposure pathway, and air quality criteria based on particle sizes are
used worldwide (US EPA 2009). However, information on the amounts and types of microplastics present in
particulate matter is not known apart from the few air studies cited above.
Treatment of source water for drinking is expected to filter out large particles, leaving behind particles in the
low micron-to-nanometer range (Abbott Chalew et al. 2013), though uncertainties remain as to whether or how
drinking water delivery systems (e.g., plastic piping) contribute microplastics to finished water. It should also be
noted that approximately 15 million Americans obtain their drinking water from private wells that are
unregulated (US EPA 2017). The need for more information about the bioavailability of microplastics and their
additive chemicals also applies to human health concerns.
Although the impacts of particulate exposure to human health are relatively well-studied, much less is known
about the composition of complex particulate mixtures such as house dust, which is known to be highly relevant
to human exposure to PBT chemicals (e.g., polybrominated diphenyl ethers (PBDEs)) that are used in furnishings,
electronics and other household products, including plastic products (reviewed by Stubbings & Harad 2014).
Humans are estimated to spend up to 90% of their time indoors in their homes, work places, schools and
vehicles (reviewed by Cincinelli & Martellini 2017), and therefore data on the types of particles that comprise
house dust and dust from other sources will be informative to human health risk assessment and may also
provide information on product wear.
The use of technology to remove pollutants based on size for protection of human health means that
nanoplastics are expected to be highly relevant to human exposure (reviewed by Galloway 2015; Koelmans et al.
2015; da Costa et al. 2016). Only a few studies have been published measuring nanoplastics in the laboratory;
quantifying nanoplastics is challenging due to the potential for high background contamination, and very few
methods are available. There is also on only one study that has quantified nanoplastics in the environment (Ter
Halle et al. in press). Knowledge of the properties of engineered nanomaterials may be informative in
understanding the potential risks of nanoplastics (reviewed by Rist & Hartmann 2018).
Biofilms may also be relevant to human exposure, as pathogenic organisms may grow on microplastic particles
that are taken up by commercial species such as shellfish (reviewed by Keswani et al. 2016; Harrison et al. 2018).
There are currently no data on the occurrence of microplastics in humans due to food or drinking water
consumption, and no studies on human exposure to chemicals via microplastics ingestion. Finally, the risks
posed by PBTs sorbed to or present in microplastics may be relevant to humans via exposure pathways such as
seafood consumption.
19
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Model IV: Human Exposure & Impacts of Microplastics
Exposure Mode
Intentional
Sources
Source
Water
Water Delivery
(PVC Pipes, Bottled
Water)
Drinking Water
(Treated/ Untreated)
Fish, Shellfish,
Sea Salt
Cosmetics
(Microbeads)
Dust & Aerosols
(Indoor/Outdoor/
Recreational; Soot)
| Little information; low confidence
[Some information; moderate confidence
[Most information; good confidence
Exposure Pathway
Receptor
Medical
" Applications
IggHSSI
1 (Pharmaceuticals,
! Devices)
tBSSBa
~Y~
Bioavailability of Particles and Associated
Chemicals (Additives and Sorbed)
20
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f. iclusions
Microplastics pollution is complex and ubiquitous, and microplastics research is in its infancy. Microplastics have
been found in surface waters worldwide and, as indicated in recent studies, are present in various foodstuffs
including seafood. Studies of other sample types for which data are limited, such as air and soil, also indicate
that microplastics pollution is widespread.
However, the potential risks associated with microplastics exposure are unknown for both humans and wildlife,
largely critical information needed to conduct risk assessmentsexposure and effects dataare lacking. The
uncertainties associated with understanding the potential impacts of microplastics to ecological and human
health therefore warrant urgent attention to minimize these uncertainties.
This workshop report aims to identify and summarize the scientific information needed to inform Agency
regulatory and research objectives relative to assessing human and ecological health impacts of microplastics.
Among other things, the document presents a set of linked conceptual models that address the fate of
microplastics from their sources to the environment through various human and ecological exposure pathways,
including consideration of the amount of information currently available and a list of suggested priority
information areas.
