Abstract
Advances in adding nanomaterials to various matrices have occurred in tandem with the identification of potential hazards associated with exposure to pure forms of nanomaterials. We searched multiple research publication databases and found that, relative to data generated on potential nanomaterial hazards or exposures, very little attention has focused on understanding the potential and conditions for release of nanomaterials from nanocomposites. However, as a prerequisite to exposure studying release is necessary to inform risk assessments. We identified fifty-four studies that specifically investigated the release of nanomaterials, and review them in the following release scenario groupings: machining, weathering, washing, contact and incineration. While all of the identified studies provided useful information, only half were controlled experiments. Based on these data, the debris released from solid, non-food nanocomposites contains in varying frequencies, a mixture of four types of debris. Most frequently identified are (1) particles of matrix alone, and slightly less often, the (2) matrix particles exhibit the nanomaterial partially or fully embedded; far less frequently is (3) the added nanomaterial entirely dissociated from the matrix identified: and most rare are (4) dissolved ionic forms of the added nanomaterial. The occurrence of specific debris types appeared to be dependent on the specific release scenario and environment. These data highlight that release from nanocomposites can take multiple forms and that additional research and guidance would be beneficial, allowing for more consistent characterization of the release potential of nanomaterials. In addition, these data support calls for method validation and standardization, as well as understanding how laboratory release scenarios relate to real-world conditions. Importantly, as risk is considered to be a function of the inherent hazards of a substance and the actual potential for exposure, data on nanomaterial release dynamics and debris composition from commercially relevant nanocomposites are a valuable starting point for consideration in fate and transport modeling, exposure assessment, and risk assessment frameworks for nanomaterials.
Highlights
Solid nanocomposites [1], made by combining conventional composite matrices with nanoparticulate additives, have been demonstrated to exhibit material properties superior to those of conventional composite (e.g. [2,3,4])
We were motivated to review the literature with a focus on understanding what is known about releases from solid, non-food commercial nanocomposites during normal uses, disposal, or recycling – conditions with a far larger exposure potential for consumers and the environment
Consumers and the environment will interact with nanocomposites, from which the added nanomaterials must first be released before any exposure can occur
Summary
Solid nanocomposites [1], made by combining conventional composite matrices with nanoparticulate additives, have been demonstrated to exhibit material properties superior to those of conventional composite (e.g. [2,3,4]). We were motivated to review the literature with a focus on understanding what is known about releases from solid, non-food commercial nanocomposites during normal uses, disposal, or recycling – conditions with a far larger exposure potential for consumers and the environment. Release scenarios Through consumer product use, disposal or recycling, nanocomposites encounter potentially degrading mechanical, thermal and/or chemical energy inputs that may result in the release of the embedded nanomaterials. We highlight the experimental studies, given the dearth of data at this time, we believe the results from both observations and experiments provide potentially valuable insights into release dynamics Even, within this limited data set there much information that should serve as a useful benchmark for the state of knowledge on the release of nanomaterials from nanocomposites (Figure 2)
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