Peer Consultation Public Meeting on

The Material Characterization of Nanoscale Materials

Discussion Topics

Meeting Background and Purpose

	EPA is convening a public scientific peer consultation meeting on
material characterization for nanoscale chemical substances
(“nanoscale materials”) to inform the development of its Nanoscale
Materials Stewardship Program (NMSP) under the Toxic Substances Control
Act (TSCA).  The peer consultation is one of several actions EPA is
taking to better understand the potential risks and benefits of
nanotechnology.

	 On October, 18, 2006, EPA invited the public, industry, environmental
groups, other federal agencies and other stakeholders to participate in
the design, development and implementation of a stewardship program for
nanoscale materials.  On July 12, 2007, EPA announced the availability
of a NMSP concept paper and related documents and a public meeting on
August 2, 2007 to discuss and receive comments on these materials
(http://www.epa.gov/oppt/nano/nmspfr.htm).

 	The NMSP will complement and support the Agency's new and existing
chemical programs under TSCA and will help provide a firmer scientific
foundation for regulatory decisions by encouraging the development of
key scientific information and appropriate risk management practices for
new and existing chemical nanoscale materials.  The NMSP is intended to
include but not limited to engineered nanoscale materials manufactured
or imported for commercial purposes as defined in 40 CFR 720.3 (r).  The
NMSP is envisioned to have two parts: 1) a Basic Reporting Program and
2) an In-depth Program.  This discussion paper and the public peer
consultation meeting are intended to support the NMSP by identifying
material characterization data that participants could submit under the
Basic Program if they are in the participant’s possession or are
reasonably ascertainable as defined in 40 CFR 720.3 (p).  The data and
experience generated by the basic reporting phase will help to inform
the types of in-depth data to be developed.  In-depth data development
could begin at any time and would entail, among other types of data,
development of material characterization data in a greater amount of
detail.  In-depth data development could also include additional types
of material characterization data if they are identified.

	EPA received input in November, 2005 from the National Pollution
Prevention and Toxics Advisory Committee (NPPTAC) regarding a voluntary
stewardship program for nanoscale materials.  A NPPTAC ad-hoc work group
on nanoscale materials developed an overview paper that stated that a
voluntary stewardship program should:  

Give EPA, and the public to the extent possible recognizing legitimate
CBI issues, a better understanding of the types of engineered nanoscale
materials; the physical, chemical, hazard and exposure characteristics
of such substances; the volume of such substances; and the uses of such
substances;

Help EPA develop capacity and a process to identify and assess risks of
engineered nanoscale materials;

Help EPA determine what information it needs about engineered nanoscale
materials and articulate those information needs to industry and other
stakeholder groups;

Help EPA understand what risk management practices are being used at
production, processing, use and disposal stages, and what additional
risk management practices  need to be implemented;

Prompt or reinforce the implementation of risk management practices; and

Provide the information and experience needed to develop an overall
approach to the treatment of nanoscale chemical substances under TSCA
that builds public trust in nanoscale materials while enabling
innovation and responsible development.

	EPA will utilize all public input, including that from NPPTAC, other
stakeholders, public meetings and peer consultations to further inform
the development of its Nanomaterials Stewardship Program and TSCA
program for nanoscale materials.

Meeting Objectives

	The EPA public peer consultation meeting on material characterization
needs for nanoscale materials will help clarify which data and elements
should be included in the NMSP Basic Program and/or In-depth Program. 
The goal is to have an applied discussion that considers 1) the
currently available understanding of material characterization as it
relates to nanoscale materials and 2) how this understanding can be used
to guide the Agency’s thinking regarding the material characterization
data elements that would be most useful and important to include in the
NMSP.  The specific objectives of the public peer consultation meeting
are as follows:

To inform industry and the public of EPA’s level of understanding of
the material characterization needs for nanoscale materials in general
and for the NMSP;

To further develop EPA’s understanding of how nanoscale materials are
engineered or manufactured to achieve specific properties and
characteristics; 

To further develop EPA’s understanding of which chemical
identification elements and physical-chemical property data are
generally relevant in characterizing nanoscale materials and which
identification elements and property data are most important in
characterizing specific classes of nanoscale materials;

To discuss what analytical procedures and test methods are available for
acquiring these material characterization data, and where procedure and
method validation or development is needed;

To discuss how these material characterization data needs should be
prioritized for the NMSP Basic and/or In-depth Program;

Discussion Overview

Despite the rapid advancement of nanotechnology, the breadth of
nanoscale material types coupled with the limited hazard data available
for many of these materials pose a challenge in understanding and
measuring their benefits and risks.  Numerous efforts are underway to
begin to address these challenges.  The International Life Sciences
Institute (ILSI) Research Foundation/Risk Science Institute, for
example, convened an expert working group to develop a strategy for
identifying hazards associated with engineered nanoscale materials. 
Focusing on the limited data available, the working group developed a
screening strategy for hazard identification (rather than a detailed
testing protocol) that includes a broad data gathering effort.  

