(560b) Nanotechnology: Chemical and Toxicological Risk Assessments Issues with Antimicrobials

Nanotechnology: Chemical and Toxicological Risk Assessment Issues With Antimicrobials

By

A. Najm Shamim, and Jenny Tao

US EPA, Antimicrobials Division, Potomac Yard, Arlington, VA, USA

Shamim.Najm@epa.gov and Tao.Jenny@epa.gov.

The United States Environmental Protection Agency (U.S. EPA) Office of Pesticide Programs (OPP) is a regulatory office that is responsible for pesticides registration for distribution and sale in the U.S. OPP is mandated by the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA) to conduct hazard and exposure risk assessments to ensure that agricultural and antimicrobials pesticides and biopesticides, when become commercially available, do not pose unreasonable adverse effects to humans or the environment (air, soil, water, terrestrial and aquatic organisms). OPP reviews enormous amount of scientific and technical data submitted by the registrants as well as has the burden of making regulatory decisions on these pesticides. The new nanoscience and nanotechnology, which may be used in pesticides, present an enormous challenge to the Agency in both domains.

The antimicrobial pesticides are handled in the Antimicrobial Division (AD) in OPP. Uses, application rates, and application scenarios of antimicrobial pesticides are relatively less than those of agricultural pesticides. However, antimicrobials are more used at homes, institutions, hospitals, and other residential-related fields, such as, construction materials, playground and recreational equipments, swimming pool and spa, etc. There are 12 categories of antimicrobial pesticides based on their use patterns. Of these use patterns, eight are categorized as indoor/residential. Some outdoor antimicrobial uses include heavy duty wood preservatives and antifoulants Each use pattern triggers a set of data requirements.

Nanotechnology opens a completely new world for science and technology; meanwhile, it also brings a considerate uncertainties and concerns. It is too early to assess the full impact and importance of nanotechnology. Nanotechnology is still in the development stage, and a full risk assessment and benefits of nanoproducts can not be completed at this time. Some characteristics of nanomaterials have been understood but a wide variety of issues and concerns still remain unanswered. This has been demonstrated in the recent research works ( Xu1) and presentations (Najm Shamim2 ACS Meeting, New Orleans, April 2008).

The existing technique to identify, characterize and quantify nanomaterials is expensive, although newer and relatively cheaper methods are being developed. Using the existing analytical techniques 3,4, it has been pointed out that by the year 2030, there will be five categories of nanomaterials (Roco5). As of today research and applications have reached third category. For each category EPA/OPP will have to devise a unique set of data requirements for registration. The uncertainties and issues in the generation of scientific data and regulatory policies continue. Then there are Nanotechnology Oversight issues (J. Clarence Davies6).

Because of their nanometer-range size and high surface area and/or reactivity, nanomaterials possess unique physiochemical properties, and in turn, the toxicity of nanomaterials might be different from conventional materials. Some of the critical issues that EPA is struggling with and may continue to dos so for the foreseeable future are:

? How useful are the data generated on conventional size pesticides? Is data bridging between conventional size chemical and nanomaterial possible?

? Would current data requirement be adequate to address the hazard/exposure and risk concerns of a nanopesticide?

? Would Agency need nanopesticide-specific data ?

? Would the current test guidelines be suitable and adequate for testing nanopesticide or existing guidelines be modified or would new test guideline(s) be needed?

? For toxicity risk assessment would traditional animal testing model be appropriate for testing nanopesticide? What kind of dosimetrics would be appropriate for testing nanomaterial, surface area/activity-based and/or particle size/number-based in addition to mass-based?

? Could the results derived from ?non-traditional? in vivo method (e.g., intratracheal) be used in hazard characterization and risk assessment?

? Would the data generated on 10 nm nanomaterials be the same, for example as those of 30 nm ones?

? How nanomaterials enter, travel through, and deposit in the body - PK/PD of nanomaterials in animals?

? How would aggregation/agglomeration affect the toxicity of nanomaterials in organisms and environmental media.

This presentation focuses on chemistry and toxicity scientific and regulatory issues and concerns. From chemistry perspective the scientific uncertainties in the unambiguous full characterization of nanomaterials, size and size distributions, shape and morphology of nanomaterials, surface area or surface reactivity parameters and issues and concerns about the use of the present regulatory data requirements will be discussed.

From the toxicity perspective, the uncertainties of interpretations in the in vitro and in vivo mechanistic studies as well as the limitations of the existing regulatory data requirements are presented.

References

1. Parakash Nallathamby, Kerry Lee, Xiao-Hong Nancy Xu, 2008: acsNANO, Volume2(No.7), pp 1371-1380

2. A. Najm Shamim, April 7, 2008: ACS Meeting, New Orleans

3. Guor-Tzo Wei, and Fu-Ken Liu, 1999, Journal of Chromatography A, 836, pp 253-260

4 C. Degueldre et.al, 2004, Analytica Chimica acta, 519, pp137-142

5. Mike Roco, 2008 : Presented at: International Food Policy Research Institute (IFPRI), Washington, DC

6. J. Clarence Davies, 2008: Nanotechnology Oversight, Project on Emerging Nanotechnologies 13, Presented at: Woodrow Wilson International Center for Scholars.