EPA to Hold Public Meeting to Discuss Nanotechnology

August 20, 2007 // Published as a news service by IHS

The meeting is to help develop the EPA's Nanoscale Materials Stewardship Program (NMSP) under the Toxic Substances Control Act (TSCA).

At the meeting the EPA will request comment on:

• Characteristics currently used or potentially available to characterize nanoscale materials.
• Rationale for the use of these characteristics.
• Issues to consider regarding use of these characteristics in the Nanoscale Materials Stewardship Program.

Information about the meeting can be found in the Federal Register notice at http://www.epa.gov/fedrgstr/EPA-MEETINGS/2007/August/Day-13/m15780.htm.

In October 2006, the EPA launched a collaborative process and invited stakeholders to participate in the design, development and implementation of a NMSP under the TSCA.

The goal is to provide a scientific foundation for regulatory decisions by encouraging the development of key scientific information and appropriate risk management practices for nanoscale materials, said the EPA.

The specific objectives of the public peer consultation meeting are:

1. To inform industry and the public of the EPA's level of understanding of the material characterization needs for nanoscale materials in general and for the NMSP.
2. To help the EPA understand how nanoscale materials are engineered or manufactured to achieve specific properties and characteristics.
3. To help the EPA understand 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.
4. 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.
5. To discuss how these material characterization data needs should be prioritized for the NMSP basic and/or in-depth program.

Types of nanoscale materials, structures and chemical compositions
Based on structure and chemical composition, the EPA grouped nanomaterials into four categories for purposes of this discussion:

1. Simple organic molecules.
2. Simple inorganic molecules.
3. Polymeric substance including dendrimeric substances.
4. Composites.

A fifth category, biological compounds, will not be addressed in the peer 6 consultation, said the EPA.

While all of these categories can be divided further only the organic category will be divided further into molecules based predominantly on carbon such as fullerenes and nanotubes and all other organic substances such as salts of carboxylic acids.

This grouping is similar to the American National Standards Institute (ANSI) Nanotechnology Standards Panel approach presented at the September 2004 meeting at the National Institute of Standards and Technology (NIST), said the EPA.

Physical-chemical properties
The importance of nanoscale materials is due to their potential for unique or greatly enhanced properties.

The EPA said it uses a base set of physical-chemical property data such as melting point, boiling point and vapor pressure and water solubility for a variety of programs such as high production volume challenge, new chemicals and decision-making.

As mentioned previously, certain material properties are important 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, according to the EPA.

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, said the EPA.

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, said the EPA.

Nanoscale manufacturing and processing
The number of manufacturing and processing methods for generating nanoscale material continues to grow and become more sophisticated, according to the EPA.

The two primary areas for this discussion include physical reduction methods such as milling and engineering methods such as particle stabilization, vapor deposition and self assembly.

Impurities
Impurity content is a growing area of interest in nanotechnology due to improved performance observed in some cases such as solar cells and semiconductors and deleterious effects observed in others such as quantum dot quantum computers, said the EPA.

The confounding effects that impurities have with respect to toxicological endpoints are also being studied.

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, said the EPA.

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, according to the EPA.

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."

Modeling
Empirical modeling can be a useful approach to predict physical-chemical properties when experimental data are not known or ascertainable, said the EPA.

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, said the EPA. Some estimation methods were developed for specific property endpoints but many others are lacking.

Source: U.S. Environmental Protection Agency (EPA).