In summary, the workshop participants find that the following are priority needs within the four research topic
areas discussed:
Establish reliable and reproducible methods for microplastics quantification and characterization;
Conduct research on the sources, transport, fate, degradation, and distribution of microplastics
in the environment to be used in risk assessment of human and ecological health impacts,
particularly to understand and characterize: (a) how consumer product use and wear, agricultural
practices and waste management processes in the US contribute to microplastics in the
environment, and (b) in which ways particle characteristics such as chemical composition (i.e.,
polymer type) affect microplastics behavior (transport, fate, degradation, and distribution);
Create standardized toxicity tests for microplastics in test organisms and ecologically
representative organisms and systems (including field studies) to understand the ecological
impacts of microplastics, considering whether standard laboratory tests and endpoints can be
applied to microplastics toxicity assessments, bioavailability of microplastics and their additive
chemicals (especially particle translocation and chemical bioaccumulation) and how dose-
response relationships can be developed for microplastics; and
Create methods and conduct research to characterize human exposure to microplastics in
drinking water (including source water), seafood, freshwater fish and indoor/outdoor dust to
assess potential human health risks.
21
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Appendix 1: Workshop Agenda
EPA Microplastics Expert Workshop
Crystal City Marriott at Reagan National Airport, Salon F (Mezzanine floor)
June 28-29, 2017
Agenda
Workshop Facilitator: Lee-Ann Tracy, CSRA
Wednesday, June 28th
8:00 am Registration Begins
8:30 am Welcoming remarks by Benita Best-Wong
Acting Deputy Assistant Administrator, EPA Office of Water
8:40 am Introductions (Participants/facilitator)
8:50 am Meeting overview
Meeting purpose and expectations
Major discussion topics
Agenda and framework documents
Guidelines/housekeeping matters
Outcomes and "what next"
9:00 am Focused presentation: Microplastics methods
9:10 am Discussion begins
Validate framework questions and modify as needed
Identify scientific information needs/next steps for these questions
10:35 am Break
10:50 am Continue discussion
Prioritize scientific information needs/next steps
Wrap-up topic
12:20 pm Lunch
1:20 pm Focused presentation: Sources and fate of microplastics in the environment
1:30 pm Discussion begins
Validate framework questions and modify as needed
Identify scientific information needs/next steps for these questions
3:00 pm Break
3:15 pm Continue discussion
Prioritize scientific information needs/next steps
Wrap-up topic
26
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5:00 pm
5:15 pm
Wrap-up
End of Day 1
Thursday, June 29th
8:00 am Arrive at workshop venue
8:15 am Focused presentation: Ecological impacts of microplastics
8:25 am Discussion begins
Validate framework questions and modify as needed
Identify scientific information needs/next steps for these questions
10:00 am Break
10:15 am Continue discussion
Prioritize scientific information needs/next steps
Wrap-up topic
11:45 am Lunch
12:45 pm Focused presentation: Human health impacts of microplastics
12:55 pm Discussion begins
Validate framework questions and modify as needed
Identify scientific information needs/next steps for these questions
Prioritize scientific information needs/next steps
Wrap-up topic
2:30 pm Break
2:45 pm Review priority needs from each session and develop overall priorities
4:15 pm Wrap up/Summary and next steps
4:30 pm End of workshop
27
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Appendix 2: Workshop Framing Document (6/28/17)
EPA Microplastics Expert Workshop
Framing Document to Facilitate Discussion
Workshop Purpose: To identify and prioritize the scientific information needed to inform science-based policies
on the ecological and human health risks associated with exposures to microplastics in the United States.
Purpose of the Framing Document: To briefly summarize the state-of-the-science on four discussion topics and
outline the key questions to be addressed at the workshop. The workshop agenda will follow this Framing
Document. Participants are invited to expand the scope of the discussions beyond what is included in this
Framing Document, but the key questions included in it will be addressed, at minimum. Following the
workshop, the Framing Document may serve as an outline for the participants to produce the workshop report
and a short summary document for policymakers. This framework is not intended to comprise either a research
strategy/program for any one entity.
Basis of the Framing Document: The Framing Document uses a risk assessment approach: problem
identification, exposure assessment, effects assessment and risk characterization. This framework and workshop
will not address specific information needs for risk management options, e.g., recycling, green (or "sustainable")
chemistry, etc. The workshop may identify categories for such needs, however, and may allude to them in
discussion of the uncertainties associated with a better understanding of microplastics impacts on ecological
and human health.