	The ILSI report describes the characterization of nanoscale materials,
in addition to in vitro and in vivo screening, as a key third aspect of
an overall screening strategy due to the likely dependence of the
biological activity of nanoscale materials on physical-chemical
properties not often considered in toxicity screening studies. 
Additionally, given the difficulties associated with characterizing many
nanoscale materials, nanoscale material characterization is a subject
appropriate for detailed investigation and discussion.

Numerous national and international standards organizations, including
the American National Standards Institute (ANSI) and the International
Organization for Standardization (ISO), have also convened committees to
begin to address many of these same challenges and in particular the
need for methods standardization.  Several of these committees have
indicated that, given the breadth of nanotechnology and its data issues,
the initial products the committees develop may be in the form of best
practices rather than actual test protocols.  

	The remainder of this paper discusses a proposed approach for the EPA
scientific peer consultation meeting on nanoscale material
characterization.  EPA recognizes that the different chemical classes of
nanoscale materials would make universal application of any particular
characterization endpoint or methodology impossible.  The premise of the
Basic Reporting phase of the NMSP is that some information is known or
reasonably ascertainable.  The approach for this panel is therefore to
discuss what data are known or reasonably ascertainable to characterize
nanoscale materials.  This will be followed by a discussion on the
methodology used to obtain and use characterization endpoints of
interest.  

Discussion Topics

Characterization of Nanoscale Materials 

1.	Description of nanoscale materials 

Types/categories of nanoscale materials

2.	Physical-chemical properties of potential interest

Particle size and distribution

Particle shape and dimensions

Agglomeration and aggregation

Surface area

Surface charge

Surface chemistry

Chemical composition

Crystal structure

Impurity identification and levels

3.  Design to achieve unique properties

Manufacturing and processing methodologies

Chemical transformations

Methodologies for Characterizing Nanoscale Materials

Obtaining characterization data for nanoscale materials 

Analytical methods for detecting and quantifying nanoscale materials

Analytical methods measuring physical-chemical properties (measurement
techniques and testing protocols)

Models to predict properties and effects

Metrology 

Methods validation

Standards and harmonization

Prioritization of characterization data and data gaps 

Miscellaneous – Do Panel members have additional topics to discuss?			
   

Discussion

	This section provides additional information on specific technical
issues to facilitate discussion at the meeting.  The information will
include literature findings as well as questions on the specific
discussion topics.

Types of Nanoscale Materials & Their Structures and Chemical
Compositions

	Based on structure and chemical composition, EPA has grouped
nanomaterials into 4 distinct categories for purposes of this
discussion: 1) simple organic molecules; 2) simple inorganic molecules;
3) polymeric substance (including dendrimeric substances); and 4)
composites.  A fifth category, biological compounds will not be
addressed in the peer consultation.  While all of these categories can
be divided further, only the organic category will be divided further
into molecules based predominantly on carbon (e.g., fullerenes,
nanotubes) and all other organic substances (e.g., salts of carboxylic
acids).  This grouping is similar to the American National Standards
Institute Nanotechnology Standards Panel approach presented at the
September 2004 meeting at the National Institute of Standards and
Technology in Gaithersburg Maryland.  

Question 1: Are there any other significant categories, based on
structure and chemical composition, that should be included in this
discussion because they are substantially different from the categories
mentioned (e.g., hybrids, self- assembly devices, others)?

Question 2: For the different categories of nanoscale materials, what is
the current state of knowledge about structure and chemical composition?
 

Question 3: Can structures and chemical composition be correlated to
specific properties and is this correlation quantifiable?

Physical-Chemical Properties

	The importance of nanoscale materials is due to their potential for
unique or greatly enhanced properties.  	EPA routinely uses a base set
of physical-chemical property data (e.g., melting point, boiling point,
vapor pressure, water solubility) for a variety of programs (e.g., High
Production Volume Challenge, New Chemicals) and decision-making.  As
mentioned previously, certain material properties are of significant
importance in characterizing nanoscale materials.  Recent research
suggests that particle size, surface area, and surface chemistry (or
surface activity) are initially some of the most important properties to
measure.  

	As expected for most chemicals, class 1 substances having specific
molecular structures and formulas may be more readily studied and
characterized at the nanoscale than the polymer and composite
categories.  For example, carbon-based nanoscale materials as well as
metal oxide nanoscale chemicals are often well characterized. 
Structural and physical-chemical property data therefore are likely to
be well documented for these types of materials.

