Ecotoxicology of Engineered Nanomaterials

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1 Ecotoxicology of Engineered Nanomaterials Jeffery Steevens, Tony Bednar, Mark Chappell, Jessica Coleman, Katerina Dontsova, David Johnson, Alan Kennedy, Igor Linkov, Mohammed Qasim, Jacob Stanley, Charles Weiss U.S. Army Engineer Research and Development Center Vicksburg, MS

2 ERDC Nanomaterials Risk Research Cluster Material characterization Fate and transport Ecotoxicology Computational chemistry Risk and decision analysis

3 Risk Assessment of Nanomaterials Problem Formulation Analysis and Risk Characterization Risk Management Exposure Effects Identify and quantify the environmental attributes of nanomaterials. Sources of nanomaterials? Fate and transport mechanisms? Likely exposure scenarios? Biological effects resulting from exposure? Goals: Characterize physical / chemical interactions between engineered nanomaterials and environmental media. Establish computational approach for predicting relevant characteristics (persistence, fate, toxicology).

4 Conceptual Model

5 Fullerene Source Material MWCNT TEM 1 nm (Manufacturer) 14, 36 nm agglomerates (DLS) Zeta potential: -1 to -3 mv Surface area =.1 m²/g Aluminum Oxide (Al 2 3 ) TEM 2-3 nm diameter; 1-2 um length 1:1 aspect ratio; > 95% purity Zeta potential: TBD Surface Area = m²/g Fullerene Soot (Waste) TEM 11, 4-8 nm (Manufacturer) 12-17, 3-5 nm aggregates (DLS) Zeta potential: TBD Surface area = m²/g Contains: fullerenes, tubes Metals: B, Ba, Ca, Cr, Cu, K, Mg, Na, Ni, Sr, Zn (ICP-MS)

6 What is the best dose metric? Physical and chemical characteristics Size Electron microscopy (SEM, TEM, AFM) Dynamic light scattering Field Flow Fractionation-ICP MS Surface area BET (Brunauer, Emmett and Teller) Morphology Electron microscopy Confocal microscopy Surface Chemistry Zeta potential Confocal Microscopy DLS BET SEM

7 Characterization of C6 Water Concentration (mg/l) PARTICLE CONCENTRATION Time (d) PARTICLE SIZE MilliQ MHRW 5 PPT 2 PPT Magnetically stirred C6 dispersions Particle stability inversely related to ionic strength Mechanism for dispersion Weathering of larger aggregates/ agglomerates with time Particles gain charge (as zeta potential) Repulsion combats van der Waals attraction PARTICLE CHARGE Particle size range (nm) day / 1 day 8 day / 1 day 16 day / 1 day 35 day / 1 day 35 day / 7 day particle size with mixing 5 ppt MHRW MilliQ

8 Aquatic Toxicity of C6 C6 prepared in MQ by stirring, allow to settle for 24 hrs, then add salts to make MHRW Ceriodaphnia 48 hr exposure, Acute toxicity and uptake Target concentrations 2, 1, 5, 2.5, 1.2 mg/l Spec and DLS analysis of water Stock of C6 Mix for 28 days Treatment Measured Concentration Mean Survival (mg/l) Control n/a 95 ± 1% 6%.51 ±.5 8 ± 28% 13% 1.28 ±.49 1 ± % 25% 1.9 ±.4 1 ± % 5% 2.9 ±.3 95 ± 1% 1% 5.15 ±.6 1 ± % * Concentration in water measured using spectrophotometer of toluene extract 5. mg/l C6 48 hrs uptake MHRW Water 24 hrs elimination

9 Other Aquatic Toxicity Data Material Preparation Organism hr LC5 Units Study C6 THF / Filtered Daphnia magna mg/l Lovern and Klapper 26 C6 Sonicated / unfiltered Daphnia magna mg/l Lovern and Klapper 26 C6 Magentic stirring Copepod (marine) 96 >25.5 mg/l Oberdorster et al 26 C6 Magentic stirring Daphnia magna 54 >5 mg/l Oberdorster et al 26 C6 THF Daphnia magna 48.8 mg/l Zhu et al 26 C6 Magentic stirring Daphnia magna 48 >35 mg/l Zhu et al 26 C6 Stirring Fundulus 144 > 9.7 mg/l Blinkey et al 26 C6 Magentic stirring Hyalella azteca 96 >7 mg/l Oberdorster et al 26 C6 Magentic stirring Orzias latipes 96 >.5 mg/l Oberdorster et al 26 C6 Magentic stirring Pimephales promelas 96 >.5 mg/l Oberdorster et al 26 C6 Magnetic stirring Ceriodaphnia dubia 48 > 5 mg/l Kennedy et al 26 Cd(Se core) Ceriodaphnia dubia mg/l Bouldin et al 26 Cd(Se core) Ceriodaphnia dubia mg/l Bouldin et al 26 TiO 2 Filtered Daphnia magna mg/l Lovern and Klapper 26 TiO 2 Bath Sonicated / unfiltered Daphnia magna 48 >5 mg/l Lovern and Klapper 26 Most data is for C6 Most used extensive preparation Short term exposures Range of values down to.46 mg/l to max prep for C6 All data are reported using traditional metrics (some limited characterization information)

10 Examine Relevant Fate & Toxicity Water bodies are the ultimate repository for many chemicals Unknown nanomaterial behavior in environmental media Particle charge Functional groups Ionic strength Dissolved organic matter Determine influence of material surface and solution chemistry Fate studies dictate which toxicity bioassays are relevant Sediment bioassays settling / aggregation of hydrophobic materials Water column bioassays dispersed colloids / total suspended solid loads