"Microplastics" size definition. For the purposes of this workshop, the participants will adhere to the generally
accepted definition of microplastics found in much of the literature: 5 mm in any one dimension and below.
Overarching Considerations for Workshop Discussion:
1. Relevant microplastic size ranges. Discussions of scientific information needs and determinations of
scientific priorities during the workshop will include a definition of the particle size range that is relevant to
the question under discussion. This range may include nanoplastics, recognizing that there are substantial
scientific uncertainties associated with nanoplastics compared to microplastics, and that these needs
comprise an entire body of research needing further consideration.
2. Plastic particle type/geometry: Discussions of scientific information needs and determinations of scientific
priorities during the workshop will include a definition of the plastic particle type(s) (including polymer
types) or geometry (e.g., fragment, pellet, fiber, film) that is/are relevant to the question under discussion.
3. Heterogeneity: Microplastics are highly heterogeneous in their geometry, polymer composition, and
environmental distribution. This variation in microplastics characteristics, concentration and composition
can make it difficult to take representative environmental samples. The documented heterogeneity in
microplastics distribution in the environment should be taken into account during discussions of scientific
information needs and determinations of scientific priorities.
4. Future scenarios: Plastics production is projected to continue to increase. The potential impacts of this
increasing production should be taken into account during the workshop discussions.
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Proposed Workshop Discussion Topics:
A. Methods for the separation, quantification and characterization of microplastics (Workshop Day 1, AM)
What we know:
- There are no standardized or validated methods currently available for microplastics quantification or
characterization, including QA/QC practices. Microplastics methods and data are reported inconsistently.
This lack of methods is hindering the understanding of microplastics occurrence and potential effects.
- Existing characterization methods rely on time-consuming instrumental methods (Raman/FTIR
spectroscopy), often with visual identification of microplastics as the first step. There is currently no
validated high-throughput method for microplastics.
- Organic material can confound microplastics signatures (including biofilms) and impede microplastics
separation in sediments or biological samples.
- Toxic chemicals present in microplastics (additive chemicals) or sorbed to microplastics surfaces have
raised concern. Methods are available in the literature for examining the sorption/desorption of
conventional contaminants (e.g., POPs) to and/or from various plastics. Plastics additives are measured
less commonly, though methods are also available.
Key questions for discussion:
1. Which, if any, of the published methods is most appropriate for quantification of microplastics of a given
size/type and in a given matrix (e.g. water, sediment, tissue)? Why?
2. What are the advantages/disadvantages of the different methods?
3. What information/technology is needed to achieve low-cost, high-throughput microplastics analysis
(i.e., isolation, extraction, characterization)?
4. What are the barriers to development of standardization and validation of microplastics methods?
5. What are the barriers to development of better microplastics methods, including QA/QC methods?
6. What are the short-term scientific information needs in this area for the next 5 years?
B. Microplastics sources, distribution and fate in the US (Exposure assessment; Workshop Day 1, PM)
What we know:
- Microplastics have been found in virtually every environmental medium across a diversity of freshwater
and marine habitats. That is, in water, wildlife, sediments and air samples. Microplastics have also been
found in the terrestrial environment.
- Microplastics in the environment are highly heterogeneous (in amount, polymer type, geometry, etc.).
- Plastic polymer properties and particle propertiesdensity, specific gravity, susceptibility to UV radiation,
geometry, etc.can to some extent be used to predict microplastics distribution.
- Microplastics are present in wastewater treatment plant (WWTP) effluent and sewage sludge at various
concentrations. POTWs show varying efficacy in removing microplastics, with some studies reporting
>95% removal and other showing much less. Studies reporting >95% removal caution that WWTPs are still
likely significant sources of microplastics.
- Sewage sludge may be a source of microplastics to the environment depending on how it is used, e.g. land
application of biosolids may introduce microplastics into the terrestrial environment.
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Key questions for discussion:
7. Which plastic polymers are included in "microplastics"? Are e.g., synthetic waxes also microplastics?
8. What are the timescales and mechanisms of polymer/product degradation to form secondary
microplastics under environmental conditions?
