Archived Comments for:
Principles for characterizing the potential human health effects from exposure to nanomaterials: elements of a screening strategy
The Nanotechnology Panel of the American Chemistry Council submits the following comments on the Oberdorster et al. paper on a screening strategy for nanomaterials.
“Principles for characterizing the potential human health effects from exposure to nanomaterials: elements of a screening strategy” (Oberdorster et al. (2005) provides a valuable contribution in describing principles of a research strategy for evaluating human health aspects of nanoscale materials, but has limitations in describing a means to evaluate environmental, health and safety risks. Although screening and characterization could be helpful, the “principles” would be more usefully applied to an existing testing framework (e.g. globally harmonized OECD guideline) than developing specific hypothesis driven tests.
Specific comments are noted below.
• There is an over emphasis on in vitro methods. Although these may be of some use in hazard identification, exposure-relevant tests by a suitable route, with an array of standard end-points would be of more value as a basis for decisions regarding risk. Interpretation of in vitro studies would likely require validation by comparison with in vivo data. Globally harmonized test protocols (e.g. OECD and EPA OPPTS) are intended to evaluate a broad spectrum of potential effects, rather than addressing a specific hypothesis regarding the effects of a material. The principles described in the Oberdorster paper may be more usefully applied to enhance globally harmonized tests for test material characterization and evaluating potential end points of concern. In theory, globally harmonized tests could be applied to oral, inhalation and dermal exposure, though specific development may be needed to conduct a relevant exposure.
• The recommendation that “independent characterizations of nanomaterials (beyond information provided by producers and suppliers) are carried out where possible" is inappropriate. Documented analysis (e.g. by GLP procedures) is acceptable to regulatory agencies for industrial and agricultural chemicals as well as drugs; a different standard would serve no purpose. Basic GLP test material characterization should be possible. We recognize challenges in that some innovative analytical methods may not be available as GLP procedures.
• The importance of characterization is recognized, though some balance will be needed. Traditionally, test materials are characterized for identity, total purity, specific impurities above 0.1%, and stability. A suitable judgment about resources will be needed to determine the appropriate amount of characterization, particularly for a lower tiered study. Also, characterization in the body (versus test material and material in dosing vehicle), is beyond the scope of normal testing. These evaluations should be considered a research project or pharmacokinetic study, not a part of a routine study to evaluate effects.
• Developing computational toxicology is a worthwhile long term objective, but it is limited in current applications for routine chemical EHS evaluation. There is insufficient validation of methods with nanoparticles to implement computational toxicology in the near to mid-term.
The Oberdorster et al. report is an excellent starting point for the evaluation of potential health hazards of nano materials. Many recommendations by Oberdorster et al. have value in providing adjunctive information to that from validated study protocols. The report would have been more informative if it included the rationale for selecting the tests contained in Tiers 1 and 2 and provided an explanation for moving between Tiers. We believe that the preferred approach to consider for tiered testing is to rely on validated test methods with protocols established by the OECD.
Comments on Oberdorster et al.
25 January 2006
COMMENTS ON THE RSI NANOTECHNOLOGY PUBLICATION
(Oberdorster et al., 2005)
23 December 2005
Dear Sir:
The Nanotechnology Panel of the American Chemistry Council submits the following comments on the Oberdorster et al. paper on a screening strategy for nanomaterials.
“Principles for characterizing the potential human health effects from exposure to nanomaterials: elements of a screening strategy” (Oberdorster et al. (2005) provides a valuable contribution in describing principles of a research strategy for evaluating human health aspects of nanoscale materials, but has limitations in describing a means to evaluate environmental, health and safety risks. Although screening and characterization could be helpful, the “principles” would be more usefully applied to an existing testing framework (e.g. globally harmonized OECD guideline) than developing specific hypothesis driven tests.
Specific comments are noted below.
• There is an over emphasis on in vitro methods. Although these may be of some use in hazard identification, exposure-relevant tests by a suitable route, with an array of standard end-points would be of more value as a basis for decisions regarding risk. Interpretation of in vitro studies would likely require validation by comparison with in vivo data. Globally harmonized test protocols (e.g. OECD and EPA OPPTS) are intended to evaluate a broad spectrum of potential effects, rather than addressing a specific hypothesis regarding the effects of a material. The principles described in the Oberdorster paper may be more usefully applied to enhance globally harmonized tests for test material characterization and evaluating potential end points of concern. In theory, globally harmonized tests could be applied to oral, inhalation and dermal exposure, though specific development may be needed to conduct a relevant exposure.
• The recommendation that “independent characterizations of nanomaterials (beyond information provided by producers and suppliers) are carried out where possible" is inappropriate. Documented analysis (e.g. by GLP procedures) is acceptable to regulatory agencies for industrial and agricultural chemicals as well as drugs; a different standard would serve no purpose. Basic GLP test material characterization should be possible. We recognize challenges in that some innovative analytical methods may not be available as GLP procedures.
• The importance of characterization is recognized, though some balance will be needed. Traditionally, test materials are characterized for identity, total purity, specific impurities above 0.1%, and stability. A suitable judgment about resources will be needed to determine the appropriate amount of characterization, particularly for a lower tiered study. Also, characterization in the body (versus test material and material in dosing vehicle), is beyond the scope of normal testing. These evaluations should be considered a research project or pharmacokinetic study, not a part of a routine study to evaluate effects.
• Developing computational toxicology is a worthwhile long term objective, but it is limited in current applications for routine chemical EHS evaluation. There is insufficient validation of methods with nanoparticles to implement computational toxicology in the near to mid-term.
The Oberdorster et al. report is an excellent starting point for the evaluation of potential health hazards of nano materials. Many recommendations by Oberdorster et al. have value in providing adjunctive information to that from validated study protocols. The report would have been more informative if it included the rationale for selecting the tests contained in Tiers 1 and 2 and provided an explanation for moving between Tiers. We believe that the preferred approach to consider for tiered testing is to rely on validated test methods with protocols established by the OECD.
Competing interests
None declared