11 Fate: Particle Aspect Ratio High aspect ratio CVD CARBON BLACK ACTIVATED CARBON RAW MWNT Percent of Original Absorbance Printex - MQ Printex- MHRW Printex- 2 ppt Percent of Original Absorbance TOG-CA - MQ TOG-CA - MHRW TOG-CA - 2 ppt Percent of Original Absorbance MWNT - MQ MWNT - MHRW MWNT - 2 ppt Time (minutes) Time (minutes) Time (minutes) Relevance to sediment toxicity exposures

12 Fate: Role of Surface Chemistry Raw MWNT MWNT-OH MWNT-COOH Functional groups reduced settling rate Percent of Original Absorbance MWNT settling in MHRW 1 day stirring, 24-h settling MWNT MWNT-COOH MWNT-OH MWNT settling in MHRW 1 day stirring, 24-h settling MWNT MWNT (1 ppm NOM) MWNT-COOH MWNT-COOH (1 ppm NOM) MWNT-OH MWNT-OH (1 ppm NOM) Organic matter stabilizes MWNT Time (minutes) Time (minutes)

13 Humic / Fulvic Acid Stabilization Raw MWNT stirred into organic matter MWNT concentration increases with: Organic matter concentration Stirring duration Stabilization efficiency Humic > fulvic acid Effective diameter decreases with: Increasing organic matter concentration Increasing stirring duration Presence of humic acid 35 5 Concentration (mg/l) Time point 1d / 1d 7d / 1d Effective Diameter Time point 1d / 1d 7d / 1d 7d / 7 d Fulvic Humic Fulvic Humic

14 MWCNT Dispersed in Water Are the humic substances acting as surfactants? Mean particle diameter (nm) MPD Polydispersivity Humics added (mg L -1 ) MPD Polydispersivity SDS added (mg L -1 ) Polydispersivity Natural organic material increased dispersvity = Increased mobility

15 Nano Aluminum Nano aluminum (Al) is used as an oxidizer in energetics / propellants due to its high energy release during its oxidation to Al2O3. Use of nano-al (< 1 nm) can significantly increase propellant burning rate, heat of explosion, and lower ignition time. Al2O3 flocculates in water; sediment toxicity and bioaccumulation studies performed. Evaluate toxicity and uptake in Lumbriculus variegatus, Tubifex tubifex and toxicity in Hyalella azteca No change in survival Decrease in growth Hyalella azteca Mean weight per surviving organism (mg) Bulk Control Nano Control Bulk Al2O3 Nano Al2O Sediment Al concentration (mg/kg) p =.22 * Hyalella azteca 1-d growth Confocal image of Hyalella exposed to nano aluminum oxide

16 Soil Compare bulk to nanometal Nano Aluminum Evaluate toxicity and uptake in earthworms (28-d study) Study avoidance behavior Results No change in survival Decrease in cocoons produced Significant increase in Al uptake Significant avoidance behavior Eisenia Soil Avoidance Chamber Al 2 O 3 Tissue Concentration (mg/kg) Bulk Nano Aluminum Oxide Soil Concentrations (mg/kg) C Al Control Nano Al Bulk Al

17 Nanomaterial Waste Implications cps/ev C O Energy Dispersive x-ray Spectroscopy Gd Metallofullerene Soot Graphite Rods Electric Arc Process Gd and Cu metal recovered in processed soot Cu Gd Cu.5 Al > 9% waste Nanomaterials Metals concentration (mg/kg) Enriched soot Gd Cu Processed soot 25 1 Soot sample (kg)

18 Nanomaterial Waste Implications Assessed 2 carbon waste materials Arc deposition process Impurities (metals and solvents) Toxic to aquatic organisms Toxicity mainly from metals Concentration (ug/l) CMC = CMC = CMC = 97 CMC = 51 CMC = 11 Zn Fe Pb Al Cu Gd MHRW, ph = MHRW, ph = HRW, ph = Percent Survival 12% 1% 8% 6% 4% 2% % Pimephales promelas MHRW MHRW (EDTA) Control 6% 13% 25% 5% 1% Percent Survival 12% 1% 8% 6% 4% 2% % Ceriodaphnia dubia MHRW MHRW (EDTA) HRW Control 3% 6% 13% 25% 5% 1% Percent Survival 12% 1% 8% 6% 4% 2% % Daphnia magna MHRW MHRW (EDTA) Control.1%.1%.1% 1% 1% 1%

19 Periodic Table and Classification System Develop Framework for Comparative/Relative Risk Analysis Statistical Approaches for Clustering Nanomaterial Parameters and Environmental Attributes 2D Stress:.7 PCB A E E Periodic Table Multi-Dimensional Approach Multidimensional Scaling (MDS) and Hierarchical Classification (clustering) Steevens et al., 28 Linkov, I., Satterstrom, F., Steevens, J., Ferguson, E. and R. Pleus. 27. Multi-Criteria Decision Analysis and Environmental Risk Assessment for Nanomaterials. Journal of Nanoparticle Research. 9:

20 Conclusions Characterization is very important in all aspects of ecotoxicology studies Source and use of materials should be informed from developers/manufacturers Understanding fate of materials in relevant media is important For example, humic acids are likely to increase dispersivity, mobility of carbon nanomaterials Toxicity of materials may be unexpected Catalysts such as copper can be highly toxic Our goal is to predict behavior of NM to help technology developers