9. What are the major land-based sources and fluxes of macro- and microplastics in the U.S.?
10. How does derelict fishing gear contribute to microplastics loadings?
11. Does the current understanding of microplastics types and composition capture the major sectors of the
U.S. plastic industry/market? Are any of these sectors un- or under-represented in plastics/microplastics
inventories? (Agriculture? Tires re: microfibers?)
12. How are microplastics distributed within the water column and in sediments in aquatic systems? What is
the fate of microplastics in aquatic systems?
13. What are the loadings of macro- and microplastics from major river systems into U.S. coastal waters?
14. What are the concentrations of microplastics in wastewater and sludge/biosolids?
15. What are the concentrations of microplastics in drinking water?
16. What are microplastics sources in the terrestrial environment? What are their sources in air? What are
their concentrations in air under various scenarios?
17. How can models or model systems be used to understand microplastics sources, transport and fate?
18. What are the short-term scientific information needs in this area for the next 5 years?
C. Ecological impacts of microplastics in the US (Exposure & effects assessment; Workshop Day 2, AM)
What we know:
- Microplastics ingestion has been documented for many aquatic species across a wide range of body sizes
and trophic positions. Ingestion is incidental in some species and intentional in others.
- The amount of microplastic ingested can range from a few particles to tens or hundreds per individual.
- Microplastics may be transferred across trophic levels.
- Microplastics contain known toxicants in the form of plastic additives or due to sorption of environmental
contaminants to microplastics surfaces.
- Microplastics exposure effects can be physical (e.g., anatomical tissue damage) or chemical (toxicity), or
both.
- Biofilms form rapidly on microplastics in the environment. These biofilms may contain pathogenic,
invasive or opportunistic species.
- There is less information available on other routes of exposure apart from ingestion (uptake through gills
or inhalation).
- Some organisms, such as microorganisms, fungi and caterpillars, are known to degrade some plastic
polymers.
- Microplastics are one stressor to organisms living in a multi-stressor environment.
- Most laboratory toxicity studies test microplastics concentrations that are well above environmental levels
and with sizes of microplastics that are smaller than those generally quantified.
- Risk assessment of engineered nanomaterials may be informative to understanding the potential
ecological impacts of nanoplastics.
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Key questions for discussion:
19. What are the gut residence times of ingested microplastics, and how are these influenced by particle
size/shape?
20. Are microplastics absorbed into bodily fluids during digestion?
21. What are the impacts of microplastics in exposed organisms?
22. Are existing ecotoxicity tests and endpoints sufficient to capture microplastics effects? Are new
endpoints/biomarkers needed? Are new standard toxicity tests needed?
23. What are the population-level and food web effects of microplastics exposure (Darwinian fitness
parameters)?
24. Are there transgenerational effects of microplastics exposure?
25. What are the impacts of microplastics to microbial communities? What impacts do microplastics
biofilms have on ecosystems?
26. Are traditional toxicological reference values (e.g., NOECs, TRVs) appropriate for microplastics? If so,
what information is needed to determine these values?
27. What information do we need to conduct risk assessments for microplastics?
28. What are the short-term scientific information needs in this area for the next 5 years?
D. Human health impacts of microplastics in the US (Exposure & effects assessment; Workshop Day 2, PM)
What we know:
- The major pathways for human exposure to microplastics are likely ingestion and inhalation.
- Microplastics have been found in dust, shellfish and finfish and in sea salt.
- There are no microplastics exposure data for humans.
- There are few mammalian toxicity studies of microplastics, and limited toxicology data for humans.
Medical/surgical use of plastic devices may provide information relevant to both exposure and effects.
- Risk assessment of engineered nanomaterials may be informative to understanding the potential human
health impacts of nanoplastics.
Key questions for discussion:
29. What is the exposure dose to humans from the consumption of shellfish, especially when consumed
after minimal cleaning and/or preparation?
