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Nanoscale Silver

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Technical Report
Technical Report

Integrated Risk Information System Program

Author: U.S. EPA (2015) Washington, DC: U.S. Environmental Protection Agency, IRIS. HERO ID: 192196

[Less] The U.S. Environmental Protection Agency's (EPA) Integrated Risk Information System (IRIS) Program provides . . . [More] The U.S. Environmental Protection Agency's (EPA) Integrated Risk Information System (IRIS) Program provides health effects information on chemicals to which the public may be exposed, providing a critical part of the scientific foundation for EPA's decisions to protect public health. EPA has made several changes to this important Program over the past few years, streamlining the assessment development process, improving transparency, and creating efficiencies within the Program. In April 2011, the National Research Council (NRC) made several recommendations to EPA for improving the development of IRIS assessments. The N RC's recommendations were focused on the development of draft assessments, and the NRC was clear that their intent was not to delay assessments. EPA has made progress in implementing these recommendations. Consistent with the advice of the NRC, EPA is implementing these recommendations using a phased approach and is making the most extensive changes to documents that are in the earlier steps of the assessment development process. For assessments that are in the later stages of development, including assessments that have been posted on the IRIS database since the release of the NRC report, EPA is implementing the recommendations as feasible without taking the assessments backwards to earlier steps of the process. Phase 1 of implementing the NRC recommendations has focused on editing and streamlining documents and using more tables, figures, and appendices. EPA is now in Phase 2 of implementing the NRC recommendations and will soon publicly release two draft IRIS assessments that represent a major advancement in implementing the NRC recommendations. EPA is using a new document structure for these draft assessments, including an Executive Summary presenting major conclusions, a Preamble describing methods used to develop the assessment, distinct sections on Hazard Identification and Dose-Response Analysis, and more tables and figures to clearly present data. Additionally as part of Phase 2, EPA is addressing all of the short-term recommendations provided by the NRC. As part of this effort, EPA will make several changes to IRIS assessments. Highlights include: evaluating and describing the strengths and weaknesses of critical studies in a more uniform way; including toxicity values for multiple effects associated with the chemical, if applicable and where the data allow; routinely considering the use of multiple data sets of combined multiple responses in deriving toxicity values, where appropriate; and evaluating existing guidelines to establish clearer criteria for study selection. Phase 3 of implementation will incorporate the longer-term scientific recommendations made by the NRC. The U.S. Congress has directed EPA to issue a progress report to the House and Senate Committees on Appropriations and relevant Congressional authorizing committees to describe EPA's implementation of the NRC recommendations. This report provides Congress, stakeholders, and the public with an update on the IRIS Program and EPA's progress toward implementing the NRC recommendations and improving the Program.

Archival Material
Archival Material

Exposure and Fate Assessment Screening Tool version 2014 (E-FAST 2014)

Author: U.S. EPA (2014) HERO ID: 4216154


Archival Material
Archival Material

TSI-AeroTrak model 9000 nanoparticle aerosol monitor

Author: TRS Environmental (2012) Available online at http://www.trs-environmental.com/Model/TSI_AEROTRAK_9000.aspx. (Aug 2, 2012). [Website] HERO ID: 196057


Archival Material
Archival Material

Analytical electron microscope

Author: NCEM (2012) Available online at http://ncem.lbl.gov/frames/aem.htm. (Aug 6, 2012). [Website] HERO ID: 625607


Archival Material
Archival Material

Silver in history

Author: The Silver Institute (2012) HERO ID: 1257623


Archival Material
Archival Material

Aerosol time-of-flight mass spectrometers series 3800

Author: TSI Inc. (2012) HERO ID: 1257625


The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Detecting nanoparticulate silver using single-particle inductively coupled plasma-mass spectrometry

Authors: Mitrano, DM; Lesher, EK; Bednar, A; Monserud, J; Higgins, CP; Ranville, JF (2012) Environmental Toxicology and Chemistry 31:115-121. HERO ID: 1006094