	

Question 4: Which physical-chemical properties are relevant to nanoscale
materials and how?  Which are known or reasonably ascertainable and
which have data gaps?

Question 5: Are there properties that would have little or no relevance
under the NMSP?

Question 6: Which properties are associated with aggregated or
agglomerated nanoscale materials, as opposed to properties that are
inherent to the material regardless of physical form?

Question 7: Are there routine manipulations of nanoscale materials that
result in physical-chemical properties changes or other defining
characteristics (e.g., surface modifications of nanotubes to enhance
solvent dispersibility)?

Question 8: How should physical-chemical property data be prioritized
for the NMSP?  Based on availability, effect (toxicity or exposure
criteria), or other factors?

Nanoscale manufacturing and processing

	The number of manufacturing and processing methods for generating
nanoscale material continues to grow and become more sophisticated.  The
two primary areas for this discussion include physical reduction methods
(milling) and engineering methods (e.g., particle stabilization, vapor
deposition, self assembly).  

Question 9: What are the common processes used to manufacture nanoscale
materials?

Question 10: How are processes used to produce specific characteristics
or properties?

Question 11: Which methods reduce particle size but do not result in
property changes?  Which methods reduce particle size and result in
property changes?  

Impurities

	Impurity content is a growing area of interest in nanotechnology due to
improved performance observed in some cases (e.g., solar cells and
semiconductors) and deleterious effects observed in others (e.g.,
quantum dot quantum computers).  The confounding effects that impurities
have with respect to toxicological endpoints is also being studied
(National Nanotechnology Initiative 2006 Environmental Health and Safety
research report).

Question 12: How important are impurity identity and impurity levels to
the understanding and characterization of nanoscale materials?  

Question 13: Are there routine purification procedures that can
effectively control or remove impurities, when desirable, for certain
classes of nanoscale materials?  

Obtaining characterization data 

	Determining identity, quantifying the nanoscale particle range, and
measuring physical-chemical properties for that identity and particle
range are essential to the characterization of nanoscale materials. 
Because of the challenges associated with size, shape, surface
characteristics, and possibly other aspects of nanoscale materials, an
evaluation of existing measurement techniques is critical to nanoscale
material characterization.  The National Nanotechnology Initiative
report stated that “...Accurate and useful measurement techniques are
also important because agglomerated nano materials may either retain or
lose their emergent properties - or take on new properties - thus
affecting the potential biological response.”  

Question 18: Are validated methods available for the different
categories of nanoscale materials?

Question 17: Are there techniques that can be universally applied?

Question 19: For small quantities of materials, are there sampling,
handling, and collection techniques as well as sample integrity,
accuracy and precision QA/QC methodologies available?

Question 20: What is the status of standardization efforts? Are these
efforts focused on broadly applicable characterization methods or
category-specific methods?

Question 21: What alternative or innovative methods or technologies can
be applied to nanomaterial analysis?

Modeling

Empirical modeling can be a useful approach to predict physical-chemical
properties when experimental data are not known or ascertainable.  The
initial problem with modeling is that, to accurately predict property
endpoints for a given category of substances, there must be some
experimental data available in the tool’s database for at least some
representative substances in that category.  For newly discovered or
studied materials, the minimum but necessary quantity and type of
experimental data often is not available to sufficiently populate a
tool’s database and allow accurate prediction by the tool.  Some
estimation methods have been developed for specific property endpoints,
but many others are lacking.

Question 22: Are there models that are currently used to obtain property
data for nanoscale materials?  For which properties and which nanoscale
materials?

Question 23:  Has any validation work been conducted that compares
predicted values with measured data?  For which properties and which
nanoscale materials?

Question 24: Are there current significant characterization needs for
which the NMSP should investigate model development?

 http://www.particleand fibretoxicology.com/content/2/1/8 

 http://www.ansi.org/standards_activities/standards_boards_panels/nsp/ov
erview.aspx?menuid=3

    HYPERLINK
"http://www.iso.org/iso/en/stdsdevelopment/tc/tclist/TechnicalCommitteeD
etailPage.TechnicalCommitteeDetail" 
http://www.iso.org/iso/en/stdsdevelopment/tc/tclist/TechnicalCommitteeDe
tailPage.TechnicalCommitteeDetail ? COMMID=5932

    HYPERLINK
"http://publicaa.ansi.org/sites/apdl/Documents/Forms/AllItems.aspx" 
http://publicaa.ansi.org/sites/apdl/Documents/Forms/AllItems.aspx   

 Class 1 substances are distinct chemicals with known, non-variable
molecular structures  

  http://www.nano.gov/NNI_EHS_research_needs.pdf

									

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August 07, 2007