30. What is the residence time of ingested microplastics in humans?
31. Are human health risks associated with ingestion of microplastics?
32. Are microplastics a meaningful source of fishery-relevant pathogens, e.g. Vibrio spp.?
33. Are microplastics present in drinking water? If so, how can they be quantified and characterized?
34. What are airborne microplastics concentrations in indoor/outdoor settings?
35. What is the uptake rate into the lungs due to inhalation exposure?
36. What are the human health risks associated with inhalation exposure to microplastics?
37. Are data on occupational exposure to plastics/microplastics available and informative?
38. Are reference doses needed for microplastics? If so, what information is needed to determine reference
doses?
39. What are the short-term scientific information needs in this area for the next 5 years?
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Useful References:
Reports
EPA. 2015. Summary of Expert Discussion Forum on Possible Human Health Risks from Microplastics in the
Marine Environment (EPA Human Health & Microplastics Forum convened on April 23, 2014).
EPA. 2016. State of the Science White Paper: A Summary of Literature on the Chemical Toxicity of Plastics
Pollution to Aquatic Life and Aquatic-Dependent Wildlife. https://www.epa.gov/sites/production/files/2016-
12/documents/plastics-aquatic-l ife-report.pdf.
GESAMP. 2015. Sources, fate and effects of microplastics in the marine environment: a global assessment
(Kershaw, P. J., ed.). (IMO/FAO/UNESCO-IOC/UNIDO/WMO/IAEA/UN/UNEP/UNDP Joint Group of Experts on the
Scientific Aspects of Marine Environmental Protection). Rep. Stud. GESAMP No. 90, 96 p.
http://www.gesamp. a/gesamp/files/media/Publications/Reports and studies 90/gallerv 223O/olbiiect
2.500 large.pelf
GESAMP. 2016. Sources, fate and effects of microplastics in the marine environment: part two of a global
assessment" (Kershaw, P.J., and Rochman, C.M., eds). (IMO/FAO/UNESCO-
IOC/UNIDO/WMO/IAEA/UN/UNEP/UNDP Joint Group of Experts on the Scientific Aspects of Marine
Environmental Protection). Rep. Stud. GESAMP No. 93, 220 p
http://www.gesaimp.org/data/gesairnp/filles/fille element/0c50c023936f7ffdl6506be330b43c56/rs93e.pdf (part
2)
International Joint Commission. 2016. Microplastics in the Great Lakes Workshop Final Report.
http://www.iiic.org/filles/tinvinice/uplloaded/Micropllastics in the Great Lakes Workshop Report FINAL Septe
mberl4-2016.pdf
Scientific Publications
Andrady A. 2017. The plastics in microplastics. Mar. Pollut. Bull. 119:12-22.
http://www.sciencedirect.com/science/article/pii/S0025326X1730111X
Connors KA, Dyer SD, Belanger SE. 2017. Advancing the quality of environmental microplastic research. Environ.
Toxicol. Chem. In press, http://onlinelibrarv.wiley.com/doi/10.1002/etc.3829/abstract
Horton AA, Walton A, Spurgeon DJ, Lahive E, Svendsen C. 2017. Microplastics in freshwater and terrestrial
environments: Evaluating the current understanding to identify the knowledge gaps and future research
priorities. Sci. Total Environ. 586:127-141.
http://www.sciencedirect.com/science/article/pii/S0048969717302073
JambeckJR, Geyer R, Wilcox C, SieglerTR, Perryman M, Andrady A, Narayan R, Law KL. 2015. Plastic waste
inputs from land into the ocean. Science 347:768-771. http://science.sciencemag.org/content/347/6223/768
Law KL. 2017. Plastics in the marine environment. Annu. Rev Mar Sci. 9:205-229.
http://www.annualreviews.org/doi/pdf/10.1146/annurev-marine-010816-0604Q9
Regan F, Rochman C, Thompson R. (Eds.) 2017. Themed Issue: Microplastics in the environment. Anal. Methods
http://pubs.rsc.org/en/ioyrnals/articlecollectionlanding?sercode=av&themeid=401b7ae3-2d5e-423e-96c5-
dc63f3629529
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Appendix 3: Workshop Attendee Biographies
Participants-Invited Experts
Rob Hale, Virginia Institute of Marine Science
Rob Hale is a Professor in the Dept. of Aquatic Health Sciences, Virginia Institute of Marine Science, College of
William & Mary. His research over the last 30 years has focused on the sources, bioavailability/accumulation,
environmental fate (transport, weathering and degradation) and impacts of organic pollutants; including
polymer additives (e.g. flame retardants), emerging and legacy pollutants. Multi-media problems are a special
interest, including aquatic, terrestrial and engineered environments (e.g. plastic products, indoor dust and
wastewater treatment).