[Less] The environmental prevalence of engineered nanomaterials, particularly nanoparticulate silver (AgNP), . . . [More] The environmental prevalence of engineered nanomaterials, particularly nanoparticulate silver (AgNP), is expected to increase substantially. The ubiquitous use of commercial products containing AgNP may result in their release to the environment, and the potential for ecological effects is unknown. Detecting engineered nanomaterials is one of the greatest challenges in quantifying their risks. Thus, it is imperative to develop techniques capable of measuring and characterizing exposures, while dealing with the innate difficulties of nanomaterial detection in environmental samples, such as low-engineered nanomaterial concentrations, aggregation, and complex matrices. Here the authors demonstrate the use of inductively coupled plasma-mass spectrometry, operated in a single-particle counting mode (SP-ICP-MS), to detect and quantify AgNP. In the present study, two AgNP products were measured by SP-ICP-MS, including one of precisely manufactured size and shape, as well as a commercial AgNP-containing health food product. Serial dilutions, filtration, and acidification were applied to confirm that the method detected particles. Differentiation of dissolved and particulate silver (Ag) is a feature of the technique. Analysis of two wastewater samples demonstrated the applicability of SP-ICP-MS at nanograms per liter Ag concentrations. In this pilot study, AgNP was found at 100 to 200 ng/L in the presence of 50 to 500 ng/L dissolved Ag. The method provides the analytical capability to monitor Ag and other metal and metal oxide nanoparticles in fate, transport, stability, and toxicity studies using a commonly available laboratory instrument. Rapid throughput and element specificity are additional benefits of SP-ICP-MS as a measurement tool for metal and metal oxide engineered nanoparticles.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Exposure to silver nanoparticles inhibits selenoprotein synthesis and the activity of thioredoxin reductase

Authors: Srivastava, M; Singh, S; Self, WT (2012) Environmental Health Perspectives 120:56-61. HERO ID: 1021916

[Less] BACKGROUND: Silver nanoparticles (AgNPs) and silver (Ag)-based materials are increasingly . . . [More] BACKGROUND: Silver nanoparticles (AgNPs) and silver (Ag)-based materials are increasingly being incorporated into consumer products, and although humans have been exposed to colloidal Ag in many forms for decades, this rise in the use of Ag materials has spurred interest into their toxicology. Recent reports have shown that exposure to AgNPs or Ag ions leads to oxidative stress, endoplasmic reticulum stress, and reduced cell proliferation. Previous studies have shown that Ag accumulates in tissues as silver sulfides (Ag2S) and silver selenide (Ag2Se).

OBJECTIVES: In this study we investigated whether exposure of cells in culture to AgNPs or Ag ions at subtoxic doses would alter the effective metabolism of selenium, that is, the incorporation of selenium into selenoproteins.

METHODS: For these studies we used a keratinocyte cell model (HaCat) and a lung cell model (A549). We also tested (in vitro, both cellular and chemical) whether Ag ions could inhibit the activity of a key selenoenzyme, thioredoxin reductase (TrxR).

RESULTS: We found that exposure to AgNPs or far lower levels of Ag ions led to a dose-dependent inhibition of selenium metabolism in both cell models. The synthesis of protein was not altered under these conditions. Exposure to nanomolar levels of Ag ions effectively blocked selenium metabolism, suggesting that Ag ion leaching was likely the mechanism underlying observed changes during AgNP exposure. Exposure likewise inhibited TrxR activity in cultured cells, and Ag ions were potent inhibitors of purified rat TrxR isoform 1 (cytosolic) (TrxR1) enzyme.

