A comprehensive framework for evaluating the environmental health and safety implications of engineered nanomaterials

Abstract

Engineered nanomaterials (ENM) are a growing aspect of the global economy, and their safe and sustainable development, use, and eventual disposal requires the capability to forecast and avoid potential problems. This review provides a framework to evaluate the health and safety implications of ENM releases into the environment, including purposeful releases such as for antimicrobial sprays or nano-enabled pesticides, and inadvertent releases as a consequence of other intended applications. Considerations encompass product life cycles, environmental media, exposed populations, and possible adverse outcomes. This framework is presented as a series of compartmental flow diagrams that serve as a basis to help derive future quantitative predictive models, guide research, and support development of tools for making risk-based decisions. After use, ENM are not expected to remain in their original form due to reactivity and/or propensity for hetero-agglomeration in environmental media. Therefore, emphasis is placed on characterizing ENM as they occur in environmental or biological matrices. In addition, predicting the activity of ENM in the environment is difficult due to the multiple dynamic interactions between the physical/chemical aspects of ENM and similarly complex environmental conditions. Others have proposed the use of simple predictive functional assays as an intermediate step to address the challenge of using physical/chemical properties to predict environmental fate and behavior of ENM. The nodes and interactions of the framework presented here reflect phase transitions that could be targets for development of such assays to estimate kinetic reaction rates and simplify model predictions. Application, refinement, and demonstration of this framework, along with an associated knowledgebase that includes targeted functional assay data, will allow better de novo predictions of potential exposures and adverse outcomes.

Keywords:

• Engineered nanomaterials
• nanoparticles
• life cycle
• environmental fate and transport
• transformations
• exposure
• adverse outcome pathway
• oxidative stress
• inflammation
• nanotoxicity
• human health
• ecotoxicity

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Acknowledgements

The authors thank Dr. Christine Hendren (Duke University, Center for Environmental Implications of Nanotechnology) and Maureen Gwinn (U.S. EPA Office of Research of Development, National Center for Environmental Assessment) for their extremely helpful reviews of an earlier version of the manuscript. The authors also are very appreciative of the extensive review comments from peer-reviewers selected by the Editor and anonymous to the authors. This input served to greatly strengthen the manuscript.

Declaration of interest

The authors declare that there are no financial conflicts of interest. The author’s affiliations are as shown on the cover page. The authors have sole responsibility for the writing and content of the paper. The work was conducted under the EPA Office of Research and Development Chemical Safety for Sustainability Research Program. This article was reviewed in accordance with the policy of the National Health and Environmental Effects Research Laboratory, U.S. Environmental Protection Agency and approved for publication. Approval does not signify that the contents necessarily reflect the views and policies of the Agency, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

All of the authors, with one exception, were employees of the U.S. Environmental Protection Agency, and development of this document was a portion of their job responsibilities. The exception was L. L. Thornton, who was an independent student services contractor to the EPA, and preparation of this manuscript was a portion of assigned work duties (Contract no. EP-13-C-000164).

None of the authors, with one exception, have participated in legal or regulatory proceedings regarding the content of this manuscript within the last 5 years. The exception was Dr. W. K. Boyes, who served on workgroups related to the issuance of a Toxics Substances Control Act (TSCA) Section 8(a) action: “Chemical Substances When Manufactured or Processed as Nanoscale Materials; TSCA Reporting and Recordkeeping Requirements”, and in responding to public comments related to this action (40 CFR Part 704; Fed. Reg.82 (8) 3641–3655, 2017).

This work was supported by the U.S. Environmental Protection Agency.