Paul Helm, Ontario Ministry of the Environment
Dr. Paul Helm is a Senior Research Scientist with the Ontario Ministry of the Environment and Climate Change
(MOECC) in Toronto, Canada, and an Adjunct Faculty member of the School for the Environment at the
University of Toronto. Paul's background is in the fate and transport of organic contaminants in the
environment. His research interests include legacy and emerging contaminants in aquatic and urban
environments; using passive sampling approaches for contaminant monitoring; and Great Lakes contaminant
issues in general. Paul has been leading MOECC's work on microplastics since 2014 with a focus on
characterizing the abundance in and sources to waters and sediments of nearshore areas of the Great Lakes and
their uptake into fish in the region. Ultimately, the work is aimed at providing advice and support for
management considerations to reduce microplastics to the lakes.
Jenna Jambeck, University of Georgia
Dr. Jenna Jambeck is an Associate Professor in the College of Engineering at the University of Georgia (UGA) and
Director of the Center for Circular Materials Management in the UGA New Materials Institute. She has been
conducting research on solid waste issues for 20 years with related projects on marine debris since 2001. She
also specializes in global waste management issues and plastic contamination currently working through the US
State Department International Speaker Program and United Nations Environment Programme (UNEP) Marine
Litter Network.
Kara Law, Sea Education Association
Dr. Kara Lavender Law is a Research Professor at Sea Education Association (SEA; Woods Hole, MA), studying the
sources, distribution, behavior and fate of plastic debris in the ocean. Trained as a physical oceanographer, Dr.
Law has more than 12 months of sea time on oceanographic and sailing research vessels, including in the
eastern North Pacific and western North Atlantic Oceans where plastic debris accumulates in regions dubbed
"garbage patches". Dr. Law's current research interests focus on the sources of plastic to the marine
environment, understanding how ocean physics determines the distribution of plastic and other marine debris,
and the degradation and ultimate fate of different plastic materials in the ocean. She serves as the co-principal
investigator of the Marine Debris Working Group at the National Center for Ecological Analysis and Synthesis
(NCEAS), and holds a Ph.D. in physical oceanography from Scripps Institution of Oceanography and a B.S. in
mathematics from Duke University.
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Chelsea Rochman, University of Toronto
Chelsea Rochman is an Assistant Professor at the University of Toronto. She received her Ph.D. in ecology from
the University of California, Davis and was a recipient of the Society for Conservation Biology's David H. Smith
Postdoctoral Fellowship. Chelsea has been researching the sources, sinks and ecological implications of plastic
debris in marine and freshwater habitats for the past decade, and has published dozens of scientific papers in in
the field and has led international working groups about plastic pollution. In addition to her academic research,
Chelsea works hard to translate her science beyond academia by interacting with the public, the news media
and policy-makers.
Participants - Environmental Protection Agency
Christine Bergeron, Office of Science and Technology, Headquarters
Christine Bergeron is a biologist in Office of Water/Office of Science and Technology's Ecological Risk
Assessment Branch. She was first introduced to plastics pollution issues as a co-lead on the Office of Water's
recent white paper, "A Summary of the Literature on the Chemical Toxicity of Plastics Pollution on Aquatic Life
and Aquatic-Dependent Wildlife". Christine's previous research experience focused on maternal transfer of
mercury in amphibians and the impacts of contaminants on freshwater mussels.
Rob Burgess, Office of Research and Development, Atlantic Ecology Division
Dr. Robert M. Burgess is a Research Physical Scientist employed by the United States Environmental Protection
Agency (U.S. EPA) Office of Research and Development (ORD) Atlantic Ecology Division in Narragansett, Rhode
Island, USA. His current research focuses on better understanding the partitioning and bioavailability of organic
and metal contaminants in the environment; specifically, this research emphasizes the use of passive samplers
for measuring the bioavailability of legacy and emerging contaminants, including nanomaterials, in the marine
environment. He has contributed to the authorship of approximately 100 peer-reviewed papers and book
chapters, most of which are related to geochemistry, sediment contamination and aspects of ecological risk
assessment. Dr. Burgess received a master's degree in biological oceanography and Ph.D. in chemical
oceanography from the University of Rhode Island's Graduate School of Oceanography.