CONCLUSIONS: Exposure to AgNPs leads to the inhibition of selenoprotein synthesis and inhibition of TrxR1. Further, we propose these two sites of action comprise the likely mechanism underlying increases in oxidative stress, increases endoplasmic reticulum stress, and reduced cell proliferation during exposure to Ag.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Ion-release kinetics and ecotoxicity effects of silver nanoparticles

Authors: Lee, YJ; Kim, J; Oh, J; Bae, S; Lee, S; Hong, IS; Kim, SH (2012) Environmental Toxicology and Chemistry 31:155-159. HERO ID: 1021896

[Less] The environmental toxicity associated with silver nanoparticles (AgNPs) has been a major focus in nanotoxicology. . . . [More] The environmental toxicity associated with silver nanoparticles (AgNPs) has been a major focus in nanotoxicology. The Ag(+) released from AgNPs may affect ecotoxicity, although whether the major toxic effect is governed by Ag(+) ions or by AgNPs themselves is unclear. In the present study, we have examined the ecotoxicity of AgNPs in aquatic organisms, silver ion-release kinetics of AgNPs, and their relationship. The 48-h median effective concentration (EC50) values for Daphnia magna of powder-type AgNP suspensions were 0.75 µg/L (95% confidence interval [CI] = 0.71-0.78) total Ag and 0.37 µg/L (95% CI = 0.36-0.38) dissolved Ag. For sol-type AgNP suspension, the 48-h EC50 values for D. magna were 7.98 µg/L (95% CI = 7.04-9.03) total Ag and 0.88 µg/L (95% CI = 0.80-0.97) dissolved Ag. The EC50 values for the dissolved Ag of powder-type and sol-type AgNPs for D. magna showed similar results (0.37 µg/L and 0.88 µg/L) despite their differences of EC50 values in total Ag. We observed that the first-order rate constant (k) of Ag(+) ions released from AgNPs was 0.0734/h at 0.05 mg/L total Ag at 22°C within 6 h. The kinetic experiments and the toxicity test showed that 36% and 11% of sol-type AgNPs were converted to the Ag(+) ion form under oxidation conditions, respectively. Powder-type AgNPs showed 49% conversion rate of Ag(+) ion from AgNPs. We also confirmed that Ag(+) ion concentration in AgNP suspension reaches an equilibrium concentration after 48 h, which is an exposure time of the acute aquatic toxicity test.

The "refereed" or "peer review" status of a journal comes from the Ulrichsweb Global Serials Directory (http://ulrichsweb.serialssolutions.com/), as supplied by the publisher. The term refers to the system of critical evaluation of manuscripts/articles by professional colleagues or peers. The content of refereed publications is sanctioned, vetted, or otherwise approved by a peer-review or editorial board. The peer-review and evaluation system is utilized to protect, maintain, and raise the quality of scholarly material published in serials. Publications subject to the referee process are assumed, then, to contain higher quality content than those that are not.
Peer Reviewed Journal Article

Interaction of silver nanoparticles with biological surfaces of Caenorhabditis elegans

Authors: Kim, SW; Nam, SH; An, YJ (2012) Ecotoxicology and Environmental Safety 77:64-70. HERO ID: 1021903

[Less] Silver nanoparticles (AgNPs) are being used in an increasing number of industrial and commercial applications; . . . [More] Silver nanoparticles (AgNPs) are being used in an increasing number of industrial and commercial applications; this has resulted in an increased release of AgNPs into the environment. Understanding the interaction of AgNPs with biological surfaces is important, as such understanding will facilitate predictions of the further effects of nanoparticles on biological systems. This study highlights the interaction of citrate-coated silver nanoparticles (cAgNPs) with the biological surfaces of the nematode C. elegans. General toxicity, as proxied by factors such as mortality and reproduction, was evaluated in nematode growth medium (NGM), which provides a more homogeneous distribution of cAgNPs than in K-medium. The survival and reproduction of C. elegans evidenced a clear reduction in up to 100 mg/L and 10 mg/L of cAgNPs, respectively. We also noted significant interactions of cAgNPs with the biological surfaces of C. elegans. Severe epidemic edema and burst were detected in the exposure group, which may be associated with secondary infections in soil ecosystems. We observed no evidence of cAgNPs intake by C. elegans. This is, to the best of our knowledge, the first report to investigate the nanotoxicity of cAgNPs as related to biological surfaces of C. elegans; further research is needed to study the fate of cAgNPs inside of C. elegans.