Bob Cantilli, Office of Research and Development, Headquarters
Bob Cantilli is a Senior Biologist for EPA ORD's Office of Science Policy. In his role, he works to ensure that EPA
water regulations and guidance use the best science available in making scientific decisions. Prior to working in
ORD, Bob worked in EPA's Office of Water, Office of Science and Technology, where he developed ecoregional
nutrient criteria, contributed to the National Water Strategy on climate change, and worked on the Great Lakes
Water Quality Initiative. He has a M.S. in biology from NYU and a B.S. in biology from Adelphi University.
Anna-Marie Cook, Office of Research and Development, Region 9
Anna-Marie Cook is the EPA Region 9 Superfund and Technology Liaison with EPA ORD's Regional Science
Program and has previously served over the last 26 years in a number of environmental engineering roles at
Region 9. As a member of the Superfund Division's Emergency Response Branch, Anna-Marie was the Region's
Marine Debris Program Coordinator, establishing a cross-media team which applies a multi-statute approach to
source reduction, waste management, prevention and research. In this capacity she has also been overseeing
the cleanup of Tern Island, a contaminated site in French Frigate Shoals, part of the Northwestern Hawaiian
Island chain. Among Anna-Marie's recent responsibilities has been research into microplastic toxicity and risk
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assessment, which has included the oversight of method development for the extraction and identification of
microplastics in water, sediment and tissue.
Stan Durkee, Office of Research and Development, Headquarters
Stan Durkee is an environmental specialist in EPA's Office of Science Policy located within the Office of Research
and Development headquarters, Washington, D.C. He works on a spectrum of air and multimedia science issues,
including those associated with source characterization and risk assessments, arising at the interface of policy
(e.g., regulatory actions) and research results. He holds a bachelor's degree from Amherst College and a
master's degree in public administration from George Washington University. A focus for many years has
included issues involving mercury. Recently, he has assisted the Office of Water/Trash Free Waters in its efforts
to gain more scientific information on plastics/microplastics.
Kay Ho, Office of Research and Development, Atlantic Ecology Division
Dr. Kay Ho has worked at U.S. EPA for over 20 years. She has 90 peer- reviewed journal articles and book
chapters, and has authored or co-authored over 120 presentations. Her research interests include marine
toxicology, marine benthic and community ecology, method development for assessing marine systems and
emerging contaminants in marine systems.
Greg Miller, Office of Science and Technology, Headquarters
Greg Miller is an Environmental Health Scientist and recently joined the Office of Water's Office of Science and
Technology from the Office of Children's Health Protection. His work there focused on children's regulatory and
health risk issues. Greg has participated in the review of the recent Toxic Substances Control Act (TSCA) Work
Plan chemical risk assessments as well as the development of new regulations implementing the Frank R.
Lautenberg Chemical Safety for the 21st Century Act. Greg began his EPA career in 2000 in the Office of Policy's
National Center for Environmental Economics, where he worked on the America's Children and the Environment
indicators reports. He is a graduate of the University of Michigan School of Public Health.
Margaret Murphy, AAAS S&TP Fellow, Office of Water, Headquarters (not an EPA employee)
Margaret Murphy is an AAAS Science & Technology Policy Fellow hosted by the Office of Wetlands, Oceans and
Watersheds in the Office of Water at EPA. She earned her Ph.D. in zoology/toxicology from Michigan State
University, and then was a postdoctoral fellow, assistant professor and associate professor in the Department of
Biology & Chemistry at City University of Hong Kong until 2016. Her research focuses on ecological and human
health risk assessment of legacy and emerging contaminants such as persistent organic pollutants and
pharmaceuticals and personal care products, and on the development and use of bioassays for toxicity testing.
Participants - Federal Agencies
Kathy Conn, US Geological Survey
Kathy Conn is the Water-Quality Specialist for the United States Geological Survey (USGS) Washington Water
Science Center in Tacoma, WA. Her recent interests include river suspended sediment-bound contaminants and
pathways of contaminants into Puget Sound food webs. The USGS is developing a Microplastics Lab in the
Tacoma office with the primary goals of: 1) providing water and sediment analytical services to the USGS
community and cooperators through a modified National Oceanic and Atmospheric Administration (NOAA)
method, and 2) developing a quality assurance/quality control protocol for microplastics analysis.
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Carlie Herring, National Oceanic and Atmospheric Administration
Carlie Herring received her M.S. in environmental sciences in the Marine and Estuarine Science Program at
Western Washington University with a thesis in ecological risk assessments. She completed a B.S. in marine
sciences at the University of Maine, Orono. For her B.S., she conducted marine debris research, dealing
specifically with plastics in the ocean. As the Research Coordinator, Carlie is responsible for overseeing research
projects funded by the Marine Debris Program (MDP), staying up-to-date on new marine debris research and
literature, and is involved in the MDP's Marine Debris Monitoring and Assessment Project.
Emanuel Hignutt, Food and Drug Administration
Emanuel Hignutt, Jr., MPH is currently a Subject Matter Expert in Chemistry for the U.S. FDA Division of Seafood
Safety, Center for Food Safety and Applied Nutrition. Prior to joining the FDA, Mr. Hignutt served as Chemistry
Section Supervisor with the Alaska State Environmental Health Laboratory. Mr. Hignutt's research interests
include analysis of Marine Biotoxins by Liquid Chromatography/Tandem Mass Spectrometry. Mr. Hignutt
earned his bachelor's degree in chemistry from the University of California, Davis, and a Master of Public Health
degree from the University of North Carolina at Chapel Hill.
Amy Uhrin, National Oceanic and Atmospheric Administration
Amy V. Uhrin is the Chief Scientist for NOAA's MDP where she oversees the Program's research portfolio. Prior
to joining the MDP in June 2015, Amy spent 15 years with NOAA as a seagrass ecologist in Beaufort, NC. Her
interest in marine debris started in 2007 when she received MDP funding to estimate the abundance and
distribution of derelict spiny lobster traps across various benthic habitats in the Florida Keys using divers towed
behind a boat. She holds a Master of Marine Science degree from the University of Puerto Rico and will defend
her Ph.D. dissertation at the University of Wisconsin Madison in Spring 2018.
Observers
Ashleigh Armentrout, ORISE Participant, Office of Wetlands, Oceans and Watersheds, Environmental
Protection Agency
Juliette Chausson, ORISE Participant, Office of Wetlands, Oceans and Watersheds, Environmental
Protection Agency
Sandra Connors, Deputy Director of the Office of Wetlands, Oceans and Watersheds, Environmental
Protection Agency
Richard Engler, Senior Chemist, Bergeson & Campbell, PC
Kathryn Gallagher, Office of Science and Technology, Environmental Protection Agency
Claudia Gelfond, ORISE Participant, Office of Science and Technology, Environmental Protection Agency,
Alix Grabowski, Senior Program Officer, Packaging and Material Science, World Wildlife Fund
Andrew Horan, Office of International and Tribal Affairs, Environmental Protection Agency
Laura Johnson, Office of Wetlands, Oceans and Watersheds, Environmental Protection Agency
Mike Levy, Senior Director, Plastics Foodservice Packaging Group, American Chemistry Council
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Emma Maschal, ORISE Participant, Office of Wetlands, Oceans and Watersheds, Environmental
Protection Agency
Sarah Mazur, Office of Research and Development, Environmental Protection Agency
Noemi Mercado, Office of Wetlands, Oceans and Watersheds, Environmental Protection Agency
Kate O'Mara, Office of Research and Development, Environmental Protection Agency
Brian Rappoli, Office of Wetlands, Oceans and Watersheds, Environmental Protection Agency
Grace Robiou, Office of Wetlands, Oceans and Watersheds, Environmental Protection Agency
Surabhi Shah, Office of Wetlands, Oceans and Watersheds, Environmental Protection Agency
Bernice Smith, Office of Wetlands, Oceans and Watersheds, Environmental Protection Agency
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